night rating

A v i a t i o n T h e o r y C e n t r e

Night Flight

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D a v i d R o b s o n

Avia t ionT h e o r yC e n t r e

Night Flight

David Robson

© Aviation Theory Centre Pty Ltd 2008First EditionJuly 2003Reprintedwith revisionJanuary 2008

PublishedbyAviation Theory Centre Pty LtdA C N 088 462 87323/ 148 Chesterville RoadCheltemham VIC 3192AustraliaTe1261 (0)3 9532 5421FaX261 (0)3 9532 5423E‐mail: [email protected] .auThe contents of this manual are protected by copyrightthroughout the world under the Berne Union and theuniversal copyright convention.Al l rights reserved. No part of this publication may bereproduced in any manner whatsoever ‐ electronic,photographic, photocopying, facsimile, or stored in aretrieval system- without the priorwritten permissionof theauthor.

DisclaimerNothing in this tex t supersedes any operational documentsissued by the Civi l Aviation Safety Authority, AirservicesAustralia, aircraft, engine and avionics manufacturers, or theoperators of aircraft throughout the world.ISBN 1 875537 70 8

Graphics, typesetting and index:Aviation Theory Centre

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mailto:[email protected]

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Table of Contents

Editorial Team. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

Why Fly at Night, Especially in a Single-Engine Aircraft? . . . . . . . . viiNight ‘Visual’ Flight. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .viii

Part One: RefreshmentInstruments and Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Pressure Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Gyroscopic Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6Compass Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Other Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10Preflight Checks of the Flight Instruments. . . . . . . . . . . . . . . . . . .11Pitot‐Static System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Vacuum System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13Electrical System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Autopilot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Meteorology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Clouds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19Thunderstorms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22Air Masses and Fronts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29Icing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30Fog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37Visibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41Astronomical Times . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

Chapter 3: Human Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45The Role of the Pilot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45Vision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51Visual Illusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58Hearing and Balance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68

Part Two: Night VFR Rating, Rules and RequirementsChapter 4: Night Flight Rules and Requirements . . . . . . . . . . . . . . . . . . . . . . . .83

What is Night? . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . .83How to Determine if a Pilot is Suitable to Fly Night VFR . . . . . . . .83Aircraft Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87Is the Route Suitable to be Flown? . . . . . . . . . . . . . . . . . . . . . . . .92

iii

iv Night Flight

Weather Requirements for Night VFR . . . . . . . . . . . . . . . . . . . . . . 97Aerodrome Lighting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100Aerodrome Suitability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

Part Three: Piloting TechniqueChapter 5: lnstrument Flight Technique . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113

Flight Control versus Flight Performance . . . . . . . . . . . . . . . . . . 113instrument Scanning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114Attitude instrument Flying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Chapter 6: Night Flight Technique. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123Preparation for a Possible Night Flight. . . . . . . . . . . . . . . . . . . . . 123Preparation fora Planned Night Flight . . . . . . . . . . . . . . . . . . . . . 124Flight Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130Night Circuits . . . . . . . . . . . . . . . . . . _. . . . . . . . . . . . . . . . . . . . . 142

Chapter 7: Abnormal Operations at Night . . . . . . . . . . . . . . . . . . . . . . A. . . . . 145Risk Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145Things that May GoWrong in the Flight . . . . . . . . . . . . . . . . . . . 146Emergency Radio Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . 148Engine Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156Electrical System Failure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158Pitot‐Static System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159Failure of Aerodrome Lighting . . . . . . . . . . . . . . . . . . i . . . . . . . . 160Limited‐Panel instrument Flying . . . . . . . . . . . . . . . . . . . . . . . . . 161ExtremeAttitude Recoveries: Full Panel . . . . . . . . . . . . . . . . . . . 166Unusual Attitude Recoveries on Limited Panel . . . i . . . . . . . . . . 171

Part Four: Night Flight Planning and NavigationChapter 8: Planning a Night Flight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

Planning a Night Flight from Wagga Wagga to Canberra . . . . . . 177Planning the Fight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183Flight Notification and SARTiME . . . . . . . . . . . . . . . . . . . . . . . i . 186Escape Routes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191Point of No Return. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192

Chapter9: Radio Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195Orientation in Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195Non~Directiona| Beacon (NDB) . . . . . . . . . . . . . . . . . . . . . . . . . . 199Automatic Direction Finder . . . . . . . . . . . . . . i . . . . . . . . . . . . . . 202VOR A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216Distance Measuring Equipment (DME) . . . . . . . . . . . . . . . . . . . . 232Global Positioning System (GPS) . . . . . . . . . . . . . . . . . . . . . . . . . 235

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 251

Editorial Team

David Robson 'DavidRobson isa career aviator havingbeen nurtured on balsa wood, dope (thelegal kind) and tissue paper. He made his first solo flight shortly after his seven‑teenth birthday having made his first parachutejump just after his sixteenth. Hisfirst job was asajunior draughtsman (they weren’t persons in those days) at theCommonwealth Aircraft Corporation in Melbourne. At that time he was alsolearningto fly in Chipmunks with the RoyalVictorian Aero Club. Hejoined theRoyalAustralian Air Force in 1965 and served for twenty‐one years asa fighterpilot and test pilot. He flew over 1,000 hours on Mirages and 500 on Sabres. Hecompleted the Empire Test Pilots’ course atBoscombe Downin 1972,flying eve‑rythingfrom gliders to Lightnings andArgosies. He completedat o u r in Vietnamasa forward air controller in support of the First Australian Task Force. He was amember of the Mirage formation aerobatic team the Deltas,which celebrated theRAAF’s 50th anniversary.

After retiring from the A i r Force he became a civilian instructor and lecturerand spent over ten years with the Australian Aviation College. During 1986‑88 he was the editor of the Aviation Seyfety Digest (the ‘Crash Comic’) whichw o n the Flight Safety Foundation’s international award. He was awarded theAustralian Aviation Safety Foundation’s Certificate of Air Safety in 1997 andthe Award for Excellence in training in 2001. He continues to fly atMorrabbin, Ballarat and Temora.

Melanie WaddellMelanie began flying in 1994 and was awarded a Bachelor of Technology inaviation studies from Swinburne University in 1997. She currently holds anATPL, with multi‐engine and command instrument ratings, and isagrade‐oneflight instructor at Essendon. To broaden her aeronautical knowledge andexperience, she instructed the Air Training Corps and was appointed actingflight commander of 5 Flight in the Victorian Squadron. She has also workedfor Airshows Downunder. She continues to pursue achallenging career in avi‑ation. Melanie and Darren were recently married in a DC-3!

Juliet DyerJuliet began flying training at the age of 15in Melbourne, and when she c o m ‑pletedhighschool, she moved to Newcastle to attend that University’s aviationdegree program. She successfully studied for aBachelor of Science (Aviation)

degree while working part‐time and continuing her flying training. Aftergaining a Commercial Pilot’s licence, she was employed asa scenic pilot con ‑ducting flights along the beautiful South coast of N SW She returned toMelbourne to complete her tertiary studies at Swinburne university, concen ‑trating on Aviation Business Management. At the same time,Juliet completeda Flight Instructor’s rating at Moorabbin.

Avia t ionT h eo r yCen t r e

vi

Introduction

Night flight is magnificent. It is smooth, uncluttered and easy, provided youlearn the correct technique andyou fly regularly. Night flying technique is thesame asday flight, except you probably will n o t have avisual horizon. Thereis, therefore, only one way to fly at night: by the instruments. However, thereare t w o ways of navigating (Visually and by navaids) and t w o sets of rules andprocedures (IFR andVFR). Each has its ow n pros and cons.

Why Fly at Night, Especially in a

Some of the aspects that can make night flight such a pleasant experienceinclude smooth conditions, good Visibility, reduced wind, traffic, talking andthermal activity, wonderful sunsets (and sunrises if you are an early riser) andbeautiful patterns of stars and lights. But night flight has its potential hazards ‑you may n o t see an embedded thunderstorm inside a stratus cloud, the ADFneedle can give false indications atnight, and there are few lights andmany illu‑sions over sea, desert and mountains. Like all forms of flight, night flightshould beapproachedwith due respect, but mo re sobecause there is less r o o mfor error or inaccuracy and fewer escape options.Single‐engine flight at night can be quite safe. Some pilots tell tales of

engine noises, fluctuating oil pressure and rough running at night or over thesea, but the engine doesn’t know that it’s night, or that it’s over mountains orwater. So why does it seem to make strange noises? I don’t know ‐ perhapswehear What isn’t there because of heightened sensitivity. If you know theengine’s maintenance history and have personally checked the fuel and oil, theengine should be very reliable. However, realise that aforced landingmay n o tbe an option in some areas. Choose your rou te with this in mind. A trackwith rivers, beaches, lakes or straight, l i t highways gives some chance ofsurvival. Your autopilot, attitude indicator and t u r n coordinator become asimportant asthe engine. A powerful and reliable engine is useless if you haveno attitude reference.Night flight in amulti-engine aircraft is potentially safer than in a single‑

engine one. However, engine failure and asymmetric control at night aredemanding exercises in themselves, especially immediately after take‐off.Don’t forget your emergency self‐brieffor these possibilities.

vii

Equally important is the built‐in redundancy in the lighting, electrical andinstrument systems. Unless you are current, confident and competent atlimited or partial panel instrument flight, choose an aircraft with a standbyattitude indicator. This is required for night passenger charter anyway and is awise precaution for all night operations.

i ' V i s ’ “ I tNight flight is not visual flight despite being called night VFR and the weatherconditions being called night VMC. The official definition of night flightrelates to weather conditions or to regulations and rules that apply, but n o t tothe techniques of controlling the aircraft.

The definitions and regulations regarding day V M C and night V M C do n o tspecify a clearly defined horizon. Night flight is instrument flight ‐ make nomistake. If there is no visual horizon, you are flying on the clocks. During theday in reducedvisibility and over level terrain, you may get away with averticalreference below the aircraft asa guide to aircraft attitude and flightpath. Atnight, it is t o o risky Uneven distribution of lights and stars gives subtle butmisleading cues asto which way is up, which way is down and whether or n o tthe aircraft is level. You must fly attitude on instruments and be able to do socompetently when talking on the radio, reading charts, writing downinstructions and looking for ground features and other traffic.

In some circumstances, navigation may use visual references, but m o s tnavigation at night also requires reference to navaids. In the circuit, the aircraftmay be positioned by reference to the runway or ground features, but it isflownby reference to the instruments.

This book highlights the hows and the how nots for safe night flight. Use theautopilot ‐ it can be a good friend, but unlike your best friend, don’t trust itabsolutely. Keep aweather eye. The same advice applies to the GPS.

If you fly smoothly, confidently and regularly, you will enjoy night flying.

viii

Part One

Refreshment

Chapter 1: Instruments and Systems . . . . . . . . . . . 3

Chapter 2: Meteorology. . . . . . . . . . . . . . . . . . . . . 19

Chapter 3: Human Factors. . . . . . . . . . . . . . . . . . . 45

Chapter 1

Instruments and Systems

Flight instruments fall functionally into three categories: pressure instruments,gyroscopic instruments and compass instruments. Pressure instruments include theairspeed indicator (ASI), the altimeter and the vertical speed indicator (VSI).Gyroscopic instruments include the attitude indicator (Al), the heading indi‑cator (HI) and the t u r n indicator or t u r n coordinator. Compass instrumentsuse a magnetic reference. In support of the flight instruments are the pitot‑static system, the vacuum system and the electrical system. All of these arebrought together by the greatest aid to the pilot ‐‐ the autopilot.

Pressure InstrumentsAirspeed Indicator

The airspeed indicator displays indicated air‐ Redline

speed (IAS). Indicated airspeed is a \\measure of dynamic pressure, which is the _. \160 AIRSPEED 40difference between the total pressure of ~ “ , KNOTS

the pitot head and the ambient static pres‑sure. The airspeed indicator will have thefollowing specific speeds marked on it:' V50 ‐ stall speed at maximum weight,

undercarriage down, flaps down, poweroff;

° V31 ‐ stall speed at maximum weight, Altitude 7,000“

undercarriage up, flaps up, power off; Temp+1°°c

' VFE ‐ maximum speed, flaps extended;' VNO ‐ maximum structural cruising

speed (for normal operations); and AIR???° VNE ‐ never‐exceed speed (maximum

speed, all operations).

/

, a“ormal Operatmg ‘ F'lPRmBEPs

In addition to showing indicatedairspeed, some airspeed indicators are ableto Show tme airspeed (TAS) These ASIS Figure 1-1ASI and lAS/TAS Indlcators.

TAS 147 knots

4 Night Flight

have a manually rotatable scale to set outside air temperature (OAT) againstaltitude, allowing the pilot to read TAS aswell asIAS.

Airspeed IndicatorErrorsDensity Error. Density error occurs any time anaircraft is flying in conditionsthat are other than standard atmospheric conditions (ISA) at sea level. This iswhy the ASI does n o t indicate TAS.Compressibility Error. Compressibility error increaseswith airspeedbut is onlyrelevant above 200 kt.Position Error. Position error occurs because ofpitot~static system errors. Errorsvary with speed and attitude and includemanoeuvre‐induced errors. Pressure errorcorrection (PEC) is shownin thepilot’s operatinghandbook. Indicatedairspeedcor ‑rectedfor pressure and instrument error is called calibrated airspeed (CAS).Instrument Error. Instrument error is due to small manufacturing imperfec‑tions and the large mechanical amplification necessary for small sensedmovements. Instrument error is insignificant in general aviation (GA) aircraft.

AltimeterThe altimeter converts static pressure at thelevel of the aeroplane to register vertical dis‑tance from a datum (the reference fromwhicha measurement is made). At lower altitudes,atmospheric pressure reduces by approxi‑mately 1hPa for each 30 ft of altitude. For alloperations below 10,000 ft, the area QNH orthe aerodrome QNH is set. Since the heightof terrain and obstacles shown on a chart isabove meansea level (AMSL), this becomesyouraltitude reference when QNH is set. Above10,000 ft, standard pressure (1,013 hPa) is setand flight levels are reported to the nearest100 ft (e.g. 11,500 ft is FL115), although cruising levels are usually whole thou‑sands of feet (eg. FL120). For all operations at or below 10,000 ft (the transitionaltitude),pilots are requiredto use the current aerodromeQNHor the areaQNHandthen set 1,013 hPawhenClimbingthrough 10,000 ft. The setting ischangedfrom standard pressure to QNHwhen descending through FL110 (the transitionlevel). Above 10,000fi AMSL, set 1013 in the subscale. At and below 10, 000ftAMSL, set the aerodrome QNHor the area QNHin the subscale.

Figure 1-2Altimeter.

1: Instruments and Systems 5

Altimeter ErrorsBarometric Error. Barometric error is induced in an altimeter when atmos‑pheric pressure at sea level differs from standard atmospheric conditions. Thecorrect setting of the barometric subscale removes the error.

Temperature Error. Temperature error is induced when the temperature(density) differs from standard atmospheric conditions. Note that there is noadjustment.Position Error. Position error occurs because of static system errors and isminor.Errors vary with speed and attitude and includemanoeuvre‐induced errors.Instrument Error. Instrument error is due to small manufacturing imperfec‑tions and is insignificant.Lag. Lag occurs when the response of the capsule and linkage is n o t instanta‑neous. The altimeter reading lags slightly when height is increased ordecreased rapidly.

Altimeter CheckWhenever an accurate QNH is available and the aircraft is at an aerodromewith aknown elevation, pilots mus t conduct an accuracy check of the altim‑eter before take‐off. The altimeter is checked by comparing its indicatedaltitude to a known elevation using an accurate QNH setting. For VFRoperations, the altimeter should indicate site elevation within 100 ft (110 ftfor sites above 3,300 ft).When operating o u t of aprimary or secondary airport, you will have access

to an accurate QNH; however, you may need to make an allowance for thedifference between the aerodrome reference point and the position of youraircraft at the time. Basically, a QNH that is provided by a tower, ATIS orremote‐reporting aerodrome sensor can be considered accurate. Do n o t use aforecast QNH for this test.If t w o altimeters are installed, the most accurate one is to be used as the

master instrument. When t w o altimeters are required for the category ofoperation, o ne mus t read the reference height to within 60 ft. If the secondaltimeter has an er ro r between 60 and 75 ft, flight under IFR to the firstlandingpoint where the altimeter can be rechecked ispermitted. If the checkreveals that the altimeter error is in excess of 60 ft, the instrument isunserviceable for flight under IFR. If the aircraft has t w o altimeters but thecategory of flight only requires one altimeter, one mus t bewithin 60 ft. If theother has an error in excess of 75 ft, it mus t be placardedunserviceable and themaintenance release appropriately endorsed.

6 Night Flight

Vertical Speed IndicatorThe vertical speed indicator (VSI) indicatesthe rate of change of altitude. The VSI ism o r e sensitive to static pressure changesthan the altimeter, and soit responds m o r equickly to an altitude change. However,there will always besome lag. Its principleof operation depends on lag. Generally,the trend is obvious almost immediately,but the precise rate will take afew secondsto be indicated. With large and suddenattitude changes, the V81 may brieflyshow a reversed reading before a steadyrate of climb or descent is indicated due todisturbed airflow near the static vent . Thisis also likely in rough air. The lag can last aslong asseveral seconds beforethe rate can be read ‐ therefore fly attitude.

Figure 1‐3Vertical speedindicator (VSI).

G V i , ,Attitude Indicator

The attitude indicator (AI) is the only instrument that gives a direct and imme‑diate picture of the pitch andbank of the aircraft. You should become familiarwith the specific attitudes you need to select and maintain for your aircraft.

Z i . A d j u s t m e n tlR~0121 EPS

Fifteen and thirty degrees left 'H-0122-EPS

Figure 1-4 Pitch attitude. Figure 1-5 Bank attitude.


Attitude IndicatorErrorsThe attitude indicator is a reliable and accurate instrument. However, it maybe subject to failures of the gyroscope drive system and precession errors.If theAI suffers afailure of its ro tordrive, it willbecomeunstable. An electrically

drivenAI will usually have awarningflag to alert you of apower failure. If apowerfailure occurs, the AI will beunreliable andprovide false attitude information. Afailure in avacuum‐driven AI will produce the same result. To guard against this,you must monitor the suction gauge at regular intervals to ensure that anadequatevacuum pressure of between3 and 5 inches of Hg isbeingprovided.TheAI suffers from errors duringsustainedaccelerations and turns because the

erection switch senses afalse vertical. A linearaccelerationwill exertg‐forces thataffect the self‐erectingmechanismof the AI. Duringarapidacceleration, ascanoccur at take‐off, the gravity sensors on the bottomof the gyroscope tend to getleft behind and cause the gyroscope to precess forward at the top, moving thehorizonbar downslightlyproducingafalse indicationof aclimb. It respondsjustlike its pilot’s inner ear, and acceleration is sensed as a tilt (somatogravic illusion).These can cause false indications of pitch attitude andbank angle. The errors areusually small and are easily identifiedand corrected. Be careful immediately afteranight take‐off, to maintain apositive rate of climb.

Turn and Balance InstrumentsBalance Indicator (Balance Ball/SkidBall)If anaircraft is n o t in balanced flight, it will be either slipping or skidding. Acurved glass tube filled with damping oil and containing a ball is provided toindicate slip or skid. It acts like apendulum. The position of the ball is deter‑minedby the resultant of centrifugal reaction (CR) and gravity (\X/). The ballis n o t connected to the t u r n gyro.

ma.“lEa<Balanced Slip (too much bank) Skid (not enough bank)

(too little rudder) (too much rudder)

Figure 1-6 Balance ball.

Figure 1-7 Turn indicator.

.‘GH lNFOH/Me°?\ 47’0

Figure 1‐8 Turn coordinator.

////O

A,\:\\\\\m/ ///

Figure 1‐9Heading indicator.

Night Flight

Turn Indicator/Turn CoordinatorOn a turn indicator, the pointer is calibrated toShow standard‐rate * or rate one ‐‐ turns, left orright. A standard‐rate t u r n causes the headingtochange at 3° per second, hence acomplete t u r nof360°will take 2 minutes. Note that thewingsare pivotedin the centre anddon o tmove upordown to indicate changes in pitch attitude. Toavoid confusion with the attitude indicator,many t u r n coordinators are labelled With thewarning, nopitch information (figure 18).

Heading IndicatorThe heading indicator (HI), sometimes referredto asthe directional gyro (DG), is a directionalinstrument, but it has no inherent magneticalignment. It contains a gyroscope poweredby either a vacuum system or the electricalsystem. It relies on the pilot to manually alignit with the magnetic compass after start andregularly in flight.

Heading Indicator ErrorsThe gyroscope in the HI does drift and needsto berealignedperiodically (everylS minutes).

Heading Indicator ChecksAfter startup, the electrical or vacuum powersource shouldbe checked. Once up to speed,the heading should be aligned with the mag‑netic compass. While taxiing, the HI shouldbe checked for correct functioning:'turning right, heading increases; and°turning left, heading decreases.On line‐up just prior to take‐off, the HIshould again be checked against the magneticcompass and the runway direction. In flight,the aircraft must be straight and level andstabilisedwhenever the H1 is being aligned.


Compass Instruments

Remote Indicating CompassA remote indicatingcompass combines the functions of the magnetic compass andthe heading indicator. It employs amagnetic sensor, called aflux valve oramag‑neticfliix detector, that ispositionedwell away from other magnetic influences inthe airframe, usually in awingtip.

The sensor detects the earth’s magnetic field and sends electrical signals tothe gyro to automatically align it and therefore show the correct magneticheading of the aeroplane. This process is known asslaving. It eliminates theneed to manually realign the H I .

There is usually a small slaving knob on the instrument to allow the pilot tomanually align the compass card quickly if the indicated heading is grossly inerror. A small slaving annunciator is usually provided to assist manualalignment and allow the pilot to check that normal automatic slaving isoccurring. This is indicatedby small, regular oscillations of the slaving needle.Alignment is also crosschecked with the magnetic compass.

The gyro‐stabilised magnetic compass is also used to drive the compass cardin the radio magnetic indicator Radio navigation information issuperimposed on the heading indication (figure 1‐10).

The more modern horizontal situation indicator (HSI) also presents a gyro‑stabilised magnetic heading on a rotating card (figure 141). This may bepresented with other useful guidance information on a mechanical instrumentor an electronic display aspart of an electronicflight instrumentation system (EFIS).

L8 ‘3‘///ii\\\\\\\Figure 1‐10 Figure 1-11

Radio magnetic indicator with heading Horizontal situation indicator.'bug' at the t o p and t w o ADF needles.

70 Night Flight

Magnetic CompassThe magnetic compass, or direct indicatingcompass, is the fundamental headingref‑erence. In steady flight, magnetic heading appears under the lubber line, whichindicates the nose of the aircraft. Small errors in the readingwil l occur becauseof the influence of additional magnetic fields generated by the aircraft and itscomponents. A cockpit placard, known asthe deviation card or compass correctioncard (figure 1‐13), enables the pilot to allow for these errors. The deviation isvery small. In straight and level, unaccelerated flight, the compass is accurate.

Lubber line

512 IE 6 .Il i i i i i i i i l i i i

m.Headi090 MFigure 1‐12 Magnetic compass. l Figure 1-13 Deviation (compass

correction) card.

The indications of the direct indicating compass are subject to significanterrors when the aeroplane is turning (especially through north or south), andwhen accelerating (especially on east and west). These errors arise because ofthe adverse effect of magnetic dip, which is caused by the vertical component ofthe earth’s magnetic field. The indications can also be misread asthe directionto t u r n appears in reverse.

ClockOne of the most important instruments for night operations is the clock, whichisoftenplacedon the control column. Make sure you are aafaitwith the func‑tions of the clock, whether digital or analogue, before going night flying. Aspilot in command, you should get into the habit of always wearing a suitablewatch which indicates hours, minutes and seconds. There should also be astopwatch (elapsed time) function.

It is usual to have the clock set to coordinated universal time (UTC). The timemus t be accurate to within 30 seconds. The time can generally be Checked


through listening to the automatic terminal information service (ATIS) of aninternational airport.For example, if you tune into 132.7 in the Melbourne area, a time check

wil l begiven at the end of the ATIS for Melbourne.

During the preflight inspection, check that the pitot cover is removed andthat the pitot tube and the static vents are n o t obstructed in any way. Tocheck the pitot heating system, switch on the master switch and pitot heat.Carefully feel the pitot tube with your fingers within 30 seconds of turningon the pitot heat. Check pitot heatingwith caution; the pitot heater is capa‑ble of burning your hand.Do n o t forget to switch the pitot heat o f fafter testing. The pitot heat should

n o t be left on for longperiods on the ground.Once in the cockpit, check that all the glass coverings of the instruments are

intact, the balance indicator contains fluid and the ball is at the lowest point,the magnetic compass contains fluid that is free of bubbles and n o t discolouredand the deviation card is in place.After starting the engine and switching on the alternator, listen for any

unusualmechanical noises asthe gyros spin up. The airspeed indicator shouldindicate zero, the V31 should indicate zero, and the altimeter should indicatethe aerodrome elevation to within i100 ft (VFR) or i 6 0 ft (IFR) with QNHset. Check that the clock is wound (i fapplicable), the correct time is set andthe stopwatch is functioning. When the gyros have erected, set the Al’sminiature aeroplane against the horizon line and align the HI with themagnetic compass.Check the vacuum gauge. There should be no red warning flags on the

electrical gyroscopic instruments, and there should be sufficient suction (3 to5 inches of Hg) for the suction‐driven instruments ‐ a suitable check wouldbe: ‘ A IandHI erect and aligned, noflags, suction checked’.When taxiing, check the H I , t u r n coordinator and the balance ball during

gentle turns (turning lefl‘, heading decreasing, skidding right, wings level, ADPneedle tracking and turning right, heading increasing, skidding left, wings level,ADF tracking.If desired, the AI can be checkedby gently applying the brakes until the nose

drops slightly. At the holding point and when stationary, the HI can berealignedwith the magnetic compass. On the runway, check that the headingand the runway direction are within 5°.

12 Night Flight

t ‘ S V S t e _You will recall that three flight instruments are connected to the pitot‐staticsystem:0 the airspeed indicator (static pressure and total pressure);‘ the altimeter (static pressure only); and- the vertical speed indicator (static pressure only).

Problems in the static system will affect all three pressure instruments.Problems in the pitot system will affect the airspeed indicator only.The pitot tube measures total pressure, also known aspitotpressure or ram air

pressure. The static vent, or static port, measures only static pressure. Thedifference is dynamicpressure.

Staticpressure

Relativeairflgw_>‐> /

‐ ‐ > rm“. Alternate I ’ ,Pitot pressure y4: static source r ’ fl fl r r ”(total pressure) _______________ ‐‐j i é l a t i v e ; 2 m m

””””””””””'‐" airflow

Figure1-14 Pitot‐static system.

Many aeroplanes have tw o static vents, one on each side of the fuselage, andthis is known as a balanced static system. This reduces the errors caused bysideslip. Some aeroplanes have a combined pitot‐static tube. An alternatestatic source may also be available in the event of a static system blockage,usually the static pressure within the cockpit. This static pressure is usually lessthan the external static pressure andwil l cause significant position error to thealtimeter andA81. There is normally a correction table in the flight manual ifthe alternate static source is used.

Blockage of a Static VentIn a climb with a blocked static vent, the altimeter will indicate a constantaltitude, the V51 will indicate zero and the ASI will underread due to thetrapped static pressure being greater than the ambient static pressure. In adescent with ablocked static vent, the altimeter readingwil l n o t change, the


V81will indicate zero and the ASI will overread. This can be dangerous, asadescent into high terrain could occur without the descent being indicatedby the altimeter and VSI. The pilot could also react to the overreadingASIby reducing speed and inadvertently stalling the aircraft. This reinforces thevalue of knowing the power/attitude combinations for your aircraft.

Blockage of the Pitot TubeIf the pitot tube isblocked,only theA81isaffected. The pitot tube isparticularlyvulnerable to icingbecauseof itspositionin the airflow,henceaircraft haveapitotheater to prevent ice formation. The pitot heater should be on whenever theaeroplane is operating in visible moisture (e.g. cloud, mist, rain) with anOAT ator below +10°C, and at all times when the OAT is less than 0°C.If the pitot tube becomes blocked, the total pressure in the tube wil l

remain constant at that value. Therefore, asthe static pressure reduces in aclimb, the airspeed indicator will overread. Conversely, the airspeedindicator will underread in adescent. For example, if the pitot heat is left offand ice forms during the climb, the airspeed reading wil l increaseprogressively and the pilot wi l l be tempted to raise the nose to reduce speed,thereby risking astall.Remember to always set attitude and power. Whenever the aeroplane is to

beparked for an extendedperiod, apitot cover should be fitted. Do n o t forgetthat wasps and other insects can block apitot tube.

Gyroscopes that are vacuumpoweredhave the instrument casingpartially evac‑uated by an engine‐driven pump. Air is drawn into the instrument case anddirected at high speed on to the gyro rotor. A common arrangement has theattitude indicator and the HI driven by suction and the t u r n indicator or tu rncoordinator driven electrically. Alternatively, an electrically driven standbyattitude indicator is fitted ‐ amuch safer optionWith aloss of electrical power, the t u r n coordinator could be lost, but the

attitude indicator would still be available. With a loss of suction, the attitudeindicator could gradually become erratic and then fail completely, but the t u r ncoordinator would remain serviceable.However, it is possible for an individual instrument to fail because of an

internal fault rather than apower supply problem. The suction gauge shouldbe checked periodically. Power failure to an electrically driven gyroscope isusually indicated by a redwarning flag on the affected instrument(s).

74 Night Flight

Inlet air :3vacuum VacuumDischarge air m pump

,, Overboardvent line

Vacuum systemair filter

\ i": :°'. » ' Vacuum relief valve

Attitudeindicator

Suctiongauge

LowvacuumwarninglightCircuitbreaker

N55v“?!qu.x ,. 4 0 ‘SDirectionGyro

ssum};1/,Mm,9 Low vacuumwarning switch

216.TlF

Figure 1-15 Typical vacuum system.

Electrical SystemThe electrical system powers the lights, radios, navaids and engine starter, butn o t the engine ignition (spark plugs). The electrical power is either 14or 28volts DC and is connected directly to a bus bar.The bus bar distributes all the electrical power. The cur rent then flows

through a re t u r n wire attached to the aircraft metal structure to complete thecircuit. Composite structures have a separate earth re tu rn wire.

AlternatorAs well asproviding the power for lights, radios and other services, a veryimportant function of the alternator is to recharge the battery. Some aircrafthave awarning light that illuminates when the engine rpm is insufficient forthe alternator to charge. When taxiing with lights and navaids on, you mayneed to set 1,200 rpm or so (more than idle rpm).


BatteryAlthough the engine ignition is independent of the electrical system, otherservices ‐such aslights, radios and perhaps flaps ‐ are n o t . The battery is theelectrical life belt. Do notfly at night with a less thanfully charged battery.

" t ° " ° " _, .The autopilot is a vital element of night VFR. It is another tool available tothe competent pilot, and it is designed to relievepilotworkload sothat the pilotcan concentrate on situational awareness and flight management.

Modes of the AutopilotA very simple autopilot may only provide limited hands-free operation in theform of the following:° flight stabilisation in one or mo re axes;- manoeuvre control through holding a heading, altitude or attitude setting; and' system coupling in following anavaid or course command.The autopilot provides these services by taking information from attitude,

performance and navigation sensors, assembling the data and responding inaccordance with the pilot’s settings. The autopilot has the additional means ofphysically moving the control surfaces to achieve the desired flightpath. Thefirst autopilots, nicknamed George, were attached to the control column andphysically actuated the controls as if the pilot were flying. Now withelectrically signalled, electromechanical or hydraulically operated controls, theautopilot has become simple, small and reliable, and autopilot modes havebecome the primary means of piloting the aircraft.

SensorsAttitude SensingAn autopilot system senses and maintains attitude with reference to a gyro‑scopic horizon. It literally flies on instruments, just asapilot would in cloud.There are t w o types of gyros that are relevant:

° a rate gyro, which senses angular movemen t or deviations, roll or yaw; and- an attitude gyro, which provides pitch and roll attitude.Roll and Yaw Rate. The turn coordinator is used in basic autopilots to provide theroll and yaw rate signals and therefore functions asthe sensor for the basic,wt'ngs-leveller autopilot, i.e. it quickly senses any deviation.

76 Night Flight

Longitudialaxis

AGKv21025=s

Figure 1-16 Turn coordinator ‐ yaw and roll sensitive.

Attitude. The attitude indicator uses a vertical gyroscope, the r o t o r of whichis kept vertical, or erect, by gravity‐sensing devices on the bottomof the unit.By fitting electronic pick‐ups to this vertical gyro, anelectricalsignal represent‑ing both pitch and roll attitude can beprovided to the autopilot.

Bank Index Gimbals (pivots)

AGK‐ZIOSEPS

Miniature aeroplane

Spin axis maintainedi vertical by gyro rigidity

Horizon bar

Figure 1-17 Attitude indicator - pitch and roll sensitive.

Stabilisation (Inner Loop)With the autopilot engaged, any deviation in roll (or pitch) causes anerror signalto be generated, and the appropriate response mus t occur. The computeramplifies the signal and sends it to the servo. This servo is the power (muscle)that will cause aileron displacement. The aircraft responds, and when theWings are level, the error signal is cancelled.


Roll attitude change-<

ControlIR0." surfacesensmg ,gyro Aileron

TGV Feedback

ClutchComputer g Aileronamplifier ’ Smirt‘g

ASK-2106.335

Figure 1‐18 Inner loop of a single channel.

ControlThe autopilot provides the aircraft with an automatic flight stabilisation anderror correction system. Should the aircraft be displaced from its gyroscopicreference, it will be returned to that reference. For control, the stabilisation istemporarily overridden to allow appropriate control surface movements toinduce the requiredmanoeuvres. It is the same as the control system having toovercome the stability of the aircraft.The pilot n o w commands the autopilot to t u r n left. This can be done with

control-wheel steering (CWS) or a rotary roll (bank) control switch, or by settinga desired heading. The autopilot then produces a false error signal, which isthe equivalent of the aircraft banking to the right, to the inner loop.

. -‐ ‐ ‐ ‐ ‐ ‐‐ ‐ ‐ ( ‐ ‐ ‐ ‐ ‐ ‐‐ ‑‘ Roll attitude change : ControlRoll surfacesensmg ‘ L 0gym AileronV

‐ ClutchComputer g Aileronamplifier ’ servomotor

Mode selector his!AGK»2107.EPS

Figure 1-19Inner and outer loop of a single channel.

18 Night Flight

System CouplingSome very useful autopilot modes are make available by manoeuvre controland system coupling. After the autopilot is engaged, push buttons allow thepilot to select various modes. The selectedmode is indicated on the annunci‑ator. Autopilot modes depend on the complexity of the system, e.g. airspeedhold, altitude hold, localiser track or ILS glideslope. Some also have au to ‑throttles.

Additional Autopilot Features

RotaryRol/ SwitchThe rotary rollswitch overrides the wings leveller and allows the pilot to t u r n theaircraft to a desired heading or perhaps to make an orbit (a complete 360°turn). When the knob is centred, the aircraft wil l be returned to wings‐level.An arrow on the R M I or HSI shows the selected heading. The knob has acentral, spring‐loaded detent.

Electric TrimWhile n o t asubsystem of the autopilot, electric tr im is often fitted. It simplyprovides ameans of electrically driving the tr im tab to relieve controlpressures.A spring‐loaded, self‐centring switch, which moves fore and aft in the samesense asthe control column, activates an electric m o t o r that drives the manualtr im system. Some aircraft have very powerful electric trims, and if they mal‑function, they can require considerable force to control them.There are specific limitations on all autopilots in light aircraft; the flight

manual autopilot supplement is the best reference. Typically:0 during climb or descent, it is n o t permitted to operate the autopilot below200 ft AGL; and

- in the cruise, it isn o t permitted to operate the autopilot below 1,000ft AGL.

All modernautopilots have abuilt‐in, self‐test function. The autopilot mus tn o t be engaged in flight unless it has been tested before flight on that day.Note. Electric trim, like anautopilot, is usually reliable, but it can malfunc‑tion. Although you can physically overpower the autopilot, it is essential toknow the location of the autopilot disconnect switch and electric trim cir‑cuit breaker sothat either system can beswitched offshould they n o t behaveasdesigned.

Chapter 2

Meteorology

loudsGrouping of Clouds

Clouds are described according to asystem of classification derived from fourmain forms Which indicate cloud appearance:0 cumulus (or cumulo‐) are heaped-type clouds;- stratus (or strato‐) are layer‐type clouds;° nimbus (or nimbo‐) has a dark, dense appearance (suggestingheavy moisture)

and are rain‐producing clouds; and0 cirrus (or cirro‐) has a hair‐like or fibrous appearance.

Clouds are further classified by the height of the base of acloud abovegroundlevel (AGL). The height of an individual cloud base falls into one of threegroups (note that these height ranges can vary with latitude):0 low, which is less than 6,500 ft AGL;0 middle, which is 6,500 to 20,000 ft AGL; and0 high, which is above 20,000 ft AGL.

Clouds With vertical development, known as convective clouds are alsodescribed. There are t e n main cloud groups, and their abbreviations and heightbands are given in table 2‐1.

Cloud Group Abbreviation Cloud Heightstratus St Low-level cloudstratocumulus Sc Low-level cloudnimbostratus Ns Low-level cloudcumulus Cu Low-level cloud with

vertical developmentcumulonimbus Cb Low-level cloud with

vertical developmentaltostratus As Middle‐level cloudaltocumulus Ac Middle-level cloudcirrus Ci High-level cloudcirrostratus Cs High‐level cloudcirrocumulus Cc High-level cloud

Table 2-1 Table 2-1 The ten main groups of clouds.

79

20 Night Flight

Note. Other Latin terms, such asfractus (broken), lenticularis (lens shaped),mammatus (bulbous) and castellanus (towering) are used to describe sub‐cat‑egories of these main cloud groups.

Cloud and Air StabilityThe structure or type of cloud that forms depends mainly upon the stability ofthe air. When unstable moist air is liftedby any means, it will continue rising,forming heaped‐type (cumulflbrm) cloud with significant vertical developmentand turbulence. On the other hand, stable moist air has no tendency to con ‑tinue rising and will form layer‐type (stratyrorm) cloud with little or noturbulence. Some layer‐type cloud, such asnimbostratus, can form in a verydeep layer (10,000 ft or more). Air that is forced to rise (i.e. orographic) butwhich does n o t cool to its deu/point (i.e. the temperature at which water vapourcondenses) will n o t condense to form clouds.

Cumuliform cloud Stratiform cloud

Figure 2-1Cumulus cloud forms in unstable conditions and stratus cloud iorms in stable conditions.

UnstableAirSolongasavertically moving parcel of air remains warmer than its surround‑ings, it will continue to rise. This is known asan unstableparcelofalr. This cangive rise to a cur ren t of rising air called a thermal.Characteristics of unstable air include:

0 turbulence in the rising air, especially in thermals;0 the formation of cumuliform clouds (i.e. heaped clouds);° showery rain (precipitation); and° good visibility between the showers (the risingair carries pollutants away in it).

Stable A i rWhena risingparcelof air achieves the same temperature asthat of the ambientair, it will stop rising, because its density will be the same asthat of the sur‑

2: Meteorology 21

roundings. An atmosphere in which air tends to remain at the one level iscalled a stable atmosphere.

Characteristics of stable air include:0 the formation of stratiform clouds (i.e. layer‐type cloud);° steady precipitation, if any;' poor visibility if there are any obscuring particles; and- the likelihood of smooth flying conditions with little or no turbulence.

There could be an inversion, which traps pollution and reduces visibility.Fog may also result.

Formation of CloudsClouds are formed when moist air is forced to rise, and then it condenses. Thevarious means (called triggers or stimuli) of causing the vertical motion of apar‑cel of air include:0 convection (or thermal turbulence);° orographic lift (i.e. the forced uplift of air over high ground);' turbulence and mixing; and' slow, widespread ascent of an air mass (e.g. a cold front).

PrecipitationTypes of PrecipitationPrecipitationrefers to falling water that finally reaches the ground. It includes:0 rain, which consists of liquid water drops;0 drizzle, which consists of fine water droplets significantly smaller in size than

raindrops and falls from a continuous and dense layer of low stratus cloud;' snow, which falls asbranched and star‐shaped ice crystals;° hail, which falls asballs of ice; and0 freezing rain or freezing drizzle, which consists of water drops or droplets

that freeze on contact with a cold surface, such asthe ground or an aircraftin flight.Note. Rain that does n o t reach the ground is called viiga.

Intensity of PrecipitationThe intensity of precipitation, irrespective of its type, can be described aslight,moderate or heavy. These three terms have different codes and abbreviations inweather forecasts, and these are shown in bothERSA and the AIP. Precipitationcan fall either asshowers, or asintermittent or continuous rain, snow or drizzle.

22 Night Flight

Showers are characterised by sudden stopping and starting, and they aresubject to rapid andsometimes violent changes in intensity. The cloud isquitelikely to break up, or even clear, between the showers.Intermittentprecipitation in the form of rain, snow or drizzle is n o t continual

at the surface of the earth, even though there is no break in the associatedcloud. Intermittent precipitation differs from showers in that it does n o t startor stop suddenly, and there is no clearing of the cloud between the periods ofprecipitation.The type of precipitation depends on the type of cloud fromwhich it falls.

Rain, snow or hail falling asshowers comes from cumuliform clouds, with theheaviest rain showers falling from cumulonimbus. Non‐showeryprecipitation,on the other hand, usually falls from stratiform cloud, mainly altostratus ornimbostratus. It is therefore possible to use precipitation as a means ofidentifying cloud type.Non‐showery precipitation, such assteady rain, light snow or drizzle, fall

from stratiform clouds, mainly altostratus and nimbostratus (figure 2‐2). Rainor snow showers generally fall from cumuliform clouds (figure 2‐3).

Figure 2-2 (Above) non-showery (Le. steady)preclpltatlon from stratlform clouds.

.\M: t . . .. .\‘h‘l‘v‘l’fll‘l‘v.l”lV'l‘iWWWlhwlwwyiy ‘ , ,

Hhi-lmfillvlh‘lllfit‘ "\ \ V‘ it n ilfii‘n‘il'mu tin WM1 ivMim i immian \ t u \ IHHH‘OHH“ l l m v\‘Yl‘vlflt‘!’\\‘l“\|yi:|v\ywhme Mgi‘l‘w‘fl v l \lyll1H“A‘\W‘\(v‘\(¢lKv‘iKvVIHHH ‘ \llillfllv‘vllmltl‘fli‘fll‘illl‘lm‘ll‘n‘v “will ‘5 v«mm | Ampuvypfu“ w‘.if‘i‘|gi‘,i‘yflil‘v‘3%u ‘ i

HVHll‘ Millhll'fln‘ l l l N M | 'slimline tillitititttitltltlltlmit MW»: “*‘nl‘l‘t‘cl‘l mm Figure 2-3 (Left) showers fall from

' v- ’ ' z 'cumullform clouds.

T u s o r S , . ; . , . » . . . fi w p ,

Characteristics of ThunderstormsA thunderstorm is storm cloud with one or more sudden electrical discharges,evidenced by aflash of light (lightning) and asharp rumbling sound (thunder).The noise knownasthunder is the soundof the lightningdischarge. As the speedof light ismuch faster than the speed of sound, lightning isseen some time beforethunder is heard. When these two phenomena appear to be simultaneous, theclose proximity of a thunderstorm is indicated. Thunderstorms are associatedwith cumulonimbus clouds only and generate spectacular anddangerous weather,often accompaniedby heavy rain, hail, squalls, microbursts andwindshear.

2: Meteorology 23

In its mature stage, the top of a storm cloud can reach up as far as thetropopause, which is around 36,000 ft above the earth’s surface in temperatelatitudes and 55,000 ft in the tropics. The mature storm cloud may have thetypical shape of acumulonimbus, with the top spreading o u t in ananvil shapein the direction of the upper winds.The mature stage of a thunderstorm typically lasts between 20 and 40

minutes and is characterised by updraughts, downdraughts and precipitation.There issomuchwater falling through the cloud towards the endof the maturestage that it starts to wash o u t the updraughts. The forces are greatest justbefore the storm breaks (i.e.just before heavy rain starts to fall).

Warm, moistair

Gustfront

Figure 2-4 The mature stage is characterised by updraughts, downdraughts and precipitation.

It is possible for an updraught of say 4,000 fpm to be adjacent to adowndraught also of 4,000 fpm, resultingin ashear of 8,000 fpm. Asthe colddowndraughts flow ou t of the base of the cloud at a great rate, they changedirection and begin to flow horizontally. On approaching the ground, thestrong downdraughts tend to spread o u t in all directions, with the forward edgein front of the cloud forming agustfrom. Strongwindshear will occur, and thishas caused the demise of many aircraft, large and small.

24 Night Flight

lR-29‘05.EPS '

Figure 2-5 Cross‐section of a typical gust front.

The outflowing cold air will undercut the inflowing wa rme r air and n ewsto rm cells can form. A gusty wind and a sudden drop in temperature mayprecede astorm. A roll cloud may also develop at the base of the main cloudwhere the cold downdraughts and w a r m updraughts pass, indicating possibleextreme turbulence.

HailstonesLarge hailstones often form inside cumulonimbus clouds aswater adheres toalready formedhailstones and then freezes, leading to even larger hailstones. Incertain conditions, hailstones can grow to the size of oranges. Almost allcumulonimbus clouds contain hail, mos t of which melts before reaching theground, where it falls asrain.

Downbursts and MicroburstsStrong downdraughts that spread o u t near the ground are known asdownbursts.A very strong downburst n o t exceeding 4 km in diameter is called amicroburst.A typical microburst has the following dimensions:

- horizontal distance of 4 km;° life time of 10minutes;' horizontal windshear of 50kt; and' vertical depth of cold air outflow of LOGO‐4,000 ft.Aeroplanes may n o t have the performance capability or the structural

strength to combat the extremely strong downdraughts, turbulence andwindshear in downbursts and microbursts. Many aeroplanes have crashed asaresult.

2: Meteorology 25

Base of thunderstorm/,Downburst

Projected flightpathof aircraft if nointervention by pilot m m e fl s

Figure 2-6 Landing through a downburst results in a change of flightpath.

Downbursts and microbursts are often associated with cumulonimbus clouds,but they may also occur with any heat cloud, such ascumulus cloud, or withclouds from which Virga is falling. As rain falls from high cloud and evaporates(i.e. virga), it absorbs latent heat and creates a very cold parcel of air that mayplummet toward the groundasadownburst or amicroburst. This can sometimesbe detected visually by aring of dust that is blown up where the microburst hitsthe ground and spreads o u t . In e x t r e m e cases, microbursts have been known toblow hundreds of trees down in aradial pattern and to blow trains offrails.

Microbursts and downbursts may appear very suddenly and may or may n o tlast very long. Even though one aircraft might make a satisfactory approachunderneath a large cloud, a following aircraft may n o t . There has been anumber of accidents to illustrate this, soalways be on the watch for clouds withthe following:° virga;° a lowering cloud base;- a bulbous cloud base (called mammatus);° a dust ring or waves on the surface below a cloud; and' a dark shaft of rain falling from a cloud.

WindshearWindshear is defined asa change in wind direction and/or windspeed over alimited horizontal and/or vertical distance. Any changes in wind velocity ordirection asyou move from o n e point to another is aWindshear. The strongerthe Changes and the shorter the distance within which they occur, the strongerthe Windshear.

26 Night Flight

There are many causes of windshear. They include:- obstructions and terrain features that disrupt the normal smooth wind flowclose to the ground; and

' localisedvertical air movements associatedwith thunderstorms, cumulonimbusand other large cumuliform clouds, such as gust fronts, downbursts andmicrobursts, with the windshear formed from updraughts and downdraughtsregardedasthe most hazardous.The t e r m low-levelwindshear is used to specify any windshear occurring near the

ground in the vicinity of the final approach path, runway or take‐0&7initial climbareas. Windshear near the ground (i.e. below about 3,000 ft) can be hazardous.

Storm Hazards to AviationThunderstorms present a severe and potentially lethal hazard to aviation, andthey must be treated with the utmost respect. Moreover, the dangers to avia‑tion from athunderstorm do n o t exist only inside and under the s to rm cloud,but for quite some distance around it . Strong wind currents associated withthunderstorms may throw hailstones well o u t from the core of the storm, pos‑sibly several miles, where they may fall in clear air. Thunderstorms are bestavoided by at least 10nm and, in severe situations, by perhaps 20 nm or more.Diverting downwind of a s t o rm should be avoided.The violent updraughts and downdraughts (which are very close to each

other in amature thunderstorm) cause extremely strongvertical windshear andturbulence, which can cause structural failure of the airframe. The rapidlychanging direction from which the airflow strikes the wings could also cause astall. Flying into a mature cumulonimbus cloud is very risky. The greatestturbulence within the cloud is found in the lower to middle part of the s t o rmaround the freezing level.Most advanced aeroplanes are equipped with weather radar and/or

stormscopes which enable pilots to identify the position of s to rm cells.Without weather radar, a pilot is forced to use eyesight and common sense.However, it wil l be difficult to see a s t o rm if it is embedded and rising o u t ofa general cloud base or o u t of layers of cloud that obscure s to rm clouds.Frequent lightning from within a cumulonimbus cloud, the presence of raincloud, and the presence of aroll cloud indicate a severe thunderstorm.SIGMETs are issued to w a r n pilots of active thunderstorm areas and other

meteorological hazards. Some obvious dangers to aeroplanes fromthunderstorms include:0 severe windshear, which may cause large flightpath deviations and handlingproblems, loss of airspeed and possible structural damage;

2: Meteorology 27

0 severe turbulence, which may cause aloss of control and possible structuraldamage;

' severe icing, possibly the very dangerous clear ice that forms from large,supercooled water drops striking abelow‐freezingsurface;

- hail damage to the airframe and cockpit windows;' reducedvisibility;° damage from lightning strikes, including electrical damage; and' interference to radio communications and radio navigation instruments.Note. When flying in the vicinity of athunderstorm, especially atnight, youmay experience St. Elmo’sfire, a spectacular discharge of static electricityacross the windscreen or from sharp edges or points on the aeroplane’s struc‑ture. St. Elmo’s fire is n o t dangerous.The most severe flying conditions, such asheavy hail and destructive winds,

may be produced in a line squall, which is a non‐frontal band of very activethunderstorms, possibly in alongline that requires alarge detour to fly around.This line (or sometimes more than one line) of thunderstorms can form in therelatively warm air ahead of acold front and can bequite fast moving. A linesquallmay contain anumber of severe thunderstorms, destructivewinds, heavyhail andpossible tornadoes and can present amos t intense hazard to aircraft.

Avoiding ThunderstormsIn the southernpart ofAustralia, thunderstormactivity isoften scattered,mak‑ing it easier for apilot to avoid individual cells. Sometimes there may bealineof thunderstorms associated with, for instance, a cold front. In the tropicalparts of Australia, there may belarge, isolated thunderstorms, or there may beawhole line of them.When diverting to avoid a thunderstorm, it is generally better to track

upwind of the s to rm by at least 10nm, where there is less likelihoodof severeturbulence andhail. If there isintense thunderstorm activity in your flight planarea, it may beadvisable to postpone your flight until the thunderstormactivityhas ceased. If in flight, divert to a nearby suitable aerodrome, land and waituntil the thunderstorm activity has passed or ceased.If you climb and cruise below the general cloud base, provided the LSALT

permits this, thunderstorm cells can usually beidentifiedbyheavy rainfall fromthe cloud base if the thunderstorm has developed to the mature stage. It canalso be identified by a very dark cloud base due to the vertical extent of thecloud and its moisture content preventing sunlight penetrating from above.If you are able to climb and cruise above the general cloud tops, then storm

cells will beeasy to spot, since the cumulonimbus clouds containing them will

28 Night Flight

t owe r above the general cloud. However, there is a danger of inadvertentlyentering a s t o rm cell when climbing through cloud layers in anattempt to getabove the cloud tops (unless you have aweather radar or stormscope). Icingmay compound the problem.Do n o t fly under thunderstorms asyou may encounter hazards such assevere

turbulence, strong downdraughts, microbursts, heavy hail or windshear. Ifthere is apossibility of approaching the edge of athunderstorm, the best courseof action is to make a gentle 180° t u r n and head to the smoother air you leftbehind.

Turbulence Penetration TechniquesSometimes turbulence cannot be avoided, andyou need to fly the aeroplane inamanner that enables it to handle the turbulent conditions aswell aspossible.Slow down. Some aircraft have a turbulence penetration speed (VB) specifiedin the pilot’s operating handbook. You should reduce to below this speed, oth‑erwise to below the manoeuvring speed (VA). The turbulence penetrationspeed is an intermediate speed that will be fast enough to prevent astall at thelow endof the speed range but slow enough to avoid overstressing the airframeat the high end of the range. Ply attitude.Manoeuvring speed is higher when the aircraft is heavy, so a well‐laden

aeroplane ismore stable in turbulent air and less susceptible to overstressing dueto gust loads. In turbulence, you should normally leave the undercarriage inthe retracted position and the flaps up, since the strength of the airframe isgreater in this configuration.If you cannot avoid flying through or near a thunderstorm, steer aheading

that wil l take the least time, establish apower setting for turbulence penetrationspeed, t u r n on the pitot heaters and other anti‐icing equipment, keep thewings level and be prepared to allow the altitude to vary in updraughts anddowndraughts. Avoid over controlling the elevators in turbulence asthis mayoverstress the airframe structure. Hold the attitude rather than the altitude. Ifpossible, avoid turns asthey increase g‐loading, and continue straight ahead.Allow the speed to fluctuate in turbulence, and avoid rapid power changes.Finally, report the presence, position and extent of the thunderstorms, aswellassevere turbulence and icing.

2: Meteorology 29

ir Masses and FrontsFrontal Weather

Air MassesAn air mass is a large parcel of air withfairly consistent properties (such as t e m ‑perature and moisture content)throughout. It is usual to classify airmasses according to the following:° origin;- path over the earth’s surface; and' whether the air is diverging or c o n ‑

Warmer airat the surface ‑

Cooler airat the surface

Figure 2-7 A cold frontVerg lng- asdepicted on a weather chart.

Cold FrontA cold front occurs when a cooler air mass undercuts a mass of w a r m air anddisplaces it at the surface. On weather charts, the boundary between the t w oair masses at the surface is shown asaline with barbs pointing in the directionin which thefrom is travelling. The cold front moves quite rapidly, with thecooler frontal air at altitude lagging behind the air at the surface. Cold frontsare common in Australia.

Warmer air

Figure 2-8 Cross-section of a cold front.

A i r that is forced to rise with the passage of a cold front is unstable and thechanges in weather accompanying the passage of a cold front can be quitepronounced. Atmospheric pressure will fall asa cold front approaches, andonce the front has passed, the pressure may rise rapidly. There may be cumuluscloud and possibly cumulonimbus cloud with heavy rain showers,thunderstorm activity and squalls. A squall line may also form ahead of the

30 Night Flight

front. There may be a sudden drop in temperature ‐ the cooler air mass willcontain less moisture than the wa rm air, and the dewpoint will be lower afterthe cold front has passed. There may be low‐level windshear as, or just after,the front approaches andachange in wind direction, with the direction shiftinganticlockwise in the SouthernHemisphere (i.e. backing), and clockwise in theNorthernHemisphere (i.e. veering).Flying through acold front may require diversions to avoid weather. There

may be thunderstorm activity, violent winds (both horizontal and vertical)from cumulonimbus clouds, squall lines, windshear, heavy showers of rain orhail or severe turbulence. Icingcould also be aproblem. Visibility away fromshowers and clouds may be quite good, but it is still a good idea to avoid thestrong weather activity that can accompany cold fronts.

a»:7 ‘m;...m:zm‐;:

The E e t flc ing on AircraftIce accretion on the airframe or within anengine inductionsystem can have seri‑ous consequences for an aircraft in flight. There can be adverse aerodynamiceffects caused by ice building up on the airframe, resulting in amodification ofthe airflow pattern aroundaerofoils (e.g. the wings or propeller blades). This canlead to a serious loss of lift and thrust and an increase in drag. If ice blocks theengine air intake in sub‐zero temperatures or if carburettor ice forms in moist airup to +25°C, loss of engine power or even acomplete engine failure can result.The aircraftwill increase in weight (ice isheavy) andthere maybeanunbalancingof control surfaces or of the propeller, perhaps causing severe vibration and c o n ‑trol difficulties. Ice can block the pitot tube and/or static vent, producing errorsin the pressure instruments. Radio communications and radio navigation aidperformance can be affected if ice forms on the antennas and the formation ofice on the windscreen can reduce visibility.

Conditions Conduciveto the Formation of IceFor ice to form on the airframe, three general conditions need to exist:' there mus t be visible moisture (cloud or rain);° the outside air temperature must be at or below freezing (0°C); and0 the airframe temperature mus t be less than 0°C.Note.At speeds above 300 kt IAS,heatingdue to friction makes airframe icingunlikelyTemperature decreases with increasingaltitude (unless there is aninversion),

often referred to asthe lapse rate. The average lapse rate of temperature decrease

2: Meteorology 31

is 2°C/ 1,000 ft. In standard conditions, you can apply the more accurate lapserate of 3°C/ 1,000 ft for dry air, known asthe dry adiabatic lapse rate (DALR)and 1.5°C/1,000 ft for clouds, known as the saturated adiabatic lapse rate(SALR). Thefreezing level is the altitude awhich the ambient temperature is0°C. For example, if the temperature is +8°C at 2,000 ft and the cloud base isat 4,000 ft, the freezing level would bejust over 5,300 ft.The wo r s t icing conditions are usually found near the freezing level in heavy

stratiform clouds or in rain. Icing is possible up to at least 8,000 ft but lesscommon above this Where droplets in clouds are already frozen. However, incumuliform clouds with strong updraughts, largewater droplets may becarriedto higher altitudes, and this makes structural icing apossibility up to very highaltitudes. Moreover, in cumuliform clouds, the freezing level is distortedupwards in updraughts and downwards in downdraughts, often by manythousands of feet. This leads to the potential for severe icing to occu r at almostany level.Airframe icing is most likely to accumulate rapidly in conditions of freezing

rain (rain ice). This may occur at sub‐zero temperatures underneath the faceof aw a rm front with nimbostratus cloud from which rain is falling.

Warm lair

Eregziflgfizvgj,_i_r _ _ _; _ -r';

6 .Continuousrain or drrizzie COOLER AIR

Figure 2-9 Danger area for icing beneath a warm front.

Types of IcingClear IceClear ice is the mos t dangerous formof airframe icing. It is formedwhen alargewater droplet has a temperature of just below 0°C. The droplet does n o t freezeall at once. Some of it freezes on impact, and the rest flows back over the air‑frame and freezes asit flows.It is possible for liquidwater drops to exist in the atmosphere at temperatures

well below the normal freezingpoint of water (0°C), possibly at ‐15°C or even

32 Night Flight

lower. This is referred to assupercooled water. One situation in which this canoccu r iswhen rain falls from air warmer than 0°C into abelow‐freezing layerof air beneath. Supercooled droplets are in anunstable state andwill freeze oncontact with a below‐freezing surface, such asthe skin of an aeroplane, theintakes or the propeller blades (especially leading edges).The freezing of each drop will be relatively gradual due to the latent heat

released in the freezing process, which allows part of the water drop to spreadrearwards before it freezes. The slower the freezing process, the further thewater drop will spreadback before it freezes. This spreading back is greatest attemperatures just below 0°C. The result is a sheet of solid, clear, glazed icewith very little air enclosed. This makes clear ice difficult to remove.The surface of clear ice is smooth, usually with undulations and lumps.

Clear ice can alter the aerodynamic shape of aerofoils quite dramatically andreduce or destroy aerofoil effectiveness. Along with the increasedweight, thiscreates ahazard to flight safety. Clear ice is very tenacious, and if it does breako f , large chunks could damage the airframe.A good indication that freezing rain may exist at higher altitudes is the

presence of ice pellets. lce pellets are formed by rain falling from warmer airand freezing on the way down through colder air, i.e. the presence of icepelletsusually indicates cold air that is below freezing (0°C) with alayer of warmer airabove.Wet snow is an indication of warmer air at your level and below‐freezing

temperatures at higher altitudes. The snow formed in the sub‐zerotemperatures of the air above melts to form we t snow asit passes through thewarmer air near your level.

a Water flows back B 5 k § § 5and gradually freezes 5 5 s |t s / st s:* °eFigure 2-10 Clear ice is formed from large, supercooled water drops.

Rime IceRime ice occurs when tiny, supercooled liquidwater droplets freeze instantly oncontact with asurface the temperature of which isbelow freezing. Because thedroplets are small, the amoun t of water remaining after the initial freezing isinsufficient to cause clear ice. A mixture of tiny ice particles and trapped airresults, givingarough, opaque, crystalline deposit that is fairly brittle and is rel‑atively easy to remove.

2: Meteorology 35

PrecipitationRaindropsand drizzle from any sort of cloudwill freeze if contact ismadewithasurface of below 0°C. You therefore need to be cautious when flying in rainat freezing temperatures. This could occur, for instance, when flying in thecool sector underlying the wa rme r air of aw a rm front fromwhich rain is fall‑ing. Icing can occu r in temperatures well above zero, and a pitot (or pitot‑static) heater system is provided to prevent this from happening.

Avoiding IceIn order to avoid ice, make use of forecasts and advisories and plan your flightto avoid areas of known icing, unless your aeroplane is equippedwith appro‑priate de‐icing (for removal) or anti‐icing (for prevention) equipment. Flightinto known icing conditions is prohibited in aircraft that do n o t mee t designstandards and/or are n o t certified for such flight.It is a good idea to have the pitot heat turned on when flying in rain, even

at temperatures greater than 0°C. This helps to keep moisture o u t of the pitot‑static system.Wings contaminated by ice will lengthen the take‐off r u n because of the

higher speed needed to become airborne An ice‐laden airframe may even beincapable of flight. Ice or frost on the leading edge and upper forward area ofthe wings is especially dangerous. If taXiing or taking o f f in below‐freezingtemperatures, avoid splashing water or slush on t o the airframe, since it couldfreeze on t o the structure (ifyou wash away frost or ice with water, the watermay refreeze). Prior to take‐off, check that all aerofoils are clean and that thereis full and free movement of the controls, flaps and trim.When in flight, ice of any kind on the airframe or propeller or in the

carburettor and induction system should be removed immediately. Use de‑icing and anti‐icing equipment in the manner recommended for your aircraft.If the equipment is n o t coping, change heading or altitude to fly o u t of icingconditions asquickly aspossible. If icing occurs in freezing rain, climbing ordescendingmay take you into warmer air. Considermakinga180° tu r n . (Youmus t notify ATS of any changes to your flight plan.)Carry alittle extra airspeed to give an addedmargin over what could be an

increased stalling speed, and avoid abrupt manoeuvres. Be alert for incorrectreadings from the pressure instruments, even if the pitot heat is on .If possible, avoid cumulus cloud asclear ice may occur at any altitude above

the freezing level. If icing occurs while you are in stratus cloud, either descendto warmer air or climb to colder air, say ‐10°C or less. Act quickly anddecisively to prevent the build‐up of clear ice becoming so great that it causes

36 Night Flight

significant deterioration in aircraft performance. Usually, the safest course ofaction is to t u r n back, but this course of action mus t be taken early.Even though the temperature is below freezing, flying above cloud layers in

clear air will n o t cause ice to accumulate on the airframe. At the flight planningstage, especially duringwinter when the freezing level is low, you should checkthe cloud base, tops and amount, taking into account actual reports frompilotsin flight. In general, you should plan a cruise level that is below or abovebroken (BKN) cloud, taking LSALT into account (you can usually manoeuvrearound scattered (SCT) cloud, but manoeuvringaroundbroken cloud ismuchmore difficult). If there is significant cloud, it may be necessary to plan analternative route over terrain offering a lower LSALT. This will provide agreater safety marginwhen attempting to avoid clouds, rain and icing.If ice accumulates in flight, appropriate action would include:

0 increasing power towards maximum continuous power (to maintain speedand to provide asafety margin over apotentially increased stall speed);

0 checking that the pitot heat is on;- checking that the stall warning and fuel vent heat is on (i ffitted);° checking that the windscreen heat is on ( i ffitted);- checking that the propeller de‐ice is on (i ffitted);0 checking that the airframe leading edge surface de‐ice is on (i ffitted); and0 flying ou t of the icing conditions.

FlyingOut of Icing ConditionsThe following is recommended for flying o u t of icing conditions:- descending into warmer air above 0°C provided the LSALT permits this;0 diverting, which may involve a change in track towards lower terrain, or itmay mean a 180° t u r n back ou t of the localisedicingconditions (takingintoaccount that ice accumulationmay increase the stall speed significantly, espe‑cially in aturn); or

° climbing ou t of icing conditions, which is usually the least‐preferredoption.To avoid icing, you should be absolutely certain from reports and your o w n

observations through breaks in the cloud that climbing to get above cloudwilln o t involve t o o great a change of level and thus prolonged exposure to moreicing (certainly n o t mo re than 1,500 ft for alight aircraft). Icewil l mos t likelycontinue to accumulate during aclimb, possibly at an even greater rate becauseof the slower airspeed and the greater exposure of the under surfaces of theaeroplane. Also, keep in mind that if the cloud layers are extensive, you mayhave to descend through more icing conditions with further ice accumulationapossibility.

2: Meteorology 33

Rime ice often forms on leading edges and can affect the aerodynamicqualities of anaerofoil or the airflow into the engine. It does n o t usually causea significant increase in weight, because it contains much trapped air andaccumulates slowly.

The temperature range for the formation of rime ice can be between 0°Cand ‐40°C, but rime ice is m o s t commonly encountered in the range between‐10°C and ‐20°C.

Hoar Frost (White Frost)Frost occurs when moist air comes in contact with a surface at temperaturesless than 0°C. Rather than condensing to form liquid water, the water vapourchanges directly into ice and deposits in the form of frost, which is a whitecrystalline coating that can usually be brushed off. Typical conditions for frostto deposit on the ground or on aparked aeroplane include a cool, clear night,calm conditions and high humidity. Frost can form on anaeroplane when it isparked in temperatures of less than 0°C (this occurs asthe result of the freezingof adew deposit). Frost can also occur in flight when the aircraft descends frombelow‐freezing temperatures to w a r m e r moist air, or when climbing througha temperature inversion.

Although frost is n o t asdangerous asclear ice, it can obscure vision througha cockpit window and affect the l i f t characteristics of the wings. Frost does n o talter the basic aerodynamic shape of the wing like clear ice does, but it candisrupt the smooth airflow over the wing. This causes early separation of theairflow from the upper surface of the wing, resulting in a loss of lift. Frost onthe wings is especially dangerous during take‐off, when it may disturb theairflow or increase weight sufficiently to prevent the aeroplane becoming orremaining airborne.

Icing and Cloud TypeCumulus CloudCumulus cloud consists predominantly of liquidw a t e r droplets at temperaturesdown to about ~23°C, below which either liquid drops or ice crystals may pre‑dominate. Newly formed parts of clouds will tend to contain more liquiddrops than in mature parts. The risk of airframe icing in cumulus clouds issevere in temperatures between 0°C and ‐15°C, moderate in temperaturesbetween ‐15°C and ‐23°C and only light in temperatures of less than ‐23°C.Airframe ice is unlikely in temperatures of less than ‐40°C.

Since there is a lot of vertical motion in convective clouds, cloudcomposition may vary considerably at any one level, and the risk of icing may

34 Night Flight

exist throughout awide altitude band in (and under) cloud. Updraughts willtend to carry the wa t e r droplets higher and increase their size. If significantstructural icing does occur, it may be necessary to descend into warmer air.

Figure 2-11 Icing in cumulus clouds.

Stratiform CloudsStratiform clouds consist entirely or predominantly of liquidwater drops downto about ‐15°C andpresent arisk of airframe icing. If significant icing is apos‑sibility, it may be advisable to fly at a lower levelwhere the temperature is above0°C, or at a higher level where the temperature is below ‐15°C. In certainconditions (e.g. stratiform clouds associatedwith an active front or orographicuplift), the risk of icing is increased. A continuous upwardmotion of air gen‑erally means a greaterretention of liquid water in the clouds.

Orographic LiftThe extra uplift brought about by mountainous terrain causes clouds to formand enables them to carry additional moisture, thereby increasing the risk oficing. There will be a greater potential for severe clear ice to form, and thefreezing levelwill be lower.

Effect of Cloud Base TemperatureWarm air can holdmoremoisture than cold air. Therefore the severity of icingin a convective cloud is liable to be greater in tropical latitudes than temperateones and greater in summer than in Winter.

High-LevelCloudsHigh‐level clouds, such ascirrus clouds with bases above 20,000 ft, are usuallycomposed of ice crystals that will n o t freeze on to the airframe. Therefore, therisk of icing is almost ni l when flying at very high levels.

2: Meteorology 37

® Climb

® Divert

Figure 2-12 Descending,diverting or climbing to avoid icing conditions.

Fog is defined asa concentrated suspension of very small wa te r droplets whichresults in the horizontalVisibility atground level falling to below 1,000m. Fogseverely restricts vision near the ground and is the mo s t frequent cause of lowvisibility at aerodromes.

Formation of F09The condensation process that causes fog is associated with the cooling of airby the following means:' an underlying cold ground or water surface, which causes radiation fog oradvection fog;

' the adiabatic cooling of a moist air mass moving up a slope, which causesupslope fog;

° the interaction of t w o air masses, which causes frontal fog; and’ very cold air overlying awa rm water surface, which causes steaming fog.

The smaller the temperature/dewpoint spread and the faster the temperatureis falling, the sooner fog will form. An airport with an actual air temperatureof +6°C and adewpoint of +4°C (i.e. a temperature/dewpoint spread of 2°C)early on a calm, clear night is likely to experience fog when the temperaturefalls 2°C or mo re from the current +6°C.Note. A METARprovides both temperature and dewpoint.

38 Night Flight

Radiation FogRadiation fog forms when air is cooled to below its dewpoint by the loss ofheat energy through radiation.

Thicknessdependson ‘xing

Figure 2-13 Formation of radiation fog.

Conditions suitable for the formation of radiation fog include:0 cloudless nights that allow the land to lose heat by radiation to the a tmo ‑

sphere and thereby cool, causing the air in contact with the ground to loseheat (leading to a temperature inversion);

0 cold landsurfaces that promote radiation (radiation fog rarely forms over thesea);

- moist air and a small temperature/dewpoint spread (i.e. a high relativehumidity) that only requires alittle cooling for the air to reach its dewpoint,causing the water vapour to condense o n t o small condensation nuclei in theair and form visible water;

- light Winds (5‐7 kt) that promote the mixing of the air at low level, therebythickening the fog layer; and

° the presence of condensation nuclei ‐ some types of particles (such assalt)promote fog since they are highly hygroscopic (water absorbing).These conditions are commonly found With ananticyclone or high‐pressure

system.

No wind: dew/frost Light wind: mist/fog Strong wind: stratus

Figure 2-14 Wind strength wil l affect the formation oi dew/frost, mist/fog or stratus cloud.

2: Meteorology 39

A i r is avery poor conductor of heat, soif the wind is absolutely calm, onlythe very thin layer of air (1‐2 inches thick) in contact with the surface willlose heat to it. This will cause dew or frost to form on the surface itself,rather than cause fog to form in the air above i t . If the wind is stronger thanabout 7 kt, the extra turbulence may cause t o o much mixing and, instead ofradiation fog forming right down to the ground, a layer of stratus cloud mayform above the surface.The temperature of the sea remains fairly constant throughout the year,

unlike that of land, which warms and cools quite quickly on a diurnal basis.Radiation fog is therefore much more likely to form over land, which coolsmore quickly at night, than over the sea.

Dispersal of Radiation FogAs the surface of the earth begins to wa rm up after sunrise, the air in contactwith it will also warm, causing fog to gradually dissipate. It is c ommon for thisto occur by early or mid‐morning. The fog may rise to form a low layer ofstratus cloud before the sky fully clears. However, if the overnight fog is thick,it may act asablanket, shutting o u t the sun and impeding the heating of theearth’s surface after sunrise. As a consequence, the air in which the fog existswill n o t bewarmed from below, and the radiation fog may last throughout theday. An increasing windspeed could c rea te sufficient turbulence to dragwarmer and drier air down into the fog layer causing it to dissipate.

Advection Fog (CoastalFog)A warm, moist air mass flowingaswind across asignificantly colder surfacewillbe cooled from below. If its temperature is reduced to the dewpoint, fog willform. Since the t e r m advection refers to the horizontal flow of air, fog formedin this manner is known as advectionfog and can occur quite suddenly, day ornight, if the right conditions exist. Advection fog depends uponwind to movearelatively w a rm and moist air mass over acooler surface.

Light moderate wind . >‐ >‐> Stronger wrnd

‘ / ‐ ‐ > _ ‐ >Warm, moist Warm, moist

airflow airflow

Figure 2-15 Fog or stratus cloud caused by advection.

40 Night Flight

Advection fog can be more persistent than radiation fog; for instance, awarm, moist maritime air flow over a cold land surface can lead to advectionfog. Unlike radiation fog, the formation of advection fog is n o t affected byoverhead cloud layers, and advection fog can form with or without cloudobscuring the sky. Light to moderate winds wil l encourage mixing in thelower levels to give a thicker layer of fog, but winds stronger than about 15 ktmay cause stratus cloud, rather than fog, to form. Advection fog can persist inmuch stronger winds than radiation fog. lSea FogSea fog is advection fog. It may be caused by the following:° tropical maritime air which moves towards the North or South Poles over acolder ocean or meets a colder air mass; and

' air flow off a w a rm land surface which moves over a cooler sea, affectingairports in coastal areas.

Dissipation ProcessThe only way advection fog will dissipate is through a shift in wind directionthat changes the source of the air. If the wind is stronger than about 15 kt, theou t come is more likely to be low stratus cloud, which may cause overcast c o n ‑ditions over wide areas.

Upslope FogMoist air moving up aslope will cool adiabatically, and if it cools to below itsdewpoint, fogwill form. This is knownasupslopefog. It can form whether orn o t there is cloud above. If the wind stops, the upslope fogwill dissipate. Bothupslope fog and advection fog depend upon wind to exist (but n o t radiationfog). Upslope fog may be experienced on high ground close to the coastwhenever an onshore wind is blowing, but the air needs to be very moist. Asaresult, upslope fog is more likely to be observed in tropical areas.

Frontal FogFrontal fog forms from the interaction of t w o air masses in one of t w o ways:' as cloud that extends down to the surface during the passage of a front,known ashillfog, asit mainly forms over hills; or

° asair that becomes saturatedby the evaporation of rain, known asprecipitation‑inducedfog.These conditions may develop in cold air aheadof awa rm front or anoccluded

front. The pre‐frontalfogmaybevery widespread, giving the impression that thecloud extends firom ahigh level all the way down to the ground. This situation isakiller, asanunwary visual pilot can become trapped in it.

2: Meteorology 41

3%9%!

g . . 8 F

. vlImbostratus . . . o_8 :‑E ;:x ii0 xi

Cold air becomes saturated and fog forms200 400 600 nm

1SSAEPS | | I

Figure 2-16 Fog associated wi th a warm front.

Rain or drizzle falling from relatively w a r m air into cooler air may saturatethe air forming precipitation‐induced fog, which may be thick, long‐lastingand spread over quite wide areas. Precipitation‐induced fog is m o s t likely tobe associated with a w a r m front, but it can also be associated with a slow‑moving cold front. This fog moves with the frontal system.

Steaming FogSteaming fog can form when cool air blows over a warm, moist surface (aw a r m sea or w e t land), cooling the w a t e r vapour which rises from the moistsurface to below its dewpoint, thereby causing fog. Low~level turbulence canbe present in steaming fog, and there is also a risk of severe icing.

sibilityVisibility is a measure of how transparent the atmosphere is to the human eye.Meteorological visibility, as given in aerodrome weather reports and forecasts,refers to the greatest distance at which a person of normal sight can correctlyidentify distant objects. The same criteria apply at night, except that speciallyselected lights are used to measure visibility.

The minimum visibility, either observed or forecast, is always given in aMETAR, SPECI or TAE If the minimumVisibility covers more than halftheaerodrome, or when visibility is fluctuating rapidly and significant directionalvariations cannot be given, this is the only visibility information reported.

An accurate assessment of visibility isafactor in determiningwhether or n o tan alternate aerodrome is required. The visibility quoted in an aerodromereport or forecast is an indication of the real conditions used to determine ifthe aerodrome meteorological minima can be m e t .

42 Night Flight

Astronomical TimesSunrise and Sunset

Sunrise occurs when the upper limb of the sun is on the Visible horizon and is thefirst part of the sun to be seen. Sunset occurs when the upper limb of the sun isjust disappearingbelow the Visible horizonand is the lastpart of the sun to be seen.

TwilightThe periodof incomplete light (or incomplete darkness) either before sunrise orafter sunset is called twilight. The period from the start of morning twilight untilthe end of evening twilight is called daylight. Morning civil twilight begins when thecentre of the sun is siX degrees below the celestial horizon. It is usually lightenough to see the horizon clearly, yet dark enough for bright stars to be Visible,depending on atmospheric conditions. Similarly, evening civil twilight (and day‑light) ends when the centre of the sun is six degrees below the celestial horizon.

“‘ motionof the Sun aroulmth“99936 6Earl};

Sunlight

Daylight

tDuration

of evenintwilight

morningtwilight

Figure 2-17 Morning and evening civil twilight.

Duration of TwilightIn the tropics, the sun will rise and set at almost 90° to the horizon, which willmake the period of twilight quite short and the onset of daylight or night compar‑atively abrupt. In higher latitudes towards the North and SouthPoles, the sun willrise and set at amore oblique angle to the horizon, hence the period of twilightwill bemuchlonger, and the onset of daylight or darkness will befar more gradual.

2: Meteorology 43

Sunlight Sunlight

Horizon

Tropical latitudes Middle latitudes “ 4 2 ” ”

Figure 2-18 Sunrise at tropical and middle latitudes.

During Winter inside the Arctic and Antarctic Circles, a period of twilightmight occur, but the sun might n o t actually rise above the horizonat all duringthe day.

No sunlight

Twilight only (iii

Polar latitudes i1~12e£i=s

Figure 219 Winter twil ight in polar latitudes.

DaylightFactorsAffecting the Duration of DaylightThe beginningof daylight (morningcivil twilight) and the end of daylight (eveningcivil twilight) depend upon date and latitude.

Date. In summer, the beginning of daylight (BOD) is earlier and the end of day‑light (EOD) is later, i.e., daylight hours are longer in summer than in winter.

Latitude. In figure 2‐20, places A, B, and C are all on the same meridian oflongitude, and therefore all have the same local mean time (LMT). However,they are on different latitudes and therefore have different conditions of day‑light and darkness:0 at A, the sun is well up in the sky and this location is in full daylight;

44 Night Flight

° at B, the sun isjust about to rise (i.e. North Pole

beginning of daylight); and' at C, the sun has yet to rise ‐ it istherefore still dark (i.e. night‐time).The shadow line caused by the sun

on the earth is called the terminator.l1-1S.EFS

Figure 2-20 PlacesA, B and 0, although onthe same meridian, experience different

. . conditions of da Ii ht and darkness due toFaetors AffeCtmg Day/lght diffe‘i'egt latitudes.ConditionsThe time atwhich the sun risesor sets will dependuponthe altitudeof the observer.For example, to someone on the ground, the sunmay appear to have set, but anaer‑oplane directly abovemaystillhave the sunshiningon it. It ispossible to bedeceivedby brightness at altitude, asdaylight may have already endedat lower altitudes.

WSunsetSunlight

_ _ _ . ‐ ‐ ‐ ‐ ‐ > l - < ‐ ‐ - TWlll h tSunlight , 9 DarknessDaylight “J N

/ I I H J EPS

Figure 2-21 An aeroplane can be in sight of the sun after it has set on the earth below.

High ground to the west of an aerodrome will also reduce the amount oflight asnight approaches ‐ remember this when flying.When the sun isbelow the horizon, the brightness or darkness of the sky may

vary considerably from day to day and place to place, depending upon suchfactors asthe amoun t of cloud cover or other atmospheric variables, including:0 visibility;° air temperature;° air pressure;0 humidity; and° atmospheric refraction.The amoun t of high ground between the sun and your position can also

affect the brightness of the sky.

Sunlight Light

Figure 2-22 Local sunrise and sunset is affected by terrain.

Chapter 3

Human Factors

he Role 0 he Pilot

The Complete PilotWe tend to think of pilotingan aeroplane asaphysical skill. However, there is more to it ‑muchmore. Aircraft control~ the manipula‑tion of controls to achieve a desiredperformance ‐ is important,but it is only oneelement of the pilot’s total task. The pilotmust assemble information, interpret data andassess its importance, make decisions, act,communicate, correct and continuously reas‑sess. We call this total processpiloting.

Decision MakingThe essential, fundamental role of the pilot isto make decisions ‐ reliably, safely andpromptly. But fortunately or unfortunately,pilots are only human.

Emotions in DecisionsEmotion plays a significant, often a domi‑

Figure 3-1 The pilot is the dataprocessor.

nant, role in the decision‐making process. We often make decisions on thebasis of what we w a n t to happenrather than what is m o s t likely to happen. Wecan be cautious in o u r expectations, or we can be ambitious, especially if wehave previously pushed boundaries and got away with it.

Decisions also depend on personality and confidence. What chances do wewrongly perceive rather than correctly knowing what the odds really are? Dowe er r on the positive side or the negative? In terms of safety, the negative isn o t a bad thing. It is cautious and survival‐oriented rather than goal/successoriented ‐ I made it ! You must learn to make asmuch of a song‐and‐danceabout sensible, reserved decisions and actions asyou would about taking a riskand getting away with it.

45

46 Night Flight

Decisions and StressInternal Stressors. Indecision causes stress. While you are deciding and areunderpressure to decide, your levelof stress can becomeunreasonable. Avoidingadecision also causes stress asyou know that ultimately the problemwill have tobe addressed ‐ it won’t go away. The solution is to make a decision and go forit. Stress is relievedby action, either fight or flight.External Stressors. External pressures have a significant effect on decisions.You havehumanwants, needs and fears ‐ wanting to please,wanting to impresspeople, wanting to earn mo re money or be promoted, needing to be loved,needing to be noticed, needing to be rewarded, fearing criticism or ridicule,fearing job loss, fearing injury... A completely objective decision is made inisolation to such external pressures, and such decisions can often only be maderetrospectively ‐ what should havebeendecided rather thanwhat was decided.Accident investigations are removed from such external pressures because they

don o t ‐ cannot ‐ know the pressures underwhich aparticular decisionwasmade.We can rationalisewhy apilot shouldhavemade acorrect decisionwhenwe readan accident report. It’s obvious to us. No t obvious are the emotional stringsattached to that decision. Makingcorrect decisions sometimes takes considerablecourage or, to use anold term, moralfortitude.

Destination ObsessionDestination obsession (also known asget-there-itis) is getting there today at allcosts. It seems n o t to be the result of a conscious, foolish decision but mo relikely of delaying adecision to t u r n back and land until it is no longer safe todo so. Illusions andmisinterpretation of the seriousness of a deteriorating sit‑uation complicate the decision‐making process.

Low Cloud, Pressing OnThe problemof pilots pressing on under lowering cloud iswell‐known withinthe aviation industry, and yet it just does n o t go away (fatal accidents continueto occur). The solution to the problemis elusive. The decision‐makingproc‑ess obviously involvesjudgement of distances and attitude (distance from cloudand height above the terrain). With fewer cues available, those cues that canbe read are given greater importance. They appear more pronounced andmo r e compelling in their meaning. They invite greater reliance on what theyare telling you. The main effect is to deny a proper and accurate assessment ofheight above terrain and distance fromobstacles and cloud, andyou have afalseappreciation of level attitude.

3: Human Factors 47

With restricted forward Visibility, your judgement of height, attitude anddistance will be so distorted asto be unsafe. You could fly very close to treesor ground without realising. But by then it’s far too late. We’ve all seen newsreports of aircraft engine noise low overhead, often for longperiods before theactual impact.

Reduced light/visibility

Figure 3-2 Limited cone of vision.

Incredibly visual meteorological conditions (VMC) do n o t require a visualhorizon! True we can estimate the horizontal by perceiving the vertical ‐ bylooking down ‐ but this is n o t always reliable. What if the terrain is n o t level?

Figure 3‐3 Rising terrain ‐ false horizontal.

48 Night Flight

Many aircraft that have crashed into rising terrain under cloud have stalledwhile under full power. With alimitedfield of View, there is atendency to usethe ground asa reference for level flight. The closer you get to the groundwithout a clear attitude reference, the more prone you are to using the verticalasan indication of level flight. In this situation, the climb angle will increaseasthe slope increases until the inevitable stall.A l l of this adds up to the unsurprising conclusion that most, if n o t all, pilots

who continue too far under cloud have no idea how low they are actuallyflying until they hit something or wind up in the ‘soup’ itself‐ blind in cloud.In such circumstances, the destination obsession which affected their decisionmaking and distorted their judgement must have been very powerful indeed.

Personality and Matters of ChoiceThe idea that some personalities are mo re prone to taking higher risks thanothers is n o t especially controversial. Many of us do know people who wewould rate asmore‐likely‐than‐most to take ahigher risk, andacommon con ‑viction among such risk takers is‘it won’t happen to me’. The sort or type ofperson who takes higher risks is usually defined by a hazardous attitude.Five hazardous attitudes that contribute to poor pilot judgement have been

identified:

Antiauthoritarianism (don’t tell me).Impulsivity (do something quickly).Invulnerability ( i t won’t happen to me).Machismo (I can do it).Resignation (what’s the use).

Formal Decision-Making ProcessesYou can learn to make better decisions by itemising the co r rec t decision‐mak‑ing process asfollows:

Identify the decision to be made or problem to be solved.Collect relevant information.Generate alternatives.Analyse alternatives.Decide on the most acceptablealternative.Action the alternative.Monitor the outcome: if satisfactory, proceed; if not, repeat steps 2‐7.

3: Human Factors 49

While this may seem time consuming, these steps give structure andmethodtothe decision‐makingprocess and ensures that no conclusions arejumped to. Mostairlines use these steps in crew resource management (CRM), decision making andtraining. It isavalid way to make decisions and to check if your normal decision‑makingprocess covers all options.There is another important element: how much time you have to make a

decision. There is a well‐known model for decision making based on themnemonic DECIDE which takes reaction time into account:

Detect a change.Estimate the need to react.Choose an outcome.Identify actions.Do the necessary action.Evaluate the effect.

However, this model implies that a decision is always a reaction tocircumstances, a situation or a change in events. A better way to make decisionsis to anticipate ‐ to be proactive rather than reactive. Have the decision madebefore it is needed ‐ on standby ‐ aswhenwe practice emergency procedures sowe can anticipate a decision point and be able to respond appropriately. Crises?Decisions should ideally n o t be made under duress asin a crisis situation. Theyshould bemade under controlled conditions andbe stored and ready for use.A different model for decisionmakingisbasedon the mnemonicACTION:

A Anticipate and assess the possible scenarios.C Consider actions and outcomes.T Time ‐ if available, immediate decision or nominate decision point (go/no-go

point) and criteria.I implement decision ‐ make a control input, transmission etc.0 Observe the result and correct ‐ fine tune.N Nominate next milestone, decision point or potential hazard.

Many problems arise from a lack of decision making or a delayed decision.Decisions are easy to defer. Deferring decisions is only acceptable if anominateddecisionpoint ismade andadhered to. By deferringadecision untilit is too late, you could be forced into asituation where there is no decision leftto make.

50 Night Flight

Assembling What-lfsSesame Street (Envisioning Outcomes) IA fabulous episode of Sesame Street involved a child who was encouraged toimagine outcomes before crossing the road:- What if I r u n o n t o the roadwithout warning . . . ?- What if I r u n ou t in front of aschool bus . . . ?0 What if I r u n across the road and trip . . . ?' What if I cross Without looking in both directions . . . ?This is exactly the ‘what‐if’ attitude apilot needs to develop.

Choosing the Best OptionPriorities. The first priority for the pilot mus t be to arrive safely, but this pri‑ority is often neglected or compromised for other concerns: ‘must arrivetoday’, ‘must get to ameeting on time’, ‘must land before dark’, ‘haven’t timeto top up the tanks, complete a fuel check, complete an engine run‐upcheck’...Bets and Betters. We endlessly evaluate bad decisions, but what about gooddecisions? For example, it is better to spend a cold night in a sleeping bag in aten t under the wing of the aeroplane than flying into deterioratingweather andimpacting terrain. It isbetter to arrive late, even the n e x t day or the nex t week,than n o t atall. If you have to besomewhere, have analternative plan: ‘I will leaveearly enough so that if the weather deteriorates over the mountains, I can landat . . . and take the bus and then pick up the aeroplane on the way home’.It is better to land and leave yourselfand your passengers safely on the ground

than to risk injuringyourselfandall of thembecause you had to get to abusinessmeeting. It is better to pay several hundred dollars for taxis and hotel rooms atanunplanned stop andmiss animportant family event than to have your familyattend your hospital bed. You bet!On ‘Def’ Ears. Two common elements lead to dangerous situations. They are:- deference; and- deferral.Deference is when you relinquish a decision to someone else or allow

another person’s views to dominate. This can occur when you avoid discussionin order to, for example, avert apossible conflict, or when you wish to pleasesomeone and say What they want to hear or do what they wan t you to dodespite your inner feelings telling you that your actions are perhaps risky.Deferral isavoidingmakingadecision until later,perhaps until it is t o o late (thisis c ommon when pilots delay turning back).

3: Human Factors 51

Choosing when to lmplementa Decision. Knowing when to implement adecision is asimportant asmaking the decision itself. But when is the righttime?° Immediately?0 Before sunset?° Before reaching the point 0an return (PNR)?' Before becoming fatigued?- Before becomingstressed due to weather or terrain?Most decisions need to be made on the spot, but there are some occasions

when agate or milestone can be set. For example, if you say to yourself, ‘I willcontinue while I canmaintainsafe terrain clearance, I have adefinedhorizonandI have at least a 500 ft vertical separation from cloud. If I lose the horizon or if Ifeel squeezed between ground and cloud, I will immediately t u r n right.’ Thispre‐emptive decision‐makingprocess generates go/no‐gopoints that involve theleast risk and decision criteria that are set andnon‐negotiable. Youmust set youro w n milestones, gates and go/no‐go points and stick to them.

VisionEyesprovide the brainwith avisual image of the environment. The basic functionof the eyes is to collect light rays reflected from an object, use the lens to focusthese rays into an image on ascreen (the retina) and convert this image into elec‑trical signals, which are sent Via the optic nerve to the brain. This is howwe see.The brain then matches the image to previously stored data so the object can berecognised (perceived). The connection of the optic nerve to the brain is so closeand integral, and the importance of the messages sent to the brain is sodominant,that the eyes can almost be considered an extension of the brain.

Structure of the EyeThemain components of the eye are the cornea and lens, the retina andthe optic nerve.

CorneaThe cornea is a transparent cap over the lens through which light rays first pass.The surface of the cornea iscurved, and light is refracted (bent) asit passes through.

LensThe lens, like the cornea, is transparent to light, but the curvature of the lensis changed with the ciliary muscles surrounding it, allowing light rays to befocused. The lensprovides the fine focus for Vision ‐ the greater the curvature,the greater the convergence.

52 Night Flight

Eye muscles,above and belowand each side,move the eye ball Ciliary muscles

and ligaments,modify lens curvature

Retina(light-sensitive) Concentration

of rods onretina

Concentrationof cones on

Foveairegion

Optic nerve /to the brain

Figure 3‐4 Structure of the eye.

The ability of aneye to change its focus, e.g. from afar object to anear object,is known as accommodation. The power of the eyes to accommodate varies,especially with tiredness and age. When a person is fatigued, accommodationdiminishes, andblurred images are the result. Also, the lens becomes less flexibleand less able to modify its curvature with increasing age. This reduced focusingcapability, known aspresbyopia, is noticed by middle‐aged people, and readingglasses are usually necessary.

IrisBetween the cornea and the lens is acoloured membrane known asthe iris. Thecolour of the iris determines the colour of the eye. At the centre of the iris is asmall, roundaperture knownasthepupil. The pupil changes its size to restrict theamount of light entering the lens. In very bright light, the pupil becomes quitesmall. In very dim conditions, the pupilwidens to allow more light to enter.

RetinaThe retina isalight‐sensitive layer locatedat the back of the eye. It is the screenonto which the lens focuses images, and these images are converted into elec‑trical signals that pass along the optic nerve to the brain. The retina containst w o types of light‐sensitive (or photosensitive) cells: cones and rods.

3: Human Factors 53

Cones. Cones are concentrated around the central section of the retina, espe‑cially the area of the retina directly opposite the lens, which is known asthefoveal region. Cones are sensitive to colour, details and distant objects, and theyare mos t effective in daylight and less effective in darkness. They provide thebest visual acuity (the ability to resolve fine detail). The foveal region iswheremos t objects are focused, and it is this area that provides central colour visionin good light conditions. Objects focused on the foveal region in very dimlight (as at night) will n o t stimulate the cones to transmit amessage along theoptic nerve, so the image will n o t be seen.Rods. Rods are concentrated in a band outside the central foveal region andare sensitive to movemen t but n o t to detail or colour. Rods are effective inboth daylight and darkness, and are responsible for peripheral Vision (off-centreVision), which helps orientation and night vision. Objects in dim light aretherefore most easily noticedwhen the image falls on the peripheral area of theretina where the rods are concentrated. You can utilise this at night by delib‑erately looking slightly to the side of anobject, rather than directly at it asyouwould during daylight.

Binocular VisionBinocular vision describes the process whereby optical information is receivedandprocessed from t w o eyes. To track amovingobject with both eyes, they need tomove in harmony, and this means coordinated control of the two sets of eye mus ‑cles by the brain. In a fatigued person, this coordination sometimes fails, andeach eye perceives adiflerent image of the one object, resulting in double vision.When focusing on near objects, the visual axis of each eye will be turned‐in

slightly; when focusing on distant objects (more than siX metres away) thevisual axes of the eyes will be nearly parallel.When the eyes are focused on aninfinitely distant point, they look straight

ahead (i.e. they are parallel). When focusing on nearby objects, distances areestimated by the convergence angle of the eye. Light from aparticular object,especially a near one, will enter each eye at a slightly different angle, causing

HF-D202.eps

Figure3-5 Estimating distance ‐ binocularvision.

54 Night Flight

different images to be formed by each eye. This is called stereopsis. The brainuses these tw o different images asameans of estimating the distance of nearbyobjects (the difference in the tw o images is greater for nearby objects than fordistant ones) and the rate of closure.Absolute distance is judged by triangulation (the convergence of sight lines),

and this is the prime reason for binocular vision. The other reason is tocompensate for the blind spot in each eye.

The Blind SpotThe blind spot is the small area onthe retina where the nerve fibresfrom the light‐sensitive cells (i.e. rodsandcones) lead into the optic nerve. Blind spotAt this point, there is no coating oflight‐sensitive cells, and any lightfalling herewill n o t register, i.e. it isliterally ablind spot. However, it isn o t possible for an image to fall onthe blind spot of both eyes simulta‑neously because it will be in a different relative position for each eye ‐ when animage falls on the blind spot of one eye and is therefore n o t registered, the brainwill receive amessage from the other eye, and the object will still be seen.You can observe the existence of the blind spot in each eye by viewing the

figure below.

Retina

HF-(IZOCZA.EPS

Figure 3-6 The blind spot.

Figure 3-7 The blind spot illustrated.

3: Human Factors 55

Hold the page at arm’s length, cover your right eye, and then with your lefteye focus on the aeroplane on the right. This aeroplane will be focused onyour retina and will be clearly recognisable asabiplane. Stay focused on thebiplane and move the page closer. You will notice that the helicoptereventually disappears. Its image has fallen on the position on the retinaoccupied by'the optic nerve, i.e. the blind spot.When scanning the sky, you must be careful that another aircraft is n o t

blocked from view by the magnetic compass or some part of the windscreenstructure. If an aircraft is blocked from the view of one eye, you will lose theblind spot protectionprovidedby binocular vision and you may n o t see it.

Empty Field MyopiaWhen you are n o t trying to focus on any particular object and you are, forinstance,just gazing o u t the windscreen into anempty blue sky, the natural t en ‑dency is for the eyes to focus somewhere in the range of one to t w o metres.This condition isknownasemptyfieldmyopia, also referredto asemptyfieldshort‑sightedness or empty sky myopia.A pilot flying Visually must continually scan the sky for other aircraft and

obstacles and then focus on any that are observed. In anempty sky, it requires effortto focus on distant objects, since the eyes tend to focus on amuch closer point.

Vision LimitationsRods andcones are the endings of the optic nerve. As anextension of the brain,they will be affectedby anything that affects the brain. With ashortage of oxy‑gen (hypoxia) or an excess of alcohol, medication or other drugs, your sense ofsight will suffer. High positive g‐loadings, asin strenuous aerobatic manoeu‑vres, will force blood into the lower regions of the body and temporarily starvethe brain and eyes of blood, leading to greyout (black‐and‐white tunnel vision)or blackout (unconsciousness).

Colour VisionColours are detected in the central foveal region of the retina by the conereceptors, which are only active in fairly bright light. When these receptorsare insensitive to certain shades of light, defective colour vision, or colour blind‑ness, results and usually shows up asadifficulty in distinguishing between redand green. Colour blindness may cause problems during night flying, aswellasin poor Visibility, asred and green navigation lights of other aircraft are usedfor recognition, and apotential problemmayexist with the visual signals fromthe control tower.

56 Night Flight

Night VisionAt night, there are some special considerations regardingvision. Your attentionduring night flying will be both inside and outside the cockpit, and there willbe variations in light intensity. It takes the eyes some minutes to adapt to adarker environment (as mos t of ushave experiencedwhen walking into adark‑ened cinema). The time it takes for the eyes to adapt to varying levels of lightdepends to alarge extent on the contrast between the brightness of light previ‑ously experienced and the degree of darkness of the n e w environment.Conversely, when adarkened environment is suddenly lit (aswhen the lights areturned on at the end of amovie) the opposite effect takes place. In dim light,the cones become less effective or even totally ineffective, and there isachemicalchange in the rods to increase their sensitivity. Thus we adapt more quickly tobrightening lights rather than dimming ones. Whereas the cones adjust rela‑tively quickly to variations in light intensity (they take about seven minutes tore turn to normal), the rods take some 30minutes to adapt fully to low light.It is a common misconception that, at night, we are using our night vision

in the cockpit or when looking at the runway. When we are looking atsomething that is well illuminated, we are using normal Vision. The nightfighter pilots of World War I I , for example, did use their night vision. Theysat blindfolded in adarkened r o o mbefore taking offfromunlit aerodromes andused red cockpit lighting (and ate carrots) so that they could look for otheraircraft or ground features that were n o t illuminated ‐‐ there was ablackout (thedisadvantage of red cockpit lighting is that red lines or tints on amap do n o tshow up). The only equivalent in civil operations is when we are looking forground features, such asalake or coastline or the shadow of hills on amoonlitnight. Otherwise, we use normal vision and can a reasonable level of lightwithin the cockpit (subject to reflections). The cor rec t balance is found whenthe instruments are easily read and external lights can be readily detected.Therefore, keep the internal lighting to an acceptably low level to minimise

reflections and to allow the best transmission of light through the transparencies.It’s the same asother natural processes ‐ the transmission depends on the energydifference from outside to in. More light outside and less light inside providesthe best transmission of light through the windows. Even consider wearing adark coloured shirt for night flying asthe traditional white pilot’s shirt addsconsiderably to the reflections of the face of the instrument glass. Avoid brilliantlights asthey temporarily reduce the sensitivity of the eyes to lesswell‐lit objects.Be especially careful when viewing sunsets and then trying to see down-sun atthe darkened earth. Exposure to glare and bright sunlight should be avoidedbefore night flights ‐ wear sunglasses. Vision is also affected by reduced oxygenlevels, and so at night in an unpressurised aircraft, avoid smoking and use

3: Human Factors 57

supplemental oxygen (recommended above 4,000 ft). Note that night vision issusceptible to hypoxia at cabin altitudes above 4,000 ft.

Visual Scanning by NightBecause the central (foveal) region of the retina is n o t sensitive to low levels oflight, this causes anarea of reducedvisualsensitivity in your centralvision. Periph‑eral vision ismore effective. An object at night is more readily Visible when youare looking to the side of it by ten or twenty degrees, rather than directly at it.Objects will n o t be assharply defined (focused) asin daytime foveal Vision.The most effective way to use your eyes during night flight is to scan small

sectors of sky more slowly than you would in daylight. This permits off‐centreviewing of objects in your peripheral vision and allows you to deliberatelyfocus your perception (mind) afew degrees fromyour visual centre of attention(i.e. direct your eyes atapoint but use your peripheralvision to look for objectsor lights around it).Since you may n o t be able to see another aircraft’s shape at night, you will

have to determine its direction of travel by making use of its visible lighting:° the flashing or rotating red beacon (usually on the top of the fin);- the red navigation light on the left wingtip;' the green navigation light on the right wingtip; and° a steady white light on the tail.

Green to greenRed to red Red is safeis safe Green Red

Red Green

HF-OZILEFS

Figure 3-8 Determining aircraft direction of travel from aircraft lights.

58 Night Flight

Visual IllusionsSometimes what we perceive (whatwe think we see) is n o t what is actually there,because images sent from the eyes can sometimes bemisinterpretedby the brain.

Relative MovementWe are all familiar with the effect that a moving vehicle has on the occupantsof an adjacent, stationary o n e (they think they are moving). The occupants ofan aircraft moving slowly into an air bridge may feel that they have sped up ifan adjacent aircraft is pushed back.

AutokinesisThe visual illusion of auto/einesis, or self‐motion, can o c c u r at night if you starecontinuously at a single light against a generally dark background. The lightwill appear to move, perhaps in anoscillating fashion, after only afew secondsof staring at it , even though it is stationary. You can lose spatial orientation ifyou use this single light asyour sole point of reference. The m o r e you try toconcentrate on it , the more it can appear to oscillate.

You can guard against autokinesis at night by maintaining eye m o v e m e n t innormalscanning and by frequently monitoring the flight instruments to ensurecorrect attitude. Beware also of false horizons at night (see page 60).

False ExpectationsFrom o u r experiences in the physical world, we build a scale of measurement‐ size versus distance. For example, if abus is small in o u r View, it is perceivedasfar away, and if aperson appears larger than the bus, the person is perceivedascloser than the bus. This works well when objects fall within the scale.

However, it can be tricky in flight ‐ is an object in the sky a large aircraftthat is a long way away or a small aircraft that is quite close? We need toconsider the aircraft type. For example, if it has a very tall fin and under‑wing pods, it is probably aWide‐bodyjet. If it has ahigh wing and afixedgear, it is probably a small aircraft (be careful ‐- it could be a Twin Otter).We also need to asses the rate of closure (the rate at which the size of theobject changes).

Environmental Perspective (Atmospheric Perspective)From birth, we develop a mental model whereby indistinct objects are inter‑preted asdistant and clear objects are interpreted asnearby. This is n o t alwaysso, asatmospheric conditions can alter visibility and can cause pilots to incor‑

3: Human Factors 59

rectlyjudge distances on approach or from mountains (e.g. haze can give afalseimpression of distance on final).

Judgement of Distance and AnglesThe brain often has to make sense of apattern of lines, and the interpretationmay n o t always be correct. Does a stick bend upwards as it is put it into abucket of water? No, it does n o t , but it certainly looks asthough it does. Thisis because our brain and eyes assume that light travels in straight lines, which isn o t always the case aswe know from an understanding of refiaction.

V V The light ray reachingthe eye from point X

\\ is refracted (bent)

Where theeye imaginespoint X to be

Appearance Reality

Figure 3-9 Refraction alters the appearance of straight lines.

An aeroplane on approach through heavy rain can sometimes experience abuild‐up of water on the windscreen, and this water can refract light raysentering the cockpit, potentially causing anillusion like the ‘bent’ stick (figure3‐10). Knowledge of this effect can offer some protection to the pilot.

Path of light rayfrom runway to eye

Watel Emld'up Where the eye imagines0” Wm screen the runway to be (lower

down and further away)

Windscreen

Figure 3-10 Refraction by water on a windscreen can alter the pilot’s perception of the runway.

60 Night Flight

False HorizonsSloping layers of cloud by day, angled lines on the ground or areas of light bynight can sometimes present a pilot with a false horizon. False horizons canbevery misleadingand can occu r with aragged, lowering cloudbase and asso‑ciated drizzle or rain obscuring the natural horizon.

HF-OZZIEFS

Figure 3-11 False horizons.

3: Human Factors 61

Visual Illusions in the Circuit

Visual Estimation of HeightA pilot flying a right circuit may get the impression that the aircraft is higherthan normal. This illusioncould occur to apilotwho, while flying left circuits,has developed the habit of Visually judging circuit height andpositionby relat‑ing the position of the runway lights to some feature of the aircraft, such asaparticular position in a side window. While such a rule of thumb may worksatisfactorily for the more typical left circuits, it could lead apilot to descendlower to achieve the same picturewhen making right circuits. Like mo s t hab‑its, such apractice could happen unconsciously.

Left downwind ‐ night

Right downwind ‐ correct

Figure 3‐12 Perception of height can be skewed between right and left circuits.

62 Night Flight

Visual Illusions on ApproachRunway SlopeMost runways are of standard width and are on flat ground. On everyapproach, you should t ry to achieve the same flightpath angle to the horizontal.Your eyes will become accustomed to this; by keepingyour view of the runwaythrough the windscreen in a standard perspective, you will be able to makeconsistently good approaches along an acceptable approach slope. However,when approaching asloping runway, the perspective will be different.

A runway that slopes upwards will look longer, and you will feel that youare high on slope, when in fact you are right on slope. The tendency will befor you to go lower or make ashallower approach.

‘7ac 5\Ope

“eda931,} oma\. 00 heMore attitude change i

in the flare than fora horizontal runway

Horizontal

" “ “ ’ a ' 5 2 . .‘ ' E g l l l l l a i a m . _ : t ” :

Figure 3-13 Upsloping runway.

A runway that slopes downwards wil l look shorter, andyou will feel that youare low on slop, when in fact you are on the correct path. The tendency willbe for you to go higher and make asteeper approach.

Anticipate and avoid XV

Smaller attitudechange in the flare,

compared with ahorizontal runway

,.(l.~ 1%.!mg! l‘x" liilii r;

Figure 3-14 Downsloping runway.

3: Human Factors 63

If you know the runway slope, you can make allowances for being high orlow on approach in your Visual estimation (refer to figure 3‐15).

Figure 3‐15Runway slope can alter perception of

approach path.

Runway SizeA runway that is wider than usualwill appear to be Closer than it reallyis. Conversely, arunway that is nar‑rower than usual will appear to befurther away than it really is.Because of the angle at which youView it peripherally in the finalstages of the approach and landing, awide runway will also cause an illu‐ , _, . Figure 3‐16 RunwayWidth can alterS l o n of belng t o o low, and you may perception of distance to a runway.flare and hold‐off t o o high as aresult. This may leadto ‘dropping‐in’ for aheavy landing. A narrow runwaywillcause anillusion of being too high, andyou may delay the flare andmake contactWith the runway earlier (andharder) than expected. If you know that the runwayiswider or narrower thanyour regularairfield, you can allow for this in your Visualjudgement of flare height.

NightApproachAt night, apoweredapproach ispreferred. Powergives thepilotmoreprecise con‑trol, a lower rate of descent and a shallower approach path. The approach to theaimpoint shouldbe stabilised asearly aspossible (constant airspeed, path, attitude,

64 Night Flight

thrust and configuration). Use all the available aids, such asthe runway lightingand aVisual approach slope indicator (VASI). If the runway edge lighting is the onlyaid, correct trackingandslope isachievedwhen the runwayperspective is the sameasin daylight. On centreline, the runway will appear symmetrical. Guidance onachieving the correct approach slope is obtained fiom the apparent spacingbetween the runway edge lights and the distance of aimpoint below the horizon.If the aircraft is low, the runway lights wil l appear to be closer together or

closing. If the aircraft is above slope, the runway lights wil l appear to befurther apart and separating. VASI will provide co r r e c t indications, but theperspective provided by runway edge lighting may be misleading due torunway slope or width.

....uiiimsumlhliiliiWill-ii. H... .’ l l...n.im..iiuihni[With-n. ..fl it , I In

C.0". 0..

O

wn.“4anNgiI

Becoming low Correct Becomin highLight spaces decreasing Light spaces increasing

Figure 3-17 Runway lights indicating approach path.

Black-HoleApproachFlying an approach to a runway with no other visible references can often bedifficult. This can occur when approaching a runway on adark night wherethe only visible lights are the runway edge lights, with no t ow n or street lightsor any other indication of the nature of the surrounding terrain. This isknownasa blade-hole approach. Alternatively, there could be city lights in the areabeyond the airfield but no visual cues near the threshold. Black‐holeapproaches also occu r on tropical atolls, at remo te desert airfields and onapproaches to runways that are surrounded by water.The tendency is to think that you are higher than you actually are, resulting

in an urge to descend and fly ashallower approach ‐ to sink into the abyss, theblack hole.The wo r s t black‐holeproblemof all occurs in remote airfields on dark nights

(say under cloud) where there is no other light source or any ground texture,and autokinesis might generate an impression of movemen t when there isnone. Rely on the instruments, n o t your eyes, to maintain horizontal andvertical navigationplots.

3: Human Factors

. .....rlu..~wmrlw-arm. ...I‘ . l '

re erenceBlack-hole aproachFigure 3‐18 Lack of visible ground references at night can cause difficulty in flying an

approach.

Bright city l ights

HFOZQSEEPS Unlit ocean or featureless terrain

Figure 3-19 Black hole approach causes a shallower approach.

HFruzacfiPsObscured approach Normal perspective

Figure 3-20 Lack of ground references causes a difficult approach.

65

66 Night Flight

If VASI is n o t available, crosscheck the vertical speed indicator to ensure thatthe ra te of descent is proportional to the approach speed (V Asaguide,the rate of descent should be close to 5 times the groundspeed for a 3°approach.A similar situation to ablack‐hole approach, known asawhite‐oat approach,

arises in conditions where the ground is covered with snow, making itfeatureless. The lack of a visual horizon and details around the runwaythreshold make depth and slope perceptionmuchmore difficult.

SummaryA variety of atmospheric and terrain conditions can produce visual illusions onapproach. When you encounter these situations, you can anticipate and com ‑pensate for them.

Situation Illusion Result

Upslope runway or terrain Greater height Lower approach

Narrower than usual runway Greater height Lower approach 9

Featureless terrain Greater height Lower approach %

Rain or the windscreen Greater height Lower approach 3

Haze Greater height Lower approach

Downslope runway or terrain Less height Higher approach (0

Wider than usual runway Less height Higher approach 3

Bright runway and approach lights Less distance Higher approach 2

Table 3-1 Summary of visual illusions on approach.

Focal PointThe most c ommon visual illusion is n o t somuchan illusionasdistortedjudge‑ment . It is based on a familiar phenomenon known asthe inappropriate habit.Let’s say you routinely fly into agiven airfield. You assess that you have reachedthe base t u r n position on the basis of a that-looks-about-réght distance assessment.The distance that looks about right during the day in clear conditions wil l

be greatly different from the distance that looks about right at night, or underheavy overcast conditions or through light rain. The basis of your distancejudgement is stored knowledge accumulated over the number of approachesyou have made along that same track to that same runway. The vast majority

3: Human Factors 67

of your flights through these points will have been made in good weather ‑clear skies, bright sunlight and great visibility, n o t in gloom or darkness.If you are aware of potential V‑

illusions, you can make correctionsto your perceptions. If your imageof agiven runway at agiven airfieldis based on past experience in clearconditions, the tendency will be foryou to fly closer to that same runway Looking at single pointuntil you can match that image in reggg'g‘sehsigggflgnflfignterms of contrast or intensity whenconditions are poor. You will needto use discipline and other referencefeatures to get the right distance.The problem is compoundedwhen you are preparing to t u r n final. In good

weather, you have a complete picture of the runway centreline, which isnecessary to position on final. When visibility is limited, you lack one of thet w o points neededto project the line, i.e. the extendedcentreline. Instead,youconcentrate on the nearest, clearest point on the runway ‐ the threshold (whereelse?). This is the focal point. Your cue to t u r n final is activated by yourjudgement of an angular relationship with the runway, which in this situationyou cannot determine.If you are focusing solely on the one point in poor Visibility, you simply

cannot establish the correct lead angle at which to commence the final tu rn .You need to force yourself to scan, looking at each end of the runway in t u r nto imagine acentreline.

HF-0219A,EPS

Figure 3 2 1Single point lock-on problem.

End-to-endscanning suppliesangular reference

HF‐D2190.EPS

Figure 3‐22 Conscious scan for centreline and glideslope information.

68 Night Flight

The problem is worse at night, and the need for a formal scan is greater.There is asimilar problemwith lookingat the runway on approach. Focusingunconsciously or otherwise on one point denies you glideslope information.You will only get that through a conscious scan.Another important reference isany light on the horizonwhich ison or close

to the projected runway centreline. It puts everything into perspective.

Hearing and BalanceW W W W W .: W m m mW m m g fi , 5"a:

The ears provide t w o senses ‐ hearing and balance. Hearing allows us to per‑ceive sounds and to interpret them. Balance allows us to interpret which wayis up andwhether or n o t we are accelerating. After vision, balance is the ne x tmos t important sense for apilot.Balance and acceleration signals from the balance mechanism in the inner ear

pass to the brain aselectrical signals for interpretation. The interpretation issometimes tricky in the case of an airborne pilot, since the brain is accustomedto astate of being upright and slow‐moving on the earth’s surface.

Structure of the EarThe ear is comprisedof three parts: the outer ear, the middle ear and the inner ear.

Ossicles

esiibular apparatus

Auditory nerve

H a m m e r s

Atmosphericpressure Outer canal

Cochlea

Ear drumEustachian tube

Outer ear Middle ear Inner earI¥ J L J g

v v v

Figure 3‐23 The structure of the ear.

3: Human Factors 69

Outer EarThe ou te r section of the ears includes:' the external ear (knownasthepinna or auricle), which is usedto gather soundsignals;

- the outer canal through which pressure waves pass; and0 the eardrum, which is caused to vibrate in harmony with pressure waves.Any obstruction to the ou te r canal, such asearplugs or anexcess of wax, can

prevent sound pressure waves from reaching the eardrum. Similarly, apaddedcover over the external ear can prevent sound waves entering the ear (unlessthe cover isaheadset that blocks external noise but has asmall speaker for radioand interphone messages).

Middle EarThe middle ear is an air‐filled cavity containing three small bones, known asossicles. The ossicles are forced to move by the vibrating eardrum, convertingthe pressure‐wave energy into mechanical energy of motion. The ossicles arearranged like a series of levers to increase the effect of the initial movement.This energy then passes on to the cochlea in the inner ear. Together with theeardrum, the ossicles constitute the conductive tissue.The air in the middle ear ismaintainedat ambient atmospheric pressure via

the Eustachian tube, which connects the interior of the middle ear to the nasalpassage. There shouldbe no leakage of air across the eardrum, and there shouldbe easy passage of air through the Eustachian tube to equalise pressure, e.g.when climbing or descending. The passage of air is sometimes hindered bymucous, swelling or inflammation (e.g. when apersonhas acold) and can leadto serious consequences. Interference to the movement of the three smallossicles or their joints will reduce or distort sound signals. This can be causedby ear infections, damage to the bones or joints or a blocked ear with airtrapped inside (barotitis).The region of the middle ear provides sensations of movement and balance,

and for this reason middle ear infections can affect the sense of balance.Furthermore, disturbed signals frommiddle‐ear sensors can lead to afeeling ofnausea. In extreme cases, this can result in vertigo ‐ the total loss of balancewithmassive and disturbing disorientation.

InnerEarThe innermost section of the ear contains three very important pieces of appa‑ratus: the cochlea, the vestibular apparatus and the otolithic organs. The cochleaconverts the mechanical energy from the ossicles into electrical signals that thentravel via the auditory nerve to the brain for interpretation.

70 Night Flight

The vestibular apparatus consists of three fluid‐filled semicircular canals thatsense angular acceleration. There is a cluster of small hairs at the base of eachsemicircular canal. These sensinghairs sit at the base of each canal in achamberknown asthe cupvla. Interaction between the hairs and the fluid in the canalsprovides sensations of movemen t .In the same region are the otolithic organs, which detect linear (fore and aft,

up anddown) acceleration or deceleration. The otolithic organs are co‐locatedwith, but separate from, the vestibular apparatus. Fluid in the cochlea ismovedby the mechanical energy from the ossicles, and this causes awavy mo v emen tof small hairs protruding into the fluid. The movement is converted intoelectrical signals at the bottomof each hair, and these signals are sent along theauditory nerve to the brain.

BalanceThe sense of balance makes it possible for us to remain upright. The mos t pow‑erful reference for balance is the visual channel. If you can see, you can tellwhether or n o t you are vertical (providing there is avertical or horizontal refer‑ence). If you close your eyes, your orientation is n o t so easy to gauge ‐ you canconfirm this by standingon one legwith your eyes closed. The secondary sensingmechanisms (i.e. other than vision) are those fromwhich your brainmightbe sentorientation messages. The secondary signals are feeble compared to visual cuesand reallyonly supplement visual perception. In other words, they can only makesense in partnership with the vastly more powerful visual picture. These sensorymechanisms are designed for three‐dimensional orientationbut n o t three‐dimen‑sionalmotion or acceleration. If you have no visual horizon, these other sensorswill supply fall‐back information, albeit information that isn o t reliable.In the absence of a powerful visual cue, your system will crave orientation

signals andaccord them equalweight. The secondary sensingmechanismswill beperceivedasvery strong, but they will always bemisleading. You cannot rely onany of them, andyou must neveruse themtojudge your flightpath. However,youcan guardagainst their influenceby knowingwhat they will try to tell you andbybecoming familiar with their illusory signals.

Spatial OrientationOrientation is the ability to determine your position and alignment in space.It is usually achieved by acombination of three senses:° vision, which is the mos t powerful sense;° balance, which is the vestibular sense (gravity, acceleration andangular acceler‑ation); and

' bodily feel or what pilots call seat of thepants, which is theproprioceptive sense.

3: Human Factors 71

The brain uses all available information to assemble a picture, but if thereare conflicting signals, vision is given first priority. In mos t situations, vision,balance and bodily feel reinforce each other. However, this is n o t always thecase in flight, where each of these senses can sometimes have its messagesmisinterpretedby the brain. When you are denied external vision andflyingis solely by reference to the instruments, a range of false sensations can beperceived. N o t knowingyour attitude in relation to the horizon (i.e. whichway is up) is calledSpatial disorientation. Whenyou are denied external vision,you need to rely totally on your flight instruments and scan to check that theyagree with each other.

Human Balance MechanismThe balance mechanism, the vestibular apparatus, is designed to keep usupright ‐ i.e. vertical and balancedwhile standing or moving. In the absenceof visual references, the inner ear can sense what is perceived asverticality bysensing tilt (angle) and sensing tilting (motion ‐- backwards/forwards orleft/right). The angle of tilt is sensed by the otoliths (apendulous mass whichsenses gravity), and the tilting motion is sensed by the fluid‐filled semicircularcanals.

Sensing Gravi ty (Verticality)Gravity is detected by the sensory hairs in the otolithic mgans, which can bethought of asmembranous sacs filledwith gelatinous material. The outer mem ‑branes of the sacs are studded with small crystals of calcium carbonate calledotoliths, hence the t e rm otolithic organs.The otolithic organs have a resting position when the head is upright.

The brain interprets the message sent from the small hairs at this time asup,i.e. a direct downward force of 1g. If the head is tilted to one side orforwards or backwards, the otoliths move under the force of gravity and takeup a new position. This bends the hairs, which then send a different signalto the brain.The otolithic organs can detect the direction of g‐forces, but they cannot

distinguish the origin of the forces ‐ e.g. whether it is the force of gravity or acentripetal force pullingyou into acoordinated tu rn . We must remember thatthe body is designed for fairly slow motion on the face of the earth with aconsistent 1gforce of gravity exerted on it and n o t for the three‐dimensionalforces experienced in flight (or zero g for that matter). In aturn , the otolithicorgans will recognise a false vertical.

72 Night Flight

Head upright Head tilted

V Up

0 0 o

.l.liil.l.‘ ‘ ’9 (down) 9 (down) HF-ozm.EPs

Down Down HF-0332.EPS

Figure 3-24 Gravity sensed bythe otholithic organs.

Total force

Total force

Straight-and-Level Balanced turn

Gravity ResultantGravity

Figure 3-25 In a turn, the otholithic organs will recognise a false vertical.

3: Human Factors 73

Sensing LinearAccelerationWhen ou r bodies are tilted or accel‑_ righterated, we naturally lean to av01d rotation

. . ||falling over. In the absence of aV i s ‐ (r0 )/ \ual reference, the body cannot Fore and Nosediscriminate between tilting and “US$330”accelerating, and our correctionsmay n o t be appropriate. I Left and right

FA - u s fl AEPS - I'Otallon

. Fi ure 3-26 The semicircular canals.SensmgAngular Movement 9The three semicircular canals of theinner ear (part of the vestibularapparatus) contain fluid. Thecanals are at right angles to eachother (they are orthogonal) like thepitch, roll andyaw planes of anair‑craft. Therefore, they can detectangular acceleration (the change inthe ra te of rotational speed) inpitch, roll and yaw.The cupula is a saddle‐shaped

chamber at the base of each canal asdepicted in figure 3‐27. It has acluster of fine hairs that protrudes into the fluid. Movement in the fluid issensed by these hairs. Nerve endings at the base of the hairs sendcorresponding signals to the brain for interpretation (perception).The semicircular canals are not designed to detect linear changes in motion

or linear acceleration because the upper and lower volumes of fluid are self‑cancelling. For example, if the fluid at the top of the semicircular canal triesto move anticlockwise around the canal due to an acceleration forwards, thefluid at the bottomwill t ry to move around clockwise to the same degree. Thene t effect is there will be no relative movement of the fluid, and the sensoryhairs of the cupula will remain straight.The vestibular apparatus senses angular acceleration by recognising changes

in rotary motion due to the lag of the viscous fluid. During angularacceleration, the relevant semicircular canal moves around a mass of fluid thatlags. This lag in the fluid bends the sensory hairs, and this sends a signal to thebrain that the head is rolling, yawing or pitching (three dimensions ‐ threechannels ‐ three canals). ‘

HF-DMS.EPS

Figure 3-27 The cupula.

74 Night Flight

During linear acceleration (forward or rearward),fluid inertia self cancels. No movement of hairs. HF ‐oslsEPs

Figure 3‐28 Linear acceleration no t detected by the semicircular canals.

Once the rate of roll steadies, i.e. there is no mo re angular acceleration, thefluid will catch up with the surface of the semicircular canals, and the sensoryhairs of the cupula will straighten. For this reason, you wil l detect an entry toa roll but n o t its continuing steady state. Similarly, you will sense anoppositeacceleration asyou stop aroll (decelerate) at the required bank angle.

Vificgjus P PU! . \

Fluid staysstationary ashead moves

Nerve hairs

HF -u sanPs

Figure 3-29 Lag in the viscous fluid causes the detection of angular acceleration.

NormalSensations Associated with a Level TurnAs is the case with any stimulus or sensation, there is a threshold below whichmovement Will n o t be detected. For example, you will sense asharp changein roll rate, but you may n o t sense agentle change. In reality, you do n o t n e c ‑essarily detect the angular acceleration that commences a roll asa rollingsensation. You will feel the entry into a roll asa rolling sensation if the roll issharp enough. Similarly, you will sense the rotary deceleration that stops arollat the selectedbank angle. You may also sense rollingsignals from adjustmentsto the control input While amending either roll rate or angle of bank. How ‑ever, in many flight regimes, your control inputs will be sogentle that you willn o t detect any rollingsensation at all. In such situations, the potential for con ‑fusion is serious.

3: Human Factors

There is angular acceleration when you entera t u r n . Angular deceleration occurs when youstop the roll at the desired bank angle. The rollonset (build‐up) period is very brief ‐ fromwhen you m o v e the controls until the roll isunderway ‐ a fraction of a second. The stop‑the‐roll period is also brief. Nonetheless, theseaccelerate‐decelerate stages may or may n o t besensed by your semicircular canals, dependingon whether or n o t the accelerate‐deceleratestages exceed the minimum threshold ofdetection. Very low rates will n o t be noticed,but you will sense the commencement andcessation of a sharp roll.

When a roll is induced, the pilot’s head alsorolls, and the little sensing hairs are immediatelybent by the fluid lagging in the canal. The fluidflows relative to the canal, but it is actually thecanal (your head) that is moving around thefluid. Owing to inertia, the fluid temporarilylags until friction with the walls of the canalbrings it ‘up to speed’.

The hesitant fluid in the canal bends thehairs. Electrical signals go to the brain: ‘We arerolling to the left’. Once asteady roll is underway,the fluid will catch up, and the hairs will r e t u r nto their normal, erect position. The sensationof rolling thus dissipates, although the roll couldbe continuing. However, as rollmovements are brief, the dissipation of the rollsensation is n o t significant. The rollwill usuallybe stopped before the hairs are neutralised.

In a sustained turn, there is no rolling motion.

m o s t

75

HF-031 sAiEPS

Tilting or rolling(lagging fluid

tilts hair) HF-03183.EPS

Balanced turn or '-steady (slow) roll rate

(hairs and otoliths erect) HF-DSlBC.EPS

Figure 3‐30 The semicircular canalwi l l sense the angular acceleration(deceleration) of a roll into (outo f ) a

turn, provided it is large enough.

The bank angle is constant. The resultant of the force of gravity and centrifiigalforce aligns the otholithic organs to afalse vertical. In aperfectly coordinated 60°banked turn, you will experience a 2gforce exerted by the seat on your body atan angle of 60° to the vertical. With no visual reference,you will feel asif you arestill sitting upright with respect to the external forces. You cannot know if youare levelor in abanked turn . You needvisual cues to confirmyour actual attitude.

76 Night Flight

Total forceTotal force

Total force

Total force

Total reactionTotal reaction

Figure 3-31 No rolling motion in a balanced turn.

It’sjust like a carousel.

Left rotation (turn)

AGx-nanuEFsy 5 ’ ' : 1

Figure 3‐32 000 weee!

Sensations in Turning FlightIn abalanced turn, a full glass of water on the instrument shroud will remainunspilled ‐ the fluid will remain level with respect to the glass. It is asif theweight of the fluid is acting through the normal axis of the aircraft. It is. Theapparent weight is the result of gravity and centrifugal reaction.

Straightand level Balanced

turn

Down?

Figure 3‐33 Water will not be spilled in a balanced turn.

3: Human Factors 77

Your body will also sense up and down asacting in that same axis. In theexample illustrated in figure 3‐31, the start roll and stop roll movements aresensed, and the latter cancels ou t the residue of the former. There will nolonger be any rolling sensation. No r is there any other sensation source apartfrom the seat of the pants. In other words, once you are established in a turn,you will feel asif you are in straight and level flight, and that feeling will be thesame regardless of the bank angle (although load factor will vary).

Disorientation and IllusionsThe LeansWhenyou combine afalse sense of vertical with the sensation of rolling, the braincan become very confiised. This condition is known asthe leans. The leans caninterfereprofoundly with your mental equilibrium, but only if you let them.Consider the situation in which an entry into a right t u r n is very gentle.

The entry is n o t sensed by the semicircular canals, but the stop‐rolldeceleration is detected. The end result is quite discomforting. The gentleonset of roll into the t u r n would n o t be perceived, and no sensation would beavailable during the steady‐state roll. If stop‐roll control movemen t s are madebriskly, the angular deceleration that stops the roll and establishes the bankangle would be felt ‐ strongly. However, it would be felt asa roll to the left.As there would be no cancelling sensation available, the sensation of rolling ‑continuous rolling‐ would persist, though it would slowly dissipate asthe fluidstops moving and the sensory hairs stand up straight again.In entering this right turn, the only sensation perceived would be the stop‑

roll angular deceleration. The signal sent to the brain would be read asroll tothe left. With no corresponding cancelling sensation, it would be a sensationof continuous rolling. If you then roll o u t of the t u r n and the roll‐out isbrisklycommenced (i.e. enough to be detected), you would then experience thesensation that the left‐roll movement has become faster.Perception of rapid roll rates can quickly produce strong sensations of

disorientation. You can also get the leans during t u r n entry or eXit. That is:0 you might be wings level and yet absolutely convinced you are rolling intoor established in a turn; or

° equally, you might be in a t u r n and yet be certain that your wings are level.

We have seen that slow rates of roll (ormovement around the other t w o axes)will n o t be detected. However, brisk control inputs will induce sensations, andthe brisker the input, the stronger the sensation.A common leans scenario would be when you slowly let awing drop then

suddenly notice the wing-low condition. To coun t e r this, you spontaneously

78 Night Flight

‐ and rapidly ‐ roll to wings level (and perhaps be looking down at amap orover your shoulder for the runwayafter anight take‐off). You then feel astrongrolling sensation ‐ the leans.

Nose-Up Pitch Illusion of LinearAccelerationWhenyou tilt your headback or leanbackwards, the otoliths act astiny weightswhich cause the sacs of the otolithic organs to slump in the same direction.The corresponding sensor‐hair movemen t tells your brain that your verticalaxis is n o w inclined rearwards. The same sensation is caused by linear acceler‑ation. Under acceleration, the sacs lagbehind and the sensor‐hair movementsends amessage to your brain that you are tilting backwards. This sensation isknownasthe somatogravic illusion (somatomeaningoriginating in the body,gnu/itmeaning sense of gravity).Pilots experience somatogravic illusionasor the sensation of the nose rising

during acceleration (nose-uppitch illusion), and the greater the acceleration, thestronger the feeling. Obviously, this is n o t a problem when there are clearVisual cues, but it can have very serious consequences when there are few orno cues, ason adark night. In these conditions, forward acceleration throughtake‐offand then to climb speedwill be sensed asbackwards tilt, i.e. asahighernose‐attitude and pitch‐up than actually exist, and there will be a temptationto lower the nose ‐ which if carried through could prove fatal.

Erect (noacceleration)

Tilt (rearward) Acceleration(forward

acceleration)(* or deceleration to stop

HF-oazIEPs from rearward motion)

Figure 3-34 Nose-up pitch illusion due to linear acceleration.

Nose-Down Pitch Illusion of LinearDecelerationThere is aconverse to the somatogravic illusion, but it n o t asserious asit is lesslikely to happennear the ground. Deceleration in flight is sensed astilting for‑wards (figure 3‐35).

3: Human Factors 79

u I o ' ‘ ’

‘.l.lIll’l’.Tilt (forward)

Correctlysensed

Decelerationor tilt?

ConfusedHF-DSEDEPS

Figure 3‐35 Nose-down pitch illusion due to linear deceleration.

This nose‐down pitch illusion is particularly noticeable in higherperformance aircraft when thrust is reduced and speed brakes are extended.If the aircraft is already descending, the deceleration will be sensed as asteepening descent. Again, if there is a clear Visual reference, the sensation ishardly noticeable. However, if there is no visual reference, the illusion willbe m o r e powerful. Fly attitude.

Mot ion SicknessMotion sickness is usually caused by motional overstimulation of the balancemechanisms in the inner ear. In airsickness, this overstimulation can be causedby turbulence or by manoeuvres in which abnormal forces are experienced(such assteep tu rns or spins), especially if there is no clear horizon. A hot,smelly cockpit does n o t help. Psychological aspects can also play a role in theonset of airsickness. In particular, anxiety makes the condition worse asthiscan cause a sufferer to lose control over where he or she looks and focusesattention. For a pilot suffering from airsickness, visual scanning is likely tobecome purposeless, random or fixed.

If messages from non‐visual channels (the balance organs) are accordedpriority over visual ones, the sensory confusion causing motion sickness willpredominate. If anairsick pilot focuses on the horizon, the visual messages willbegiven achance to assert their authority and to t o n e down the strength of thesignals coming from other sources.

Many pilots experience airsickness, especially early in their training whenstress levels are usually high and slightly unusual attitudes and g‐forces areencountered, perhaps for the first time. Therefore, do n o t be discouraged if youoccasionally experience airsickness.

Night Flight

To avoid airsickness:anticipate and/or avoid areas of turbulence, asgauged from weather forecastsand by your o w n knowledge of local effects such asthe side of hills (ifyouare n o t a local, seek the assistance of someone who is);eat lightly before flight;fly the aeroplane smoothly and gently, and maintain tr im and balance;focus on the horizon asmuch asyou can;avoid manoeuvres involving unusual<g‐forces; andventilate the cabin with agood supply of cool, fresh air.

If turbulence is encountered with an airsick passenger on board:fly at best speed;relax (don’t fight) and maintain attitude;have the airsick passenger look outside the aeroplane into the distance (e.g.to help identifil ground references) or at the horizon;as a last resort, recline the airsick passenger’s seat to reduce the effect ofvertical accelerations, and keep an airsickness bag handy; andland assoon asis reasonably possible ( i fnecessary).

Part Two

Night VFR Rating,Rules and Requirements

Chapter 4: Night Flight Rules and Requirements. . . . . 83

Chapter 4

Night Flight Rules and Requirements

A night VFR (NVFR) ratingallows flight at night under Visual meteorologicalconditions. Although flying in visual conditions, there may n o t be a visualhorizon. Therefore, night flight requires a greater understanding of the oper‑ation and utilisation of flight instruments and navigation aids. There are alsoadditional considerations with regard to regulations andprocedures to be takeninto account when planning aflight at night.

NWEWWLWWW‑Night is defined in the Aeronautical Information Publication (AIP) as theperiodbetween the end of evening civil twilight and the beginningof morningcivil twilight. Day isdefined in the AIP asthe period of time from the begin‑ning of morning civil twilight to the end of evening civil twilight. Civiltwilight is the twenty‐minute period after sunset and before sunrise.

How to Determine if a Pilot is SuitablewawwwwwwmwmwwwmwwwReferences: CAO 40.2.2; CARS 5.01/1, 5. 74, 5.80, 5.82, 5.107 and 5.109.As the holder of a night VFR rating, you are authorised to fly in Australia atnight in V M C aspilot in command of an aircraft with a take‐off weight n o texceeding 5,700 kg in the private or airwork categories. A night VFR ratingwill remain in force for aslong asyou hold aflight crew licence. If your nightVFR rating test was conducted in a single‐engine aircraft, the rating is onlyvalid for single‐engine and centreline‐thrust aircraft.

Student PilotsOperational RequirementsStudent pilots may be authorised to fly in the circuit area at night provided:' the flight is authorised by a qualified flight instructor;° the whole flight is conducted under the direct supervision of a qualified flight

instructor;- weather conditions permit the flight to be conducted under the VFR;

83

84 Night Flight

an entry must is into the student’s log book stating that the student has sat‑isfied the night VFR handling requirements in an aircraft of the same cate‑gory asthe aircraft used for the flight; andthere are no passengers in the aircraft.

Handling RequirementsWhile flying dual, astudent pilot m u s t m e e t the following requirements beforebeing sent solo in the circuit area at night:

during daylight hours, the student m u s t recover from unusualattitudes solelywith reference to the aircraft’s instruments;in daylight or at night, the student must manoeuvre the aircraft in the wayslistedbelow:‐ alevel t u r n of up to 30° angle of bank;‐ a climbing t u r n at a constant airspeed to an altitude previously deter‑

mined by the instructor;‐ a descending t u r n at a constant airspeed to an altitude previously deter‑

mined by the instructor;‐ straight and level flight; and‐ climbing and descending;during the hours of night, the student m u s t fly the aircraft by reference toVisual cues and by the aircraft’s instruments in the following sequences:‐ circuits;‐ baulked approaches (go‐arounds);‐ entry to the glide configuration from straight and level flight; and‐ entry to the glide configuration from a climbing attitude.

Recent ExperienceIn order to fulfil recent‐experience requirements, a student pilot mus t satisfyeither of the following conditions:

the student must have completed three take‐offs and landings in the previous30 days while acting aspilot in command at night (or the previous 90 days ifaGFPT is held); orthe student must have completed one take‐off and landing in the previous30 days while flying dual and while flying at night (or the previous 90 daysif a GFPT is held).

Private or Commercial PilotsThe private or commercial pilot must have fulfilled the following requirements:' within the last year, the pilot must have flown one flight of atleast one hour’s

duration while flying aspilot in command, acting in command under super‑vision or dual; and

4: Night Flight Rules and Requirements 85

- the pilot mu s t have completed at least one of the following:‐‐ in the last six months, the pilot mus t have carried o u t one take‐off andlandingwhile flying aspilot in command, in commandunder supervisionor dual;

‐ the pilot mus t have passed the aeroplaneflight review or an aeroplane prof‑ciency test where part or all of the flight was undertaken at night; or

‐ the pilot mus t have passed aflight test which was conducted at night asarenewal or asan initial test for an aeroplane pilot rating.

Operational RequirementsPrivate and commercial pilotsmay beauthorised to fly in the circuit area at nightwithout anight VFR ratingprovided the following requirements are met:0 pilots are authorised by a qualified flight instructor;’ the whole flight mus t be conducted under the direct supervision of anauthorised flight instructor;

° weather conditions mus t permit the flight to be conducted under the VFR;° an entry has been made in the pilot’s log book stating that the pilot hassatisfied the night VFR handling requirements in an aircraft of the samecategory asthe aircraft used for the flight;

' there mus t be no passengers in the aircraft.

Handling RequirementsPrivate or commercial pilots mus t m e e t the same handling requirements asthose for the student pilot (refer to page 84).

RecentExperienceReference: CAO 40.2.2, Appendix 1, para 5.The following night recency requirements mus t be m e t by private and commer ‑cial pilots:° completion of a night flight of one‐hour duration in the previous year aspilot in command (PIC), acting in command under supervision (AICUS) ordual; and

' one take‐off and landing in the previous 6 months while flying at night asPIC, AICUS or dual or during an aeroplane flight review (AFR) or flighttest at night.

Passenger RequirementsReference: CAR 5. 82 and 5.109.To carry passengers, the pilot must have conducted three take‐ofls and landings atnight in the previous 90 days while acting aspilot in command or dual or havecompleted aflight test.

86 Night Flight

Night VFR Aeronautical ExperienceIn order to fulfil eligibility requirements for the nightVFR rating, the pilotmust:° hold aPPL;' complete 10 hours flying at night;' complete 5 hours in the category of aircraft for the rating sought;0 complete 2 hours in the circuit (one of the 2 hours in the circuit mus t be incategory of aircraft used for the test);

' complete 5 hours dual navigation; and' complete one dual cross‐country flight of at least 3 hours and 100 nm duringwhich the pilot mus t land at another airfield that is n o t in an area withsufficient ground light to create a discernible horizon.

Flight TolerancesAll manoeuvres and sequences conducted at night mus t be flown to the toler‑ances given in table 4‐1.

Heading 110°Speed :10 ktHeight :200 ft

Table 4-1 Flight tolerances.

Privileges and LimitationsReference: CAO 40.2.2 (8), (9), Appendix 1, para 3.

A pilot must n o t exercise the privileges of anight VFR rating unless that pilothas satisfactorily filled the recency requirements mentioned above. A nightVFR ratingauthorises the holder to fly anaircraft at night aspilot in commandfor private flights within Australia, providing the aircraft has a take-offweightn o t exceeding 5,700 kg.

TestingReference: CAO 40.2.2, Appendix 1.No theory exam is required for the night VFR rating (only an oral test priorto the flight test). To satisfactorily pass a night VFR test, the applicant mus tprove to be efficient and safe in the manoeuvres described below.


Manoeuvres by Sole Reference to InstrumentsThe applicant mus t demonstrate:- recovery from unusual attitudes;' normal turns of at least 180° left and right;' climbingand descending turns to apredetermined altitude and ataconstantairspeed;

' straight and level flight; and- climbing and descending flight.

Manoeuvres Using Visual Cues at NightThe applicant mus t complete:' a take‐off, circuit and landing;' abaulked approach; and° asymmetric flight in the cruise configuration for multi‐engine aircraft;

Correct Manipulation of the NavigationAidsfor which Endorsement is DesiredThe applicant must demonstrate:' anability to intercept andmaintain adesired track to and from astation; and- the solving of orientation problems.

Aircraft equipment mus t be considered carefully in determining whether orn o t an aircraft is suitable to fly at night. Considerations include external andinternal lighting, cockpit instrumentation, emergency equipment, radioequipment and radio navigation aid equipment. The following outlines theminimum equipment that must be serviceable for night flight.

Lighting

References: CAO 20.18 Appendix V; CARS 195 and 196.ExternalAircraft LightingAt night and in conditions of poor visibility, all external lights required forVFR flight must displayed. If any lights required for night VFR fail in flight,air traffic control must be notified immediately If you are unable to notify airtraffic control, you mus t land assoon aspossible.

88 Night Flight

Under VFR, the following external lighting mus t befitted for flight:one landing light;Note. In the case of charter flights with passengers, t w o landing lights arerequired; however a single lamp with t w o separately energised filaments isacceptable.asteady red light (the po r t navigation light), which m u s t be projected aboveand below the horizontal plane through an angle from dead ahead to 110°to the left of the aircraft; ‑asteady green light (the starboard navigationlight), which m u s t beprojectedabove and below the horizontal plane through anangle from dead ahead to110° to the right of the aircraft;awhite light (tail light), which m u s t project above and below the horizontalplane rearward through an angle of 140° (70° either side of the tail);an anti‐collision light, which mus t consist of aflashing red light visible in alldirections within 30° above and 30° below the horizontal plane of theaeroplane; andNote. Two anti‐collision lights are usually fitted ‐ o n e on the upper fuselageor fin and the other on the underside of the fuselage).wingtip clearance lights, which are required if the wingtips of the aircraft arem o r e than 2 metres from the navigation lights (wingtip clearance lights m u s tbe steady and of appropriate colours).Any aircraft parked on or adjacent to a m o v e m e n t area at night must be

clearly illuminated or lit, unless the area the aircraft occupies is marked byobstruction lights.

InternalAircraft LightingInstrument Illumination. Instruments and equipment essential for the safeoperation of the aircraft and used by the flight crew m u s t be illuminated andmus t m e e t the following requirements:

any illuminated instrumentation or equipment must be easily readable ordiscernible (as applicable);any direct or reflected rays must be shielded from the pilot’s eyes;the power source must be arranged so that if a failure of the normal sourceof power occurs, an alternative source is immediately available; andthe light m u s t emanate from fixed installations.

Intensity Control. There must be an intensity control for the instrument lightsso that the brightness of the lights will n o t affect the pilot’s ability to ready theinstrumentation and conduct the flight safely in all flight conditions.


Note. If it can be demonstrated in all flight conditions that the instrumen‑tation can be readadequately when n o t dimmed, an intensity control for theinstrument lights is n o t required.

Lighting in Pilot and Passenger Compartments. There mus t be sufficientlighting in the pilot compartment to enable pilots to readmaps and flight doc‑uments. Al l passenger compartments mus t also be lit.

Emergency Lighting. A shockproof electric torch is required for each c rewmember on board.

Cockpit InstrumentationThe following instrumentation mus t be serviceable:' anairspeed indicator;- an altimeter with an adjustable pressure datum graduated in millibars (hec‑topascals);

- amagnetic compass;0 an accurate timepiece ‐ either a fixed clock in the aircraft or a timepiececarried by the pilot ‐ that indicates hours, minutes and seconds;

° an outside temperature indicator;' anattitude indicator (artificial horizon);' a heading indicator (directional gyro);' a turn-and‐slip indicator (or only aslip indicator if asecond attitude indica‑

t o r usable through aflight attitude of 360° of pitch and roll is installed); and' an indicator that shows whether or n o t power is being supplied to the gyro‑scopic instruments.

Private,Airwork and Charter under Night VFR

Reference: C A 0 20. 18.The flight manual (or approved alternative) for each aircraft will stipulate theinstruments and indicators required for flight. The airspeed indicator andaltimeter mus t be able to be supplied by either a normal or an alternate staticsource, but n o t both sources simultaneously. Alternatively, the airspeed indi‑cator and altimeter may be connected to abalancedpair of flush static ports.For aircraft operating under the charter category, the attitude indicator,

direction indicator (DI) and turn‐and‐slip indicator mus t have duplicatedsources of power unless the turn‐and‐slip indicator (or a second attitudeindicator) has a separate source of power which is independent of the powersupply for the gyroscopic instruments.

90 Night Flight

The instruments mus t be serviceable prior to take‐off for all charter flightsunless:' flight with the unserviceable instrument is permitted by CASA;- the unserviceability is apermissible unserviceability asset o u t in the mini‑m u m equipment list for the aircraft; or

° in the case of an approval to fly with an unserviceable instrument, any c o n ‑ditions stipulated by CASA are followed.Any unserviceable instruments mus t be either removed from the aircraft or

placarded as‘Unserviceable’.

Emergency EquipmentReference: C A 0 20. 11.The pilot in command is responsible for ensuring that appropriate and ade‑quate equipment is available on boardanaircraft for emergency situations. Thepilot in command must make provisions for equipment and other resourcesappropriate to terrain and climate asrequired for sustaining life.

Over Water FlightsLife jackets, life rafts and emergency signalling equipment are required underthe circumstances outlined below.Life Jackets. Lifejackets are required for:' single‐engine aircraft when the aircraft is flying ou t of gliding range of land;and

0 multi‐engine when flights over water exceed 50 nm .

Note. Al l occupants must wear life jackets during flight over water at orbelow 2,000 ft in single‐engine aircraft outside gliding range of land.There mus t be one life jacket on board for each occupant, and life jackets

must bestowedat‐ or adjacently to ‐ each occupied seat. If infants are carried,suitable life jackets must be made available and they must be easily accessible.Life Raftsand Signalling Equipment. Life rafts are required when flying adistance over water equivalent to 30 minutes at normal cruising speed or100 nm, whichever is the lesser. Life rafts are carried in addition tocompulsory lifejackets, and there mus t be sufficient places available in life raftsfor all occupants on board the aircraft. Life rafts mus t be clearly marked ifstowed in compartments or containers, and they must be readily accessible inthe event of any ditching situation.


Signalling equipment must be carried on all flights requiring life rafts. Thisequipment includes:° one emergency [orator transmitter (ELT) when one life raft is carried and at least

t w o beacon transmitters when two or more lift rafts are carried; and' asupply of pyrotechnic distress signals.Note. Single‐engine aircraft are n o t required to carry life rafts but arerequired to carry lifeackets. They mus t carry anELT if they are n o t capableof continuous air‐ground communications. The beacon transmitter mus tbe able to operate on frequencies 121.5 MHz and 243 MHz and mus t bestowed where it can be easily accessed in an emergency.

Briefing of PassengersOn flights where survival equipment is required, all passengers must be briefedon the location and use of all emergency equipment before take‐off.For charter operations, this briefing mus t be specified in the aircraft’s

operations manual or in another document as specified in the company’soperations manual.The briefingmust take place before take‐off if the flight is to depart directly

over water, otherwise it mus t take place and be completed before the overwater segment of the flight.Emergency Locator Transmitter (ELT)An ELT mus t be carried on all flights except:' flights conducted wholly within 50 nm of the departure aerodrome;' when conducting agricultural operations; and° when special permission has been granted by CASA.

Radio EquipmentReferences: A IP GEN 1.5; A IP ENR 1.1para 19.1.The following radio equipment is required for all night VFR flights:° one VHF radio capable of continuous communications with ATS from onthe ground at the departure aerodrome until 0 11 the ground at the destina‑tion aerodrome; and

0 aHF radio if flying through aremo te designated area without anELT or ELBon board.Aircraft radio systems mus t beproperly installedand befunctioning prior to

departure. They mus t also be of a type approved by CASA.Note. In all night VFR operations, the VHF communications systems mus tbe able to operate on all VHF frequencies necessary for required reports andbroadcasts along the flight asspecified in AIP E N R 1.1paragraph 19.1.

92 Night Flight

Charter OperationsFor charter operations, one HF radio is required if continuous communicationcannot be maintainedwith ATS. This HF radio m u s t be capable of communi‑cations with ATS during the required period, and it mus t have fiequenciesappropriate to the area of operation.

HF radio is n o t mandatory if the requiredreports and broadcasts throughout theflight can be satisfied and radio communication can be maintainedwith aproperlytrained company representative who is able to communicate with ATS by phone.

Radio Navigation EquipmentReference: A IP G E N 1.5.When flying under night VFR, a minimum of one of the following navaidsm u s t be carried and be serviceable:° ADF;' V C R ; o r- GPS.

Note. GPS is subject to AIP GEN 1.5, section 8.

TranspondersNight V F R flights mus t have the following codes displayed on their Mode 3Atransponder:° 3000 when operating in controlled airspace;- 1200 when operating outside controlled airspace; or0 the code designated by ATC.

Suitable to be Flown?43'~7e;~:;s:;:,:;:mm,gzlgqaisgmag‘ 21., A v

Lateral Navigation RequirementsFlight under the VFRWhen operating at or below 2,000ft, the aircraft m u s t be navigated byvisual reference to ground or water.When navigating by visual refer‐ DME i 2 “mence to ground or water7 the pilot Table 4-2 Navaid tracking tolerances ‐ controlled

mus t positively fix the aircraft’s a'rSpace'

position every 30 minutes by reference to features on topographical charts.AT C must be notified if your track diverges by more than 1 nm from the

clearance given by AT C in controlled airspace. You must also notify AT C if you

Navaid ToleranceLocaliser or VOR half-scale deflectionNDB or locator ¢ 5 °


are navigating by reference to a navigation aid and your track diverges by morethan the tolerances listed in table 4‐2.

Flying with Reference to NavigationAidsIf you are to navigate with reference to navigation aids, you mus t only specifyon your flight plan the navigationaids with which your aircraft isequipped andwhich you are qualified to use. You are deemed to have suitable qualificationsfor navaid use if you are:- IFR‐rated; or- both night VFR‐rated and endorsed on the particular navigation instrumentspecified; or

- aPPL holder or above who has been instructedby aqualified flight instructorto navigate on anaid asthe sole means of navigation and is competent to usethat aid.You must obtain a positive radio fix at intervals n o t exceeding 2 hours. A

positive radio fiX is determined by the passage of anaircraft over anNDB, V O Rstation or DME or by the intersection of t w o or mo r e position lines fromNDBs,VORs, DMEs or localisers (positionlinesmust intersect atanangle of n o t less than45°). If the position lines that determine afix are entirely fromNDBs, the NDBsmust bewithin arange of 30nm from each other.

Range of NavigationAidsNDBs. An ND Bmay contain more than one range depending on the time (dayor night) and on the terrain the signal is travelling over. For example, theext rac t from ERSA for the N D B atWynyard reads, ‘071/1.0 Range 65 (HN60), OW 160 (HN 110)”. This tells us that the NDB is 071°M from the r u n ‑ways at a distance of 1 nm and the ranges are:° 65 nm during the day over land;' 60 nm at night over the land (HN = hours of night);° 160 nm during the day over water (OW = over water); and- 110 nm during the night over water.Note. NDB ranges are found in ERSA.

94 Night Flight

VORs or DMEs. Reference:A IP G E N 15) para 2' 2. Aircraft Altitude Rated Coverage_ Below 5,000 ft 60 nm

Table 4‐3 lists the rated cove 5,000 ft to below 10,000 ft 90 nm

“ a g e for VORS or DMES- 10,000 f t t o below 15,000 ft 120 nmAlthough V C R ranges are 15,000 f t t o below 20,000 ft 150 nmn o t found in ERSA, it does 20,000 ft and above 180 nminclude information onrestrictedrange or errors thatmay occur. An example ofthis is the Wonthaggi VOR, for which the extract from ERSA reads, ‘ VORWO N 115.9 S38 28.3 E145 37.4 (2) Pilot monitored’. This means that theV C R atWonthaggi operates on afrequency of 115.9 MHZ, and it is located ata latitude of 38° 283' south and 145° 37.4’ east.The ‘(2)’ in the extract means that n o t e 2 applies to the navigationaid. Note

2 states, ‘RESTRICTION: AVBL only for enroute navigationABV 4000 FTB T N305 ‐ 030 8c110 ‐ 190 & ABV 8000FT B TN 031 ‐ 109 & 1 9 1 ‐ 304.’This means that the Wonthaggi V OR may only be used for navigation whenflying above 4,000 ft in the region from 305° to 030° and 110° to 190° fromthe V C R andwhen flying above 8,000 ft in the region from 031° to 109° and191° to 304° from the VCR.Localisers. Table 4‐4 o u t ‑lines the rated coverage for

Table 4-3 VOR/DME rated coverage.

Aircraft Altitude Rated Coverage. . A12,000ftAGLwithin 110° 25 nmlocalisers nominated for of course line.

Position fixing at ranges Below 5,000 ft 30nmbeyond 25 mm 5,000 ft and above. 50nm

Table 4-4 Localiser (LLZ) rated coverage.TimeWhen flying, you must ensure that your timepiece is accurate to within i 3 0seconds. Some aerodromes also have a time check at the end of the ATIS, e.g.if you listen to 132.7 kHz in the Melbourne area, you can obtain atime checkto the nearest 30 seconds.

Diver-ting Off TrackWhen flying in controlled airspace, you mus t request a clearance prior todiverting off track except in the case of an emergency. If you are in controlledairspace and you consider adiversion necessary due to weather but you are o u tof radio contact with flight service, you should declare apan‐pan on the appro‑priate frequency.


Avoiding ControlledAirspaceVFR aircraft operating in Class G or Class E airspace using NDB, V O R / TA Cor dead reckoning (DR) asmethods of navigation must apply the appropriate

_tolerances to ensure that controlled airspace is avoided. The tolerances, whichmay be rounded up to the nearest halfdegree, are asfollows:' N D B i690 ;' V O R / TA C i 5 2 0 ; and0 DR i12°.

Note. When tracking via DR, Height AGL Tolerance to_ bei 9 ° maybeusedif the initial track appl'ed at mghtguidance is provided by NDB, At or below Z'OOOft :2 nmV C R o r TA C A N and there i sn o 2'001 t o5'000 f t * 3 " msubsequent change of track. 5001 to 101000 ft “:5 “m

_ . . . 10,000 ft to FL200 :8 nmVisual. For Visual nav1gation, FLZOSt FLSOO 12. . 1night VFR aircraft mus t apply the 0 nm

. . F|305 to FL400 : 1 8 nmtolerances listed in table 4‐5 toavoid controlled airspace (unless Table 4-5 Tolerances foravoiding controlled

airspace ‐ Visual navrgatlon at night.you have a clearance to enter).

Cruising Levels 000°

Reference: AIP ENR 1.7, para 5.Flights are to be flown according to ICAOconvention: VFR

EVEN' for magnetic tracks between 360°/000° and Thousands ODD

179°M-‐ odd thousands plus 500 ft; and Plus Thousands500 Plus

500° for magnetic tracks between 180° and359°M ‐ even thousands plus 500 ft.Note. The same rule applies above the tran‑sition level ‐ odd or eve levels plus 500 ft.VFR pilots may fly at random levels below Figure 4-1 VFR cruising leVElS‑5000 ft if outside controlled airspace.

180° VFG‐OZDEPS

Traffic Separation ServiceATS provides separation between VFR and IFRflights in Class C and Class Dcontrolled airspace. In Class E controlled airspace, GAAP control zones andClass G non‐controlled airspace, no separation is provided by AT C and thepilot is solely responsible for maintaining separation. Flight is n o t permitted inClass A airspace.

96 Night Flight

Vertical Navigation RequirementsLowest Safe Altitude (LSALT)References: CAR 174B;AIP G E N3.2 and 3.3.The LSALTS specified on the charts are for IFRflights, but they may be used forVFR flights. The minimumpublishedLSALT is 1,500 ft. If you are studying alow‐altitudeERC, the LSALT isspecifiedadjacent to the distance bubble. Thereisalso agrid LSALT:- on the ERC ‐L and the TAC, the grid LSALT is displayed in the centre of agrid square of 1° of latitude by 1° of longitude; and

- on anERC‐H, the grid square is 4° of latitude by 4° of longitude.

Height Required above an Obstacle. For a night VFR flight, you mu s t plan tofly at least 1,000 ft above the highest obstacle located within 10 nm of yourflight‐planned track except:' during take‐off and landing;' when the destination aerodrome is in sight and you are within 3 nm of theaerodrome (circling area); or

- when you are being radar‐vectored.

Additional Tolerances for Obstacle Clearance. For obstacle clearance, a radiusof 5 nm plus an additional 20% of the air distance flown from the last positivefix must be applied to the DR position if:' the navigation of the aircraft is inaccurate;0 the aircraft is deliberately flown off track; or' anormally available radio navigation aid has failed.In any of the above cases, the aircraft mus t be at least 1,000 ft above obstacles

within the specified area.

Descent below LSALTunder Night VFRAn aircraft flown under night VFR may only descend below the LSALT if:t the pilot has positively determined that acritical obstruction has beenpassedand the aircraft remains at least 1,000 ft above any other obstacles within 10nm of track; or

° the aircraft is Within 3 nm of the aerodrome and the pilot has the aerodromein sight; or

° the aircraft is in controlled airspace and the pilot is given the clearance:‘. ..cleared visual approach’, in which case descent may be commencedwhen the aircraft is within 3 nm of the aerodrome and the pilot has theaerodrome in sight.

4: Night Flight Rules and Requirements

Note. If you are cleared for avisual approach, you mus t nand headingascleared by AT C untilwithin 3 nm of the amust join the circuit asdirected by ATC.

Weather Requirements for Night VFR H, x‘ ‘ A W }

Reference: A IP E N R 1. 1.When planning for anight flight, you must consider cloud, visibility, wind andother generalweather conditions asyou would for aflight by day. However, it ismuch m o r e difficult to see cloud at night, soyou must make a careful study ofthe weather in conjunctionwith the terrain in the vicinity of your plannedflight.

For night VFR, you m u s t plan for an alternate during the currency of, andup to 30 minutes before, the commencement of any of the conditions listed intable 4‐6:

Cloud A total of more than SCT below 1,500 ft.Visibil i ty Less than 8 km or greater than 8 km, but the forecast con‑

sists of a percentage probability of fog, mist, dust or anyother phenomenon that reducesthe visibility below 8 km.

Wind A crosswind or downwind component, which is greater thanthat specified as the maximum for the aircraft you are flying.Table 4-6 Weather requiring an alternate for night VFR.

Cloud amounts are cumulative; for example, FEW010 and FEW012 wouldn o t require an alternate asyou have up to 2 oktas at 1,000 ft and up to 2 oktas at1,200 ft (2 oktas + 2 oktas = 4 oktas). However, FEW010 + SCT012 wouldrequire an alternate asthe cloud is up to 2 oktas at 1,000 ft and up to 4 oktas at1,200 ft (2 oktas + 4 oktas = 6 oktas > SCT).

The following list is used determine cumulative cloud amounts:FEW + FEW = SCT;FEW + SCT = BKN; andSCT + SCT = B K N or OVC.

What if the Weather Conditions are Forecast to Improve?f the weather conditions are forecast to improve, you do n o t need to plan toLOld for analternate if you carry enough fuel to holduntil the time the weather; forecast to improve plus anadditional 30 minutes. For example, you plan torrive at Point Cook at 1045 U T C and you obtain the following TAF:

AMD TA F YMPC 0 8 2 0 8 0 0 0 FEWOOB SCT010 3 6 0 2 0 K T F M 11 9 9 9 9SCT020 BKN040 3 6 0 1 7 K T Q 1 0 1 5 1 0 1 4 1 0 1 2 1 0 1 1 T 1 6 1 5 1 3 1 2

/ Night Flight

/T his indicates that the weather is forecast to improve to above the alternateminima from 1100 UTC . Therefore, you can either plan for an alternate orcarry sufficient fuel to reach your destination plus an additional holdingamount of 45 minutes (this includes the time from your expected time ofarrival (ETA) to the time the weather is forecast to improve (i.e. fifteenminutes) and the thirty~minute buffer required by the AIP).

What if the Weather is only below the Alternate Minima duringIntermittent (INTER) or Temporary (TEMPO) Periods?

In the case of weather that is only below the alternate minima during intermit‑ten t (INTER) or temporary (TEMPO) periods, you do n o t have to plan foran alternate. However, you mus t carry holding fuel for the period of theINTER or the TEMPO plus 30 minutes either side. If the forecast indicatesan INTER, the holding amo u n t is 30 minutes. If the forecast indicates aTEMPO, the holding amoun t is 60 minutes.

Examples of INTER and TEMPOAMD TAF YMPC 0820 8000 FEWOZO SCTOlO 36020KT INTER 08165000 FEW008 SCTOlO Q 1 0 1 5 1 0 1 4 1 0 1 2 1 0 1 1 T 16 15 13 12

In this example, holding fuel mus t be carried due to visibility below 8 kmand cloud greater than SCT below 1500 ft for periods of less than 30 minutesfrom 0800 U T C to 1600 UTC . You mus t also add a thirty‐minute buITereither side. Therefore, if you plan to arrive between 0730 U T C and 1630UTC, you must take 30 minutes of holding fuel or sufficient fuel to fly to asuitable alternate aerodrome.

AMD TAF YMPC 0820 8000 FEWO2O SCTOlO 36020KT TEMPO 08165000 FEW008 SCTOlO Q 1015 1014 1012 1 0 11 T 16 15 13 12

In this example, holding fuel mus t be carried due to visibility below 8 kmand cloud greater than SCT below 1500 ft for periods of less than 60 minutesfrom 0800 U TC to 1600 UTC. You must also add a thirty-minute buffereither side. Therefore, if you plan to arrive between 0730 U T C and 1630UTC, you mus t take 60 minutes of holding fuel or sufficient fuel to fly to asuitable alternate aerodrome.

Thunderstorms and Severe TurbulenceIf thunderstorms, severe turbulence or aprobability of either phenomena areforecast, you must plan for analternate unless these conditions only occur dur‑


ing INTERor TEMPO periods. If these conditions occur during an INTERor TEMPO, you mus t carry 30 or 60minutes of holdingfuel asspecifiedabove.

What if There Is a From (FM) Period on the Forecast?If afrom (FM) period results in the weather deteriorating below the alternateminima, you must plan for an alternate from 30 minutes before commence ‑m e n t of the deterioratingweather.Examplesof FM Periods. AMD TAF YMPC 0820 8000 FEWOZO SCT030

36020KT FM11 9999 SCT008 BKN010 36017KT Q 1015 1014 10121 0 1 1 T 1 6 1 5 1 3 1 2

In example 8‐3, the cloud is greater than SCT below 1500ft from 1100UTC.Youmust place athirty‐minute buffer atthe commencement of the deterioratingweather. Therefore, if your ETA is 1030 U T C or after, you mus t plan for analternate. If the FM period results in the weather improving from that forecastbelow the alternate minima, you must plan for analternate from 30minutes afterthe weather is forecast to improve.

AMD TAF YMPC 0820 8000 SCT008 BKNOlO 36020KT FM11 9999FEWOZO SCT030 36017KT Q 101 5 1 0 1 4 1 0 1 2 1 0 1 1 T 16 15 13 12

In example 8‐4, the cloud is greater than SCT below 1500 ft up unti l 1100UTC . You must place a thirty‐minute buffer at the commencement of theimprovingweather. Therefore, if your ETA is 1130 U T C or before, you mustplan for an alternate.

What if the Forecast Is Provisional?If the destination forecast is provisional (PROV), you mus t plan for an alternateaerodrome that has afirm forecast (you cannot plan to fly to analternate that hasaprovisional forecast).

TTF versus TAFIf you are flying to an aerodrome that has avalid trend typeforecast (TTF), thereis no requirement to apply buffers during the time the TTF is valid. Therequirement for buffers is removed from TTFs asthey provide a continuousweather watch for aperiod of 3 hours. If the TTF has t w o visibilities, you willneed to plan for analternate if the greater Visibility is less than 8 km.

Joining the Circuit in Class G Airspace (OCTA)Whenyou approachaCTAF atnight,you shouldhave afair ideaof thewind con ‑ditions from the drift experienced throughout the flight and from the forecast

100 Night Flight

obtained prior to departing. However, unless the aerodrome has an ATIS orAWS, it isrecommendedthat you overfly andcheck the primarywindsock to ver‑ify wind direction and strength.When you are within 3 nm of the aerodrome and have it in sight, you may

descend below the LSALT. You should remain at least 500 it above the circuitheight (i.e. 1,500 ft AAL) until you have determined which runway you areusingandyou are positioned on the dead side. You must complete at least threelegs of the circuit and sothe latest you mayjoin the circuit is downwind. Also,you may n o t descend in the circuit; therefore, the mos t practicalpoint to join thecircuit is crosswind or upwind (deadside). If you choose to join downwind, youshould only descend to circuit height outside the circuit area. You must n o t flyfrom the dead side of the circuit to the live side and descend while on the liveside. Also no t e that some airfields have restricted circuit direction at night.Note. A straight‐in approach may be impracticable at a CTAF aerodrome,depending on your LSALT. Asdescent below your LSALT isn o t alloweduntilwithin 3nm of the aerodrome,youmayhave insuflicient time to descendwith‑ou t an excessive rate of descent.

Aerodrome LightingReferences: A IP AD 1.1para 4.

Permanent Runway LightingPermanent Threshold LightsPermanent threshold lights are green, and the spacing and pattern of these,lights vary depending on the aerodrome (spacing dimensions can be found inAIP AD 1.], paragraph 4). Permanent threshold lights are green only in thedirection of the approach, with the exception of the outer light at either sideof the runway, which are in line with the runway edge lights and are omni‑directional.

Runway Threshold Identification LightsThere may be t w o flashing white lights (strobes) when a runway thresholdneeds to bemade more conspicuous (for example, when the runway thresholdis displaced). There will be one light on each side of the runway in line withthe threshold, and these lights will flash at afrequency of anywhere in between60 and 120 flashes per minute. These lights are visible only in the direction ofthe approach to the runway.


DisplacedThreshold LightingLighting is used to indicate displaced thresholds in the following situations:' if the threshold is temporarily displaced, apattern consisting of t w o groupsof three lights with agroup of lights on either side of the runway is used;

0 if the runway is available for taXiing or take‐off prior to the thresholdbecoming displaced, the runway end has red, unidirectional lighting that isscreened from approaching aircraft;

- if any length from the other end of the runway is available for take‐off orlanding prior to the threshold becoming displaced, the runway edge lightsare white and are screened from approaching aircraft; and

0 if the threshold is displaced due to an unserviceable runway, yellow ororange lights are used to outline the area of unserviceability.

RunwayEdge LightingThe longitudinal spacing of runway edge lightingfor instrument approach r u n ‑ways is 60metres. The longitudinal spacing of runway edge lighting for n o n ‑instrument or non‐precision approach runways at country aerodromes is 90m.Runway edge lightingiswhite, except for adisplaced threshold, in which case

the runway end lights are red in the approach direction. Runway edge lightingis omni‐directional when the intensity stages are between 1 to 3, and it isunidirectional when the intensity stages are between 4 to 6. For precisionapproach runways, the lighting in the final 600 metres of the runway is yellow.For anarrow runway (i.e. with awidth of less than 30 metres), the lateralspacingof the runway edge lights isbased on that of athirty‐metre wide runway.

Runway EndLightingThe far end of arunway isnormally indicatedwith six evenly spaced redlightsthat are unidirectional. If the runway end and the threshold lights are c o ‑located, the lights are bidirectional and coloured red (towards the runway) andgreen (towards final approach).

Runway Centre/ine LightingThe centreline (i flit) has white lights from the threshold to apoint 900 metresfrom the end of the runway. The lights then alternate between red and whiteto apoint 300 metres from the end of the runway. The lights for the final 300metres are red.

Runway Touchdown Zone LightingRunway touchdown zone lighting isprovided for all runways with aCategoryII instrument landing system (ILS) installed. The first 900 metres of the

702 Night Flight

runway consist of fifteen crossbars (barrettes) of white, uni‐directional lights.There are six stages of intensity available.

UnserviceableAreasUnserviceable areas are illuminatedwith steady red lights.

Stopway LightingStopway lighting is only provided if the runway is less than 1,500 metres inlength. Both the side lights and the end lights are red, and they are screenedfrom aircraft approaching to land from over the stopway.

Taxiway LightingThere are t w o types of taxiway lighting:- side lighting, which consists of fixed, blue lights located on either side of thetaxiway; or

0 guideline lighting, which consists of fixed, green lights along the centreline ofthe taxiway.

Apron Exit LightsApron exit lights are only used if there is an extensive system of taxiways. Thetaxiway lights at the exit from the apronwill flash the same colour asthe taxi‑way lights.

Runway Exit LightsThe taxiway centreline lightingis extended to the runway centreline on taxiwaysused to exit runways. These runway exit lights are spacedatfifteen‐metre inter‑vals and continue to the holdingpoint. This lighting consists of alternate greenand yellow lights.

Rapid-Exit Taxiway LightsOn rapid‐exit taxiways, the taxiway centreline lighting is extended from therunway centreline by lights spaced at fifteen‐metre intervals. This lightingextends to the point at which the taxiway changes from ahigh-speed taxiwayto anormal taxiway (i.e. it shows the rapid‐exit radius).

Taxi-Holding Position LightingTaxi‐holding position lighting consists of three yellow lights in the direction ofthe approach of the runway. On taxiways with side lighting, there are only t w oyellow lights in line with the holdingpoint.

4: Night Flight Rules and Requirements >

Hold-Short LightsHold‐short lights are only installedon runways usedfor landand hold’ww‘m rations (LAHSO). These lights indicate the position of the hold‐short line,which is 75 metres from the intersecting runway centreline. The lights arewhite, unidirectional and are situated in a r ow of siX across the runway. Theyoccult (fade in and out) approximately thirty times per minute.Note. There are also runway intersection signs and hold‐short positionmarkings.If a pilot is instructed to land and hold short, that pilot mus t n o t cross the

hold‐short lights. However, a clearance to take‐off, land or cross theintersection after completing a LAHSO permits the pilot to cross the hold‑short lights.

Apron LightingFlood lighting is used for apron areas, and care is taken to minimise glare andshadows.

Approach LightingThere are six stages of intensity for precision approach lightingand three stagesfor other multi‐stage systems. The tower controller usually selects the initialintensity according to conditions, but the intensitymay bevaried at the requestof the pilot.Note. Pilotsmay request for alower or higher intensity, rather than aspecificsetting.Pilots will be advised when the equipment is selected in a visibility of

5,000 metres or less.

SimpleApproach Lighting (Lead-inLights)Simple approach lighting is used for non‐precision instrument approach run ‑ways or non‐instrument approach runways. These lights are white andsituatedin a line (figure 4‐2).

Basic approach lighting

W ‘ 3 0 m

lR-lO29A.EP5

Figure 4-2 Simple approach lighting.

x////6/4 Night Flight

//PrecisionApproach Lighting (Lead in Landing Lights)Precisionapproach lighting is also white. It consists of a coded line for a cate‑gory I (CAT I) precision landing system asshown in figure 4‐3. Five bars arestandard; however, there are locations with four or six bars.

5 . . . . . . . . . - - - - - - - - - - Precision approach: ' ' ' ° - " ~ 3 2 . . . . . 2 1 : |ightinngat.1

. ' IR-l0293.595

Figure 4-3 CAT I approach lighting.

Approach lighting for a category II (CAT II) precision approach is shown infigure 4‐4:

Precision approachlighting: Cat. 2

IH-10290.EPS

Figure 44 CAT II approach lighting.

Aerodrome BeaconsAerodrome beacons are designed to be visible from a distance of at least 8 kmfrom altitudes rangingfrom 1,000 ft to 5,000 ft in restrictedvisibility. The bea‑con may show alternating white and green flashes or white flashes only.Beacon lighting is on at the following times where ATS units are established:' at night;° during times of reducedvisibility; and' during the day when the ATS unit is open.If there is very little traffic at an aerodrome, the beacon is only displayed for

known movements, but it is available on request.

Obstacle LightingObstacles or terrain at an aerodrome are lit if they lie within:' the obstacle limitation surface area; or' the movemen t area.


Note. Obstacles will n o t be lit if they are shieldedby obstacles or terrain thatare already lit.There are three types of obstacle lighting:

' asteady, low‐intensity red light;' amedium‐intensity flashing red light for use when anearly or special w a r n ‑ing is required (this is also known asahazard beacon); and

0 a flashingwhite lightwhichmarks tall structures and is used in day andnightoperations (this is also known asastrobe).

Lane of Entry Strobe LightsSome lanes of entry near GAAP aerodromes are lit with strobe lights which aresituated along the centreline of the lane of entry (LOE). These strobe lightsare indicated on relevant visual terminal charts (VTCs).

Pilot-Activated LightingPilot-activated lighting (PAL) is a system through which the pilot can t u r n on alightingsystem using acoded VHF carrier wave. The availability of the systemwill be noted on the aerodrome/landing chart and in ERSA for the aerodromeconcerned. The following lighting is included:' runway lighting;° taXiway lighting;' apron lighting;' VASIS lights; and° wind indicator lights.

How to Activate PALReference: ERSA INTRO.To activate PAL, select the correct VHF frequency prior to taXiing or within15 nm of an aerodrome. Push the transmit button three times ~ each transmis‑sion may be no more than five seconds and no less than one second duration.While there is no limit on the length of the break between each transmission,the three pulses mus t be completed within 25 seconds (e.g. say ‘pilot activatedlighting’ three times slowly with abutton release in between).The lights will illuminate for a minimum of 30 minutes, and the wind

indicator lights will flash continuously for 10 minutes to wa rn when therunway lights are about to extinguish. To reset the lights, repeat the activationprocedure.

706 Night Flight

Aerodrome FrequencyResponse Unit with PAL (AFRU+ PAL)PAL operations are provided asan additional function for some aerodromefre‑quency response units (AFRUS) on the CTAF frequency associated with anaerodrome. This lighting is only available at night or during periods of poorvisibility, and it will n o t activate when the natural lighting is above a presetlevel. On some units, there is also a discrete frequency so that the lights maybe activated Via the discrete frequency or via the CTAF frequencyWhen PAL is combined with an AFRU system, the following procedure

mus t be followed in order for the system to activate:0 the correct frequency mus t be selected;' apulse of no more than one second must be transmitted three times; and- the breaks between each pulse must beof no more than one second duration.When the AFRU + PAL system is activated via pilot transmission, the

runway and wind indicator lights will illuminate. The aerodrome frequencyresponse unit will also transmit a standard reply consisting of the aerodromename and the CTAF (as applicable) followed by ‘ranway lights on’.Note. If the runway lights do n o t illuminate, the message ‘no runway lights’ willbe heard.The lights will remain on for 30 minutes. After 20 minutes, the windsock

lights will flash at one‐second intervals, and the aerodrome frequency responseunit will transmit the message, ‘ranway lights 10 minutes remaining’. If the pilotretransmitts to activate the lights, they will be reset for 30 minutes again.

Wind Direction Indicator LightingThe primary wind indicator is illuminated during night operations. Otherwindsocks may also be illuminated. The Wind direction indicator lighting isincluded in the PAL system unless ERSA specifies otherwise.

Visual Approach Slope Indicator System (VASIS)There are t w o types of visual approach slope indicator system (VASIS) lightingapproved for use within Australia: the T‐VASIS and the precision approach pathindicator (PAPI). The T‐VASIS is ahigh‐intensity lightingsystem, which con ‑sists of white lights. The PAPI system uses both red and white lights. Bothsystems may be used during day and for night operations. Standard systemsprovide an obstacle clearance of at least elevenmetres above a19° slopeWithinan azimuth splay of 7.50 either side of the runway for a distance of 5 nm fromthe threshold and a distance of up to 7 nm from the threshold of an ILS‑equipped runway


FVASISThe T‐VASIS system uses lights in the shape of a T. When only the lights ofthe crossbar are lit, an on‐slope indication is represented. Lights above thecrossbar indicate that the aircraft is t o o high and shouldfly down. Lights belowthe crossbar indicate that the aircraft is t o o low and should fly up (figure 4‐5).

High: fly down On slope Low: fly up a n m s m

Figure 4-5 T-VASIS and lead-in lights.

The height of your eyes above the threshold with reference to the lights isgiven in table 4‐7 (the T‐VASIS aim point is 1,000 ft in from the threshold).

Approach Slope Indication Eye Height above Threshold

3L igh ts f | y up 0 f t ‐ 7 f t

2 Lights fly u p 7 f t ‐25 f t

1 Light fly up 25 f t ‐41 f t

On slope 49 ft

1 Light fly down 57 ft ‐ 75 ft

2 lights fly down 75 f t ‐94 f t

3 lights fly down 94f t ‐176f tTable 4-7 T‐VASlS indications.

At night, the azimuth splay is usually increased to 30° to allow the T‐VASISto be seen on the base leg. However, the T‐VASIS should n o t be used for slopeguidance until the aircraft is aligned with the runway. This is because theobstacle clearance is n o t guaranteed until the aircraft is within the runwayapproach obstacle limitation surface.There is also an abbreviated version of the T‐VASIS, known as the AT‑

VASIS, for which equipment is located on one side of the runway only(generally the left).

108 Night Flight

PA Pl Legend

The precision approach path indicator sys- I RedEl White Too hight e m consists of a r o w of four light boxes

(slightly)aligned at right angles to the runway. D E I D ‑The lights are usually positioned on theleft‐hand side of the runway abeam theaim point. Some PAPIs use lights onboth sides of the runway. PAPI indica‑tions are given in table 4‐8. |___] E] I I

Note. The four red lights will remainVisible until ground impact, and youwill n o t be given any further indica‑tions of descent below the 2.5° D. I I

On slope

Too low(slightly)

Ifi-24DS.EPS

gIIdCSIOPe' Figure 4-6 PAPI.

Lights Indication Glideslope

Four white lights Too high glideslope is more than 3.5°

Three white lights and Slightly high glideslope is approximately 33°one red light on the right

Two white and two red lights On slope glideslope is 3°

One white light and Slightly low approximately 2.7"three red lights to the left

Four red lights Too low less than 2.5° slope

Table 4-8 PAPI indications.

Aerodrome SuitabilityIs the Departure Aerodrome Suitable?

Aerodrome suitability is necessary to consider in the event the departure aero‑drome becomes the destination aerodrome. This type of situation could occurif the weather on track is n o t asforecast and a re tu rn is necessary, or if there arein‐flight problems with the aircraft and a return to the destination aerodromeis required.

Is the Destination Aerodrome Suitable?Prior to departure, you must determine if the destination aerodrome issuitable.An alternate aerodrome m u s t be planned if you have any doubts about the


availability, suitability or reliability of lighting, navigation aids, standby power,a responsible person or weather.

LightingThe following conditions at the destination mus t be me t :0 for aerodromes with portable lighting, aresponsible person must be in atten ‑dance from at least 30minutes before ETA to the time landingand taxiing hasbeen completed;

' for aerodromes with electric lighting (including PAL) without standbypower, there mus t beportable runway lightingandaresponsiblepersonmus tbe in attendance for 30 minutes before the ETA to the time landing andtaxiing has been completed; and

0 for aerodromes with PAL and standby power, a responsible person must be inattendance from at least 30 minutes beforeETA to the time landingand taxiinghas been completed.If flyingto anaerodrome that does n o t havePAL,you must ensure that the lights

are working flom30 minutes before the expected arrival until landingand taxiingis completed. If conditions at the destination aerodrome are n o t met, flight to analternate aerodrome needn o t beplanned if the aircraft has sufl‘icient fuel on boardfor flight to the destination plus holdinguntil first light, aswell asenough fuel forafurther 10minutes (plus the fixed reserve).

NavigationAidsThe flight mus t provide for asuitable alternate within one hour’s flight time ofthe destination, unless the destination aerodrome is served by aradio navigationaid (NDB/VOR) and the aircraft is fittedwith the appropriate radio navigationsystem capable of using the aid, or the aircraft is fitted with an approved GPSand the pilot is rated.

WeatherThe destination aerodrome isn o t suitable for night VFR flights if weather con ‑ditions fallbelow the alternateminimumduring the currency of, or 30minutesprior to, the forecast commencement o f the following:0 total cloud cover of more than SCT below the alternateminimum (1,500 ft);0 visibility less than the alternate minimum (<8 km);0 visibility greater than the alternate minimum, but the forecast is endorsedwith a percentage probability of fog, mist, dust or any other phenomenonwhich restricts visibility below the alternate minimum; or

0 crossvvindor downwind component of more than the maximumfor the aircraft.

770 Night Flight

When weather conditions are expected to be as stated above but areexpected to improve by a specific time, there is no need for an alternateaerodrome if sufficient fuel is carried to allow the aircraft to hold until thatspecific time plus 30 minutes.When thunderstorms or intermittent or temporary deterioration in the

weather are forecast, there is no needfor an alternate aerodromeproviding thatadditional fuel is carried to allow the aircraft to hold for the following:- 30 minutes for INTER; and' 60 minutes for a TEMPO.

Is the Alternate Aerodrome Suitable?If the destination aerodrome requires an alternate, you must ensure that thealternate aerodrome is suitable.Reference: A IP ENR 1.1-85.LightingFor non‐regular public transport (RPT) aircraft, RPT cargo only or RPTbelow 3,500 kg maximum take‐offweight (MTOW), there is no requirementfor a responsible person to be in attendance where an alternate aerodrome isserved by PAL, providing that the aircraft is equipped with dual VHF, or it isequipped with single VHF and HF communications and carries 30 minutesholding fuel to allow for ground staff to be alerted in the event of a failure ofthe aircraft’s VHF communications.In the event that the aircraft has only one VHF, the alternate mus t have

lightingwhich isn o t pilot‐activated or, if it has PAL, aresponsible person mus tbe on the ground to manually switch on the lights. An alternate aerodromewith electric or PAL lighting need n o t have stand‐by power or stand‐byportable lighting.

NavigationAidsThe alternate aerodrome must bewithin on hour’s flight time of the destinationandbeservedby aradio navigationaid (NDB/VOR) that the aircraft isequippedto use. The pilot is responsible for ensuring familiarity with obstacles surround‑ing the aerodrome within the circling area and that the aircraft ismanoeuvred ataheight sufficient to maintain obstacle clearance in the circling area.

WeatherWeather requirements for alternate aerodromes are the same asfor destinationaerodromes.

Part Three

PilotingTechnique

Chapter 5: Instrument Flight Technique . . . . . . . . 113

Chapter 6: Night Flight Technique . . . . . . . . . . . . 123

Chapter 7: Abnormal Operations at Night . . . . . . 145

an. kfim

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Chapter 5

Instrument Flight Technique

Flightuontr I v e s“ i f ” a w “:use m y , “

There isadirect relationship between the techniquesused for instrument flight and those used for visualattitude flight. In Visual flight, an attitude is set byreference to the Visualhorizon together with apowersetting (and/or configuration change) to achieve adesired performance. The performance of the air‑craft is assessed by scanning performanceinstruments, and then, if necessary, small adjustmentsto attitude and/or power are made to ensure thedesired performance is eventually attained. Oncethis happy state of affairs has been reached, the air‑craft is trimmed to ensure the selected attitude can bemaintained with minimum effort on o u r part.

In instrument flight, the visual horizon issubstituted for an arty‘icial horizon displayed on theattitude indicator. The other important considerationis the need to develop a more systematic approach toinstrument scanning. Also, it is fair to say thatinstrument flying requires a more measured andprecise technique for aircraft control and trimming,i.e. aslower and softer touch is required.

Pitch and bank attitudes are established using theattitude indicator. However, it is important toappreciate that relatively large pitch‐attitudechanges against the natural horizon are representedin miniature on the instrument. For instance, for atypical light aircraft in straight and level flight atcruise speed, the Wing bars of the miniatureaeroplane might appear against the horizon line ofthe instrument. At low airspeed, the wings mightbe one or even t w o bar widths above the horizon,whereas for aclimb attitude in the same aircraft, the

173

Figure 5-1 Pitch remains pitch.

774 Night Flight

wingbars of the miniature aeroplane might be positioned tw o or three barwidths above it (or 10° if the AI has degree increments). In a turn, the wingbars of the miniature aeroplane wil l bank alongwith the real aeroplane, whilethe horizon line will remain horizontal. The centre dot of the miniatureaeroplane represents the position of the nose relative to the horizon.

InstrumentScanningW m fi m a fl fi y m m m a m a fi e m

Simple ScansEachscan issimple, startingat the atti- Itude indicator and radiatingo u t to the :relevant instrument before returning : /

ll

again to the attitude indicator. Theattitude indicator is the focal point ofeach scan because it is the primarycontrol instrument. The scan patternradiates ou t from and back to the atti‑tude indicator no mat ter what theaircraft is doing. This is called aselec‑tive radialscan.

IIl| .|llI. _ [ a c umen

Figure 5-2 A simple scan for balance.

The aeroplane can be accuratelyand comfortably flown without anyexternal visual reference, providedthe instruments are scannedefficiently and the pilot controls theaeroplane adequately in response tothe information provided by theinstruments.The attitude indicator (AI) shows

pitchattitude andbank angle directly,but it does n o t show yaw. Balanceinformation is obtained simply bymoving the eyes from the attitudeindicator diagonally down left to thebalance indicator to confirm that theball is centred. The eyes mus t thenre tu rn to the attitude indicator a ‘(figure 5‐2). I m a m

Figure 5-4 A simple scan for airspeed.

5: Instrument Flight Technique

Heading is obtained from theheading indicator (HI) ormagnetic compass. From theattitude indicator, the eyes movestraight down to the headingindicator to check headingbefore returning to the attitudeindicator (figure 5‐3).Airspeed is easily checked by

moving the eyes left from theattitude indicator to theairspeed indicator (ASI) beforereturning to the attitudeindicator (figure 5‐4).To read altitude, the eyes move

from the attitude indicator to therightwhere the altimeter (ALT) islocated before moving back tothe attitude indicator (figure 5‐5).The rate of climb or descent isread by moving the eyes fromthe attitude indicator diagonallydown to the right to the verticalspeed indicator (VSI) beforereturning to the attitude indica‑t o r (figure 5‐6).Turn rate isreadfrom the t u r n

coordinator (TC) once the bankangle is established. The normalrate of t u r n in instrument flyingis 3°/second, known asstandard‑rate turn or a rate one turn. Turnrate is clearly marked on the t u r ncoordinator or t u r n indicator(figure 5‐7).

775

Figure 5‐6 A simple scan for vertical speedinformation.

33 ivs°«\\\‘\:£"I//z,zs}

Figure 5-7 A simple scan for turn rate.

Control Instruments and Performance InstrumentsThe combination of attitude plus thrust determines the flightpath of the air‑craft. Accordingly, the tw o instruments that indicate these ‐ the attitudeindicator and the power indicator ‐ are known asthe control instruments. The

776 Night Flight

pilot has no direct indicationof flightpath so the performance instruments are usedto deduce the flightpath from altitude, airspeed, rate of climb and descent,headingor heading change indications. Further, the aircraft’s position isshownby the navigation instruments.

/ E u r ‐ 0 ' \Atti tude Power

33 Ivowmr,A’ ’1’;MANIFOLDEB, ‘a' 4/ | \I I/ \\r’ 6 Wu I \\\\“1,\ ’

,o s ' EL /i

Navigation(position)

3 5 4 5 , 9 5

Figure 5-8 Functional grouping of instruments.

The performance instruments show the flightpath (as a result of the powerand attitude selected) in terms of:° altitude, on the altimeter and vertical speed indicator;' direction, on the heading indicator and t u r n coordinator; and' airspeed, on the airspeed indicator.

Configuration also determines performance (eg. airbrakes, flap position,cowl flaps and undercarriage). For simplicity, a constant configuration isassumed When we say attitude and power determines performance.

Because continuous reference to power is n o t necessary, the power indicatoris situated slightly away from the main group of flight instruments. It can bescanned easily, but it is n o t in the main field of View. It can also be set by thetone of the engine and by throttle position (avery important cue).

5: Instrument Flight Technique ‘_K 777

Selective Radial Scan~7§\t

\AlRSPEED /‘)%so more 40 i

As stated, the technique of look‑ingfrom the attitude indicator to aselected instrument and returningto the attitude indicator is knownasa selective radial scan.Selective radial scanning is a

logical process, and it ensures thata high priority is given to the ‘attitude indicator ‐ the primary "“ ' lR-O114.ES

control instrument ‐ aswell asthe Figure 5-9 Selective radial scan.performance instruments relevantto the manoeuvre being undertaken, i.e. when climbing, turning ordescending, the relevant performance instruments take their appropriate place.Let us examine how radial scanning works in practice.

ClimbingWith climb power selected, the estimated climb attitude is set on the attitudeindicator, andwhen stabilised, the aircraft is trimmed. Reference is thenmadeto the airspeed indicator to confirm that the selected pitch attitude is co r r e c t .(The airspeed indicatorprovides the pilotwith the neededfeedback.) If the air‑speed indicator shows anairspeed that has stabilisedbut is t o o low, alowerpitchattitude on the attitude indicator is required (perhaps a halfbar width lower).A few seconds must then be allowed for the airspeed to settle.

r ima r yperformance Pitch

guide to correc attitudepitch attitude control

0‘ 4/ \\ _Val/unfit»;

Figure 5-10 The airspeed indicator is the primary instrument in the climb to confirm and adjustpitch attitude.

178 Night Flight

Levelling o f fand CruisingWhen approachingcruise altitude, attention ispaid to the altimeter to ensure thatthe aeroplane levels offat the desired altitude aspitch attitude is lowered on theattitude indicator.The altimeter and vertical speed indicator are guides to the rate of Change of

attitude. When straight and level, any minor deviations from altitude can becorrected with small changes in pitch attitude. Therefore, altimeter is theprimary performance guide for pitch attitude in the cruise. It is supportedbythe vertical speed indicator.If climb power is maintained after levelling at cruise altitude, the aeroplane

will accelerate. At the desired cruising speed, the power should be set to theappropriate cruise power setting.Heading is monitored with reference to the heading indicator, and any

deviations are corrected with small, coordinated heading changes. Theheading indicator will show whether or n o t balanced, Wings‐level flight isbeing conducted. The heading indicator is therefore the primary feedback tomaintainingwings level.The balance ball is used to cancel sideslip.

Primaryperformanceguide to pitch

iR~Ui10.EPS

Figure 5-11 The altimeter is the primary instrument in the cruise to confirm and adjust pitch attitude.

Use the LogicalScan for EachManoeuvreStarting with the attitude indicator, scan the performance instruments whichare relevant for the manoeuvre beingconducted. To determineWhether or n o tthe pitch attitude selected on the attitude indicator is correct, primary pitchinformation is obtained from the altimeter during cruise flight, and it isobtained from the airspeed indicator during climbs and descents. There is no

5: Instrument Flight Technique 179

needto memorise particular scan patterns, asthey will develop naturally asyourtraining progresses.Avoid fixating on one instrument asthis will certainly cause abreakdown in

the scan pattern. Fixation on any one instrument may also result in delayedrecognition offlightpath and/or airspeed deviations. For example, fixation onthe heading indicator might enable agiven heading to bemaintained, but thiswould beof no use in the detection of altitude and airspeed errors ‐ errors thatwould be seen (and corrected) if the altimeter, vertical speed indicator andairspeed indicator were scanned. Keep the eyes moving, but re tu rn to theattitude indicator.Occasionally, other items in the cockpit will need to be attended to ‐ for

example settingengine andmixture controls followingapower change, checkingfuel, suction and electrical system gauges, reading instrument approach charts,tuning radios, filling in aflight logand soon. Consequently, the scan will needto beexpanded and attentionwill need to be drawn away momentarily from theattitude indicator and performance instruments to enable these important tasksto be accomplished. In the process, aircraft control mus t remain the highestpriority. The attitude indicator remains the focal point of the scan.

Returning todesired heing

" ’ “ Aircraft s strayed ,off desired heading '

IR»D112EP5

Figure 5-12 The heading indicator is the primary instrument in straight flight to confirm wings level.

Abbreviated ScansOn some occasions, it is necessary to have a fast scan, aswhen on final for aninstrument approach. However, on other occasions the scan can be morerelaxed, aswhen cruisingwith the autopilot engaged.

720 Night Flight

If you are performing other tasks while flying a constant heading, such asreadinganen rou te chart, avertical scan from the attitude indicator down to theheading indicator and back again is appropriate (figure 5‐14).With practice, you wil l develop suitable scans for every situation.

(‘AIRSPEED /‘ I l " '2' ‘AIfiSPEEDI E 160 m o t s 4 “ : g g , /\‘ ‘ ~ ' 4 ° / ‘

K / V ‘ , i. r ‘ t 3 > - 1, /" ‘

, a | \‘ 4’1/1il||\\\‘\§b\/L/

R-Ol14.EPS

Figure 5-13 A suitable scan during straight andlevel flight.

suit En route chart , ‘ I

Figure 5-14 The vertical scan.

Attitude l n s t r tlyingAsmentioned, there is adirect relationship between visual and instrument atti‑tude techniques ‐ in fact, they are identical. In instrument flight, attitude isestablishedwith reference to the attitude indicator insteadof the natural horizon‐ no matter what manoeuvre isperformed.

Attitude (andPower) ControlThe two parameters over which the pilot has direct control are attitude andpower.Attitude is establishedon the attitude indicator. Power is set with reference to thepower indicator. Configuration changes, suchasflap andundercarriage selection,will also influence aircraft performance.

Figure 5-14 Precise attitudes.

5: Instrument Fright Technique 127

A specific power setting and attitude will result in apredictable performanceoutcome, and this holds good for any aircraft. For example, aPA‐31Navajowil l cruise straight and level at approximately 155 kt with cruise power at 65%and a wings‐level attitude with zero pitch (i.e. bar superimposed on thehorizon). Similarly, the operations manual states that, at anaverage weight, aBoeing 737‐300 airliner in the initial approach configuration will fly straightand level at 150 kt with a thrust setting of 69% and a pitch attitude of eightdegrees. It’s that simple.

Performance is Flightpath plus SpeedAswith visual attitude flight, a given flightpath and speed is reflected by theperformance instruments. In addition, there are standard techniques to opti‑mise performance and accuracy when changing from one manoeuvre toanother ‐ for example, when levellingo f fat cruise altitude from aclimb (atti‑tude, power, trim, etc.).

Climb, Cruise, DescentFor most flight profiles, the power is set to afigure recommendedby the man‑ufacturer. The pilot then sets an appropriate attitude to achieve a desiredflightpath and speed. You will need to learn the power settings and the atti‑tudes for your aircraft. Having set the appropriate attitude, wait until theperformance instruments stabilise (they lag).The attitude is then adjusted to achieve the primary flightpath parameter:

' for the climb, the airspeed indicator is the prime reference;- for the cruise, the altimeter is the prime reference;- for the descent, the airspeed indicator (or sometimes the vertical speed indi‑cator) is the prime reference; and

- for a turn, the tu rn coordinator is sometimes used to adjust the bank angleto achieve acertain rate, otherwise the headingindicator is used to maintainor roll o u t on heading.Having set power and attitude, it is most important to fly the aircraft

accurately and to keep it balanced. Table 5‐1 includes asummary, in order ofimportance, of the primary performance instruments that are checked for eachmanoeuvre. Flight tolerances or accuracy standards that mus t be observed arespecified for instrument flight, and these are also listed in table 5‐1.

122 Night Flight

Manoeuvre Flightpath indicators lFR flight CommentsVertical Horizontal tOIerances

Climb ASI HI : 1 0 kt For climbing with constantVSI TC + Ball : 5 ° HDG power, (e.g. climb power),ALT adjust attitude if required

to climb at a given speed.Use 10% rate of climb aslead for levelling off (e.g.500 fpm, start levelling offat 50 ft to go).

Straight and ALT Hl : 5 ° HDG Increase or decrease powerlevel VSI TC+ Ball : 100 f t and adjust attitude to

ASI ALT regain altitude for devia‑tions greater than 100 ft.

Descent ASI HI : 1 0 kt For descending with con ‑VSl TC + Ball : 5 ” HDG stant power (e.g. idleALT power), adjust attitude if

required to descend at agiven airspeed. Fordescending at a constantIAS, adjust power todescend at a given rate.Use 10% of rate of descentat lead for levelling off (e.g.800 fpm, start levelling offat 80 ft to go).

Climbing turn ASI HI : 1 0 kt Commence roll ou t of turn(usually no VSl TC+Bal| : 5 ° angle using one third of bankmore than 15° ALT of bank angle as lead (e.g. 15°angle of bank) angle of bank, use 5° lead

to roll ou t on heading).

Level turn VSI (in HI :100 ft Commence rolling out ofsmooth TC+ Ball ALT turn using one third of

air) : 5 ° angle bank angle as lead (e.g. 30°ALT of bank angle of bank, use 10° lead

to roll out on heading).

Descending ASI HI :10 kt Commence rolling out ofturn VSI TC + Ball : 5 ° angle turn using one third of

ALT of bank bank angle as lead (e.g. 20°angle of bank, use 7° aslead to roll out of heading).

Table 5-1 Flightpath references.

Chapter 6

Night Flight Technique

eparation for s s i b l i g h t Flight

TransitionsMost private pilots are likely to use their night VFR rating asa backup in theevent of arriving later than expected at a destination airport at the end of across‐country flight. Most commercial operators may well fly the total flightby night, and this is perhaps the better way to approach night flight, asyou arephysically and mentally prepared for night operations (provided you are prop‑erly rested). A pre‐dawn departure for a daytime flight is easy if you prepareproperly for the night sector (the workload gets easier asthe sun rises). How ‑ever, the preflight and take‐of}~ stages for night flight are critical, and there isalso the possibility of having to t u r n back for anemergency night landing.

Your planningshould bethorough, and you should bewell prepared for anyeventuality The charts Should beavailable and presented for reduced lighting.The aids should betuned and identified. The navigation log should beup todate, and your position and timing should be confirmed. If you have anydoubts about the suitability of a destination you had originally planned toarrive at during daylight, you m u s t decide straightaway if you are to continue,t u r n back or land immediately. Watch o u t for fog in valleys, especially nearrivers. Generally, there is less turbulence, wind and shear before sunset andafter sunrise. However, anabatic and katabatic winds, such asthe Adelaidegully winds and the FremantleDoctor, can be strong at dawn or dusk. Heatingand thermals are minimal around dawn and dusk (this is one reason why nightflying can be sopleasant).

Flying WestFlyingwest into the sunset isfine with respect to the clearly defined horizon,butyour eyes are poorly prepared for night vision and the lengtheningshadows givea false image of terrain. If you have to tu rn back towards the east, there will benohorizon, no illumination and you will have poor night vision ‐ abad combi‑nation. If you are equippedwith bright instruments and cockpit lightingandyouare acompetent instrument pilot, you should have no problems.

723

724 Night Flight

Flying EastFlyingeast in the morningcan have its difficulties asthe risingsun can bebrightenough to obscure obstacles and high terrain. Flying east in the evening is lessdifficult asdusk will be shorter, darkness will fall earlier and your night visionshouldbe better becauseyou will n o t havebeenlookingtowards the bright set‑ting sun.

Take-Off and Landing into the Setting or Rising SunWhen taking offor landing into the setting or rising sun, t ry to choose ar u n ‑way in annortherly or southerly direction. Make sure the windscreen is clean(you did clean it before your flight, didn’t you?). IIf you expect the sun to cause difficulties with the landing flare, delay the

approachuntil the sun has gone down or landthe other way (windpermitting).Wear quality sunglasses for the eye‐shattering periods before sunset and after

sunrise ‐ sunglasses reduceglare andthe time it takes to adapt to reducedcontrast.

TurningWhen you turn, do n o t look down ‐ fly the clocks. Be careful around the endof civil twilight asthere could be a clear horizon in one segment of the t u r nbut none in the other. Cross‐refer to the attitude indicator ‐ frequently.

aratim‘. i g h t F'ihtV i .1

Preflight PreparationNight flying requires careful attention to preflight preparation and planning.While weather conditions in the vicinity of the aerodrome are obvious duringdaylight hours, the situation is different at night. Stars might be clearly visibleoverhead one minute, but they may be unexpectedly covered by low cloud thenext, and this couldhaveasignificant effect on your departure. Study the availableweather reports and forecasts, paying especial attention to any item that couldaffect Visibility and your ability to fly atasafe operating height.Some of the main items to consider include:

0 cloud base and amount;° weather (e.g. rain and fog);0 temperature to dewpoint relationship (the closer they are, the mo re likelyfog is to form asthe temperature drops further); and

° wind direction and strength, including the possibility of fog beingblown inand the likelihood of windshear due to the diurnal flirt.

6: Night Flight Technique 725

Note. The diurnal effect refers to alight surface wind with astrong wind atheight resulting from reduced vertical mixing.Check any special procedures for night operations at both the departure and

arrival aerodromes. The en rou te part of the flight is similar to an IFR flightand, as always, the more thorough the preflight preparation, the lower theinflight workload.Check personal equipment, including the normal daylight items (e.g.

navigation computer, plotter ‐ or protractor and scale rule ‐ and pencils). Adefinite requirement for night flying is a good torch ‐ one for your preflightchecks and another for the cockpit in case of electrical failure (ensure that thetorch has afresh battery).Al l lines drawn on charts should preferably be in heavy black ‐ even white

light in the cockpit will probably be dimmed to ensure that good externalvision is retained. If redlightingis used in the cockpit, redprint on charts willbedifficult to see.

Flight NotificationDependingon your localprocedures, you may need to formally advise air traf‑fic services of your intentions to fly at night. There is often a requirement tonotify ATS at GAAP aerodromes, and there is apriority system whereby eachflying school registers interest until the maximumnumber of aircraft permittedin the circuit is reached.Some aerodromes have restrictions on circuit direction at night, and some

runways are n o t available for night operations. Your instructor will explainthese aspects in the preflight briefing. You may need to pre‐arrange runwayand taxiway lighting at country aerodromes without apilot activated lighting(PAL) system.

Radio ProceduresThere is a high cockpit workload during night circuit operations, so it helpsconsiderably if you prepare by rehearsing andmemorisingall the required radiocalls. Radio calls vary according to the local aerodrome procedures (these arefully covered for all types of aerodromes in the Aviation Theory Centre manual,FlightRadiofor Pilots ‐ VFR Operations).Some GAAP aerodromes will change to CTAF(R) after a certain time at

night, andyou will need to be familiar with the differences in radio proceduresand the changes in responsibility for traffic separation and circuit spacing.

726 Night Flight

Aerodrome AvailabilityMany aerodromes, both civil andmilitary, close at night. It is always advisable tocheck ERSA, the AIP andNOTAMs for aerodrome closing times ‐ call the aer‑odrome if you are unsure. No t only check your planned departure anddestination aerodromes, but also check those aerodromes which might be usefulasalternates en route. You must be certain that runway lightingwill be availablefor your landing. Also, there are some danger areas which are n o t active atnight.

WeatherThe weather takes on especial importance at night. All relevant informationshouldbe studied carefully, especially the aerodrome forecasts for your destina‑tion, as well as those for a number of alternates and your aerodrome ofdeparture. Remember that the closeness of the temperature to dewpoint pro‑vides a warning of mist or fog forming asthe temperature falls further duringthe night. There is also a risk of carburettor icing.

The AircraftLoadingCheck the weight and balance of the aircraft and, if appropriate, the take‐offperformance charts. Make sure that cargo and baggage are correctly loadedand restrained. Al l dubious products must be left behind (e.g. inflammables,paints, toxins, pressure cans, batteries, chemicals, petroleum, oils and soon).

Pref/ight InspectionPreflight inspectionatnight islimitedby light levels onyour tarmac. It isbetterto inspect the aircraft during daylight, and it is preferable to use the sameaircraft you have flown that day. Conduct a thorough inspection ‐ a check ofall the aircraft lights is essential. In particular, check the serviceability of theinstruments and lights required for night flying.Check the cleanliness of all transparencies ‐ night vision is already limited

and is affected by dust and scratches on the windscreen (use aChamois).Survey the area in which the aircraft is parked. If the aircraft is unlit, on

grass, near tie‐down cables or among other aircraft, you may be able torepositionit on asealed surface with tarmac lightingandwide access. Conductthe preflight inspection using a separate torch. Retain the full battery chargein your personal torch for the flight.No t only must the aircraft be checked, but the surrounding area must also be

scanned for obstructions, roughor soft groundandother aircraft. Tie‐down ropes,pitot covers, control locks andwheel checks are more diflicult to see atnight.


A typical technique during the preflight check is to begin near ‐ or in ‐ thecockpit and to do the following:0 place the master switch on;° check the instrument lighting and dimmers ( i ffitted);' check the cabin lighting; '° check the taxi light, landing lights and anti‐collision beacon (do n o t drainthe battery unnecessarily); and

° switch on the navigation lights and leave them on for the walkaround asitmay be impossible to check them from the cockpit.Carry o u t the following during the walkaround:

' check all lights and their lenses for cleanliness and serviceability;- carefully check the navigation lights (redleft, green right,white tail), the taxilight and the landinglights; and

' test any electrical stall‐warning devices.Take great care in the nightpreflight check ‐ focus the torch on each specific

item asit is checked and also r u n the beam of the torch over the aircraft asawhole. If ice or frost is present, check the upper leading edge of the wing toensure that it is also clean. Any ice, frost or other accretion mu s t be removedfrom the aircraft (especially from the lift‐producing surfaces and controlsurfaces) pr ior to flight. Do n o t forget to remove the pitot cover and to checkthe pitot heat.Al l these simple preparations help. Allow extra time to carry o u t these tasks.

You mus t n o t end up in a position in which you have to rush.

The CockpitCockpit LightingThe instrument lighting has priority. Set a comfortable light level and avoidreflections. (Incidentally, you will appreciate wearing adark shirt; the tradi‑tional, white pilot’s shirt is anuisance for night flight due to the reflections onthe faces of the instruments.)Adjust the cabin lightingsothat it is n o t distracting ‐ low rather than high ‑

to avoid both instrument and window reflections. Dim the cabin lights sothatexternal vision issatisfactory and reflectionfrom the canopy isminimised,but don o t have the cabin lights sodim that you cannot see the controls or fuel selector.Allow time for your eyes to adjust to natural night light. It may be that the

apron lighting isbright and you need abright cockpit ‐ in this case, readjustthe cockpit lighting at the run‐up bay or holdingpoint, and use the taxi timeto acclimatise.

728 Night Flight

InternalPref/ightPlace all items you might need in flight in a handy position, especially thetorch, which should be placedwhere you can find it in complete darkness ‐ ifyou need the torch, you wil l need it right then! Some pilots who fly regularly atnight include a Velcro patch on their torch and headset so they can fly handsfree if the occasion arises.

Cockpit OrganisationAllow ext ra time to settle into the cockpit and establish a comfortable lightinglevel. Become familiar with the location and operation of all controls andswitches in this semi‐darkened environment. Keep the checklist where it isreadily accessible, but it is strongly recommendedthat youmemorise all checks.Connect your headset and adjust the intercom. Do n o t use ahand‐heldmicro‑phone for night or instrument flyingunless you have no choice (i.e. emergencyuse).Cockpit organisation for a night cross‐country flight is even more important

than aday one. Have the paperwork in order ‐ assemble it in sequence of use,fold it appropriately, have it oriented to track and ensure that it is easy to see.Make it readily available and stow it in sequence. If you are alone, use the co ‑pilot’s seat as a working desktop. Have another torch handy for readingpaperwork or use anilluminated clipboard.

FrontSeat PassengerNight flying is one situation in which your flying partner can be a great aid ora great burden. Being distracted by someone sitting nex t to you can n o t onlyhinder you but can also seriously increase your workload and stress. A compe‑tent ‘co‐pilot’ is agodsend.

The PilotAdaptation of the Eyes to DarknessThere are some special considerations regardingyour vision at night. Since yourattention will be both inside and outside the cockpit during night flying, careshould be taken to ensure that your eyes can function at or near maximum effi‑ciency. As discussed in chapter 3, it takes the eyes some minutes to adapt todarkness, and the rate at which the eyes adapt to darkness depends on the bril‑liance of the exposed light and the brightness and contrast of the newenvironment. While bright lighting within the previous few minutes has thestrongest effect, bright lighting experienced for some period within the previ‑ous few hours will also have aneflect. Bright lighting isbest avoided before a


night flight. This can bedifficult to achieve, since flight planning in awell‐litroom and preflight inspection with a strong torch or on awell‐lit tarmac willalmost always be necessary. In many cases, the best that can be achieved is todim the cockpit lightingprior to taxiing and to avoid looking at bright lightsduring the few minutes prior to take‐off. Avoid looking at Strobes 0r landinglights. In particular, Strobes can be amajor distraction in mist, cloud or rain.Night vision can be affected by a lack of oxygen, so ensure that you use

oxygen when flying above 10,000 ft AMSL, and preferably above 5,000 ft atnight. Avoid smokingbefore flight asthe carbonmonoxide will displace someof the oxygen in your blood thereby reducingyour night Vision.There are some occasions when bright cockpit lighting can actually help

preserve your vision. This can be the case during an instrument flight whenflying in the vicinity of electrical storms. Nearby lighting flashes cantemporarily degrade your adaptation to darkness and your Vision, particularly ifthe flashes are in contrast to a dim cockpit. Bright lighting in the cockpit canminimise the eflect of bright lightening flashes, and although your externalvision will n o t be asgood asit would bewith dim cockpit lighting, you willavoid being temporarily blinded by lightning flashes. Electrical storms shouldbeavoided by at least 10nm. If thunderstorms are forecast in your area, stay onthe ground.

Self-CompensationYour paperwork needs to be well organised, and you need to allow for the factthat instruments and charts wil l be illuminated by artificial light. The aero‑dromes from which you normally operate will look different at night. Theaerodromes with which you are unfamiliarwill be even more soat night. Youwill need to ensure that you are atthe rightplace, andyou will needto prebriefyourself on the taxiways, runways and lighting.

The AirfieldAlways have a plan for night flight ‐ even for a local flight. In your plan,include runway in use, taxi routes, run‐up bay, holdingpoints, radio frequen‑cies, radio calls and the flight profile. Re‐study the layout of the airfield, therunways for night operations, any night circuit restrictions (directions and atti‑tudes), NOTAMs and possible wind and weather implications. Check thelocation of the illuminated windsock, and check the operation and layout ofthe aerodrome lighting. Select l i t features to assist with circuit pattern orien‑tation and spacing.

730 Night Flight

Ii ht ProceduresEngine Start

Make sure you have the park brake on before starting the engine, especially asmovement of an aeroplane is less noticeable at night. The rotating beacon ornavigation lights shouldbe turned onjust prior engine start to wa rn any personnearby that the engine(s) are about to start. Some schools flash the taxi or land‑ing lights ‐ check the standard operatingprocedures (SOPs) for your flying school.Keep agood lookout before starting the engine ‐ aspinning propeller ismoredifficult to see at night. Passengers have been struck while taking a short‐cutto the cabin or while transferring from one aeroplane to another. Do n o t startthe engine ‐ n o t even the engine on the side opposite the door ‐ before allpassengers are on board. After start, check outside to make sure that the aero ‑plane is n o t moving, and then complete your after‐start checks.

TaxiingThe responsibility for collision avoidance always rests with the pilot. Use thetaxi light, and only switch it off if it is about to point at other aircraft. The taxilight n o t only helps you see obstructions, it also makes your aircraft mo re Vis‑ible. It is usual to t u r n the taxi light on before moving from the parking areato wa r n other crews that you are about to taxi forward. Taxi slowly and care‑fully. Look at the wingtip to check your speed ‐ imagine someone iswalkingalongside your aircraft and match their walking pace.Taxiing at night requires additional attention for the following reasons:

' distances are mo re difficult to judge at night ‐ stationary lights may appearcloser than they really are;

' speed is very deceptive at night ‐ there is a tendency to taxi t o o fast; andother aircraft and obstacles are less visible at night ‐ an aircraft ahead on thetaxiway may be showingjust asingle white tail light and that light may be lostamong other lights.Taxiway lighting will be either t w o lines of blue edge lights, or one line of

green centreline lights. Taxi guide lines may bemarked on hard surfaces. Stayin the centre of the taxiway to preserve wingtip clearance, but you may like totaxi slightly off-centre to avoid bouncing the nosewheel over the centrelinelights. The ground reflection of the wingtip navigation lights, especially onhigh‐wingaeroplanes, is useful in judging the clearance between the wingtipsand obstacles at the side of the taxiway.Check your taxi speed by looking at the wingtip where taxiway lights and

reflected lightingwil l help you to judge your speed.


If there is any doubt about your taxi path, slow down or stop. If you stop,apply the park brake. The traditional lawofaviation states there isnoexcuse fora taxiing accident. The landing lights may be used to provide a better viewahead, but they draw more power and may overheat without cooling airflow.Some taxiways r u n parallel to the runway, so avoid shining your bright lightsinto the eyes of apilotwho is taking oflf, landingor taxiing. Avoid lookingintothe landinglights of other aircraft yourself‐- doingsowill seriously degrade yournight vision for afew minutes.Complete anormal instrument check while taxiing:

- turning left, skidding right, wings level, HI decreasing, ADF needle track‑ing; and

° turning right, skiddingleft,wings level,HI increasing,ADF needle tracking.

Run-UpEnsure that the park brakes are on ‐ an aeroplane can easily move during thepower check, and atnight there are few visual cues to alert the pilot. Completethe normal run‐up checks and pre‐take‐offvital actions. Adjust the lightingnow that you are away from the tarmac. During the pre‐take‐oflf checks, don o t have the cabin lighting sobright that it impairs your night vision. Thetorch can beused if bright cabin lighting isn o t desired.Pay especial attention to the fuel selection, asthe fuel selector may be in a

dim part of the cockpit. Ensure that any item required in flight is in ahandyposition. While the aeroplane is stationary, check that the heading indictor isalignedwith the compass. Although included in the normal daylight pre‐take‑of checks, this check is especially important at night asthe heading indictorwill beaprimary reference for direction ‐ both in the circuit area anden route.

HoldingPointTaxi to the holdingpoint, which may have special lights or markings. If youhave acombined taxi and landing light, avoid pointing it towards landing air‑craft. Check the windsock and anticipate the effect of wind on your take‐offand circuit. Take some time here (the ‘ten‐second think’) to consider the effectof different wind directions and speeds throughout the circuit and the allow‑ances you will need to make. Wind at circuit height will be stronger than onthe surface.Turn on the strobes and transponder. Turn on the pitotheat and leave it on for

all night flying operations. After you have received a take‐off clearance, line up,tu rn on the landinglight andturn offthe taxi light. Do n o t intrudeonthe runwayuntil you are ready, you have a clearance (i fappropriate) and the runway and itsapproaches are clear of conflicting aircraft.

732 Night Flight

A final check of cabin lightingshould be made. Ensure that it isadjusted to a suitable level andthat it isbright enough to see the i, 'major items and instruments in ithe cockpit, but n o t sobright asto seriously affect your outsidevision.

. . ....nirituIiiilkwixiixinI-u. ...I H H . ‘ I

H “ . ,1. I

Night Take-OffWhen ready to line up for take‑off, make any necessary radiocalls, t u r n on the landing lightand look carefully for other trafficon the ground and in the air.Clear the approach path to therunway, checking both left andright ‐ Clear left, clear right.Conditions are often calm at

night,makingeither direction on the runway suitable for operations. Ensure thatthe approach areas at both ends of the runway are clear. Self‐brief youremergency actions.Check the windsock. Do n o t be in ahurry to roll. If necessary, ask for thirty

seconds on the threshold when you call ready, so that the controller knows youneed the time to prepare for take‐off.Do n o t waste runway lengthwhen liningup. Line up on the centreline with

the nosewheel straight. Check that the HI agrees with the runway directionand that the AI is erect. With your feet well away from the brakes and on therudder pedals, smoothly apply full power.During anight take‐off, directional control is best achieved with reference to

the centre of the far end of the runway. Keep the runway light patternsymmetrical. Runway centreline markings may also assist. Quickly check rpmand MAP and that the A51 is reading. Avoid over‐controlling during theground run . Relax.The take‐off is the same by night asit is by day. At lift‐off speed, rotate

positively to the initial climb attitude. Fly the aeroplane away from the ground,accelerate to climb speed and adopt the normal climb attitude. Watch o u t forreflections from the landinglight and Strobes if there ismist or drizzle. The bigdifference between day and night take‐off operations is that, at night, Visual

Figure 6‐1 Night take-off.


reference to the ground is quickly lost after lift‐off, and any tendency to settleback on to the ground wil l n o t be aseasily noticed.As soon as the aeroplane is airborne and positively climbing, retract the

undercarriage and transfer your attention to the attitude indicator. Transfer toinstruments before losing the last visual references, which will typically bethelast set of runway lights ‐‐but do n o t lower the nose. The first 300 to 400 ft ofthe climb‐out should be totally on instruments, and remain on instrumentsuntil you are high enough to regain usable visual references. Retract the flapsabove 200 ft AGL and tu rn off the landinglights.Maintain the normal take‐offpitch attitude and keep the wings level on the

attitude indicator. TheA51shouldbechecked to ensure that asuitable airspeedis beingmaintainedon the climb‐out, withminor adjustments made on the AIasnecessary. Once well away from the ground and comfortable in the climb‑ou t , the HI can be checked for heading. You may n ow adjust the power andt u r n o f f the boost pump.Normally, a straight climb path is maintained until 500 ft AAL before

turning on to the crosswind leg (unless there is a good reason to tu rn earlier,such ashigh ground). Depending on your departure track and the 25 nmminimum sector altitude (MSA), you may elect to climb to 1,000 or 1,500 ftbefore making a turn. The direction of tu rn mus t conform to the circuitpat tern for night operations. You cannot t u r n opposite to the circuit untilbeyond 3 nm or above 1,500 ft.With little or no natural horizon, the instruments become very important.

If glare from the landing lights or Strobes is distracting, t u r n them off whenestablished in the climb. Mist, haze, smoke or cloud will cause distractingreflections. Some common errors are asfollows:° letting the aircraft bank slightly so it is no longer aligned with the runwayduring the after‐take‐OEchecks;

' lowering the nose while maintaining visual contact with the runway; and' relaxing back pressure on the control column as the power is reduced,thereby allowing the attitude to decrease and the aircraft to settle into areduced climb or even ashallow descent.

DepartureWhen the aircraft is stabilised on its climb path, position the aircraft over aknown location and record the time. If the aircraft is still climbing, thegroundspeed and elapsed‐time calculations will be in error. Eitherplan for theclimb (time and average groundspeed) or depart from overhead the airfield orfrom afix at cruise altitude and airspeed.

734 Night Flight

En RouteThe en routephase of the flight shouldbevery similar to anIFRflight. Remaininside the 25 nm M S A asyou climb until you are above the LSALT for the firstleg, then depart on track and continue your climb to your cruisinglevel. Depar‑ture procedures and manoeuvring to intercept track can be demanding. Useyour autopilot to free your hands soyou can complete your checks, log yourdeparture time and make the necessary radio calls. Monitor what the autopilotis doing, and in particular, keep attitude in your scan.

When settled in the cruise, tune the primary tracking radio aid to the n e x tstation, and keep asecondary aid tuned to the nearest suitable airfield.

Tidy up the cockpit for the n e x t sector, but do n o t allow yourself to relaxt o o much asyou need to stay aware of weather and your position in relation toother aircraft. Review the activity required at the n e x t turning or reportingpoint and, when ready, have abasic descent plan in mind for your destination.

Navigation TechniqueThere was once an advertisement with t w o chocolates travelling on a train; thefirst chocolate had a map and the second one asked Where they were. The firstreplied that he didn’t know ‐ the train was n o t marked on the map! We are inexactly the same boat (or aircraft in our case). You can only map read if youknow Where you are. More correctly, you can only accurately fix your positionif you know your approximate position.

H o w do we know our approximate position (yes, GPS gives precise positionswithout an intermediate step, but what if the coordinates are incorrect, thebattery fails or the signal is lost)? We know o u r approximate positionby startingfrom a known position at aknown time. By noting speed, direction and timeand allowing for forecast winds, we know where we should be at a certainelapsed time. We then look at amap for features and try to match these withthe same pattern on the ground. Pattern matching is o n e of the pilot’s greatestlearnedskills. If we read from ground to map, there isno way to patternmatchaseverything on the map will have the same relative importance.

The navigation cycle involves markingsignificant features on the map, bothon track and cross track. Note the expected time of arrival and then memorisethe pattern that the features should make. The mental overlay will match apattern on the ground Within normal navigation tolerances. The pattern willcome into focus, and minor updates on progress can then be made ‐ weleapfrog from one feature to the next .

At night, visual navigation is made difficult as a pattern of lights can beentirely different to a pattern of features on a map. Therefore, accuracy offlying and accurate log keeping are essential ‐ timing is Vital.


Trusted features include:0 coastlines with inlets and peninsulas;0 major rivers and lakes (but watch for changes with heavy rains and dry sea‑sons);

' major highways;- the relationship between country towns (by this ismean t the pattern madeby the relative position of each town rather than the shape made by eachcluster of lights);

' l i t obstructions in remote areas (eg. transmission towers);- aerodrome beacons and PAL (yes, use it to confirm position when overfly‑ing, andplan your rou te via airfields with PAL if you can); and

0 nautical beacons and lighthouses (they are shown on aeronautical charts).Add any information gained from navaids to the visual navigation picture,

but still maintain the visual scan and log.

Assembling the Complete PictureThe pilot’s primary role is to make decisions. The quality of the decisiondepends on the quality of the information ‐ the mos t recent, most relevant,mos t complete and most accurate. Given this data, the quality of a decisiondepends on the training, experience and self‐discipline of the pilot who isprocessing the data. A decision is ultimately emotional, n o t logical. At night,the pilot’s task isalittle more difficult because of the paucity of visual informa‑tion. However, if the pilot assembles all available information, the task is littledifferent from daytime flight. In the meanwhile, accurate control of aircraftattitude and heading remains fundamental.Fly the aircraft and assemble navigation information. Look for features from

map to outside. Interpretthe aids anduse themto confirm the visual data. Makesure you are at or above LSALT and on track before leaving overhead thedeparture airfield.

Heading, Time andAirspeedEver since the mailplanes first explored the possibility of reliable night aninstrument flight, abasic law was realised ‐ fly accurate heading and airspeeandmonitor the progress of time. Every other aid is used to confirm or adjust(this relationship. It is the fundamental principle of pilot navigation. To fly an]accurate heading, keep the wings level and quickly correct deviations. To flyairspeed, set the optimum power and altitude, and confirm the true airspeed(TAS). Monitor thepassingof ground features to check groundspeedand trackand to amend ETAs (also use aids to refine this).

136 Night Flight

The navigation cycle at night is no different from during the day, exceptthere is reduced visual information (this can be a good thing), andyou canno tafford to waste time on reading. However, in many parts of the country, thereis often zero visual information for awhile. Here, the options are assemblingwhatever navaid information is available, flying anaccurate heading and speedand noting the progress of time.It is Vital to keep aflight log of fixes and times sothat you have anupdated

basis for diversion, rerouting or returning your destination. Use the aids andassemble all of the information. Believe the majority of aids, if they are similar.GPS can be accurate to metres but also inaccurate by tens of kilometres. Keepit honest by makingmental approximations and then believe what it says. Don o t look for unnecessary work. Fix your position every t e n minutes or so, andfly accurately and enjoy the scenery in between position fixes.Aswe continue along track, the process is one of seeing those Visual features

that can be positively identified. There is a danger of using unexpectedinformationbecausewhenwe read the map, we do n o t knowwhat is going tobe Visible or what features wil l look like.Visual navigation at night is highly unreliable. Use all Visual and radio‑

navigation data, in support of heading, time and airspeed. If there is adisagreement, believe the majority but only if the majority agrees with yourmental progress.

DescentTo make a visual approach at night, you mus t n o t descend below theLSALT/minimum sector altitude (MSA) (or minimum vector altitude (MVA)in radar environment) for that rou te segment until the aircraft is established asfollows:- clear of cloud;° in sight of ground or water;- with aflight visibility of n o t less than 5,000 m; and0 either within the aerodrome circling area (3 nm of the aerodrome referencepoint (ARP)) or within 5 nm of an aerodrome and established on centrelineand n o t below the VASIS approach slope (7 nm for a runway with ILS).Even if the approach controller clears you to make a Visual approach or to

maintain terrain clearance Visually, do n o t deviate from the inbound track untilwithin 3 nm of the threshold.Activate the PAL.


Night ArrivalJoining the circuit pattern at night is similar to day flying, except the aircraft isprimarily flown by instruments and positioned with reference to the runwayand other lights. The normal techniques of attitude flying apply.

There is a tendency to overbank at night. Keep your head movements to aminimum, especially while rollinginto or o u t of aturn. Move your head slowly.Once the runway and aerodrome lights are seen, they should be referred tofrequently Well‐lit landmarks may also beuseful for positioning in the circuit.

R d9 Is sateRed to red Green Redis safe

Green Green

lR-2502.EPS

Figure 6-2 Recognise and respond to other aircraft navigation lights.

Allow for drift on the crosswind leg, and level offusing normal instrumentprocedures. Accurately maintain height, and carefully scan outside beforemaking any turns. A good lookout for other aircraft m u s t be maintained at alltimes, and the usual radio procedures must be followed. '

Recognise and respond to the navigation lights of other aircraft. Green tored is n o t safe, and this will be the situation if t w o aeroplanes are flying parallelon downwind. An especially careful lookout will need to be maintained.Listeningto radio transmissions will help you maintain amentalpicture of whatelse is happening in the circuit.

Complete the prelanding checks and assess the wind. The t u r n fromdownwind o n t o base legshould bemade at the normalposition with referenceto the runway lights and any approachlighting. The descent onbase legshouldbe planned so that the t u r n o n t o final commences at about 600 to 700 ft AAL,ideally with a20° bank angle ‐ certainly no more than 30°.

738 Night Flight

Night ApproachAt night, ask yourself, ‘15 the threshold the same distance below the horizon asitwould beduring a daytime approach?’ This is the only t rue measure of the correctapproach path.Note. This is sometimes referred to asthe x‐height.The aspect of the runway will change, the threshold wil l get wider and so

the ratio of width to height will also change. If you try to keep a constantaspect ratio, you will be overshooting. Complete the final checks andmake apositive decision to continue or go‐around.When the decision is made to commit to the approach, the aircraft is

configured with landing flap, propellers full fine, landing light on andundercarriage three greens confirmed. The aircraft is trimmed and willmaintain a stabilised approach. Speed should be VREF (aim for a tolerance of+5 kt minus nothing).N o w your references and techniques change. Your scan is primarily focused

on the runway for height, centreline and attitude. Scan ‘airnpoint, attitude,airspeed’.Any tendency to drift off the extended centreline can be counteractedwith

coordinated turns. Drift can be laid off if a crosswind exists ‐ use rudder toassist. Be prepared for wind changes asthe descent progresses. The differencebetween the wind at 1,000 ft AAL and at ground level is likely to be morepronounced at night than by day. It is common for the windspeed to decreaseand the wind direction to back asthe aeroplane descends.

ME1-7DI.EPS

Figure 6-3 Final approach ‐ dusk.


The aim point should stay in the same position in the windscreen. Correctthis with attitude. Maintain airspeed during the final approach by adjustingpower. Remember ‐ the runway aspect will change asyou get closer. It doesn o t stay constant, even on a constant approach path. The only constant is thedistance of the threshold (aimpoint) below the horizon.

ME1»7DZ.EPS

Figure 6-4 Runway aspect ‐ three degree glideslope.

You may n o t have a Visual horizon at night, but you can still picture thedistance of the threshold below the horizon by imagining the point at whichthe runway lights converge. This is the horizon.

MEI-7us.EPs

Figure 6-5 The runway edges converge at the horizon.

140 Night Flight

Constantapproach

path

Figure 6-6 A well executed final approach path.

Judgement is subtle, but you wil l find that, with practice, you willinstinctively feel that you are high or low or are getting either way. It is Vitalto reinforce this judgement by flying fairly frequently so that it becomes arepeatable performance.When you feel that the approach is correct, you can refine the approach by

selecting a specific aim point ‐ a point 200 ft in from the thresholdcorresponding to the central space between the first pair of white side lights isrecommended.The aim point is the point at which your eyes would impact the runway if

you did n o t flare. Continue the final approach, making continuous smalladjustments.Do n o t forget that the aircraft is equippedwith arudderwhich ismost effective

in assisting lateral corrections on final. Use it in a coordinated way with aileroninputs to point the nose.As you approach the threshold, the runway lights near the threshold should

start moving down the windscreen. Certain runway features may becomevisible in the cone of the landing light.


Flare, Hold-Off and Landing at NightThe best guide to flare height and round‐out is the runway perspective givenby the runway edge lighting. As the aeroplane descends towards the runway,the runway edge lightingyou see in your peripheralVision will appear to rise.The appearance of the ground can sometimes be deceptive at night, so

even when using landing lights, use the runway lighting asyour main guidein the flare and hold‐off, both for depth perception and for trackingguidance. (For this reason, your introductory landingsmay bemadewithoutthe use of landing lights.)Continue to the threshold. At this point, don o t look atthe runway illuminated

by the landing light, but transfer your gaze to the centre (yrthefar end if the runwayGently raise the nose of the aircraft until the flightpath changes towards this point.Straighten the aircraft with rudder using aileron to prevent any bank, and reducethe power. As you reduce the power, maintain back pressure on the controlcolumn asif you were trying to actually reach the far end of the runway Lowerthe upwindwing to prevent any drift. The aircraft will land itself.Don’t freeze or tense up ‐ you have ajob to do. Wiggle your fingers and

n o t only look at the aim point but also and scan back and forth to the far endof the runway. Do n o t become focused on one point. There is a c ommontendency to flare and hold off a little t oo high in the first few night landings,but this tendency is soon corrected. The runway perspective on touchdownshould resemble that on lift‐off, and an appreciation of this is best achieved bylookingwell ahead towards the far end of the runway. Avoid trying to see therunway under the nose of the aeroplane ‐ this wil l almost certainly induce atendency to fly into the ground before rounding ou t .As the aeroplane is flared for landing, the power should be gradually reduced as

the aeroplane enters the hold‐offphase ‐ but n o t beforeflaring. Check the throttleis fully closed asthe aeroplane settles onto the ground. Keep straight during thelandingground r u nwith rudder, and keep the wings levelwith aileron.Maintain the centreline until the aeroplane has slowed to taXiing speed.

Brake if necessary and look at the wingtip to confirm a slow speed. Taxi clearof the runway, stop the aeroplane, set the brakes to park and complete the after‑landing checks.

Touch-and‐Go LandingForatouch‐and‐go landing,you can reselect the flap after touchdown to the take‑offsetting (up) and reapply power. Becarefulwhen retracting the flap, asit ispos‑sible in some aircraft to inadvertentlyselect the undercarriage ‐ especially atnight.You may need to retrim.

742 Night Flight

Be careful n o t to look inside the cockpit for too long. Try to feel and reachthe controls and only look as a quick check. It is useful to practise andremember how long for electric tr im or how much wheel movement it takesto approximately reset the trim from landing to take‐off.Reintroduce full power, and keep straight asyou do so. Keep heading for the

black hole atthe other endof the runway. Continue for anormal take‐off, rotateon speed, focus on the attitude indicator, watch the heading indicator and beready for an engine failure.

Go-Around at NightThe flying technique for ago‐around at night is the same asby day, except thatit is done primarily by reference to instruments. The runway lighting availableduring the latter stages of the approach are no longer visible when full power isappliedandpitch attitude raised. There may be strongpitchandyaw tendenciesdue to the power increase, and these must be controlled (with reference to theflight instruments). Retract the undercarriage. Hold the desired attitude on theAI, monitor vertical performance on the altimeter, monitor airspeed and main‑tain centreline. Partially retract the flaps with apositive rate of climb.

\ fllRSPEEDr / l \ A-RSPEED //~-150 mm 40 ~ 150 mm. 4”

gun ‘n 60. o 140 \i so

Figure 6-7 Night go-around ‐ power and attitude.

Continue the initial climb to 500 ft AGL, look for aircraft that may bejoiningcrosswind and commence a normal climbing t u r n on instruments. Leave theboost (fuel) pump on for all night circuits unless advised otherwise by the flightmanual.


When established on crosswind, slowly look back at the runway to orientyourselfand to see the general picture. To look back any earlier is risky becauseyou have to t u r n further to see the runway. It ismore difficult to maintain aconstant attitude asyou do this and you also risk the leans. Do n o t move yourhead quickly, especially if you are rolling into or o u t of a t u r n ‐ the combinedmotion can induce powerful illusions.

Lef t downwind - n igh t

Right downwind ‐ correct

Figure 6-8 Perception of height can be skewed between right and left circuits.

To tu r n downwind, re turn to instrumentswith some allowance for wind. Usethe headingneedle asaguide. Remember that the aircraft isflownwith referenceto the instruments andpositionedwith respect to the runway. The aircraft is onlyflown visually on final approach and during the initial take‐OErun .

744 Night Flight

The t u r n to downwind is initiatedwith allowance for t u r n radius. The bankangle is adjusted to roll o u t at normal lateral spacing from the runway (with thewingtip overlapping or tracking down the runway). There is a need to scanthe instruments for attitude and performance. Watch the runway to assessspacing, adjust heading accordingly and look for other circuit traffic. There isa tendency to think you are closer than you should be and to over correct .Complete the downwind or pre‐landing checks ‐ you will appreciate the

value of n o t having to readachecklist. Hold the gear lever until you have threegreens.Be aware of the visual illusion that can happen on downwindwith regard to

height and spacing (refer to figure 6‐8).Start the stopwatch abeam the threshold and t u r n base at 30‐40 seconds

(whenthe aircraft is on aline 45° from the runway centreline). Initiate the baset u r n as you would during the day, but fly with reference to the attitudeindicator. Simply adjust the power, set the attitude in bank and pitch, lowerthe flap if appropriate, adjust the attitude and tr im the aircraft. There is aneedto scan from the attitude indicator to the performance instruments to therunway and thenback again ‐ similar to the downwind tu rn . This is aselectiveradial scan (as you were taught in instrument flying), but it is widened toencompass the runway. Be careful n o t to let the nose drop as the power isreduced.When the attitude, power and configuration are set for the approach,

accurately tr im the aircraft. Adjust the power to correct for any feeling ortendency of being too high or too low and for any expectedheadwindon finalapproach. Make an associated adjustment to the attitude to maintain airspeed.Turn final early, and look o u t for other traffic when on final or on the runway.

Chapter 7

Abnormal Operations at Night

Risk ManagementFirst ventures into adark night can be traumatic, especially for passengers ‐ butthese first ventures need n o t be. Night flying is n o t inherently difficult; n o r isit more dangerous. It is the same asflight by day, but it requires more activescans of the attitude indicator and the performance instruments. Night flightand situational awareness do require concentration and cockpit organisation sothat your mind is n o t diverted from important tasks. Night flying is unforgiv‑ing of error and inattention. Furthermore, your senses can become confused.The essence of safe and pleasant night flight is preparation.

WorkloadThe more workload there is in flight, the less safe you are. You need to thinkcarefully about workload when choosing anaircraft for night flying ‐ it ispref‑erable to fly a well‐equipped aircraft with autopilot, redundant systems andnavaids. It is usual to have atu rn coordinator or t u r n and balance indicator asthe backup for attitude indicator failure or vacuum failure. If anaircraft witha standby attitude indicator is available, use it ‐ it’s life assurance, asflying onlimitedpanelsignificantly increases the workload and the risk of loss of control.A headingindicator is asecond‐class alternative to amagnetically aligned head‑ing indicator. Fixed card RBIs also cause added workload asthey are muchmore difficult to interpret. If you have a choice, fly anaircraft with anR M Ior HSI. At night and in IMC, they can be anecessity, n o t a luxury.

Use the flight aids asthey are designed to be used, and use the spare capacitythey give you to manage the flight ‐ I would n o t fly solo I M C or night cross‑country without a serviceable autopilot. Do n o t trust GPS asthe sole sourceof navigation data.

Briefing a n d Using the FrontSeat PassengerLike the GPS and other devices, the front seat passenger can be agodsend or anuisance and will either ease or add to the cockpit workload significantly (andthe workload for single‐pilot night flight is already high). If sensible use ismade of this side‐by‐side aid, your flights can be apleasure. If your front seat

745

146 Night Flight

passenger is involved in the planningstage of aflight and is briefed of his or herduties, youwill have ateam playerwho can helpmakenight flyingmucheasier.Tell your front seat passenger to act asyour watchdog andmake sure that theyknow to let you know if you miss aradio call, misinterpret aninstruction, mis‑set a heading or forget an assigned altitude.Conversely, If you are the front seat passenger (spouse especially), you can

make or break a night flight and the pilot ‐‐ you can make the pilot smile orscream. There is a delicate balance between constructive and criticalcommentary. Do n o t add to a pilot’s workload by diverting attention towardsmenial things. Do n o t add to apilot’s stress levels by complaining of lateness orby trying to hurry himor her. Do keep children under control and, above all,do n o t question apilot’s decision to t u r n back or to land before dark.

Selection of Route andCruising LevelAswell asfuel, terrain and navigation considerations, select the rou te that givesbest visual references and escape options in the event of loss of power, lightingfailure or loss of navaids and communications. Flying coastal routes offers thebest options. Avoid longsectors over mountainous terrain. Stay near highwaysor rivers in remo te areas.

. , e ' i g h t .iEr'Zii

Inadvertent/Unplanned Night FlightIf you r u n ou t of daylight while cruising, immediately climb above LSALT. Flyinstruments if the horizon disappears. Engage the autopilot. Turn on thecockpit lights. Tune and identify the aids. Continue planned track if the des‑tination has lighting and an NDB. Otherwise, divert to the nearest suitablealternate. Check the fuel situation. Tell ATS what you are doing.

lnadvertently Entering CloudIf you inadvertently enter cloud, select the following:' pitot heat on;0 carburettor heat on; and° strobe lights off.Check that all seat belts (yours and those of your passengers) are fastened.

Stabilise the flightpath (constant attitude andpower), trim carefully and engagethe autopilot. If you have no rudder trim, keep the aircraft balanced with

7: Abnormal Operations at Night 747

rudder (an aircraft that is unbalanced ‐ sideslipping ‐ will confuse both yourinner ear and the autopilot). If there is lightning or dark clouds, tu rn on ‐ ortu rn up ‐ the cockpit flood lights. Stop lookingout, and keep your head still.Start aregular scan of the instruments sothat you are already on the clocks foraperiod before losing sight of the horizon.Make ano te of which direction you would t u r n if you had to descend (i.e.

the direction which offers the lowest LSALT and is clear of hills). Note theactual cloudbase when entering.

Temporarily Uncertain of PositionDo n o t trust GPS as the sole source of data. At night, it is easier to lose theplot ‐ to lose awareness of where you are or, conversely, to over‐anticipate andpanic about alack of visual information. Bepatient. If you haveplannedwelland logged the last fix, you can fly an accurate heading and anticipate what isdue nex t . You wil l be right. In the meantime, use other aids to check yourprogress. If an expected feature does n o t appear on time (and at night it mayn o t appear at all), plan ahead for the n e x t one. Heading, time and airspeed arethe navigation tenets of the old pilots ‐ and these tenets still hold true. Do n o tforget the cockpit house‐keepingduties. Maintain regular systems scans and inparticular, do aregular CLEAROF check. (Do n o t forget to check and realignthe HI ) :

Compass Align the direction indicator.Log Log departure time from known position on map(s) and flight plan.

Maintain a progressive flight log.Engine Engine temperature and pressure ‐ check in the green.

Check correct power setting for cruise.Lean mixture.

Altitude Check QNH and safelyclear of terrain.Check cruising level.

Radio Check on correct frequency.Radio calls made if appropriate.Radio navaids tuned, identified and tested.

Orientation General direction correct and map aligned with flightpath.Fuel Selected on correct tank (times logged).

In balance.Amended arrival fuel state.

Figure 7‐1 CLEAROF check.

748 Night Flight

Maintain a flight log with confirmed positions and time. Whatever you aredoingandwhenever you do it, keep the wings level‐ avery slight wingdown is themos t c ommo n cause of awandering heading, inaccurate navigation, apotentiallydiverging flightpath and, ultimately, a spiral dive. The best means of reducingworkload and keeping the wings level is the autopilot. Centre the heading bugand engage the autopilot.If the GPS fails or if the il’lCXt feature does n o t appear asexpected, double‑

check the heading you have been flying, the time and the position you shouldhave achieved and the probable direction of error. If there is a navaid nearby,track to pass overhead and plan your journey from there. Inform air traflicservices of your predicament and intentions. If you cannot track to overhead,tune t w o navaids to gain an approximate fix. Note the time, check the HI isaligned and t u r n towards your nex t waypoint. .D’in doubt, callfor assistance.

me gency Rad'o'ProceduresRequest assistance whenever you have any serious doubts regarding the safetyof a flight. Transmission should be slow and distinct, with each word pro‑nounced clearly sothat there is no need for repetition. This of course shouldapply to all radio transmissions, but it is especially important in emergencysituations.

Declaring an EmergencyAspilot in command, it is your responsibility to ensure the safety of your pas‑sengers, yourself and your aircraft. As pilot in command, you have a duty ofcare to your passengersWhether fare payingor no t . You are responsible for theirsafety andliable for any injuries they might sustain. If in doubt, declare anemer ‑gency. If you do find yourself in real difficulty, waste no time in requestingassistance from an ATS unit or on the appropriate CTAF. Timely action mayavoid an even more serious emergency.

What is Considered to be an Emergency?It is impossible to outline all possible emergency situations. The declaration ofan emergency by the pilot in command is amatter of operational judgement.Emergencies can be classified according to the urgency and to the degree ofseriousness of the consequences ‐ aspilot in command, you decide, but youmust always er r on the safe side. Some categories might be:° uncertainty of position and inability to confirm direction to proceed;' uncertainty of position and fuel reserves;


- loss of oil pressure, a rough running engine or fuel depletion that may beinsufficient to reach anairfield;

' some doubt about the serviceability of the aircraft or systems or the medicalcondition of the pilot;

° loss of electrical power;0 loss of the primary attitude indicator; and° risk of loss of control due to reducedVisibility or risk of controlledflight intoterrain due to rising ground and loweringcloudbase.It is impossible to set hard and fast rules. If in doubt, tell someone what the

potentialproblem isanddo it earlier rather than later ‐ when there isstill plentyof time and fuel. If there is any urgency, formally declare an emergency ‐ atleast apan‐pan. If there isany risk of loss of control or injury, declare amayday.

ToDeclare an EmergencyIf an emergency arises, it is your responsibility aspilot in command to assessjust how serious the emergency is (or could be) and to take appropriate safetyaction. The pilot has the ultimate responsibility for the safety of the aircraft.Many emergencies require your immediate attention and occupy you fully

for some moments, but it is advisable at the first opportune mome n t to tellsomeone. Radio can play a vital role when assistance is required; however, inan emergency, always remember that your first priority is to control andposition the aircraft.There are three degrees of emergency and aspilot in command you should

preface your radio call with either:- mayday (repeated three times) for a distress call;° pan-pan (repeated three times) for an mgemy call; and° security (repeated three times) for asafety call.

Distress Message (Mayday Call)A mayday is the absolute top priority call. It has priority over all others, and theword mayday should force everyone else into immediate radio silence (mayday isthe anglicisedspellingof the Frenchm’aidez/ [‘helpme’]). You shouldmake adis‑tress call assoon asis convenient following the onset of the emergency. Youmustuse your operationaljudgement, and you must n o t delay transmission of the dis‑tress message (e.g. by trying to determine your position precisely in the absenceof suitable landmarks or in conditions of poor visibility).When you require immediate assistance and are being threatened by grave

and immediate danger, the mayday distress message should be transmitted overthe air‐ground frequency you are presently using.

150 Night Flight

If you are currently operating on a CTAF and receive no response to yourdistress call * and if you have time ‐ repeat the call on the flight informationarea (PIA) VHF frequency asshown on enrou te charts (ERCs), visual terminalcharts (VTCs), visual navigation charts (VNCs) or ERSA. If there is still noresponse ‐ and if time permits ‐ change frequency to 121.5 MHZ (theinternational emergency frequency usually monitored by airliners and someground stations) and repeat your distress call.If your aircraft is transponder equipped, squawk code 7700 (the emergency

and urgency transponder code). If you are in a radar environment, this causesa special symbol to appear around your aircraft on the AT C radar screen andrings analarm bell immediately alerting the ATC radar controllers.For example, you experience an emergency in the Gilldoola area and

transmit your distress call on the local FIA frequency (on which you aremaintaining a listeningwatch).Pilot: Maydaymaydaymayday

Foxtrot Papa Delta, Foxtrot Papa Delta, Foxtrot Papa Deltatwo zero miles west of Gil/doo/a at this timealtitude four thousandWhite Cessna one eight two with redstripesengine failureforced landing in open paddockone person on board

There isno reference to heading, airspeedor endurance in this call, asthe pilotconsiders them to be irrelevant.Air traffic services would acknowledge this call asfollows:ATS: Foxtrot Papa Delta

BrisbaneRogermaydayDo you require assistance?

Appropriate search and rescue (SAR) action would then be commenced underthe supervision of the senior air traflfic controller. The SAR action may includeBrisbaneair traflic services imposingradio silence on all other traffic, if appropriate.If there isno immediate response from agroundstation acknowledgingyour

call, the distress message shouldbe repeatedat intervals. Other aircraft hearingthe mayday call will have imposed radio silence on themselves, but havingnoted that the distress call was n o t acknowledgedby agroundstation, they mayat this stage be able to assist by relaying the distress call to aground station.Note. The format of the mayday distress call is shown on the last page ofERSA.


UrgencyMessage (Pan-Pan Call)When an emergency exists but does n o t require immediate assistance, anurgency or pan‐pan message ismade over the air‐ground frequency in use orthe relevant FIA frequency if considered more prudent. Typical situations inwhich apan‐pan urgency message is appropriate include the following:' if you are experiencing navigational difficulties and require the urgent assis‑tance of air traffic services;

° if you have apassenger on board who requires urgent medical attention;- if the safety of an aeroplane or a ship you observe is threatened and urgentaction is perhaps needed; and

' if you are making an emergency change of level in controlled airspace andyou may conflict with trafiic below.For example:Pilot: Pan-panpan-panpan‐pan

AdelaideA/fa Charlie Echotwo zero miles south of BrokenHillat three zeroheading two five zeroairspeednine zero knotsthree thousand feetPiper Warriorexperiencing severely reduced visibility in dust stormdescending to landon agricultural strip.

Priority of CallsOf the emergency calls, the distress call has top priority. The urgency call doesn o t have ashigh apriority asthe mayday, but it isn e x t in priority. Other pilotsshould impose radio silence for asuitable period depending upon the circum‑stances. Any aircraft in an emergency situation haspriority over all other aircraft.If a situation giving rise to a mayday or pan‐pan call changes so that the

distress or urgency condition no longer exists, the pilot should cancel the callby transmitting ‘cancel mayday’ or ‘cantel pan‐pan’ and cease squawking code7700 on the transponder.

Imposition of Radio SilenceAn aircraft in distress or the appropriate ground station can impose radio silence onall other stations in the area or on any station causing interference by asking themto stop transmitting:

Pilot: All stationssilence (SEE-lance)mayday.

752 Night Flight

Loss of Radio CommunicationLoss of communication can cause problems in flight, especially when operatingin busy terminal areas. ERSA EMERG gives guidance on the procedures tofollow in the event of loss of radio (refer to figure 7‐3, page 154).If radio failure occurs in flight, you should t r y to locate and rectify the fault

(your flying instructor will show you the routine fault‐finding procedure foryour aircraft). It will involve aprocedure of checking the items asoutlined inthe following.

Failure to Establish or Maintain CommunicationAir to Ground. If the pilot is unable to communicate with the ground stationon the desired frequency, there could be a total loss of communication, or thepilot could hear the ground station without the ground station hearing thepilot (or vice versa).Check the following:

0 correct frequency selection;- sidetone;° head set plugged in correctly;0 aircraft master/avionics switch on, VHF ‐COM set on and volume correctlyset;

° squelch function and level;0 speaker/headphones correctly selected or audio selector panel ( i ffitted) cor ‑rectly set (try using the hand‐heldmicrophone in the case of head set failureor vice versa); and

0 circuit breakers/fuses, but only if easily accessible without distraction to n o r ‑mal flight.If you still have no success, t ry communicating on an alternate frequency

if available, or revert to the previous frequency in use. Alternatively, considerrequesting another aircraft to relay your message, or try any other groundstation.If operating in a radar environment andyou lose radio contact, squawk 7600

on your transponder. Stay in VMC and land at the most suitable aerodrome.Follow ERSA procedures in controlled airspace.Following a Loss of Communications Should You Land As Soon As Possible?After experiencing a radio failure, your operationaljudgement will determinewhat procedures you follow andwhether you land at the nearest suitable aero‑drome or complete the flight planned route. Do not allow the radio failure tounsettle you. The aeroplane does not need a radio tofly!


Light Signals Used at Controlled Aerodromes. If you suffer radio failure at anaerodrome at which a control tower is in operation, ATC may continue todirect your flight via light signals. These light signals are directed from thetower and are listed in the AIP and ERSA GEN. You should memorise them(refer to figure 7‐2).

EmergencyLocator Transmitter (ELT)The emergency locator transmitter (also known as the VHF survival beacon(VSB) and emergency locator beacon (ELB)) is aVHF radio transmitter capable ofsending a signal simultaneously on the international distress frequencies of121.5 and 243 MHZwhen activated. Each unit has its own power source (bat‑tery), sobefore setting o u t on aflight where the carriage of anELT is required,check that the battery recharge date (stampedon the BLT) has not expired.

14.1 Light Signals to Aircraft

nght Signal Meaning in Flight Meaning onAerodromeSteady Green Authorised to land if pilot Authorisedtotake-off ifpilot

satisfied no collision risk satisfied no collision riskexists. exists.

Steady Red Give way to other aircraft Stop.and continue circling.

Green Flashes Return for landing. Authorised to taxy if pilotsatisfied that no collisionrisk exists.

Red Flashes Aerodrome unsafe ‐ donot Taxi clear of landing area inland. use.

White Flashes No Significance Return to starting point onAerodrome.

Figure 7-2 Light signals used to control aircraft (AlP ENR 1.5 para 14.1).

ELTs can easily be activated unintentionally, possibly causing unnecessaryrescue action. As a check, it is a good idea to monitor the VHF‐COM radiobriefly on 121.5 MHZ prior to leaving the taxiing area at the commencementof aflight and when taxiing back to the parking area at the completion of theflight. If anELT signal is detected, check the status of your own ELT. If thesignal is fromanotherELT, report receptionof the signal to the nearest air trafficservices unit (refer to figure 7‐4, page 155).Action byAircraft Hearing an ELT Signal. Aircraft equipped to receive onemergency frequencies 121.5 or 243 MHZ should tune to these frequenciesonce or twice on each long flight and if convenient report any signals heard(ELTs emit asiren‐type sound). Report the reception to the particular ground

154

1.51.5.1

1.5.2

1.5.3

1.5.4

Night Flight

Communication FailureIn the event of communications failure, maintain terrain clearance throughout allprocedures.Indications by an Aircraft:a . m m

(i) during the hours of daylight - by rocking the aircraft's wings; andNOTE:This signal shouldnotbe expectedon the base andfinallegs of the approach.(ii) during the hours of darkness - by flashing on and off twice the aircraft's landing

lights or, if not so equipped, by switching on and off twice its navigation lights.b. 0n the Ground

(i) during the hours of daylight: by waggling the aircraft's ailerons or rudder; and(ii) during the hours of darkness: by flashing on and off twice the aircraft's landing

lights or, if not so equipped, by switching on and off twice its navigation lights.If VFR in Class G Airspacea. Remain in VMC.b. Broadcast Intentions (assume transmitter is operating and prefix calls with

"TRANSMITTING BLIND"),c . RemainVFR in Class G airspace and land at the nearest suitable aerodrome,d. Reportarrival to ATS if on SARTlME or reporting schedules (SAR telephone number:

1800 815 257).If in Controlled/Restricted Airspace or if IFR in any Airspace:a. Squawk 7600b. Listen out on ATlS and/or voice modulated NAVAIDs.c. Transmit intentions and make normal position reports (assumetransmitter is operating

and prefix calls with "TRANSMITTING BLIND").AND

WMd. Stay in VMC and land at the most suitable aerodrome (note special procedures if

proceeding to a GAAP).OR

if in NC or are uncertain of maintainingVMCe. if no clearance limit received and acknowledged, proceed in accordance with the

latest ATC route clearance acknowledged and climb to planned level.f. If a clearance limit involving an altitude or route restriction has been received and

acknowledged:(i) maintain last assigned level, or minimum safe altitude it higher, for three (3)

minutes, and/or(ii) hold at nominated location for three (3) minutes, then(iii) proceed in accordance with the latest ATC route clearance acknowledged, and

climb to planned level.g. If being radar vectored:

(i) maintain last assigned vector for two (2) minutes,(ii) climb if necessary to MSA, then(iii) proceed in accordance with the latestATC route clearance acknowledged.

h. It holding:(i) fly one more complete holding pattern, then(ii) proceed in accordance with the flight plan or the latest ATC clearance

acknowledged, as applicable.NOTES:1 initialand subsequent actions by the pilot at the time of loss of communications willdepend largely on the pilot's knowledge of the destination aids, the air traffic/air spacesituation and meteorological conditions en route and at the destination. Publishingprocedures that coverallradio failure circumstances is notpossible. The above proceduresensure that ATS and other traffic should be aware of the pilot’s most likely actions. Pilotsshould follow these procedures unless strong reasons dictate othenrvise.2 In determining the final level to which a pilot will climb after radio failure, ATC will usethe levelprovided on the flight notification, or the last level requestedby the pilot andacknowledged by ATC.

Figure 7‐3 Extract from ERSA EMERG.

7: Abnormal Operations at Night

'1.101.10.1

1.10.2

1.10.3

1.10.4

FIG 1.By joining strips of householdaluminium foil, construct a

155

Activation of ELTAn Emergency LocatorTransmitter (ELT) is avaluable search aid if an aircraft is forceddown. However, toobtain maximumbenefit fromthe beacon and toassist search aircraft.pilots need to observe a few guidelines for activation of the ELT.if inwater and the beacon is buoyant, the ELT should be activated in the water andallowed to float to the end of the lanyard with the aerial vertical. Donot hoist the ELT upa mast.The performance of an ELT may be degraded if it is raised above the watersurface.Lives may depend onthe correct use of the ELT.The manufacturer's instructions shouldbestudied thoroughly, and kept in the aircraft emergency kit.if you are forced down the following procedure is recommended:a.b.c.

d.

H 2 0 c m ‐ >

120cm square.

Activate the ELT immediately;Where the ELT is permanently installed in the aircraft, activate the beacon in situ;Where the ELT is not permanently installed in the aircraft, select an elevated siteclear of trees, boulders etc. and reasonably close to the aircraft.Place the beacon onthe ground on an earth mat. if an earth mat is not available,

An ELTwhich is damaged or underwreckage may still transmit some signal. (Alwaysactivate the ELT).Do not switch off the ELT unless rescue is no longer required.To avoid confusing COSPAS/SARSAT and direction finding equipment, avoidactivating two or more ELTswithin 1NM of each other.

FIG 4If y o u are required to use theELT follow the directions listedunder “EMERGENCYACTIVATIONOF ELT"

Figure 7-4 Extract from ERSA EMERG on ELTs.

FIG 2 FIG 3.Carefully fold the earth mat to Tie or tape the folded eartha convenient size. mat to your ELT

756 Night Flight

station frequency you are on. This wil l ensure that the rescue coordination centre(RCC) receives early advice of the activation of abeacon. The R C Cwill thenrequest a listening watch on this frequency by all suitable aircraft in the area.These aircraft will be asked to report their positions and altitudes (or flight lev‑els) when the signal isfirst heardandwhen it fades. Fromthis information, theR C C can plot position lines, thus localising the likely position of the BLT. Asearch aircraft can then be despatched to the area to conduct ahomingproce‑dure, which should result in the early rescue of survivors. Remember that yourELT has a total transmitting life of between 24 and 48 hours (depending ontype and age of batteries).An air traffic services unit will declare a distress phase assoon asit has been

notified of a locator beacon activation. Search and rescue procedures wil l thenbe implementedby the RCC . (Refer to CAO 2011.6 and ERSAEMERG.)

Engine Problemsm i m m w fi m m i w w fl w m m m wfi g x ‘ i “ i s : - ‘ . . : ‘ i = i §~ " - ‘ £ " i im r 3 “ " 7

Engine SymptomsIt is usual to hear slight changes in the engine note when you fly cross‐countryat night, enter cloud or rain, fly over mountains or fly over water. Mostchanges may be imaginary, but n o t all. In cloud, there can be changes inengine n o t e or airflow noise due to rain, hail, turbulence or icing. Watch therpmand oil pressure. If there is any rpm drop or fluctuation, select carby heatto hot. If there is any oil pressure drop, declare apan-pan and plan the safestrou te to descend if it becomes inevitable. Consider a diversion to the nearestsafe airfield. If there are any fuel pressure fluctuations or rough running,change tanks, select both, t u r n on the boost pump and check the mixture ‐ itcould be t o o rich or t oo lean. Check that the primer is in and locked ‐ if it iscreeping out , it will cause rough running.

Engine Failure: Single EngineTake‐OffOn the runway, anaborted take‐off is the same atnight asduring the day. Afterlift‐off, set the glide attitude, gear down, full flap, landing light on and look forany clear path. Do n o t even consider a t u r n back unless you are established inthe climb andyou can see the runway through the windscreen or side windows.

CruiseTotal engine failure at night is a crisis, and the prospect of a forced landing atnight is probably the single mos t common reason for many pilots avoiding


night flight. Again, the answer lies in the planning and route selection. Don o t forget you will also lose the vacuum (suction) system with engine failure ifyour aircraft has an engine‐driven vacuum pump. Electrics are restricted bythe capacity and condition of the battery.

Set the glide attitude and airspeed, and trim the aircraft. Carry o u t theimmediate actions and trouble checks. The likely causes are fuel (contents,selection, pump or mixture) or carburettor icing, and these may be easilycorrected.

There are few cues to locate asuitable landing area. If you have planned theflight, it may bethat you can detect abeach or lake shore. Conserve electricalpower. Turn o f f everything except one radio and the cockpit lights. Savebattery power for amayday call and briefillumination of the landing light for

A highway may be the only option,there may bepower lines. Bewary of high terrain and no te the localelevation.Wind isaconsideration if you have achoice. A forested area may beacceptableif the trees are small and you settle gently and slowly into the tree tops. Anupslope is a better option than down, and it will show better in the landinglight. You will need to flare earlier and more.

Approach a n d Landinganightappiaachand cirsuit sntmmhe same as.durlggiliéflleLOthemagte n o u g hto’glidierto therunway in the event of engine failubfeliaftefpa’ssingabeam«»the‐thresh,old_on about this when onHave a pre‐selected clear area and direction to turn in mind.

Engine Failure: TwinNight Take-OffHave your self‐briefbefore lining up. Mentally rehearse immediate actions inthe event of an engine failure before and after lift‐offor gear selection. Planyour actions to return for an engine‐out landing ‐ but don’t rush. Clean upthe aircraft and gain altitude before turning.

CruiseDuring the cruise, engine failure in a twin is n o t a major problem. Controlthe yaw and use the autopilot. Carry o u t a trouble check ‐ especially of fuelcontents and selection. Nurse the live engine by reducingpower and openingthe cowl flaps. Allow acruise descent but n o t below LSALT. Change track ifthere is an option with lower terrain.

guilt .r27

758 Night Flight

Approach and LandingEngine failure during the approach and landingis quite controllable. Continueto fly the approach while preventing any yaw. Keep the ball centred (whichmeans there is a slight sideslip, but flying wings level with the ball centred isprobably less disorienting than banking towards the live engine). During theapproach, you need low power and soperformance is probably n o t an issue.Consider retracting the undercarriage until anormal approach path is assured.Do n o t select full flap until you have reached the decision height and you havemade the decision to continue. Even then, it may be better to continue withpartial flap rather than full ‐ it will depend on the aircraft type and the effectsof flap in that aircraft.

E e c t ' i ' , . . , . .Unless your aircraft has t w o engines and t w o alternators, the electrical systemhas one power source (the alternator) and one short‐term backup (the batter ).The engine ignition, vacuum‐driven instruments, pressure instruments andflight controls are unaffected in asmall aircraft, but you may lose some or all ofthe following:° autopilot;0 some internal lights and all external lights;' some instruments (and pitot heat);° flaps (electric);° navaids; and° radios and intercom.

An electrical failure may compromise the attitude indicator, the headingindicator or the t u r n coordinator ~ but n o t all three together. It is n o tpermitted for them to share a c o m m o n power source. Some t u r n coordinatorshave anindependent power supply. An electrical failure could make the pitotheat unavailable, leading to icingproblems. An electrical failure will also causethe radios to fail eventually when the battery energy is consumed. Navigationbecomes DR unless you have a hand‐held GPS. Radar assistance may berequested, but that requires VHF ‐COM. Use your mobile phone if necessary.

You may have electrically operated flaps, so a flapless landing may berequired. You will lose all but the emergency cockpit lighting. Planano‐radiopattern entry for a flapless landing with no landing light. It is n o t asserious asit sounds. You will be able to operate each of these services for a limited timeon the battery (hopefully it was fully charged and serviceable). The pitot heat,landing lights and flap m o t o r all use significant electrical capacity. Remember


that n o t only can you n o t see other aircraft, they cannot see you ‐ eithervisually or via your transponder.

With total electrical failure,fly the aircraft. Maintain attitude while you getthe torch set up. Use your co‐pilot to assist and ensure he or she keeps theprimary flight instruments illuminated. Save what battery life you have forradio calls and abriefuse of the landinglight by switching offall non‐essentialelectrical services.

You may be able to reselect the alternator after reducing the electrical loador turning off any suspect equipment. Try it once, but only if there is noelectrical smell and no signs of electrical short or fire. Remember to fly theaircraft concentrating on your orientation, paperwork and torches. Plan theapproach and use the co‐pilot.

If there are indications of anelectrical failure, check that the master switchis on, and check any circuit breakers or fuses. Do n o t interrupt your flightinstrument scan for more than afew seconds. (Insome aircraft, master switchesalso ac t ascircuit breakers, particularly the split‐rocker type master switches.They can be turned on and off to recycle, an action which may restore full orpartial electrical power.)

No-Light LandingA night landing without the landing light is n o t difficult. Many pilots makebetter landings without the light because they are n o t tempted to fly down thebeam and they take awider View of the runway perspective. Bear in mind that

to look o u t for them.

Cockpit Lighting FailureThe loss of external lighting isn o t asserious asthe loss of cockpit lighting. Allflight isvisual ‐‐whether it isbyreference to the real‐world horizon or the min‑iature one inside the attitude indicator. To retain control, you mus t beable to seeone of these. In this situation, your fully charged, hand‐held torch will save yourlife and the lives of your passengers.

P , , .Pitot Tube Blockage

A damaged or iced pitot tube may affect the airspeed indicator. It may evenfreeze totally. The use of electric pitot heat will generally prevent the occur‑rence of icing problems in the pitot‐static system. However, a more serious

160 Night Flight

and embarrassing situation is apitot cover that has n o t been removed prior toflight. Check that the ASI reads before lift‐off.If the A81 is unusable in flight, all is n o t lost. Selecting asuitable attitude on

the AI and suitable power on the power indicator should result in the desiredperformance. Some flight and operations manuals provide tables of powersettings andattitudes for use in the event of anASI failure. If n o n e is available, itis asimple matter to commit the basic settings for the various configurations offlight to memory ‐ you should know them already.

Static Vent BlockageA damaged or blocked static system will affect the ASI, the altimeter and theV81. If totally blocked, a constant static pressure may be trapped in the system.The altimeter indication will n o t alter, and the V51will remain on zero, evenwhen the aeroplane changes altitude. The A81will indicate an incorrect air‑speed. As the aeroplane climbs, trapped static pressure will cause the ASI toreadtoo low. The danger is to follow the false ASI readingandaccelerate, pos‑sibly exceedingVNE (never exceed speed).Conversely, the trapped pressure will cause the A81 to overread on descent.

The danger on descent is to follow the false ASI indication and slow up, possiblystalling. Most aircraft are fittedwith analternate static source. If this is selected,the affected instruments shouldbecome usable, with aneed to apply correctionsto the indications in some cases.Remember that cabinpressure in anunpressurisedaircraft is slightly lower than

the external static pressure due to the venturi effect created by the motion of theaeroplane through the air. This slightly lower static pressure could cause thealtimeter to read50 ft to 100 ft t oo highand the airspeed indicator to read5 kt orsotoo The vertical speed indicatorwill show abriefclimb asthe lowerstaticpressure is introduced, but it will then settle down and readaccurately.

Failure of Aerodrome LightingMost aerodromes have astandby power supply that will operate within secondsof anaerodrome power failure, but there is apossibility that acomplete powerfailure could occur. Aircraft in the vicinity of an aerodrome without runwaylighting atnight should hold at asafe height. If the lighting isn o t returned toservice, consideration shouldbe given to diverting (at asafe height) to anearbyaerodromewhere runway lightingis available. A radar service may be availableto assist in tracking. ‘


mited-Panel InstrumentFlyingAttitude Indicator or Vacuum Failure

Although aircraft instrumentation isbecoming increasingly more reliable, manyGA aircraft are ten, twenty or even thirty years old, andwe have to consider thepossibility of one or more instruments failing in flight. The mos t serious failureisthat of the attitude indicatoror its power source ‐ anormal scan will show thatthe AI n o t responding or is toppling or that the vacuum gauge is showing alossof suction. Immediatelymistrust the AI and give greater emphasis to the otherinstruments. The AI may fail totally and suddenly, or it may wander asthe gyroslows. In either event, try to ignore it. If you do n o t have astandby attitude indi~cator, you are now on limited (partial) panel.On limited panel, you mus t use second‐hand information to deduce the

aircraft’s attitude. It is necessary to treat pitch attitude and bank angleseparately. Try n o t to change both together ‐ have one under control andstabilised before varying the other. Without the A l , the effects of inertia mayappear to be more marked ‐ make changes smoothly and gently using the‘change, check, hold, adjust, trim’ technique. Any tendency to chase theneedles mus t be consciously avoided.Due to the absence of immediate and direct presentation of attitude changes

and because the ASI, altimeter and VSI suffer lag, it is even more important tohold any new attitude (constant control position) and allow time for theperformance instruments to stabilise before making any further adjustments.Then trim.In apartial‐panel situation, reduce the rate and extent of control movement

and pause between inputs. The lag in readings will then be less severe, andthere will be less tendency to over‐control. Small control inputs should bemade then the controls checked and heldWhile the performance instrumentscatch up andsettle into their n ew readings. Fine‐tunewith further adjustmentsbefore trimming.When using a partial panel, the scan will need to be modified to bypass the

unusable instruments. A toppled AI can be very distracting because you havelearnt to trust it. Cover it if necessary. Focus on the instruments that Will giveyou the informationyou require. Refer to the turn coordinator for bank ‐ willn o t tell you the bank angle directly, but it will tell you if the aeroplane isyavvingorrollingand, if it is,whichway andatWhat rate; you can get some idea of bankangle from this. Keep the ball centred because the tu rn coordinator and tu r nindicator respond to yaw. Centre the ball, and then the little aircraft or t u rnneedle can becentred (rolled) to level the wings.

162 Night Flight

The autopilot often has its own source of attitude information (e.g. from thet u r n coordinator) if the AI isvacuum‐driven. It can be of great assistance if thevacuum system or A1 fails. For pitch attitude, you need to leave the powerconstant and use the ASI, altimeter and VSI asguides to level flight. Theposition of the control column is an important cue to attitude in relation toairspeed ‐ control column back, high attitude, low airspeed; control column alittle forward, attitude reduced, airspeed increased.For wings‐level or for a rate one t u r n (do n o t use mo r e than rate one), the

t u r n coordinator is the vital cue. The aircraft is then controlledby t w o separateinterpretations and actions ‐ pitch and roll (bank). It is vital to level the wingsand keep them level. The t u r n coordinator will lag, and soto straighten froma turn, roll towards level and centre the ailerons asthe needle passes rate one.Wait a moment and then make a correction. Then, while keeping the wingslevel, adjust the back pressure to hold a constant airspeed. If the airspeed isincreasing, the nose has dropped and Vice versa. Apply back pressure until theairspeed stops increasing, and hold (check) that position. Then trim.Flyingon apartialpanel is n o t aprecise task, and it is n o t an easy task unless

you are well practised and have no other workload. Declare an emergency(mayday) and maintain straight and level. If you mus t tu rn , tread warily anddo n o t bank past rate one.

Interpreting Pitch Attitude on Partial PanelIf the AI is unusable, the pilot can determine the pitchattitude of the aeroplaneby interpreting the indications of the ASI, altimeter and VSI. The altimeterprovides indirect information regardingpitchattitude. For example, if altitudeis constant in straight and level flight, the pitch attitude is correct for level flightat that power setting, whereas if it is increasingor decreasing, the pitch attitudeis too high or t oo low.The A81also provides pitch attitude information. If the ASI shows that the

desired airspeed isbeingmaintained, the pitch attitude is correct for the powerset. If it indicates an increasing or higher than desired airspeed, the pitchattitude is too low for the power set. Conversely, if the ASI indicates alow ordecreasing airspeed, the pitch attitude is t oo high (figure 7‐5).The A81 is an extremely valuable guide to pitch attitude when used in

conjunction with the altimeter, but it should be remembered that, because ofinertia, anaeroplane will take some time to change speed. Therefore, the ASIindication must be stabilised before it can be interpreted asan indication ofpitch attitude set. In other words, the n ew attitude mus t be held for a fewseconds to allow the airspeed to settle.


Dereasingairspeepitch attitude too high

\ A

160' €140l

' lncesig heig 'pitch attitude too high

IR-07fl2EFS

Figure 7-5 (Left) pitch attitude too high; (right) pitch attitude too low.

The VSI alsoprovides informationaboutpitchattitude. Forexample, if the VSIindication remains at zero in straight and level flight, the pitch attitude is correctfor level flight at that power, whereas a significant and sustained departure fiomZero on the VSIwould indicate apitch attitude that is either too high or too low.In a climb or descent, a steady and fairly constant VSI readingwill indicate a

steady pitchattitude, aswill the other performance instruments. Remember thatlarge or sudden changes in pitch attitude will cause the VSI to initially give falsereadings ‐ another reason to avoidover‐controllingwhenflyingonapartialpanel.The VSImay read erratically in turbulence, souse it with caution, and even thenonly when the readings are relatively steady.

InterpretingBank Attitude on Partial PanelThe pilot can determine bank attitude from the turn coordinator (with the bal‑ance ball centred). The HI ( i fit is available) and the magnetic compass are alsouseful asanindirect indicationofbank. If the aeroplane isin balancedflight (i.e.ball centred), any indication of turning will mean that the aeroplane is banked.A steady zero rate of tu rn readingon the tu r n coordinator with the ball centredwill mean that the wings are level. The normal rate of turn is standard rate orrate one, which is arate of change of headingof 3°/second.

164 Night Flight

Maintaining ControlKeep the Wings level. The turn indicator or coordinator becomes the replace‑m e n t for the AI and must become the focal point of your radial scan. Keeprecentring the t u r n needle or levelling the aeroplane symbol. While doing this,cross‐check the airspeed trend and the altimeter. Make small continuous correc‑tions. Do n o t let any parameter start to wander.

Heading4 maintained

Left turn :at rate 1

Balance ballcentred

Wings level,balance ball centred

In-omaEPs

lR-0704.EPS

Figure 7-7 Bank attitude on a partial panel w i th a turn indicator.


Entering aClimbUnder some circumstances, it may be safer to climb above acloud layer than todescend. There may be alater clear area for avisual descent. Seek radar assist‑ance. A climb is entered asfor visual flight. Apply climb power slowly andsmoothly keeping the ball centred, and allow the nose to rise alittle. Keep thewings level. Hold the nose attitude constant asthe airspeed decays. Watch therate of decay asa guide to cor rec t attitude. As the airspeed approaches normalclimb speed, hold the control column in a constant position and trim.

Entering a DescentReduce power a little (not to idle as this will give a very pronounced nose‑downpitchingand yawingmoment). Keep the ball centred andallow the noseto drop alittle. Then hold the control columnfixed. Watch the airspeed trendand adjust the control position.

Entering a TurnDo n o t consider turning unless the aircraft is stabilised and trimmed in straightand controlled flight. Gently roll into the turn, andmaintain slight back pres‑sure asyou roll. Watch the airspeedbut, importantly, don o t allow the bank tocontinue past rate one. If the airspeedstarts to increase, roll back to wings level,adjust the attitude and start again.

Descending and TurningUnless you are experienced, acombined tu rn and descent carries potential riskasthere will beatendency to overbank and for the nose to drop. Stop the bankandwatch the airspeed. Any increase that isn o t immediately corrected shouldtrigger a re tu rn to wings‐level and then to level flight.

Timed TurnsThe standard t u r n is rate one (3°/second). The most important numbers are180° in 60 seconds and 90° in 30 seconds. Do n o t focus too much on theclock. Note the time starting and coun t to yourselfwhile flying the aircraft.When you are close to the desired time, check the clock and start to roll ou t .The time should betaken from the start of rolling‐in to the start of rolling‐out.When steady, check the magnetic compass and make a correction. On full

panel, the angle of bank to tu rn at rate one depends upon the true airspeed ‑the higher the true airspeed, the larger the angle of bank required. A roughguide which assumes IAS is the same asTAS is that bank angle will be equal toairspeed divided by 10 plus 7. For example, the angle of bank required tomaintain standard rate at 100 kt is 100 + 10+ 7 = 17°.

5% WC Mm. m H373mm] __ 30560 3700 go26 #900.

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766 Night Flight

Figure 7-8Rate one turn.

IR-0506.EPS

11/2 in

ExtremeAttitude Recoveries: Full PanelAn extreme attitude is an excessively highor lowpitchattitude and/or bank anglethat, if uncorrected, leads to large and rapid changes in altitude and airspeed.Extreme attitudes are characterised as:

° a bank in excess of 45°;° anose‐high attitude with arapidly decreasing airspeed; and/or' a nose‐low attitude with a rapidly increasing airspeed.Extreme attitudes are potentially hazardous Without avisual horizon, soyou

should practice the recoveries in the clear.

How Can it Happen?An extreme attitude may result from an external influence (eg. turbulence), amechanical problem (eg. autopilot or lighting failure), or it can be induced byhumanfactors. For instance, i fa pilot becomes disoriented or confused (‘Wheream I?’, ‘Which way is up?) or is preoccupied with other cockpit duties at theexpense of an adequate scan and the bank increases, the nose will drop and thenaturalstability of the aircraftwill cause anincreasingspeed, bank andnose‐downattitude. The aircraft Will exceedVNE andwill probably suffer structural failurein the process.


Nose‐high unusual attitudes are less common, because the pilot can simply letgo of the controls, and the aircraft will soon be in anose‐low unusual attitude.Themos t difficult situations includewhen full powerhasbeenappliedfor ago‑

roundand the pilot does n o t check the nose‐up pitch (trim change), or when inthe first turn after anight take‐offand the pilot is turning and lookingover his orher shoulder at the runway.A mechanical failure can also be the reason for an unusual attitude ‐ for

example, an attitude indicator that, unbeknown to the pilot, either has failedcompletely or isgiving false attitude indications. Runaway electric trim can alsobe aproblem is some aircraft types.Whatever the cause of an unusual attitude, the immediate problem is to

recognise exactly what the aeroplane is doing. It is then a matter of safelyreturning the aeroplane to anormal flight attitude (generally straight andlevel).After the recovery, you shoulddetermine the cause of the event soasto preventany recurrence. In unusual attitudes, the physiological sensations may bedisconcerting, but don o t allow these to influence either the recognition of theattitude or the subsequent recovery action.

Recognisingan UnusualAttitudeIf you notice any unusual instrument indicationor anunexpectedchange ofper‑formance, or if you experience g‐forces or air noise, assume that the aeroplane isin (or about to enter) anunusual attitude. Increase the scan rate and determinethe actual attitude and/or whether or n o t aninstrument hasmalfunctioned.

Having Recognised anUnusualAttitude, DoNot OvercontrolIt is easy to overreact to an unusual attitude with rapid and excessive controlinputs because the occurrence is sounexpected. The simple message is ‘Don’t’!Overreaction can only worsen the situationandpossibly leadyou to overstress‑ing the aircraft or overrevving the engine. When considering recoverytechniques, there are t w o simple principles to keep in mind: i0 removal of bank will aid pitch control; and' intelligent use of power (and drag in some aircraft) will help in controllingairspeed. ‘

Nose-LowAttitude and IncreasingAirspeedIndications ,Refer to figure 7‐10. A nose‐low unusual attitude will be indicatedby anose‑low pitch attitude on the AI with the altimeter unwinding, a high rate ofdescent on the V81and increasingairspeed.

768 Night Flight

An excessive bank angle will oftenlead to a nose‐low attitude, since thenose tends to drop naturally when thewings are banked. If unchecked, thiswill result in aspiral dive (figure 7‐9).

RecoveryRefer to figure 7‐11. To reduce the .Airspe.

. . , I n c r e a s m grate of airspeed i n c r e a s e and to avord \unnecessary loss of height, reduce ggww/power ‐ even closing the throttle if _ m 30:necessary. Engine overspeed is possi‑ble if this is n o t done soon enough.

Throttling back and rolling thewings level can be done simultaneously , De I:keeping the ball centred, but do n o t Hifiggfigeri‘gh‘tum ___ _ "apply back pressure until the wings arelevel. To ease the aeroplane o u t of thedive, smoothly raise the nose through to “ W A - E “

the level flight position on the attitude Figure 7'9 Spiral diVe‑indicator.

50 mm ‘0 ,‘W-.. 60‘

Figure 7-10 Nose-low unusualattitudes.


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lR-OSUEEPS

Figure 7‐11 Regaining normal flight using the full panel.

If the control column is simply pulled back to raise the nose while theaeroplane is still steeply banked, the spiral dive will tighten. Therefore, it ismos t important to roll the wings level first using the AI and the t u r ncoordinator before easing the aeroplane o u t of the dive.There is always adanger of overstressing the airframe with large and sudden

control inputs athigh airspeeds, particularly if back pressure isappliedwhile theailerons are deflected. Hence it isnecessary to ease the aeroplane o u t of the divewith controlled elevator pressure rather than with sudden and panickymovements after rollingwings level.As the aircraft reaches the horizon and the approximate straight and level

attitude ispegged, the airspeedwill check (pausemomentarily) and then start todecrease. This checking of the indicatedairspeed is always a good sign that thehorizon has been reached.The altimeter and VSI readings will also stabilise (subject of course to the

considerable lag in the case of the V81) to indicate level flight or amanageableclimb or descent, depending upon how accurately the horizon has beenpegged. Fromthis point in the recovery,power can beintroduced,attitude canbe adjusted and the aircraft can be trimmed for straight and level flight.Alternatively, if you prefer, you can climb to regain lost altitude.

770 Night Flight

Once in steady straight flight, the heading indicator should be checked toensure that it is alignedwith the magnetic compass.

Nose-High AttitudeIndicationsRefer to figure 7‐12. A nose‐high unusual attitude will be indicatedby the AI,with the altimeter andVSI indicatingaclimb and decreasing airspeed (possiblyrapid). An extremely nose‐high attitude might result in the aeroplane stalling,i.e. the altimeter andVSI suddenly indicating adescent with the airspeed low.

RecoveryRefer to figure 7‐13. When the aeroplane is in anose‐high/reducing airspeedsituation (but n o t in or near astall), the recovery involves simultaneously apply‑ing full power, lowering the nose and rolling the wings level with coordinateduse of aileron and rudder. The level flight attitude will be confirmed by thefact that the airspeed change is checked (i.e. it stops decreasing).Having regained normal steady straight flight, you may need to realign the

heading indicator.It is important to no t e that the initial actions required to recover from an

unusual attitude differ according to Whether the nose is high or low:- for anose‐highattitude, you must lower the nose first then level the Wings; and° for anose‐low attitude, you must level the wings first then raise the nose.

1: \ r ‘ '

' 5‘16“ Runny / ,ID (V 60 ‘

Figure7-12 Nose-high unusual attitudes.


Siultaneouslylevel the wings andlower pitch attitude

.unsstD'Iso LHUVS 4“

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Figure 7-13 Regaining normal flight using the full panel.

UnusualAttitude Recoveries on L i t dW

keypoints to establish are the following:is the aeroplane nose high or nose low?; and' is the aeroplane banked?

In recognisinganunusual attitude, the

. v IAIRSPEFD , ' ‘ \\‘AlFiSPEED

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Figure 7-14 Unusual attitudes indicated bya limited panel.

smb://%E2%80%98AlFiSPEED

772 Night Flight

Nose-Low AttitudeIndicationsThe primary indication of a nose‐lowattitude will be an increasing airspeed.In addition, the altimeter and VSI willshow ahigh andpossibly increasing rateof descent, with bank (ifany) confirmedby the t u r n coordinator.

RecoveryThe recovery from anose‐low attitude isthe same asfor fullpanel, the only differ‑ence being there are fewer instrumentsavailable from which to derive informa‑tion. To recover on a partial panel, theprocedure is asfollows:° reduce power;0 reduce any g;0 level the wings using the t u r n coo r ‑

dinator; and- case o u t of the dive (the horizon is

indicated when the airspeed checksand then the altimeter stabilises).

IR-OSOGAEPS

\A .iRapid lossof height

erOBDHEPS

Figure 7-15 Establish the situation.

Figure 7-16 Recovery from nose-low and nose-high airspeed on a partial panel.


Nose-HighAttitudeIndicationsIf only apartial panel isavailable, the indications of anose‐highattitude will beasfollows:' a decreasing airspeed on the ASI with supporting information from thealtimeter and VSI; and

0 bank (i fany) indicated on the turn coordinator.

RecoveryRecovery is the same asfor afull panel but with the horizon indicated on theASI When the airspeed is checked and stops decreasing and the altimeter stabi‑lises. The Wings‐level bank attitude is achieved when the Wings are level onthe tu rn coordinator and the ball is centred.

/ _

' \ ‘AiRSPEEu /,\ 1 5 0 a l l " ; 4 0 , <

Banked andturning left

IR-OSOSEPS

Figure 7-17 Nose-high and decreasing airspeed on partial panel.

Av ia t ion

Part Four

Night Flight Planningand Navigation

Chapter 8: Planning a Night Flight . . . . . . . . . . . 177

Chapter 9: Radio Navigation . . . . . . . . . . . . . . . 195

Chapter 8

Planning a Night Flight

This chapter is designed to show the step‐by‐step process of planning anightflight. The procedures and considerations you need to take into account whenflying at night are outlined in order to demonstrate the process. The exampleused for this is aflight from Wagga Wagga to Canberra.

Planning a Night Flight from Wagga Waggato Canberram w s z w : '=:us:«.v *2»

ConsiderationsWe are using a Beech A36 Bonanza with an autopilot and a stand‐by attitudeindicator‐ this aircraft complies with the night VFR equipment criteria. Wearecarrying passengers and therefore need to m e e t the recency requirements. Fuelis adequate and loadingis within limits. Runways are adequate and the destina‑tion has lighting, emergency power and anaid. No alternate isrequired, but wehave sufficient fuel to return to Wagga Wagga from Yass if the weather turns.

Route SelectionMany factors need to be taken into consideration when deciding which routeto choose. Two choices are available to uswhen consideringwhich path to fly.The direct route Wagga Wagga ‐ Canberra (VVG‐CB) is 86 nm measured fromthe WAC, compared to Wagga Wagga ‐ Yass ‐ Canberra (WG‐YASS‐CB),the slightly longer r o u t e of 104 nm.

Why have t w o options? Why n o t take the direct route? When choosing yourroute, the quickest is often n o t the safest; in this case, the quickest rou te offershigher terrain andpoornavigationfeatures (two things you do n o t needatnight!).

Calculation of End of DaylightPrior to decidingwhich route to take, the calculation of lastlightneeds to bemadein order to determine if the flight isto beconducted entirely in darkness. Weplanto depart Wagga Wagga at 1830 hr on 30June. There are a number of ways ofdetermining first and last light; the different methods available are the AIP usingthe beginningand end of daylight charts, the AVFAX system and NAIPS.

777

\

778 Night Flight

Aeronautical Information Publication (AIP)To determine the beginning or end of daylight via the AIP, you Will need touse the graphs and tables provided in GEN 2.7. Use the steps listed below.1. Move horizontally across the bottom or top of the appropriate daylight

graph to the date required.2. Movevertically up or down from the selected date to the latitude curve asso‑

ciated with the place concerned. If the latitude does n o t correspond exactlyWith the latitude of the place concerned, you will have to interpolate.

3. N o w m o v e horizontally to the vertical scale indicatinglocal mean time

Daylight and darkness graph End of daylight Southern HemisphereMARCH APRIL MAY JUNE JULY AUG SEPT

28 10 20 31 10 20 30 1O 20 31 10 20 30 1O 20 31 10 20 31 10 20 30

1900 L1850 ¥1840

18301820

1810

1800

1750

1740

17 E00_ g 1726 LMT1720

1710

Latitude 1700Wagga Wagga 1650

28 10 20 31 10 20 30 10 20 31 10 20 30 10 20 31 10 20 31 10 20 30MARCH APRIL MAY JUNE JULY AUG SEPT NF-«oouns

Figure 8-1 End of daylight graph.

4. To convert L M T to U T C , use the conversion of arc to time table to obtainthe time variation. Look up the corresponding longitude for the locationin the table to obtain the required time increment. If the longitude is indegrees east, subtract this time from the local mean time.

5. Use Table 8‐1 to convert time in To convert time in UTC to: addU T C to Eastern, Central or Western EsuT 11hrStandard Time asrequired. EST 10hr

CST 91/2 hrWST 8 hr

Table 8-1 Australian time zones.

8: PlanningaNight Flight 779

Use the following steps to determine the end of daylight atWagga Wagga(35°09'S 147°28’E) on 30june.1.

3.

4.

Enter the end of daylight graph at30June andmove vertically up to the lat‑itude of 35°09’S. From this point, move across to the right‐handside of thepage to read off the localmean time. You should get 1726.. Now convert this time to UTC. To do this, you must subtract the timeobtained from the conversion of arc to time graph using the longitude ofWagga Wagga (147°28’E) ‐ 147° of longitude in the graph is equivalent to 9hr 48min, and 28’ of longitude is equivalent to 1minand 52 seconds. Alto‑gether you need to subtract 9 hr and approximately 50 min (49 min, 52seconds): 1726 ‐ 9 hr 50 min = 0736 UTC.To convert the time to EST, add 10 hr: 0736 + 10 hr = 1736.The end of daylight atWagga Wagga on 30June is 1736 hr.

AVFAXYouwill requireaTelstra PhoneAwaycard to obtain the beginning or endof daylight via the AVFAX system.

. Dial 1800 805 150. You will be1

. You will be given dialling options,

For pilot briefing via voice.For pilot briefing via facsimile.

*03 For pilot briefing changerequest.

asked for you r card number.Enter the card number locatedonthe back of your PhoneAwaycard. A voice will then tell youhow much money you have lefton your card.

To order a new card or otherpublications centre products.

To repeat the menu.which are found onyour PhoneA‑way Card (Table 8‐2)_ Table 8-2 Dialling options.

3.Enter *04 for AVFAX.. You will now hear, ‘Welcome to the AVFAX

system, please enter your accountnumber.’ Enter you AVFAX number. You will then hear, ‘Please enter yourpassword.’ Enteryou AVFAX password. Thenyou will hear, ‘Please enter yourfive‐digit product selection code.” Enter the appropriate code as found in theGEN section of ERSA for first and last light at the aerodrome(s) of yourchoice. For Wagga Wagga, that code is YSWG. You will begiven furtherinstructions ‐ you will berequired to press 0or 1,depending onwhether orn o t you require further product selection and to advise which number yourequire the information to befaxed to.

180 Night Flight

NAIPSTo obtain beginningor end of daylight via the NAIPS system, logon to NAIPSand select the icon at the top of the screen for first and last light or choose First‑Light/LastLight from the briefing menu at the top of the screen. A box willappear where you can enter either the location (YSWGor WAGGAWAGGA)or the latitude and longitude.

WeatherFor this example, the weather is suitable for night VFR aswe can maintainLSALT clear of cloud. There is a typical 30 kt wind from the north‐west atcruising altitude. There is alikelihood of moderate mechanical turbulence. Acold front is moving in from the south‐west with an associated wind change.It is n o t due until well after o u r departure, but it may preclude a re t u r n toWagga Wagga if Canberra closes.

MoonThere is afull moon, sowater features ‐ such asthe Murrumbidgee river andLake Burrinjuck ~ should reflect well depending on o u r relative positions.Lake George may glow in the eastern distance aswe head into Canberra.

TerrainThere is high ground on the direct track, and there are patches of high groundto the northand east. The track via Yass offers lower terrain. Due to the strongwinds, there islittle likelihoodof fog, except in river valleys andsheltered lakes.Airframe icing is likely in cloud, and carburettor icing is possible throughout.

Forced Landing AreasThe direct track passes over Tumut, which offers auseful alternate and forcedlanding ground. However, the high terrain elsewhere on the direct track issomewhat deterring. There are better forced‐landing options in the area oflower terrain on the track Via Yass, but it would be amatter of luck to find onein the event of a total engine failure at night. L i t sections of the Hume High‑way may offer asurvivable outcome, even if the aircraft were landed adjacentto the highway

8: Planning a Night Flight787

V3. (EN "33 A.MYmm,3,,v,u a :54

M a m a “, 9 4 1 m m ,Mmmws v -

Figure 8-3 ERC of planned sector.

782 Night Flight

Navigation FeaturesThe highway fromWagga Wagga to Gundagai to Yass and Yass to Canberra isbusy and well l i t near towns and major intersections. This offers good nightnavigation features asit will be clearly Visible from the sky. The BurrinjuckReservoir, asmentioned, should reflect well with the full m o o n . Yass has anNDB that we can use, although it would bebetter to t u r n towards Canberra atYass township asthe NDB takes usover higher terrain.The direct path does n o t oflfer asmany navigation features. Initially, the

highwaywill be clear, but asthe terrain builds up andTumut is reached, there areno significant navigation features except for the faint glow of Canberra in thedistance and the NDB atWeeJasper.There is a lake flying east, so the loss of Visual features is earlier than if flying

west. There will be no silhouettes of hills, and there will also be no glare fromflying into the sunset.

Selection of Cruising LevelsOur flightpath is in aneasterly direction. When choosing cruising levels, flightmus t occu r at odd thousands plus 500 ft. The LSALT requirements indicate thatyou mus t planat least 1,000 ft above the highest terrain. To addafurther safetymargin for night flight, our LSALT will be 1,500 ft above the highest terrain ina 10nm direction from track.In o u r example, the direct track takes usover higher terrainwith anLSALT of

6,300 ft (fromWAC plus 1500 ft). If we plan via Yass, the LSALT decreases to4,700 ft and then afurther 4,400 ft into Canberra. The lowest cruising levels forthe longer rou t e would be 5,500 ft, ascompared to 7,500 ft for the direct route.

Visual FeaturesThere will belittle to see on the direct track, other than the lights of Tumut andthe glow of Canberra aswe get closer. These will be obscured by high terrainfor mos t of the flight inbound. If there is aneed to t u r n back, Wagga Waggaoffers major l i t features. The aerodrome has aV C R and an NDB. The trackvia Yass 03ers amajor highwaywith frequent traffic and li t sections. It promisesto be anexcellent tracking aid. The choice is to actually follow the highway orto track to the Yass NDB keeping the highway in sight.Shouldwe track via the YASS NDB? If we pass over the NDB,we are taken

well east of the highway to Canberra, and we are placed over higher ground.It appears better to use the aid to track over the township of Yass but then tot u r n before the NDB and track Visually close to the highway inbound toCanberra.

8: Planninga Night Flight 783

Which Route to Select?By now the preferred route should be clearly evident. The slightly longerroute is often the best, and in this case the situation is true. Wagga ‐ Yass ‑Canberra offers better navigational features, lower terrain and better forcedlandingareas.

, 2 : ’"lFigure 8-4 VNC showing route options.

lanningthe FightHav1ngdecidedwhich rou te to fly, you can n ow start planningthe night flight.There are many factors that need to be taken into consideration, and the plan‑ningprocess is different to day navigation; the lightavailable is limited, and yourely heavily on your preplanning to ensure the workload in the air is mini‑mised. The easiest and simplest way to navigate at night is via amudmap.

What is aMud Map?A true mudmap was athumb‐nail sketch drawncrudely, but essentially, in sandor mud. The mudeliminated the detail and presented only the essential infor‑mation. It isdifficult to readachart atnight. It isalso diflicult to find and readinformation from ERSA and other data manuals; therefore, the creation of apaper mud map makes night flying much simpler. The mud map assemblesimportant information in anorderly and visible way.

Making a MudMapUse aWAC rather than aVNC because it shows topographic features better.Make adouble‐size photocopy (it becomes 1:500,000 if you zoom to 200% ‑

\

784 Night Flight

the same scale asaVNC), and then make a tracing with the terrain heights.Round up the heights to the n e x t whole hundred feet. From the copy, tracethe flight track on aplain sheet of paper.Use the mudmap asyour flight planand insert all the important information

required for the flight, such asthe LSALT, cruising altitude, track, distances,area frequency (obtained from the ERC), departure and arrival aerodromeinformation and navigation aid information. Highlight all major features thatwill be easily recognisable from the air, aswell asthe higher terrain.Lookingat ou r example, the first step is to draw the flight plan on the WAC

and then from there copy the diagram on aplain sheet of paper (figure 8‐6).The mud map should be a simple drawing that highlights only the major

features alongyour track and has all the flight information right in front of you.It is important n o t to make the mudmap t o o cluttered asyou wan t to beable tosee all the information clearly.When drawing your mudmap, write all the names of towns in ablack pen

with clear writing. Orientate the map so that the track is upright. Colourshould n o t beused on the map because in adimly l i t cockpit, the rods in o u reyes predominate and do n o t respond to colour.To determine the differences between large towns, small towns, roads and

water features, draw yourself akey and remember it. This allows you to easilyidentify the differences between features when flying. The key for ou r mudmap is given in figure 8‐5 (page 184). For longer routes, make a strip map(concertina folded) and keep the WAC available for diversions.From the mud map (figure 8‐6), you can

see that the pilot has all the informationrequired for the flight clearly presented. Allthe frequencies, navigation aids, airport 05mm” lbw“information and so on are included on this 0 «fawnsimple diagram. Although your mudmap has _ _all your flight information, always ensure that 0 mm" “NH /Ciifjyour navigation items are close to hand (e.g.your charts, ERSA and computer), as you M roadnever know when you may need them. The I NWkey is n o t located on the map ‐ it is the pilot’sresponsibility to memorise it so that the map $ alfPo/tis less cluttered. When creating your mud . ‑map, spend time on it and don o t rush through M '1' h M I N "the planning. 0 Nb NOR

Figure 8-5 Key for the mud map.

8: Planning a Night Flight 785

HDG Hf TIDIST 255nm E T A “

AmCanbcrroi i s s g elevahon

l7

‘1 TNR “3‘7

LERLT- ‘m Lake «use 3:: :27:[A0551 m - 35 ans “(fl/IIME

1K9 VOR “6-7

NDB 263 :17.’

Xflas N06335 2 - ‑

6 Nee JaspelN05M .

lbs} 3W5 aw i' MLCEN. 0 ‘ 6g / M \ . CEN “ mussg

o $oTt/imu’f

Cochin"!de M2650I E A055] mfl‘io M1330 72H Elewh‘an

a ' 23H06 032 o ,7 CTAF[MST 16 m pita imerLsnLT Lizoo aTI JomeE T A _ WAGGA 'm‐ 5;?

Figure 8‐6 Completed mudmap (half size).

vog “ 5 0

N08 11 'fi ‘ n

186 Night Flight

The Plan in DetailCanberra ControlThe hours of operation for Canberra control can be found in ERSA. Canberracontrol operates between0715 ‐ 2400 hr local (Monday to Friday andSunday)and 0715 ‐ 2300 hr local on Saturday. VFRapproachpoints (determined fromthe Canberra VTC) are located atYass township (at 6,500 ft) or Murrumbat‑eman township (at 5,500 ft), which is on the highway between Yass andCanberra. As ou r cruising level is 5,500 ft, we will contact Canberra approachfrom Murrumbateman.

FlightPlan DataMost of the planning requirements have been taken into consideration and themud map has been completed. Therefore, planning a night flight is just likeplanning any other flight ‐ all the information has been obtained Via normalmeans.

Wagga ‐ Yass Yass ‐ CanberraTAS 165 KTAS 165 KTASWind NW30 kt NW 30 ktMagnetic Variation 12°E 12°EHeading 052°M 142°MTrack 064°M 154°MLSALT 4,700 ft 4,400 ftCruising Altitude 5,500 ft 5,500 ftFrequency ML CEN 119.5/ 124.1 CBApproach 125.9 Tower 118.7

(from ERC) Ground 121.7 ATIS 127.45Navigation Aids Yass NDB 335 VOR 116.7 NDB 263

Table 8-3 Flight plan data.

Flight Notification and SARTIMEFlight Notification

Preparing the FormFirst Line. We need to en te r o u r callsign, flight rules and type of flight.

7. Aircraft Identification 8. (a) Flight Rules Type of Flight

’ l H I F I I I I 11 ( 0 1 l e S lNl@IMNF‐1ona.EPs

Figure 8-7 First line.


The call sign is ‘India Hotel Foxtrot’ (IHF). We have circled ‘V’ for VFRflight and ‘G’ for general aviation.

Second Line. We include our aircraft type and the category we fall into forwake turbulence. We also specify the navigation, communication and surveil‑lance equipment we have on board our aircraft.9. No Wake Turb Cat

Hi ""i®Type5556

10. Nav/Com Equip Surveillance EquipNorSand/orlD®G HI J L©R Tu®w z N A © D

NFVDMEPS

Figure 8-8 Second line.

The aircraft designator for the Bonanza is BE36. The Bonanza is below7000 kg, therefore we circle ‘L’ (‘M’ is for aircraft between 7,000 and 136,000kg and ‘H’ is for aircraft at or above 136,000 kg.)Let us suppose that you have been night VFR‐rated and endorsed on the

ADF and VCR. Therefore you can circle ‘F’ (ADP), ‘O ’ (VCR) and ‘V’(VHF) in the ‘Nav/Com Equip’ section of the flight plan. Circle ‘H’ if youhave aHF radio fitted.The Bonanza has amode‐C transponder. Therefore, you circle ‘C’ in the

surveillance equipment section.Third Line. Ween t e r the departure and destinationaerodromes, estimated timeof departure, speed, level and estimated flight time. The departure aerodromeisWagga Wagga. Enter the four‐letter designator for Wagga Wagga into sec‑tion 13. You estimate that your departure time from Wagga Wagga will be8 PM. Enter 301000 asyour estimated date/time of departure (ETD).Note. You mus t use Zulu time on the flight plan.Circle ‘N ’ for the cruising speed. This indicates that the speed you enter is

in reference to knots, n o t Mach number. The speed is entered asa zerofollowedby the TAS in three digits ‐ i.e. the TAS for IHF is 165 knots, soyouenter 0165.You select 5500 feet asyour cruising altitude to Yass ‐ this altitude is

hemispherical and above the LSALT calculated for the leg fromWagga Wagga to Yass. In the ‘level’ section of the flight plan, circle ‘A’(altitude) followed by 055.Note. The altitude is entered in hundreds of feet.The destination isCanberra. In section 16of the flight plan, you mu s t enter

the authorised designator. In this case, the authorised designator for Canberrais YSCB.

788 Night Flight

Your estimated flight time from Wagga Wagga to Canberra is 42 minutes.This mus t be entered in hours andminutes in the EET (estimatedelapsed time)section of the flight plan. Therefore, enter 00 as the hours and 42 as theminutes.There are no requirements for an alternate in relation to weather, lights or

navaids for this flight; therefore, no ALTN aerodrome has been entered.

13. DEF Aerodrome ETD . Cruising Speed evei 16. BESTAerodrome Total EET ALTN AerodromeYSWG 5 0 1 0 0 0 0155 0 5 5 YSCB 0 0 4 2

M F HR 1 MiNNF‐IIXJSEFS

Figure 8-9 Third line.

Forth Line. The intendedrou t e isnex t . Always start and end the rou te in D C T(Direct). In this case, wehaveflight plannedto Yass, soenter D C TYASSDC Tin the route sector.

15.RouieDCT YASS DCT

NF-1m5.EPS

Figure 8‐10 Fourth line.

Now in reading the flight plan in context, it would read that the departureaerodrome isWagga Wagga direct to Yass direct to Canberra with no changein altitude or speed. Yass to Canberra is a short distance. Five thousand fivehundred is still hemispherical and the lowest hemispherical altitude we canflight plan. If the lowest safe altitude were any lower, we may choose todescend to three thousand five hundred for such a short distance. In this casewe mus t stay at five thousand five hundred until it is safe to descend below thelowest safe altitude.SARTIME. The nex t sector on the flight plan includes details on SARTIME.Your flight time is 42minutes. Therefore, you would expect to be on theground at approximately 1100 Z. Allow up to 30minutes to make the call toCENSAR to cancel your SARTIME. A six‐figure date/time group mus t beused, i.e. day of the month followed by time in UTC . In this case, the SAR‑TIME is 301130. Circle ARR to indicate that the SARTIME of 1130 Z onthe 30th day of the month is for your arrival at Canberra. The unit that willhold your SARTIME is CENSAR.Note. This is already filled o u t on the flight plan asall SARTIMES are n owheldwill this centralised search and rescue unit.Enter your destination as the location where you will be cancelling your

SARTIME followed by your destination telephone number.


STS/SARTIME ToATS Unit Location nest Te] NO;DatefTime Arr

L 5 0 1 , 5 0 Dep CENSAK YSCB 0455 125 125

NFIflW EPSFigure 8-11 SAR details.

Supplementary Information. Any supplementary information is entered at thebottom of the flight plan. Our Bonanza has a white fuselage with gold andmaroon stripes and other markings (figure 8‐12).

AircraftCO'Our/marklngs WHITE WITH GOLD AND MAROON STRIPEB

Figure 8-12 Aircraft colour.

We have 200 minutes of fuel on board the aircraft. This 19. Enduranceendurance mus t be entered on the flight plan in hours and HR MIN. E/ mminutes (figure 8‐13). 5/We Will be carrying a first aid kit, water and an emergency 9

locator beaconon this trip. Therefore, we circle ‘P’, ‘M’ and ‘E’. Figure 8‘13

Endurance.S I ® D@J®Figure 8-14 Survival equipment.

Persons on BoardThere are two persons on board our flight. Enter ‘two’ inP/the first box (figure 8‐15), indicatingthat there are t w o persons P,1 : ]

on the first section of the flight (i.e. Wagga Wagga to m l :Canberra).In the final section (figure 8‐16), enter the pilot in command,

phone number, mobile number, fax number and company ( i fassociatedWith one).

Figure 8-15 POB.

Pilot-in-command Phone Mobile FAX

P-LANE 05 9125 4567 0455125125 05 9765 4521

NF‐IOI3 . 9 5

Figure 8-16 PIC contact details.

190 Night Flight

Australian Domestic Flight Notification Form _ .1 Ease7. Aircraft Identification 8. (a) Flight Rules Type of Flight

I H FI I J l l I II®IY|2 S I N I © I M9. No Type Wake Turb Cat 10. Nav/Com Equip Surveillance Equip

5 E 5 6 Hi M|© NorSand/or|D®G H I .1L©RT u®w z N A © Devel

@055ETD .Cruising Speed

5 0 1 0 0 0 0165

DCT YASS DCT

13. DEP AerodromeY5 W6

16. DEST Aerodrome Total EET ALTN AerodromeYSCB 00 42

HR I MIN15. Route

1a. (a)

(Stage 2) 13. DEPAerodrome8. (b)

I

ETD 15. Cruising Speed Level 16. DESTAerodrome Total EET ALTN AerodromeN AM F HR I MIN

15. Route

V

Y 18. (a) (Info relevant to Stage 2)

Z

(Stage 3) 13. DEF AerodromeE. (b)

ETD 15. Cruising SpeedNM

Level 16. DESTAerodrome Total EET ALTN AerodromeAF HR I MIN

15. Route

V

Y 18. (3) (Info relevant to Stage 3)

Z

18. (b) (Information relevant to all stages)

REGNHPER/

STS/SARTIME ToATS Unit Location » Dest Tel No:Date/Time C E N g A K 11565 0 4 5 5 125 125

501150 Dep

SUPPLEMENTARY INFORMATION19. Endurance Persons on Board

HR MIN Aircraft colour/markings | WHITE WITH GOLD AND MAKOON STRIPES | PI 2E, 05 20Dinghies P/

E l EE/I‐ITSI®|DI®|JI® DI | |c| P I :N/ Remarks I

PM -In- m nd Phone Mobile FAX Company

C/ F. LANE 05 9125 4567 0455 725 725 0.5 9765 4521 AVTC

Brleflng 1800 805 150 Fax 1800 805 150 PILOT PC ACCESS 0198 304 767 CENSAR 1800 814 931

Figure 8-17 The completed flight notification form.


SARTIMEReference: AIP ENR 1.10,para 2.3 andpara 2.10; A IPENR 1.10,para 2.11.

Requirement to Submit SARTIMENight VFR flights are required to submit SARTIME flight notificationwhenthe flight isproceedingbeyond 120 nm from the departure aerodrome or whenoperating in controlled airspace (except for Class E airspace andGAAP CTR).SARTIME issubmitted to ATS; alternatively aflight no te isleftwith arespon‑sible person.

InformationRequiredThe information required to be submitted to ATS for the SARTIME is asfollows:' callsign;- aircraft type;° departure point;° r ou te to be flown;' destination;' persons on board (PCB); and- SARTIME.

Escape routes and ‘what ya” should always be considered when flying at night,especially in a single-engine aircraft. You will notice that one of theconsiderations in choosing our rou te to Canberra is the location of possibleforced‐landing areas. Always have in mind the location of the closest airfieldin relation to your position. On a separate sheet of paper in your navigationfolder, write o u t the details of every airfield you will pass or that will be closeto track. This way, if you ever need to land due to weather or othercircumstances, you have the information readily available to you. Be preparedfor apossible lighting failure at your destination airfield and know the optionsavailable ‐ it is recommended that a decision bemade before committing to adescent. Plan to carry sufficient fuel to fly to analternate, even if the weatheris alright. Otherwise, calculate a point of no return. This becomes yourdecision/commitment point.

792 Night Flight

P i n fNo ReturnW m

The point qf no return (PNR) is the point beyond which it takes less time andfuel to reach the destination than to re tu rn to the departure airfield. The PNRis useful for night cross‐country flights ‐‐ especially in remote areas ‐ asit takesinto account the possible situations of the destination airfield n o t being availa‑ble and the departure airfield also being the alternate. Sometimes, it is betterto r e t u r n home than to fly to another airfield.If there is no suitable and closer alternate, the departure airfield is considered

suitable for re tu rn if the fuel carried is adequate. The PNR is the last point towhich the aircraft can be flown before the decision is made to continue orr e t u r n ‐ it is a go/no go point. It is also the point by which the destinationweather, lighting and surface conditions mus t be confirmed. If there are anydoubts, you mus t t u r n back.

Calculating PNRIn its simplest form, the location of the PNR can be found by determiningthe endurance based on the flight fuel available beingburnt at a constant fuelflow rate:

flight fuel availableEndurance = ‐ ‐ ‐ ‐ ..fuel flow in unlts per hour

For example, if we have264 litres of flight fuel available and the constant fuelflow rate is 55 litres per hour, we have:

Endurance = w55 lltres per hour

E I 4-8 (4 hours and48minutes)P N Risthat pointbeyondwhich

there will be insufficient fuel tore turn to the departure aerodrome.With ample fuel, you may reach

| 2-4 hours @ 150 kt = 360 nmI

III

your destination and still be able to IIIIII

r

return, i.e. the departure airfield isalso an alternate. In ou r example,we can fly o u t in still air for 2.4hours (i.e. half the endurance) _‑eg. this will be360 nm at aTAS of150 kt. We have used2.4 hr of our endurance and therefore have E ‐ 2.4 = 2.4hr available for return. This is the same asour outbound flight.

E = 4-8 hr PIEJR

(E ‐ 2-4) hours (5 150 k t : 360 nm

Figure 8‐18 Concept of PNR.


If there is a wind blowing, thegroundspeeds o u t and home willn o t be the same. Using ourknowledge of the still‐air situation,it is easy to develop aformula fromwhich we can find the location ofthe PNR. Since we know that thedistance o u t to the PNR is equalto the distance home from the

distance to PNRgroundspeed OUT to the PNR

= groundspeed HOME from the PNRtime out to the PNRendurance in hours

Figure 8‐19 PNR calculations abbreviations.

PNR, and since distance = time x T X0 : ( E r T) XHspeed, we can rewrite this asgiven T0 = EHrTHin figure 8‐20. TO+TH = EH

T(O + H) = EH. EHTm t PN T =1 e o R, 0 +H

Figure 8-20 PNRformula.

To calculate the distance o u t to the PNR:

Distance out to PNR = GEE‐1H (distance) X0 (groundspeed)

Distance to PNR,D = EOHO + H

Recalculating PNR In FlightPNR calculations are often required in flight. These are made from overhead apositive fix and usually involve the updating of aPNR determined atanearlierstage (eg. when flight planning prior to departure). However, in‐flight PNRcalculations may also be required under other Circumstances. For example, aflight departs with minimum fuel, based on a lack of operational requirementsat the intended destination. However, the pilot is advised enrou te that the aer‑odrome may be closed due to unforecast weather problems. An in‐flight PNRcalculation isrequired to determine howmuch further along track the aeroplanecan proceed ‐ in the hope that the weather will improve ‐ before a diversionback to the departure aerodrome, or some other suitable alternate, is required.

En rou te PNR calculations should betackled in exactly the same way asthoseinvolving climbs and descents, i.e. reduce the problem to a simple cruise‐onlycalculation by extracting the flight fuel for all sections of the flight that do n o tinvolve cruise o u t and back.

794 Night Flight

Deduct fuel for these segments to determineflight fuel available for in-flight PNR calculation

A

Cruise home

calculate return

I|l||

Ignore descent; ||

at cruise level |III

Ewa- i1Altern te

Figure 8-21 ln-flight PNRcalculations.

Note that the following applies for any in‐flight PNR calculation:0 you may ignore the climb segment after departure, aswell asall the cruisesegment lyingbehind the aeroplane;

' avariable reserve is required for the remainder of the flight only, and so theflight fuel available must be recalculated; and

- in‐flight winds and fuel flows may often differ from flight plan values (makesure you use the actual figures for wind component, groundspeed and fuelflow to calculate an accurate in‐flight PNR).

Chapter 9

Radio Navigation

The essence of radio navigation is interpreting the information displayed soasto imagine the position of the aircraft in space. Two dimensions determinegeographic position. The third dimension is displayed on the altimeter. Thefourth dimension is displayed on the clock.

The ADF needle always points directly to the station and is displayed relativeto the top of the instrument (which represents the nose of the aircraft). It isexactly the same as the clock‐code but m o r e precise. Instead of twelvedirections, we can use all 360 and be accurate to one degree. The nose (thetop of the instrument) is 12 o’clock or 360°.

The direction of the needle relative to the nose of the aircraft is called therelative bearing and can be described in one of t w o ways:- the number of degrees left or right of the nose (or tail) (e.g. 30° left or 30°

right); or- the number of degrees on the indicatorwith 360 at the top of the instrument

(e.g. 3 o’clock is 090° relative and 9 o’clock is 270° relative).

1 800 IR-0621EPS

Figure 9-1 Relative bearing is an accurate form of the clock-code.

The use of degrees left or right of the nose removes confusion with magneticbearings, tracks and headings.

795

796 Night Flight

This relative bearing information is sufficient to find our way to the station(by directly homing), but it does n o t show where we are ‐ it only shows thatthe N D B is left or right andby howmuch. We couldbe anywhere around thecircle at any distance. Note the symbol usedfor the NDB on the ERC.

NDB

Figure 9-2Same relative bearing.IR-0522EPS

If we are to use the navaid to find ou r position, we need a further reference‐ the heading of the aircraft. Once this is known, the aircraft can only be onone position line (but at any distance ‐ asdiscussed in the following).

I «3‘WI] \\\\\11? “gm 9V mamas

Figure 9-3 The heading and relative bearing provide a position line for the aircraft.

In figure 9‐4, o u r heading is 360°M (i.e. relative to magnetic north) andthe station is 90° left. Therefore, the magnetic bearing (direction or track) tothe station is 270°, and the magnetic bearing (direction or track) from thestation to the aircraft is the reciprocal of the bearing to the station ‐ in thiscase, it is 090°.

9: Radio Navigation 797

Magnetic MagneticNorth Heading

Magnetic RelativeMagnetic Heading Bearing

bearing fromthe station ’5'5\\\\lilu,3

(090°) 9 s“ A

Relative 7" MagneticNDB bearing to Bearing

the station(2700) |R-0625.EPS

Figure 9‐4 A magnetic heading of 360° and a relative bearing of 270°.

To summarise, heading + ADP = magnetic bearing to the station.Better still, imagine the aircraft is sitting on the tail of the ADF needle and

the N D B is the centre of the instruments. The tail of the needle shows theposition of the aircraft from the NDB.

090°

Figure 9-5 Imagined position.

Later, you will see reference to the hearing from the station as a radial.Strictly speaking, the t e r m radial applies to the V C R but, in practical terms,both the V C R radial and the bearing from the N D B are used in the same way(remember the strict definition for examination purposes).

The concept of the radial and the imagining of the position of the aircraft inrelation to the aid asbeing on aparticular radial are fundamental to all types ofradio navigation that use pin‐point aids (rather than area navigation aids, suchasGPS). For example, if you are on the 035 radial from Essendon,your bearingfrom Essendon is 035°M (035° radial) and the magnetic bearing to the stationis 2150M.

To pin‐point the position of the aircraft, we need to know the distance tothe station or use position lines from t w o NDBs (by noting o n e andmomentarily tuning to the frequency of the other). Some aircraft have t w oADFs with t w o needles.

798 Night Flight

/ Position line 2(030 Radial)

Distance 15nmA

_ _ _ _ _ ‐ ‐ ‐ Position line 1(090 Radial)

lR-DBZAEFS

Figure 9-6 Using two position lines to pin-point the position of the aircraft.

Given that the ADF needle and the magnetic heading of the aircraft are thet w o essential elements, you would expect these to be on one instrument. Theyare in modern aircraft, and it is much easier for the pilot to interpret them. Inolder aircraft, they are n o t only separate but the heading indicator must also bemanually aligned to magnetic north (themagnetic compass could beused, but itis remotely positioned, less easy to read and unstable in turns or in turbulence).Moremental exercise isnecessary with the older installations.

ADF and Heading Indicator CombinationTo use the information from aparticular NDB:the aircraft mus t bewithin the operational range of the NDB;the ADF must be correctly tuned to the NDB frequency;the station must be identified (Morse code signal);the ADF needle mus t ‘come alive’ in response to the signal and it must settlein adirection that seems reasonable; andthe HI must be alignedWith the magnetic compass.


Effective Range and Rated Coverage of an NDBRangeThe majority of NDBs have a transmission power ranging between 100 wattsand 500 watts. A few are considerably more powerful ‐ up to 3,000 watts (3kW). In Australia, an appreciable number of NDBs employ transistorisedtransmitter equipment and can operate at amuch lowerpower output, (usually100 watts or less) without any significant reduction in range. The maximumrange of an NDB can vary from 30 nm to well in excess of 400 nm and islargely determined by the following factors.Transmitter Power. The greater the power, the greater the range achieved ‐ todouble the range, the transmitter power mus t be quadrupled; similarly, if thedistance from the station is doubled, signal strength received at the aeroplanewill be reduced by a factor of four.Frequency of the Signal. The lower the frequency, the greater the range (forthe same transmitter power).Time of Day. The range may be considerably reduced at night owing to thevariation in the ionosphere between daylight and darkness. This has asubse‑quent effect upon N D B signals passing through it (night effect is discussed onpages 205‐207).Surface Type. The type of surface over which the signals travel can affect NDBrange. Low frequency (LF) and medium frequency (MF) radio waves sufferadditional attenuation from interaction with the surface of the earth astheymove away from the transmitter. However, they suffer far less attenuation overwater than they do over land. For example, the rated coverage of the BrisbaneND B (day) is 150 nm over land but 400 nm over water (OW).Antennas. The efficiency of the antennas can also affect N D B range.

RatedCoverageThe ratedcoverage of an N DB is the maximumdistance at which its signals maybe used to establish afix (as definedby the AIP). It is afactored distance whichtakes into account average circumstances, and it is always less than its maximumrange. Signals can be received at distances greater than the rated coverage, buttheir accuracy may be degraded and the signal may be unreliable. The ratedcoverage of every NDB is listed in ERSA (in which rated coverage is oftenreferredto, less correctly, asrange), andpilots mus t n o t rely on ADP indicationsfrom an NDB beyond the distance specified in ERSA.

200 Night Flight

In areas where radio navigation aids are sparse and there is little risk ofinterference, mo re powerful NDBs ‐ with rated coverages of 100 nm or mo re‐‐ are usual. The mos t powerful N DB transmitters are sited to provide for long‑range over ‐water flights ‐ for example, the NDBs at Perth and Darwin haverated coverages in excess of 400 nm .

LocatorsA locator isalow‐poweredNDB used to position for avisual or ILS approach.Locators are usually sited to guide aircraft to the approach descent point(between7 and 11 nm from the threshold on the extended runway centreline).For some runways, asecond locator is installed closer to the threshold (inside4 nm on the extended centreline).Locators are normally used in association with ILS approach procedures.

However, because they are located on the runway centreline, non-precisionapproach procedures ‐ such astwin‐locator or locator/DME procedures ‐ areoften an alternative.

NDB ReliabilityMost NDBs have tw o transmitters, i.e. a primary unit and a standby unit.Transmission parameters are constantly monitored and, if any of these straysoutside allowable limits, the primary unit is switched offand the standby trans‑mitter is automatically activated. In this event, the standby transmitter adds adot after the Morse code identification (e.g. Nyngan ident is NYN , whichwould become NYNE for the standby transmitter).Such beacons are pilot monitored, and the appropriate air traffic services unit

should be informed if the equipment switches to standby Navigation aids atmajor airports and terminal areas are monitoredby air trafiic services personnelthrough monitoring systems. However, an increasing number of aids aredesignated aspilot monitored, i.e. maintenance relies on pilot reports.Note. Transistorised NDBs are single transmitters. This lack of duplicationis considered acceptable because of the greater reliability of the equipment.

NDB IdentificationNDBs operating on the same frequency will be widely separated geographi‑cally, but to further avoid risk of confusion or mistuning, each NDB transmitsa t w o ‐ or three‐letter Morse code identification signal, commonly called theidem. The ident is shown on VNCs, ERCs and in ERSA. The pilot mus talways identify anNDB or locator prior to using it. Furthermore, if the samestation is to be used for an extended period, or if it is the only navaid available


for tracking, it shouldbere‐identifiedperiodically. DuringanN D B approach,the ident m u s t be monitored continuously.

A lack of anident, or adistorted or incomplete ident, may indicate that theN D B is unserviceable. Do n o t trust i t . If an N D B is transmitting whileundergoing maintenance or testing, the normal ident will be replacedtemporarily by XP in Morse code (i.e. dah-dit-dit-dah, dit-dah-dah-dit) toindicate that the N D B mus t n o t be used for navigation.

Some NDBs have an additional voice transmission capability, which allowsthe broadcast of the ATIS. In some cases, this facility may allow limited voicecommunications in the event of a VHF radio failure ‐ i.e. air traffic servicespersonnel are able to transmit messages to the pilot on the N D B frequencyTherefore, if you were to suffer a communications failure, you would listen forvoice communications on the NDB.

NDB Position CoordinatesThe position coordinates of each N D B station in Australia, together with theappropriate frequency and ident code, are shown on the following:° en rou te charts high/low (ERCS);' TACs; and° VNCs.

More detailed information about each N D B is found in ERSA, including thefollowing:° the frequency and the ident;0 the position of the ground station in precise latitude‐longitude coordinates

and, if applicable, asamagnetic bearing and distance to the reference pointof the associated aerodrome;

° the rated coverage for both day (HJ or D) and night ( H N or N) and, in somecases, over water (OW); and

0 any applicable remarks or limitations (e.g. ‘Pilot monitored’ or ‘Caution: n o tsuitable for N AV in sector 300 D E G to 340 DEG’).Note. An aerodrome/landing chart for aparticular aerodrome will also showthe position 'ofthe N D B and any other navigation aid sited at, or near, theaerodrome. Position coordinates are n o t given, but the aerodrome diagram,which isdrawn to scale, shows the position of the aids relative to the runwaysand taxiways ‐ a handy feature for orientation when inbound on an instru‑m e n t approach.

202 Night Flight

Broadcasting StationsBroadcasting stations (AM) may also be tuned and received on an ADF, sincethey transmit in the same LF/MF band. However, it is n o t wise to use broad‑casting stations asnavigationaids, n o t only because they may be distracting, butalso because they can be difficult to identify. The signal may n o t be directlyfrom the main transmitter but rebroadcast from a relay station or replayedby arural station locatedmany miles away. Furthermore, many stations do n o t havestandby generators and their hours of operation may be variable. They are n o tsubject to calibration and flight checks.

The frequency and location of all broadcasting stations in Australia are listedin ERSA (NAV/COMM), but this is primarily to allow broadcasting stationsto be usedassupplemental informationfor VFR flights. They must not be usedfor IFR navigation.

t o a i r e i o i dThe ADF is a most flexible, reliable and user‐friendly navaid. Once you arefamiliar with its operation, you will find it invaluable ‐ and there are manyNDBs.

The ADF installation has three main components:' the receiver (and control panel);- the antenna system, comprising a loop antenna and a sense antenna (or a

combined unit) which determines the signal direction; and0 the ADF indicator, which isusually placed to the lower right of the primary

flight instruments.

ADF Cockpit DisplaysADF indicators use avariety of presentations, the m o s t c o m m o n of which are:° the relative bearing indicator (RBI), with either a fixed‐card ADF or a manually

rotatable‐cardADF that can be aligned to the HI ,which in t u r n must be alignedto the compass; and

' acombined radio magnetic indicator (RMI), which has apointer that indicatesthe signal direction and presents all the information automatically on o n einstrument.

Relative Bearing Indicator (RBI)A fixed‐card display consists of anADF needle and afixed azimuth card, whichis graduated into 360°. The relative bearing indicator is c o m m o n in many old

9: Radio Navigation

general aviation aircraft. The relaative bearing of the N D B from theaircraft is the angle between theheadingof the aircraft and the direc‑tion of the NDB. For calculations(and examinations), relative bear‑ings are described clockwise from360. In flight, it is more convenientto state the bearing relative to thenose or tail of the aircraft. On theRBI, the needle can only indicate therelative hearing of the N D Bfrom thenose of the aircrqft.

Orientation Using the RBI. Theaircraft is orientated with respectto the N D B with the followinginformation:0 the magnetic heading (HDG)

of the aircraft; and° the relative bearing of

the NDB.

There are t w o methods ofestablishing the position of theaircraft:° by calculation and plotting (as

was done by the navigator); orby mentally transposing the

ADF needle o n t o the HI and

lR-1126.EPS

203

Relative/ \ ,2-,:. \ Vbearing "3

‘BRI’ bears \030° REL LEI ‘ \ \

Q“

<5}I 0§ 3 3 < Q \

Figure 9-8 Orientation ('Where am l?') using an RBI.

reading the bearing to the station (the direction of the head of the needle)and the bearingfrom the station (the tail of the needle) directly.

Calculating the Magnetic Bearing. If the aircraft is heading 280°M and theADF indicates a relative bearing of 030° (300 right of the nose), the magneticbearing to the station is 280 + 30 = 310. The bearing from the station (radial)would be 310 ‐ 180 = 130°.

Conversely, if the relative bearing is 330°, the computation is n o t sostraightforward:

280+330 = 610‐360 = 250!

204 Night Flight

However, if you use therelative bearing of 30° left of thenose as a negative value, thebearing becomes:

280730 = 250

Transposing the Needle. In fig‑ure 9‐9, the HI shows a headingof 280°. The needle is imagined

Figure 9-9 A pictorialparallel and transposed to the face method offinding aof the H1. The nose of the needle "ack ‘° 35 m m " ‑

indicates 310 to the station, and I fi - m z r s

the tail shows 130 from the sta‑tion ‐ no calculations needed.Rotatable-Card ADF. The rotatable‐card ADF allows the pilot to ro ta te thecard so that the magnetic bearing to the NDB can be read on the card underthe needle. The pilot mus t align the ADF card with the HI each time theheading of the aircraft is changed. This can become confusing and time‐con‑suming, andmany pilots leave the rotatable card set to 360 at the top and useit asa fixed card.You should manually align the ADF card with the HI any time the aircraft

changes heading (after ensuring that the H1 is aligned with the magneticcompass). If desired, the rotatable‐card can still be used asafixed‐card simplyby leaving 360 set under the index.

Radio Magnetic Indicator (RMI)The R M I display has the same ADF needle that always points at the NDB.However, behind the needle is a card that is continuously and automaticallyalignedwithmagnetic north. It is, if you like, anautomatic version of both therotatable‐card ADP and the HI ‐ all in one instrument. It is a significantimprovement._ _ _ _ _ _ _ _ T ‐ _ 7 .. _, _ Torque motor

g / Synchro ,400 HZ receiver _ _ _ _ T _ _ _ ‐ ‐ ‑

\ \ Null seeking\ ‐ I. / rotor _Detector unit remote Horizontal gyro AGK-mZIEPS

Figure 9-10 The RMIcompass card is driven by a flux valve and heading indicator.


Like all forms of ADP:° the needle will always point to the N D B (and the magnetic bearing can beread directly under the needle); and

° the tail of the R M I needle will indicate the bearing of the aircraftfrom theNDB (the aircraft sits on the tail of the needle).Whichever type of display is used, remember that the ADF needle will

always point at the NDB, no matter what the aircraft does ‐ it is asthough astring is tied between the tip of the ADF needle and the beacon. Imagine it isn o t the needle that moves but rather the fixed‐card ‐ the needle continues topoint at the station.

NDB/ADF ErrorsA number of factors can act on the signals transmitted by an NDB and causeADF indication errors and/or reduce the effective range of aground station.

NightEffectThe usable rated coverage of anNDB may be considerably reduced at night.During the hours of darkness and at distances beyond 70‐80 mmfrom the

ground station, N D B signals are subject to significant interferenceby sky wavesreflected from the ionosphere.NDBs operate in the low frequency/mediumfrequency range. Radiowaves

within this range can follow anumber of different paths to arrive at a suitablereceiver. The strongest signals consist of waves that have followed an almostdirect path from the NDB to the aircraft, staying roughly parallel with ‐ andclose to ‐ the surface of the earth. These are calledground waves. If the ADFreceives only groundwaves, the needle will indicate the co r rec t bearing to theNDB. However, this will n o t always be the case, especially at night.Many of the waves transmitted by an NDB are radiated skywards, and at

some distance above the surface of the earth, they will enter a region of theupper atmosphere known as the ionosphere. The ionosphere is composedmainly of layers of gas molecules and atoms that have been ionised by solarradiation. The height, thickness and intensity of the ionosphere, and its effectupon LF/MF radio waves, vary significantly during any given 24 hour period.During daylight hours, when direct radiation from the sun produces the

mos t intense ionisation, radio waves will encounter the lowest layer of theionosphere (the D layer) at a height of about 50 km. This layer effectivelyabsorbs (attenuates) all low frequency/ medium frequency signals.At night, however, the ionosphere contracts asdirect solar radiation ceases,

and the D layer disappears entirely. Low frequency/medium frequency signals

206 Night Flight

are no longer absorbed by this layer, and in penetrating to higher levels of theionosphere, they encounter those other layers that remain active at night.These layers, known asthe E layer and the F layer, refract (bend) a significantproportion of the NDB signals that enter them without imposing anyappreciable attenuation. Some of these refracted waves wil l r e t u r n to thesurface of the earth assky waves.During the hours of darkness, sky waves will tend to mix with the primary

ground wave signals, commencing at a distance of 70‐80 nm from the NDBground station (i.e. beyond the average skip distance for the frequencyconcerned). The tw o signals will be dissimilar (out of phase), resulting inunreliable directional information being provided to the ADF. The needlemay fluctuate wildly and continuously. This behaviour is knownasnight efikct.

‘ :/-{ ‘\ Sky waves, / / \\ reflected

Sky waves absorbed D \\in D layer in daytime \I.

Mixingiofs yand grounm u m s waves causes bearing errors

Figure 9-11At night, sky waves mix with the ground wave signals transmitted byan NDB, causing ADF indications to fluctuate.

A consequence of night effect is a reduction in the rated coverage of manyNDBs at night. During the day, sky waves are almost entirely absent (becauseof the attenuationwhich occurs in the D layer), andgroundwaves do n o t sufferany interference all the way o u t to the limits of the normal range of the station.At night, however, a ‘pure’ ground wave signal only exists o u t to adistance of70‐80 nm, after which sky waves begin to interfere, rendering the ADFunreliable for navigation.

NAVIGATIONAIDS -» Pilotmonitored.NDB HBK 323 - 835 37.6' E14727.9’ ('1. )‘1. Range 100(HN70) (55insector045to 115).

/ W k I n c / i s m

DAY NIGHT 'RANGE TOTHE EAST

Figure 9-12 Night effect reduces the rated coverage of many NDBs during the hours of darkness.


During the hours immediately surrounding sunrise and sunset, when theionosphere is undergoing the mos t significant changes, fluctuations in ADFbearing indications can be very pronounced. Increasing the transmissionpower of an NDB will n o t eliminate night effect. The strength of the directgroundwave and the indirect sky wave will both be increased so that the ratiobetween them at any given distance from the transmitter wil l be the same.Night gflfect cannot beeliminated.Locators and other low‐powered

NDBs are n o t subject to significantnight effect. The rated coverage ofthese stations is only limited (25‑45 nm on average) and because ofthe skip distance involved, night‑time sky waves are almostcompletely absent within this radius.For this reason, only a single ratedcoverage is specified for these aids.

Coastal RefractionThe paths of NDB signals arerefractedwhen they cross acoastlineat an oblique angle. Signals thatcross acoastline at right angles (90°)are n o t subject to any bending.Refraction is due to the differingconductivities of land and water.Signals bend towards the land mass‐ the shallower the crossing angle,the greater the refraction.Coastal refraction causes false

bearing indications ‐ the NDBalways appears to be closer to thecoastline than it actually is. Theeffect is greater the further inlandthe transmitting station is located.Coastal refraction is thereforeeliminated if an NDB is located. . Figure 9-13 Coastal refraction causesderCtly on the coaSthnC- false ADF bearing indications.

208 Night Flight

Terrain EffectFor transmissions in the low frequency/medium frequency bands, any signalsreceivedatmaximumrangewill bemadeup of groundwaves that have remainedin close contact with the surface of the earth during their passage from the NDBgroundstation (remember, atnight there will also beskywaves mixingwith thesesignals). Given a constant power output, the range to which ground waves willextend depends on the conductivity of the surface material over which theytravel ‐ the more conductive the surface, the lower the rate at which signalstrength is attenuated (absorbed) andthe greater the range achieved.

J

Sandy/rocky terrain Salt waterlow conductivity, rapid attenuation high conductivity, slower attenuation

therefore shorter range therefore longer range m u m s

Figure 9‐14 Terrain effect can reduce the rated coverage of an NDB over land.

Since water is a comparatively good conductor, the usable range or ratedcoverage of an N D B is much greater over water. Furthermore, the ratedcoverage over sandy desert terrain will be less than that achieved over othertypes of land surface.ERSA shows that many coastal NDB stations have an additional rated

coverage value specified for over water, which is greater than that available overland.

NAVIGA‘HONAIDSTACANDAR 84/ 113.7 81224.9' E13052.9‘ 258/04NDB DN 344 81226.0' E13057.6‘ 281/50 ('1. )DME DN 112.4171X $12 24.2‘ E13051.8' Antenna ELEV 113FTVOR DN 112.4 $12 24.2' E13051.8” 135/1111L8 IDN 109.7 81224.6' E13051.7‘ 274/119 2. )L BGT 308(38901) 512 24.5' E13051.3' 109/12 3. )

257(HowardSpringsSt2 28.2' E13102.5' 287/112 (‘4. )L HWSABN ALTNwe 8 RPM 81225.3‘ E13052.0' 23410.6‘1. Range 150(HN85)CW 450 (HN 110).

Day range Night range Day rangeover land over land over water

lR-iM M !

Figure 9-15 Extract from ERSA ‐ t h e rated coverage of Darwin NDB is significantlygreater over water than over land.


Mountain EffectWhen flying over mountainous terrain, anaircraft may receive NDB signals thathave been reflectedflom the surfaces of surroundingmountains andhills. Theseindirect reflected signals can mixwith the primary ground‐wave signal receivedat the aircraft and cause erroneous and rapidly fluctuating bearing indications.Once the affected area is passed, the ADF needle will normally stabilise andindicate correctly. At some locationswhere the terrain isparticularly unfavour‑able, NDBs may operate at a higher frequency (e.g. 1,655 kHz) to minimisemountain effect (however, this is n o t necessary in Australia).

Height EffectOver water and flat terrain, the range of anN D B is n o t significantly affected byaircraft height. However, over rough and mountainous terrain, masking andinterference (i.e. mountain effect) can occur at low altitudes, causing an ADFneedle to fluctuate or provide afalse bearing indication. If anaircraft climbs toahigher altitude under these circumstances, theADF indicationswill usually sta‑bilise, and the range of the NDB may increase.

Thunderstorm EffectThunderstorms (electrically active cumulonimbus clouds) can generate anenor ‑mous a m o u n t of radio energy, especially in the LF /MF bands. Consequently,when flying through or near an area of active thunderstorms, the ADF needlemayfluctuatewildly asit isattractedtowards the source(s) of the spurious signals.Bearing errors are possible, and in some cases, the presence of thunderstormscan render the ADF completely unusable.

Interference from Other NDBsIf aparticular NDB has been tunedbut signals are also being receivedfrom another NDB operating onthe same frequency, the ADF willgive false bearingindications due tothe mixingof the signals. As agen‑eral rule, NDBs operating on simi‑lar frequencies are well‐separated

~ ~ - - Figure 9-16geographlcafly to m m m s e the Atnight, interference from other more distantpossibility of co‐channel interfer‐ NDBs operating onthe same frequency can occur.ence. At night, however, sky wavescan extend to a far greater range than the ground waves from the same NDB,and they may be affected by other NDBs operating on the same frequency a

270 Night Flight

considerable distance away. In such cases, the ADF needle will fluctuate asit at ‑tempts to point towards the source of the interferingskywaves.

Inaccurate TuningCareless frequency selection is something that a pilot mus t never be guilty of.Remember, it will be preventedby strict adherence to the recommendedtuningchecklist ‐ i.e. NDB:° selected;- identified; and0 ADFing.

The tuning procedure specified in the operating handbook for theequipment must be followed. Digital frequency selection on modern ADFequipment has simplified the tuning task. However, identification is still vital!Accidents have been caused by incorrect tuning. If a positive ident cannot beobtained, donot use the NDBfor navigationalpurposes.

ADF AccuracyThe ADF is n o t aprecision radio navigation aid asthere are many factors thatcan reduce both the accuracy of ADF indications and the range atwhich usablesignals can be received from an NDB. When operating within the rated c o v ‑erage of an NDB, the pilot can expect the bearing indications to be accurateto within i 5 ° only.

Remember that, although N D B signals can often be received at a range wellbeyond the published rated coverage, their accuracy will be significantlydegraded, As soon assky waves or waves reflected from surrounding terrain orgenerated by nearby thunderstorms mix and interfere with the ground wavesignal,ADF accuracy will begreatly reduced. However,within these limitations,pilots may use the ADF with confidence and safety

Use of the ADF In FlightPictorial Navigation:Visualising the ADF Needle Position on the Face of the HIMentally transposing the R B Ineedle onto the HI allows aquick Visualisation ofthe magnetic track to the N D B on the head of the needle and magnetic bearingfrom the N D B on the tail of the needle. N o w imagine a model aircraft sittingon the tail of the needle pointingstraight up to the headingand the N D B asthecentre of the dial ‐ an immediate picture of the situation is presented. Forexample, visualise the situation of H D G 070 and 100° left of the nose. We areon the 150°M bearing from the station.


Figure 9-17Visualising needle position

on the HI; HDG 070 andbearing 150from the NDB.

"14211AEPS

Point to Point NavigationIf you know your bearing, you can easily select a heading to position you onanother. If you have distance information, you can actually position the aircrafton that bearing at aparticular distance from the station. This ispoint topointnavigation, which is used with R M I / H S I and D M E or in the military withTACAN. It isavery effective way ofkeeping the R N AV system (GPS) honest.

lntercepting a TrackHaving become orientated with respect to an NDB, the pilot knows theanswer to the question, ‘I/erre amI?’ and n o w asks, ‘Where do I want togo?’and ‘What heading do I steer toget there”.

Visualising Where You Are and Where You Want To GoWith H D G 070 and anRB of 100° left, you wish to intercept amagnetic track270 inbound (to the NDB) - the 090 R. Visualise your position and the desiredtrack. With a model aircraft on the tail of the needle tracking asdesired, itbecomes quite clear what turns are necessary to intercept the desired track.First, t u r n left to asuitable intercept heading, e.g. 360 for a90° intercept of the090 R while you think. Then t u r n to 310° for a40° c u t (intercept).

070

/ " Tu r n t o‘I intercept

Where I ‑\ ie want to be . ,

‘ 01“4 Here I am

Transposedneedle I _ I will turn left

mane 310° to interceptM 172

| \ \

Figure 9-18 Visualising an intercept on the HI.

1IR-1213A.EPS

272 Night Flight

If you become disoriented, asimple procedure is to take up the heading ofthe desired track. Even though n o t on track, the aircraft wil l at least be parallelto it , and the ADF needle will indicate which way to t u r n to intercept thedesired track.Note. An aircraft covers some distance during a turn, and you should antic‑ipate the desired track by commencing the t u r n o n t o track before the radialis reached. This is known asleadangle. The amoun t of lead can bejudgedby observing the rate at which the needle is falling (the faster the aircraft istravelling and the closer to the station it is, the greater the rate of needlemovemen t and the greater the anticipation required). An allowance for theradius of the t u r n is also necessary (the greater the intercept angle, the widerthe turn).

lntercepting an Outbound TrackPicture where you are (on the tail of the needle with your nose up ‐ always).Picture where you wan t to be and the track o u t bound. Imagineyour progressand needle position asyou reach your outbound track (see figure 9‐19).If you are n o t converging, you can easily visualise the heading to steer to

make an intercept (figure 9‐20).

Where you\want t be

lH-ImAEPS

Figure 9-19 lntercepting on outbound track.


outbound track

Read interceptheading \

IR-I221A.EFs

Figure 9-20 Visualising an intercept.

Maintaining TrackFlying level is a series of small and gentle climbs and descents to maintain thedesired altitudeperfectly. Similarly, tracking isaseries of small headingchangesmade to maintain the desired track.If the aircraft has diverted from the desired track, there are t w o options:

' track direct to or from the NDB on the new track; or° regain andmaintain the original track.

When flyingon atrack, the trend of the ADF needle is the important cue. Assoon asit tends to deviate, correct through the deviation by about twice theamoun t and then half the correction when back on the track. It is like thetechniques for regainingandmaintaining track with visual navigation. Imagineagain you are sitting on the tail of the needle. Turn and drag the tail back toWhere it shouldbe. For example, anaircraft has drifted right ofa desired inboundtrack (200 degree radial). Turn left through the needle to the same amoun t (to360 degree in this case). Watch the tail of the needle to check the progress.just how great each correcting t u r n should be depends upon the deviation

from track. A simple methodis to double the error. If the aircraft has deviated

274 Night Flight

10° left indicated by the RB I moving 10° right, alter heading by 20° to theright ( i fyou alter headingby only 10° to the right, the result will probably bea further deviation to the left and a further correction to the right, with thisbeing repeated again and again resulting in a curved homing to the NDB).

m u g / m s Figure 9‐21003 Transposed needle.

Having regained track, t u r n left by only half the correcting t u r n of 20°, i.e.t u r n left 10° to intercept andmaintain track.

allowancenow 10°

Turn right 20°to regain track

; RB Turn left 10°10(350) to maintain track/

Figure 9-22Regaining track by doubling the

Original error and maintaining trackrift allowance 0° thereafter. iRlZSIEPS

RB000(360)


What ToDo if Uncertain of WindEffectIf the wind direction and strength is n o t obvious, the best technique is to ini ‑tially steer track asheading (i.e. make no allowance for drift). The effect of thewind wil l become obvious as the ADF needle moves to the left or right.Observe the results, and then make appropriate headingadjustments to inter‑cept track. Double the deviation.

NDB

In-1233 . 9 5

Figure 9-23 If uncertain of wind, initially fly track as heading.

Tracking Over an NDBThe ADP needle will become more and more sensitive asthe NDB station isapproached. Minor displacements left or right of track will cause larger andmore rapid changes in bearing. For a very precise track to be achieved, youm u s t be prepared to increase your scan ra t e asthe N D B is approached and tomake smaller corrections mo re frequently and sooner. Anticipate but do n o tchase the needle. If you are close, simply maintain a constant heading.

TrackingAbeam an NDBIn order to fly past an NDB sited some distance away from track, it is some‑times useful to determine the exact abeamposition, i.e. the point atwhich theangle between the track and the bearing to the NDB is 90°. The RB I indica‑tion at the abeamposition will depend on drift:' with m'l drflrt, the pilot will be able to steer track asheading ‐ at the abeamposition, the needle will indicate either RBO9O or RB 270 (3 o’clock or 9o’clock); and

' with drift, drift must be applied to maintain the track in acrosswind, and theheadingwill differ from the track direction ‐ in this case, the R B I indicationat the abeampositionwil l be:

+ LeftWCARB 090 or RB 270 t‐-RightWCA

276 Night Flight

Ten-Degree Bearing ChangeThe 1 in 60 rule states that 1 r i m of track in 60 nm subtends an angle of 1degree. If this is applied to an aircraft passing abeam an off‐track NDB, asitflies through the 10° of arc from the point atwhich the course deviation indi‑cator (CD1) first starts to move to the point at which the needle is centred,approximately 10nm will he travelled if the aircraft is located 60nm from theground station (or 5 nm at 30 nm). At agroundspeed of 120 kt (i.e. 2 nm perminute), the time required to cross this 10° of arc abeam the V C R will be5 minutes at 60 nm or 2.5 minutes at 30 nm .In ni lwind, you can estimate the time it will take to fly directly to the station

by measuring the time for a bearing change asyou fly abeam the station andusing the simple expression: time to the station = seconds between bearings +degrees of bearing change.For example, a 10° bearing change abeam an NDB takes 5minutes. By

turning andflying directly to the VOR, the time required to reach the station is:300 sec100

At a groundspeed of 120 kt (2 nm/min), this would mean that you are 2 x30 = 60 nm from the station.

Time to VOR = = 30minutes

_ . n gmm z - m ' n z ‘ u s y 1 “ $ 3 , 3 4 3 ; m m w w u$254 . . » a t mm M: .J: xmm ‘ zr w

Principal advantages of the V C R over the NDB include:- a reduced susceptibility to electrical and atmospheric interference (includingthunderstorms); and

° the elimination of night effect, asVHF signals are line of sight and are n o treflectedby the ionosphere.The reliability and accuracy of

V O R signals allow the V C R to Wbeusedwith confidence by day or M"OLE;

by night in all weather conditions. QIt is used for: we' orientation and position fixing VHF-NAV(‘where am I?’);

' tracking to or from a V C Rground station;

- holding; and° instrument approaches.

i n m m s VOR instrument

Figure 9-24 VOR equipment in the cockpit.


Many VORs are paired with a co‐located distance measuring equipment(DME) ground station or TACAN (VOR‐TAC). Selection of the V C R onthe VHF‐NAV set in the cockpit also selects the frequency‐paired DME orTACAN, thereby providing both tracking and distance information.

VOR RadialsA V O R station transmits signals in all MNdirections. However, its mos t impor‑tant feature is that the signal in anyparticular direction differs slightlyfromits neighbours. These individualdirectional signals can be thought of 300 radialastracks (or position lines) radiatingou t from a V C R ground station inmuch the same way asspokes radiate 240 radial

360 radial330 radial 030 radial

060 radial

270 radial 090 radial

120 radialfrom the hub of awheel. IThere are 360 different tracks 210 rad'al 180 radiaI 150 rad'al

' lR-l409.EPSaway from a V C R station, each I0 Figure 9‐25separated by 1 and related to Aradial isamagnetic hearing from the VCR.

magnetic north. Each of these 360tracks is called a radial. The 075 radial is actually a line bearing O75°M fromthe V C R station. A radial is a magnetic bearingfrom a VCR. The radials of aV C R are transmitted to an accuracy of i 2 ° or better.

VOR Accuracy and LimitationsThe VOR is considered to be more accurate than the NDB/ADF combina‑tion, especially for tracking. However, V O R indications are subject to anumber of errors.

GroundStation ErrorSignal accuracy can be affected by error generated within the ground stationequipment itself. Bearingerrors from this source are small, usuallywithin 412°.

Site EffectErrorThe transmission of V OR signals is significantly affected by obstructions orirregular terrain in close proximity to the station (e.g. buildings, fences, rocksand hills). A great deal of planning and preparation of the V C R site is neces‑sary to minimise this sort of error. The immediate surroundings of V OR sitesare quite flat and cleared of obstructions and vegetation within awide radius.Even the grass is kept trimmed!

218 Night Flight

The bearing errors caused by site effect are checked (in all directions and atvarious altitudes) during the initial calibration of the station and periodicallythereafter. Errors shouldbe within i3o. Occasionally, where aV C R is sited inan area of particularly unfavourable terrain, site errors in excess of limits canno tbe avoided. Under these circumstances, the likelihood of unreliable bearinginformation (usually within specific sectors and/or at certain altitudes anddistances) will be notified in ERSA for that particular station (see figure 9‐26).

VOR 540 134.2 836 35.9 E153 0&4 (2)2 WOMMMMMmifiwWMWMMMMWQMM

m M W M M . D M E A R fl i s m AV B L m M C V O R M O M W. M n gandsacrumon224W atm m .

IZ-aiEFS

Figure9-26 Extract from ERSA detailing reduced VOR coverage.

Terrain Effect ErrorV O R signals arriving at anaircraft can be distorted by spurious signals from thesame transmitter that have been reflectedfrom terrain lyingbetween the stationand the receiver. This type of interference causes oscillations of the V C R indi‑cator needle. Rapidoscillations are called scalloping, while very slow oscillationsare described as radial bending. The maximum bearing error that may beexpected from these sources will be 12°. However, asis the case with site effecterrors, particularly unfavourable terrain can cause larger errors at certain loca~tions. Any V O R stations so affected will be noted in ERSA.

Airborne Equipment ErrorV O R indication errors may arise asa result of imperfections in the airborneequipment and its installation, but these are usually within iZO.

Vertical Polarisation ErrorVertical polarisation error is rarely encountered. V O R stations transmit hori‑zontal radio waves ‐- i.e. the waves oscillate parallel to the surface of the earthand are known ashorizontallypolarised waves. These are the only type of wavesto which anaircraft’s V O R antenna is normally sensitive. However, signals thatare reflected from large obstacles may be modified to become vertical waves ‑i.e. they oscillate at 90° to the surface of the earth. These spurious signals, ifpresent, will only be received if the aircraft is banked in a t u r n or sideslip ‐ i.e.when the V C R antenna isn o t horizontal. Vertically polarisedwaves will causelarge, rapid deflections of the V C R indicator needle. These will cease whenthe aircraft returns to wings‐level flight.


VOFI’ Aggregate ErrorThe combined effect, at any given moment , of all errors affecting V OR indi‑cations is known asthe aggregate error. The value of the total e r r o r varies andis difficult to determine. However, under normal circumstances, aggregateerror wil l rarely exceed i 5 ° .

Doppler VORsWe have said that bearing errors arising from site effect can be quite significantatsome locations. DopplerV O R stations, which are beinginstalled in increas‑ingnumbers throughout Australia, are notable for their ability to almost totallyeliminate site effect errors. This eases the constraints on transmitter locationand reduces site modification and maintenance requirements. This also pro‑vides increased bearing accuracy.

Range of VORThe V O R may be affected by the terrain surrounding the ground station, theheight of the V C R beacon, the altitude of the aircraft and the distance of theaircraft from the station. A rated coverage table for VORs (andDMEs) ispub‑lished in the AIP. For a series of height bands, the AIP shows the maximumdistance from aground station at which indications may beused to establishedapositive radio fix (eg. the rated coverage is 60 nm below 5,000 ft).

2.2 RatedCoveragesThe following ranges are quoted for planning purposes. Actualranges obtainedmay sometimes be less than these due to facilityandsitevariations (seeERSA). The localizer rangesarefor thoseinstallationsthat havebeennominatedfor positionfixingat rangesbeyond25NM:a. NDB (published in ERSA);b. VCR and DME:

Aircraft Altitude (FT) Range (NM)Below 5,000 605,000 to below 10,000 9010,000to below15,000 12015,000 to below 20,000 15020,000 and above 180

c. Localizer:Aircraft Altitude (Fr) Range (NM)At 2,000 AGL within:10°of course line 25Below5.000 305,000 and above 50

Figure 9-27 AIP rated coverage.

220 Night Flight

These rated‐coverage values are worthwhile remembering in order to assistyou in the selection of the m o s t suitable V O R stations for en rou te usage.Rated coverage figures apply equally to both day and night.

Note. The rated coverage of particular V O R stations may be reduced byspecific local factors, especially terrain close to the transmitter. Any specialrestrictions are noted in ERSA for the station concerned ‐ e.g. the MudgeeV O R is not to be usedfor navigation beyond 20 nm below 10,000ft AMSL.Navaids n o t at aerodromes are also listed in this section.

VOR IdentificationThe position, frequency and Morse code identifier of each V O R ground stationis shown on the following:° en rou te charts (ERG‐Lows and ERG‐Highs);° VNCs;° TACs; and0 in ERSA.

The positions of navigation aids at aerodromes are also shown on instrumentapproach and landing (IAL) charts. A hexagonal symbol is used to indicate theposition of aV C R station on ERCs and TACs.

If both V C R and N D B are sited at the same location, the V C R will be theprimary tracking aid, and only the V C R symbol will be shown on the ERC.For example, the V C R is co~located with afrequency‐paired D M E station atMildura (MIA), and the combined installation is depicted asaV C R / D M E inthe frequency box (113.7) (figure 9‐28). Although M I A has an N D B (272),only the V C R symbol is shown).

In addition, the latitude/longitude coordinates shown are always those forthe primary tracking aid. In this case, this is the Mildura V C R / D M E . TheM I A N D B and its frequency are shown below the coordinates. All the navaidsat Mildura share the same ident ‐‐M I A (dab-dab dit-dit, dit-dab).

On ERCs and TACs, the published routes are markedin degrees magnetic. Ifthey originate from aVCR, they will represent the radials alongwhich anaircraftmust track inbound or outbound. However, for many routes between V O Rstations, the radials are n o t always exact reciprocals of each other, especially onlong‐distance tracks runningroughly east‐west. This discrepancy occurs because:- the routes are great circle tracks which cross successive meridians at different

angles, i.e. the track, asmeasured at each meridian, changes along the lengthof the route; and

° magnetic variation differs from place to place, i.e. the magnetic hearing, orradial, corresponding to aparticular true hearing may also vary along a routebetween t w o VORs.


,, \ . ' MLCEN 127.! "Wentworih H p g Mm , “ gcm was I V a _

"°'(OSAMPLEONLwlth Max:931COHIUHVC” . iormg,"piggggflson V9

. . I

Noiyovoa 112.8 3"

534 53.1 514;».

Figure 9‐28 VOR stations are shown on en route charts (combined symbol w i th reporting point).

If it is necessary to plot a V C R radial or position line on an ERC or TAC(i.e. to measure amagnetic track to or from aV C R station), the easiest methodis to measure it relative to apublished radial from the same V OR ‐ e.g. if youWish to plot the 063 radial from the M IA VOR, this can be measured as20°anticlockwise from the published 083 radial.If it is necessary to plot aV O R radial relative to ameridian of longitude (i.e.

by reference to true north), magnetic variation mus t be applied to conver tbetween the corresponding t rue andmagnetic bearings ‐‐ variation west, magneticbest; variation east, magnetic least. Isogonals are marked on ERCs, whereas anaverage variation is quoted for the areas on TACs and instrument approachcharts.Aswith NDBs, detailed information about V OR ground stations is found

in ERSA and includes:' the frequency and ident code;° the position of the station expressed in decimal latitude/longitude coordi‑

nates and, if applicable, asamagnetic bearing and distance (nm) to the ref‑erence point of an associated aerodrome; and

0 any special remarks or limitations that apply (e.g. ‘Scallopingmay beexperiencedwithin 245 and 256 radials’ and ‘Voice usedforATIS’).

222 Night Flight

GLADSTONE ELEV64AVFAX CODE4023QLD UTC+10 ‘ YGLAS 23 52.2 E 15113.4 VAR 10DEGE CERTADOPRGladstone'CaIIiopeAD Board, PO BOX7200, KinKora.QLD.4680.PH 07 4978 1606:49782201, FAX4978 1314.

s“ ,4v836 053° 2w

~ 9” GiadstoneH I;

A NAERODROMEANDAPPROACH LIGHTINGRWY 10/28 URL (1) PAL+AFRU 118.8 SDBY PWRAVBLRWY 10 AT-VAsIS (2) PAL+AFRU 118.8 3.0 DEG49FT ,SDBY PWRAVBLRWY 10 RTIL (3) PAL+AFRU 118.8 ' SDBY PWR ” 54RWY28 T-VASIS (4) PAL+AFRU 118.8 3.0 DEGStFT SDBY F’WF °’.’0bsMpLEo(1) PAL+ AFRU requires three one-second pulses to activate. (See INTROpara _ o f]!(2) PAL +AFRU requires three one-second puises to activate. (See INTROpara 23.5), L. pan

side(3) HN. PAL+ AFRU requires three one-second puises to activate. (See INTROpara 23.5)(4) PAL+AFRU requiresthree one-secondpulsesto activate.(See INTROpara 23.5).HJPAL

activates bothVASIS onlyOTHER LIGHTINGHBN ToNE, SE&W ofADABN FLGWhite/Green 8 SEC.RADIONAVIGATIONAND LANDINGAIDS

‐> VOR GLA 116.3 s 23 51.9 E 151 12.3 (1)(1) 105/1NM t0 ARP IZ-OSEFS

Figure9-29 Detailed information about each VOR station is presented in ERSA.

VOR Cockpit InstrumentThere are various types of V O R cockpit displays used in general aviation air‑craft. However, the various types are similar in operation and in how theinformation presented is interpreted.The typical V O R cockpit display isusually referred to asthe V O R indicator

or omni-bearing indicator (OBI). The OB I card displays the radial selectedby thepilot (bearingfrom) or its reciprocal (bearing to) using the omni‐bearing selector(OBS), a small knob geared to the card.The OB I is aprimitive instrument designed to maintain track along air routesbetweenVORs. It can be confusing if you are n o t tracking directly to or fromthe VOR .

Using the VCRIf an aircraft is on the selected radial, the V O R needle ‐ known asthe coursedeviation indicator (CDI)‐ is centred (figure 9-31). If the aircraft is n o t on theselected course, the CD I will n o t be centred.


Figure 9-30 The VOR cockpit display with the 015 radial selected.

OBS course Coursecard index

Course deviation indicator(CDI)Indicates aircraft’s horizontaldisplacement relative to theselected omni bearing

Deviationscale

OFF (or NAV) TOIFROMindicator flagsWhen OFF or NAV showingindicates unusable signals.

T When this flag disappears,T0/FROM flags indicate

Omni bearing selector (OBS) whether the course selectedUsed to select the desired omni under the course index willbearing under the course index take you to or from the

I a - q u F s selected VOR station.

o559o

VOR

Figure 9-31 CDI centred. Same positionas indicated

Heading 360°Track 360° :t: drift

- ADF/VOR Bearing 120° FROMneed|e on am the station (120° Radial)

iR - IMMEPS

224 Night Flight

The V OR indicator is n o t headingsensitive, which means that, regardless ofthe position of the aircraft in relation to the selected course, the display will bethe same on any heading. The case illustrated in figure 9‐32 shows the samesituation, except that awind correction angle of 10° right is used by the pilotto counteract a wind from the right. The magnetic heading of the aircraft isn o w 025 (rather than the previous 015).

I fi - mACEFS

Figure 9-32 Wind correction.

Note the possible confusion between track, course, headingand radial. Thecourse setting for the V C R is the bearingor desired track toorfrom the station.The CD I is centred when the aircraft is on ‐ or passing through ‐ the setbearing. If the bearing from the station is selected and the C D I bar is centred,the aircraft is on or passing through that radial.Asthe aircraft passes the radial tracking in anortherly direction, the OBI /CDI

moves asshown in figure 9‐33. This can be confusing. Note that, when theaircraft is tracking approximately towards the station and abearing to the stationis selected, the CD I shows the direction to t u r n to fly to the station on that radial.This is known asa command instrument ‐ i.e. follow the needle.

I m u d s z r s

Figure 9‐33 CDI indications.

With 120°from selected, the needle shows the direction to tu rn to fly awayfrom the station on that radial. To fly to the station on the 120° radial, the pilotmus t t u r n opposite to the CD I (i.e. away from the needle).


The V OR is only to be used for navigation if:° the red of warning flag is hidden from View;° the correct Morse code ident for the selected station is heard; and0 the CD I is n o t moving erratically.If the red of flag (sometimes labelled ‘nav’) is showing, the signal strength

received is n o t adequate to operate the airborne VOR equipment. This may bethe case if the aircraft is too far from the VCR, too low for reception or directlyoverhead the V C R from which no signal is received. The same flag will bedisplayedwhen the equipment is switched off. If the aircraft is n o t on the selectedcourse, the deviation indicator needle will show the angular deviation. At alltimes, the referencewhen using the CD I is the selected course under the index.By convention, V O R (CDI)

indicators use a standard deviation scalewith 5 intervals ‐ each representing a 2°deviation ‐ each side of the centre.Typically, the intervals are indicated bydots, i.e. there will befive dots either sideof the centre.If the aircraft is on the selected course,

the CD I is centred. If the aircraft is 2° offthe selected course, the CD I is displaced 1interval or 1 dot from the centre. If theaircraft is 4° off the selected course, theCD I is displaced 2 dots. If the aircraft is M u m s

10° or more off the selected course, the ‘5 2°4°6°5°10°C D I is fully deflected at 5 dots, i.e. full‐ Figure 9-34 cm displacementscale deflection of the V C R at 5 dotsindicates adeviation of 10° or more. To summarise, aone-dot deviation (y’the C D Ion the VCR cockpit display represents 2°. Fullscale deflection represents 10°or more.

Preparing the VCR for UseA radio navigation aid is of little value if the pilot does n o t use it correctly.Prior to using the VCR, apilot must :' ensure electrical power is available and switch the VHF‐NAV on;' select the desired frequency ‐ e.g. 113.2 MH z for the Brisbane (BN) V O R‐ asfound on the applicable charts or in ERSA;

- identify the V C R (dah-dit‐dit-dit, dalz-dit, which is the Morse code for BN‐ the coded identifier specified on the charts for Brisbane); and

0 check that the of or nav flag isn o t showing ‐ this indicates that usable signalsare being received.

226 Night Flight

Orientation Using the VCROrientation is a t e rm that refers to mentally picturing approximate position.The first step in orientation is to establish which radial the aircraft ispositioned o n .

(Z)VOR ( I )VOR

)' m

P6g.9/

|R-I418.EPS

Figure 9-35 0n the 154 radial.

)

“3‘?$9"9}

To find the radial, the pilot should:0 rotate the omni~bearing selector (OBS) until the course deviation indicator(CDI) is centred; and

° note whether the toorfrom flag is showing.For example, apilot rotates the OBS until the CD I is centred ‐ this occurs

with 334 under the index and the toflag showing. Could another readingbeobtained with the CD I centred?In this case, the aircraft is located on the 154 radial, and the C D I will be

centred with either:' 334 T 0 ; or° 154 FROM.

The aircraft may be heading or tracking in any direction.

Using Two Navaids to Fix PositionRadio position lines can be determined from any convenient radio navigationaids, includingVORs, NDBs and DMEs. Many reportingpoints and turningpoints specified on charts (ERCs and TACS) are defined by means of intersect‑ing position lines determined from nearby radio navigation stations. Oneposition line alone does n o t allow apilot to fix the position of the aircraft ‐ itonly provides a line somewhere along which the aircraft lies. Two or moreposition lines are required to fix the position of an aircraft. To be of any real


value for position fixing, the t w o position lines need to intersect at an angle ofat least 45°; any c u t less than this decreases the accuracy of the fix.Note. Pilots navigating by reference to radio navaids must obtain a fix atintervals n o t exceeding t w o hours.

Distance/A 0448

53a .59/ :25

U VOR/DMEVOR 2 (co-located) 'R-"w-EPS

Figure 9-36 Fixing position requires two position lines with a good intersection.

Passing Over a VCRAs an aircraft approaches aVCR , the CD I will become mo r e and mo r e sensi‑tive asthe i10o funnel either side of track becomes narrower and narrower. Asthe aircraft passes through the zone of confusion, the CD I may flick rapidly fromside to side before settling down again asthe aircraft moves away from theVCR. The flagwill also change from to tofrom, and the redof flagmay flickerdue to the unusable signal.The zone of confusion exists because V O R ground stations are only capable

of transmitting accurate signals up to about 60°‐80° in elevation above thehorizon; within the resulting ‘gap’ overhead the station, signals are weak andconfused, and V C R indications will fluctuate wildly. As this gap is cone‑shaped, the time taken to travel through it will depend upon the height andspeed at which the aircraft passes overhead. At low altitudes, only a fewseconds will be required; however, a minute or more may go by before thezone is passed at higher levels. The CD1 andfrom flag will eventually settledown, and the ofir flag will disappear entirely once the overhead zone istraversed. The presence of this zone of confusion means that it is difficult todetermine when the aircraft is exactly overhead the station. You shouldtherefore consider V O R station passage to be indicatedby the first completelypositive and stable reversal of the to/from flag.

228 Night Flight

CDI becomes agitated andmay flick from side to side

Red OFFfIag flicks ;in and out of view

“ I k r

Zone oi confusion

Flicking

Figure 9-37 Passage over a VCR.

Fixing Position Passing Abeam a VCRA common means of checking flight progress is to n o t e the time passingabeam(i.e. to one side of ) anearby V O R station. The m o s t straightforward proce‑dure is to:0 select and identify the off‐track VCR; and0 under the index, set a course that is 90° to your track.

An aircraft is tracking 350 and will pass approximately 20 nm abeam aV C Rstation o u t to its right. A V O R course perpendicular to track is the 260 radial,and so260 (or the reciprocal of 080) should be set under the index. The C D Iwill be fully deflected if the aircraft is well away from the abeam position. It willgradually move from full‐scale deflection one side to full‐scale deflection on theother side (i10°) asthe aircraft passes by the station. The aircraft is at the abeamposition when the C D I is centred. There is no need to allow for drift astheindicator shows aircraft position relative to the station ‐ n o t the position of thestation relative to the nose of the aircraft (as it does with the ADF).


Although there are t w o OBS Track _settings that may be used to determine 3500M Passi:;g:;:a9[;13gVCRwhen the aircraft is abeam a V C Rground station, it is suggested that youalways set the appropriate radial withthe OBS (i.e. the magnetic bearingfrom the off‐track VOR station).If the 1 in 60 rule (see page 216) is

applied to anaircraft passing abeam anoff‐track VOR/DME, as it fliesthrough the 100 of arc from the pointwhere the CD I first starts to move tothe point where the needle is centred,approximately 10 run will be travelledif the aircraft is located60nm from thegroundstation (or 5 nm at 30 nm). Ata groundspeed of 120 kt (i.e. 2 nm per minute), the time required to cross this10° ofarc abeam the V C Rwill be 5 min at 60nm or 2.5 min at30 nm.In nil‐wind, you can estimate the time it would take to fly directly to the

station by measuring the time for abearing change asyou fly abeam the stationand using the simple expression: time (minutes) to station = seconds betweenbearings + degrees of bearing change. For example, a 10° bearing change abeam aV C R takes 5 minutes. By turning and flying direct to the VCR, the timerequired to reach the station is:

260 {adlal ’0VCR

lR-l423.EPS

Time to VOR = = 30minutes300 sec10°

At agroundspeed of 120 kt (2 nm/min), this would mean that you are 2 x 30= 60 nm from the station.DME distance allows the pilot to cross-check the accuracy of the track being

maintained. This sor t of cross‐check isparticularly valuable if indications fromthe tracking aids ahead or behind the aircraft are unstable.

Tracking to a VCRTo track to aVCR, select the V C R frequency, identify the station, check that thered (37warning flag is n o t displayed and select the course requiredwith the OBS.Orientate with respect to the desired radial, and then take up a suitable

intercept heading. If the aircraft is heading approximately in the direction ofthe desired track, the centre circle will represent the aircraft and the CD I willrepresent the desired track. To intercept track in this case, the pilotwould t u r n

230 Night Flight

towards the CDI . This is using the V C R indicator asa command instrument ‑i.e. commanding the pilot to t u r n towards the C D I to regain track. However,be aware that this only applies when the heading of the aircraft is in roughlythe same direction asthe selected course. For inbound tracks, the V C R willact asa command instrument if the pilot selects a course that causes the toflagto be displayed.

Tracking From a VCRTo track from aVOR:' select the V C R frequency;- identify the station (monitor the Morse code ident);0 check that the red oflwarning flag is no t displayed; and' select the desired course with the OBS.

Orientate with respect to the radial, and then take up a suitable interceptheading. If the aircraft headingisapproximately the same direction asthe desiredcourse, the centre circle will represent the aircraft and the CD Iwill represent thecourse or requested track.To intercept a radial in this case, the pilot would t u r n towards the CDI.

Again, this isusing the CD I asacommand instrument ‐ i.e. commanding thepilot to t u r n towards the C D I to regain the radial. However, again be awarethat this only applies when the heading is roughly the same asthe selectedcourse.

A Minor Complication (Easily Solved)A minor complication can arise when the aircraft is on aheadingapproximat‑ing the reciprocal of the course selected on the OBI. Under thesecircumstances, the CD I wil l n o t act asa command instrument. This situationis called reverse sensing. For example, suppose an aircraft has been tracking 140from aVCR, with 140 selected in the OBI and heading 140. The aircraft hasdrifted left of track, and so the CD I will be deflected to the right. To regainthe outbound track of 140 from the VCR, the pilot must t u r n towards the nee‑dle, in this case with t u r n right ‐ i.e. headingand OBI selection are similar, sothe CD I is a command instrument. Suppose n o w that the pilot wishes tore t u r n to the VCR ground station on the reciprocal track, which is 320 to theVCR, and turns 180° on to 320 without altering 140 set under the index.Because the V C R indicator is n o t heading-sensitive, it indicates exactly asitdid before the turn . The CD I asseen by the pilot is ou t to the right.To regain track on this reciprocal heading, the pilot would have to t u r n n o t

towards the CD I but away from it. Turning towards the CD I on areciprocal


heading to the course selected will take the aircraft further away from track ‑i.e. the CD I is no longer acting asa command instrument.The problem can be easily corrected and the CD1 returned to being a

command instrument by selecting the correct course under the index, i.e. 320,which approximates the headingbeing flown. The immediate effect will be:0 the toflag will appear, replacing thefrom flag; and° the C D I will swing across to the other side.The CD1will n o w be o u t to the left, and a left t u r n will bring the aircraft

back towards the selected course. The CD I is once again a commandinstrument ‐ it is easier to understand and easier to fly.

lntercepting a Radial Using the VCRVisualising Where You Are and Where You Want to GoA pilot needs to ask the following:' ‘Where amI?’;° ‘Where doIwant togo?’; and- ‘How doI get there?’.

RADIAL

IR-lASQAEPS

Figure 9-39 Aircraft position.

The easiest method of orientating the aircraft using the V C R is to rotate theOBS until the CD I centres. We know that this can occur on either of t w ocourses that are reciprocals. To ensure that the CD I will act asa commandinstrument, the pilot mus t select the course that mos t closely resembles theheading of the aircraft while on the desired track. With the course selected:' the to flag will show if the setting is an inbound track to the V C R station;and

- thefrom flag will Show if the setting is anoutbound track.

232 Night Flight

For example, if we centre the CD I with an OBS of 270 and the to flagshowing, we are on the 090 radial. If, on the other hand, the from flag isshowingwith the same setting, thenwe are on the 270 radial. Therefore, selectthe course on the CDI , determine the way to t u r n to intercept the radial andthen take up asuitable intercept heading. N o w that you know your radial, usethe compass face to imagine the intercept exactly asfor the ADE

istanceMeasuring Equipment (DME)Distance measuring equipment (DME) is a form of secondary radar where theground re t u r n is triggered by the aircraft. DME measures the slant range to aground station in nauticalmiles. However, for mos t practical purposes, DMEdistance is equal to the horizontal distance, except when the aircraft is withinafew miles of the DME station or is at very high altitude. Passingdirectly overthe station, the DME indicator in the cockpit will show the height of the air‑craft above the ground in nautical miles (1 nm = 6,000 ft approximately).

, E’Ab-l Wzflal‐ 9,000 ft \ a z a fi g » ;DME 20 nm AGL DME 1.5 nm DME 20 nm

l

lR-IUOZEPS

Figure 9-40 Passmgover a DME station.

DMEControls and IndicatorsThe typical DME consists of a Groundspeedcombined controller andindicatorunit which shows DME distance M Won adigital display. It is important ' ©to realise that DME stations are oFFCDEiTL

n o t selected directly by the pilot,hence the lack of a separate chan‑nel or frequency selector on thecontrol panel. The pilot ‘selects’the DME station automatically by selectingapairedV C R or ILS frequency onthe VHF ‐NAV set (frequency pairing is discussed in the following).

Distance Timeto station to station m u m p s

Figure 9-41 Typical DME controller and indicator.


To select aDME station:° ensure that both the DME andVHF‐NAV sets are on;- select the appropriate V CR or ILS frequency, which is paired with thedesired DME channel, on the VHF‐NAV set; and

' when a steady distance indication is shown on the DME indicator (it maytake afew moments for the DME interrogator in the aircraft to lock‐on tothe ground station), carefully identify the station by monitoring the auralMorse code ident signal (via the V C R selection on the audio panel).Most DME indicators can display the rate of closure of the aircraft with the

selectedDME station (i.e. the rate of change of DME distance). If it is assumedthat slant distance equals horizontal distance and the aircraft is tracking eitherdirectly towards or directly away from the DME station, the rate of closure (ordeparture) will represent the cur ren t groundspeed.Some DME indicators can also display time to the station (TTS) in minutes

at the cur rent rate of closure by automatically comparing the groundspeedwiththe DME distance. If the aircraft is n o t tracking directly towards or away fromthe DME ground station, these readings wil l n o t represent the actualgroundspeed or TTS.

Information on DMEStationsDME stations can operate in several different forms and are consequently por‑trayed in avariety of ways on en route charts (ERCs) and TAC charts. Whena V C R and DME are co‐located, the combined installation is shown asVCR/DME followed by asingle V O R frequency For example, Mallacoota is‘MCO VOR/ DME 117.5’, and the co r rec t DME channel wil l be automati‑cally tuned when the M C O VOR frequency of 117.5 MHZ is selected on theVHF‐NAVIf aDME station is n o t co‐located with aV C R station, the DME channel

number will beshown, followed immediatelyby the pairedV O R frequency inbrackets. For example, Moomba is ‘MMBDME 57X 112.0’. This means that112.0 MHz mus t be selected on the VHF‐NAV to tune the MB DMEstation and provide distance indications. However, in the absence of aV C Rstation, bearing informationwill n o t be available.The DME component of TACAN stations may be used by civil aircraft

fitted with DME equipment. To facilitate this, each TACAN station shownon a chart wil l have a paired VOR frequency noted in brackets alongside.For example, East Sale is ‘ES TACAN 82X (113.5)’. This means that whenthe pairedV O R frequency of 113.5 MHZ is selected on the VHF‐NAV, theDME receiver wi l l be automatically tuned to the cor rec t TACAN channel,

234 Night Flight

and distance indications wil l be provided (no bearing indications wil l beavailable).Informationconcerning eachDMEstation, includingany special limitations

affecting individual installations, is provided in ERSA.

DME Range and Rated CoverageDM E signals are line of sight. However, radio signals tend to follow the cur ‑vature of the earth. This means that the VHF ‘horizon’ and its UHF equivalentlie slightly beyond the line of sight visual horizon. The important considera‑tion for apilot when using any type of radio navigation aid is the rated coverageof the station. This is the maximum distance at which indications are consid‑ered accurate enough to establish apositive radio fiX. The rated coverage of aDME station will vary according to aircraft altitude, but it will always be lessthan the theoretical maximum range. To illustrate this point, the maximumDME range of anaircraft cruisingat 9,000 ft is calculatedas122 nm. However,the rated coverage at the same altitude, asspecified in the AIP, is only 90 nm .Rated coverage of V C R and DME is given in figure 9‐27 (page 219).

These rated coverage values are worthwhile memorising asthey will help youto select the mos t suitable DME stations en route.Any large physical obstructions, such asmountain ranges, can block the

passage of VHF/UHF radio signals, effectively masking the areas behind them(this is often referred to asterrain shielding).If there is high terrain near a

D M E ground station, its rated Receptloncoverage belowacertain altitude inthat direction may be reduced.You should refer to ERSA for anySpeCifiC limitations that may affeCt Figure 9-42 Terrain may block reception ofVHFan individual station. and UHFSignals.

Position Fixeswith the DMEA givenDME distance actually represents a circular position line. For instance,if the DME reads 35 nm, the pilot knows that the aircraft is somewhere on thecircumference of a circle with aradius of 35 nm centred on the DME groundstation. Indications from another radio aid may provide asecondposition linethat allows the pilot to fix the position of the aircraft, providedthe t w o positionlines give agood cu t (i.e. mee t atanangle of intercept asclose to perpendicularaspossible) and the aircraft iswithin the publishedratedcoverage of the stationsconcerned.


A co‐located V C R and DME can provide anexcellent fix consisting of:' the radial from the VCR; and- the distance from the DME. DME

However, when a circular D M E position lineis used in combination with a straight positionline obtained from aV C R or N D B Which is n o tco‐located, the accuracy of the fiX can suEer. Ifthe cu t is less than 45°, the fix shouldbe regarded asDME m m “

as doubtful. Similarly, t w o DMEs at opposrte Figure 9_43Acircularpositi°nlineends of track do n o t give aprecise position. from aDME.

\ I\\ |DME \ \\ ‘ NDB i

\ errorerror band \\\ \\ band I/l

pi

iliiil<9 Position? Il||I

DME

Isl‐1041 EPS

Figure 9-44 A good fix from a co-locatedDME and VCR.

Figure 9-45 A poor fix resulting from too finea cut between position lines.

Global Positioning System (GPS)Global navigation satellite system (GNSS) is the generic t e r m used to describe anevolving global position and time determination system. The system includessatellite constellations, aircraft receivers, system integrity monitoring and aug‑mentation asnecessary to achieve the required navigationpeifonnance (RNP) forthe particular phase of operation. The Navstarglobalpositioning system (GPS) is

236 Night Flight

the US military satellite‐based radio navigationsystem that n o w constitutes onecomponent of GNSS. It provides users with position and time information ofgreat accuracy anywhere on the earth 24 hours a day in all weather.

The Total SystemGPS consists of 24 satellites (21 operational plus 3 spares) orbiting the earth insiX orbital planes. A number of ground stations around the world monitor andcontrol the satellite system. The system has three major segments:' space (the satellites);0 control (the ground‐based tracking and system adjustment); and° user (the receiver and processor equipment).

,l Ascension\ Island

\

Monitor stations

Figure 9-46 Global positioning system.

How GPS WorksThe GPS receiver is aposition‐finder system. It uses the known position of asmany satellites ascan beacquired and it then computes athree‐dimensional fixbased on their range, calculated from the elapsed time of the signal.

Fixing PositionA three‐dimensional position in space (position and altitude) is accomplishedby the receiver determining where it must be located in order to satisfy theranges to four or m o r e appropriately positioned satellites. A two-dimensionalfix requires only three satellites to be in View if altitude is known.

9: Radio Navigation

Synchronisation of the receiver’stime reference with that of thesatellites is vital. Timing errors aredetected and eliminated by thereceiver’s computer. Figure 9‐47shows a two‐dimensional positionestablished assuming the respectiveclocks are synchronised perfectly.

However, if the receiver’s clockis, say, one second fast, asis the casein figure 9‐48, the period betweentransmission and reception withrespect to each of the threesatellites interrogatedwill be sensedinitially as taking one secondlonger. This will be represented asa gross error in all three ranges andthus, rather than producing aprecise fix, will create a very large

237

Satellite 2

Satellite 1

- 4 secondsm

5 secondsFix position

3 secondsm M. ‘ W mas" as

Satellite 3- - N A V - E P S

Figure9-47 Two-dimensional fix establishedwithperfect timing.

area anywhere within which the receiving aircraft could be positioned. Thereceiver’s computer senses this and immediately begins atrimming process untilit arrives at an answer which allows all ranges to arrive at the one and onlyposition possible. This process automatically eliminates the effect of receiverdoc/e error for subsequent tracking and position fixing.

Satellite 1

Correctedfix position

Satellite 2

6 seconds

Aircraft can be anywhere within thisarea until computer “trimming”establishes the correct position fix.

NAV-usfiFS

Figure 9-48 Effect of receiver clock error of one second on a two-dimensional fix.

238 Night Flight

Receiver DesignThe capability of makingrange calculations to three, four or m o r e satellites hasan impact on the design, cost andaccuracy of GPS receivers ‐ i.e. whether theyare single‐channel receivers operating sequentially or the more expensive andaccurate receivers providingmultiple channels operating simultaneously. GPSreceivers approved asa supplemental or primary means navigation aid havemultiple channels and come under the provisions of an FAA Technical ServiceOrder (TSO C‐129). I FR /primary navigation certification specifications forGPS equipment include a requirement for multiple receiver channels and anavigation integrity monitoring system known asreceiver autonomous integritymonitoring

ReceiverAutonomous IntegrityMonitoringReceiver autonomous integrity moni‑toring CRAIM) is a special receiverfunction that analyses the signal integ‐ $3 Receiver 2%rity and relativepositions of all satellites Q‘ ‘°that are in View soasto select only the / \best four or more, isolating anddiscarding any anomalous satellites. Atleast five satellites must be in view tohave RA IM find an anomalous situa‐ Error Error m a m

tion, and Six to actually isolate the Figure 9-49 Poor satellite geometry resulting. in high PDOP.unacceptable satellite.

When operating, R A IM ensuresthat the minimum acceptable level ofnavigation accuracy isprovided for the figgfiigir

l lparticular phase of flight. In theprocess, it ensures that the potentialer ro r ‐‐ known asthe position dilution ofprecision (PDOP) or geometric dilution (fprecision (GDOP) ‐ isminimised. ThePDOP depends on the position of the Error

satellites relative to the fix. The value Figure 9.50 Good satellite geometryof the PDOP determines the extent of resumng i“ '°W PDOP‑range and position errors.When the satellites are close

together, the tetrahedron formed covers alarge area, and results in ahighPDOP


value (figure 9‐49). However, when the selected satellites are far apart, the areacovered by the tetrahedron is much more compact, resulting in a lower PDOPvalue and therefore greater accuracy (figure 9‐50). A PDOP value of less thansix is acceptable for en rou te operations. A value of less than three will berequired for non‐precision approaches.

BarometricAidingBarometric aiding is the process whereby the digital data of the pressure altim‑eter is usedby the GPS receiver as, in effect, the range readout of a (simulated)additional satellite. It is only applicable when there are less than five satellitesin view andRA IMalone cannot beeffective. Barometric aidingprovides addi‑tional backup and RA IM capability and therefore increases the navigationcoverage of GPS.

Masking FunctionThe masking function in the GPS receiver software ensures that any satellitesin View that lie below a fixed angle of elevation relative to the receiver areignored. This is due to the range errors that will be generated because of thegreater distances that their signals wil l have to travel through the ionosphereand troposphere to reach the receiver. The fixed angle stored in the receiver isknown asthe mask angle, although in some receivers it is determined automat‑ically by the receiver, depending on the strength of the transmitted signals atlow angles of elevation, receiver sensitivity and acceptable low‐elevationerrors.When fixed, it is typically set at 75° (figure 9‐51).

Aircraft receiverElevation angle(in this case 7.5°)

m14714.593

Figure 9-51 Mask angle.

240 Night Flight

ReceiverDisplaysDisplays for the pilot vary from one GPS unit to another. Flight planningdataisusually entered via anappropriate keypadon acontrol display unit or controlpanel. The usual navigation information is displayed: position, track, ground‑speed, estimated elapsed time and, with aTAS input, TAS andwind. The unitmus t also be capable of showing satellite status, the satellites in view and beingtracked, the value of PDOP, RA IM status and signal quality.

Operating ModesGPS receivers normally provide three modes of operation:° navigation with RAIM;' navigation (two‐ or three‐dimensional) without RAIM; and0 loss of automatic navigation (annunciated asDR in some receivers).

GPS Errors and LimitationsThe GPS errors covered so far are receiver clock error and how it is resolved,the effect of PDOPon position accuracy and the accuracy (or errors) associatedwith receiver design. Other errors affecting GPS performance are brieflyexamined below.

Ephemeris ErrorEphemeris error is the error inherent in the data that defines the satellite’s c u r ‑ren t position, which in t u r n is transmitted to the receiver.

Multi-Path ErrorIn a similar manner to the behaviour of signals used by other radio navigationsystems, it is possible for some of the satellite signals ‐ i.e. the pseudo‐randomcode signals - to reach the receiver antenna after bouncing off the surface ofthe earth, aswell asdirectly from the satellite. Thus the receiver can receivesignals from different directions. This can induce a ranging error.

lonospheric Propagation EffectsThe ionosphere, which we know is the band of charged particles that liesbetween 80and 120miles above the surface of the earth, affects the propagationspeed and thus the travel time of the GPS signals, thereby degrading the accu‑racy of the position. lonospheric propagation effects can be offset by thereceiver with data received from several satellites.


Tropospheric Propagation EffectsThe lower region of the atmosphere, the troposphere, contains significantamounts of water vapour. The effect of this is to slow down the satellite signals,inducingrangingerrors. This tends to degrade accuracy. However, troposphericpropagation effects are minimisedby appropriate compensation in the receiver.

ReceiverErrorReceiver error is simply asmall ranging error brought about by the difficultyof matchingprecisely the receiver’s emitted digital pseudo‐random code withthat of the satellite.

InterferenceBecause GPS (GNSS) signals are relatively weak, interference can cause signifi‑cant degradation in navigation or, under certain conditions, complete loss ofnavigationcapability Withmore andmore extensive use of all bands of the elec‑tromagnetic spectrum, the potential for interference problems has increased.Interferenceto GPS operation can occur from electromagnetic influences on

board an aircraft (e.g. insufficient shielding from VHF transmitters and otherequipment) and from external sources (e.g. high powered radar, TV and FMstations in the Vicinity of the receiver). Minimisation techniques and shieldingsystems offset these problems. However, where GPS integrity is suspect, orthere is aloss of RAIM, or interference is experienced, occurrences should bereportedwith comprehensive details of the circumstances sothat the mat te r canbe properly recorded and investigated. GPS system verification sheets areavailable for this purpose.

TrackingAccuracy and CollisionAvoidanceTracking accuracy should n o t really be Classified asan error; rather, it is a tes‑tament to the precision of GPS. Its very quality of precision track‐keepinghighlights the increased potential for collision, particularly head‐on collision,with other GPS‐equipped aircraft operating on the same track or approachingthe same turning point. This problem is n o t helpedby the propensity of somepilots to have their heads always in the cockpit. It is essential to maintain therequired separation procedures and a thorough lookout. However, this prob‑lemis considered to be sosignificant that there havebeen discussions in the USand Europe about the notion of requiring airline operators to flight plan withsmall track offsets asa safety measure in addition to ATS separation when nav ‑igatingby GPS.

242 Night Flight

GPSError MagnitudesTypical magnitudes for GPS errors are asgiven in table 9‐1:

Sources of GPS Error C/A Code DGPS P-Code

3. Clock error 2 m 0 m 2 m

b. Ephemeris error 4 m 0 m 4 m

c. Ionospheric propagation error 8 m 0 m 1m

d. Tropospheric propagation error 3 m 0 m 3 m

e. Receiver noise error 1 m 1m 1m

f. Total pseudo range error [square root of sum 10m 1m 6 mof the squares of (a) to (e)]

9. Maximum position dilution of precision (factor) 3 3 3

Total position error [f x 9 approximately] 29 m 3 m 17m

Table 9-1 Magnitude GPS error.

Operations Without RAIMIf R A I M is lost, the accuracy of the system is considered unacceptable for bothnavigation and ATC separation purposes. Therefore, tracking must be closelychecked against other navigation systems.If in CTA, ATC mus t be advised that RA IM is lost when:

0 RA IM is lost for more than ten minutes, even if GPS isstill providingposi‑t ion information; or

0 R A I Mis n o t availablewhenATC requests GPS distance, or if anATC clear‑ance or requirement based on GPS distance is imposed; or

0 the GPS receiver is in DR mode or loses navigation function for more thanone minute; or

0 indicated displacement from track centreline exceeds 2 nm .

ATC may then adjust separation. If valid position information is lost (2Dand DR mode) or non‐RAIM operation exceeds ten minutes, the GPSinformation is to be considered unreliable. Other navigation techniquesshould be used until R A I M is restored. If R A I M is restored, the appropriateATS unit should be notified prior to using the GPS for primary navigation toallow ATC to reassess the appropriate separation standards.


Human Factor ConsiderationsWe know that in its fully operational mode, GPS has the capability of providingprecise navigation information and guidance. However, like all forms ofadvanced computer technology, its capability ‐ andtherefore ultimately the safetyof the flight ‐ isgovernedlargelyby the manner in which the equipment isoper‑ated andmonitored. This isespecially sowhen the equipment interfaceswith anautopilot, flight director or advancedautoflight system. Regardless of equipmentdesign and ergonomic factors, the pilot in command must shoulder the respon‑sibility for the safe performance of any aviation system under his or her control.Accident and incident history shows that analarmingnumber of pilots tend to

be too trusting when using advanced aviation technology. GPS operation is acase in point. There are some who are quite happy to allow the equipment to‘drive the ship’ without questioning its accuracy or applying basic airmanshipprinciples, such ascross‐checking the steering data it provides. Put simply, somepilots who operate equipment like GPS can ‐ and often do ‐ lose situationalawareness, i.e. they allow themselves to drop ou t of the loop.Generally, the tendency develops asthe result of complacency, since GPS

seems to perform soadmirably mos t of the time. However, GPS is subject toanumber of errors and limitations. It can also fail or, in some cases, lose itspower supply. There are also important errors andprocedures relatedto humanfactors applicable to GPS (and, for that matter, all automated systems) that needto be addressed.

Mode ErrorIncorrect mode selection is a very significant problem and one that has comemore into prominence n o w that fully integrated autoflight systems and flightmanagement systems are commonplace. For example, a tracking error mayoccur because the autopilot controller has been left in H DG instead of NAVmode. In the con tex t of a GPS, it is n o t possible to discuss specific modesbecause of the differences in the design of the various receiver CDUs and con ‑trol panels. However, suffice to say that when aGPS mode or function switchis operated, a positive check should always be made to ensure that the actionor function desired has actually been selected.

Data EntryErrorData entry error is caused by inserting incorrect information, usually via theCDUor panelkeyboard, into the GPS computer. It applies to allRNAVsystemsand can have catastrophic consequences. In the overwhelmingmajority of cases,incorrect waypoint position coordinates are inserted asaresult of human error

244 Night Flight

caused by inattention, unfamiliarity or typographical error when transferringdata from anavigation Chart to the GPS. Ergonomic factors can also contributeto the problem‐ some GPS receivers have complicated C D Ukeyboards or c o n ‑trol panels, or alphanumeric displays which are difi’icult to read. It is also n o tunknown for databases to carry mistakes, either through transcription errors bythe provider or incorrect navigation data supplied by the relevant aeronauticalinformationservice * all the more reason for usingonly current databases, check‑ingNOTAMs and adopting rigid data validation procedures.

Data Validation and Cross-CheckingValidation and cross‐checking procedures are designed to detect data entryerrors and, in the broader sense, confirm GPS reliability and accuracy by c om ‑paring the navigation output with other navigation sources. Therefore, it isrecommended that all data entered, either manually or from adatabase, shouldbe checked carefully by the pilot against the relevant and cur ren t navigationchart. This check should include asecond crew member in the case of amulti‑crew operation. To reduce the chance of data entry error, navigation datashould be derived fromacur ren t database that cannot be modifiedby the crew.Only data from a validated, cur rent database should be used for navigationbelow LSALT. All GPS‐generated tracks and distances of the flight plan (way‑point string) should be checked against the cur ren t chart and flight plan foraccuracy before flight, and at any time in flight prior to embarking on anamended route, such asprior to ‘direct‐to’ tracking or a diversion to analter‑nate ‐ i e . a check for reasonableness should be carried ou t . If the navigationdata is derived from a database, the database should be checked to ensure thatit remains current for the duration of the flight.Radio navigation aids, other RNAV systems, DR and visual navigation

techniques should be used to cross‐check andbackup the GPS navigation data(to keep it honest). When within coverage of conventional radio navigationaids, the navigationperformance of the GPS should be checked to ensure thattrack is maintained within the tolerances asdefined for the mos t accurate aidbeing received. If there is any discrepancy, the navigation informationprovidedby the radio navigation aids mus t take precedence.

Automation-Induced ComplacencyAutomation‐induced complacency is aman‐machine interface problem. It isone that could be characterised by the question, ‘ VVho’s in charge, Captain?’. Itis a condition whereby pilots become complacent and overdependent on theautomatic features of the aircraft. It has come more into prominence in recentyears with the advent of glass cockpit aircraft with fully integrated automatic


systems. It is usually aninsidiousprocesswhereby, over time, complacency setsin; it is asthough the magic machinery assumes the control that is relinquishedby the pilot. The pilot is usually blissfully unaware of what is really going on.It is a condition that is highly relevant to GPS operators.As mentioned previously, there is a tendency for pilots to drop o u t of the

loop. They allow the machine, in this case the GPS, to work on its ownwithout considering its limitations or potential to get things wrong. Theeffects of automation~induced complacency can be particularly significantwhen the cockpit workload is high. There seems to be a reluctance tointervene and take control away from the machinery, even when something isobviously n o t going according to expectations.Pilots lose sight of the fact that GPS is only a tool that canno t think for itself.

It works well mos t of the time, albeit within defined limitations and subject tocertain errors. However, it needs to be set up correctly, monitoredcontinuously and its data validated by appropriate cross‐checks and backupprocedures. Like other aviation technology, GPS can occasionally let youdown. Some of the cockpit disciplines necessary to combat the problemhavealready been discussed. Here are a few more tips which are relevant to theoperation of other automatic systems aswell asGPS:0 know exactly what the system’s operatingmodes, limitations and errors are;' be clear in your mind beforehandwhat you wish the system to do;- be suspicious, look for errors and always double‐check data output againstdata input and against other data sources;

- always knowwhat the equipment is doing ‐ manage it ‐ do n o t let it manageyou;

- reject the assistance of a system that is n o t performing to your expectationsor that is providing conflicting information ‐ either resolve the ambiguityproperly, or ignore the system altogether; and

° arrange your cockpit priorities ‐ flying the aircraft must always come first.

Keep in the loop. Stay in command even you delegate control.

Non‐Standardisation of GPS‐Pilot InterfaceNon‐standardisationof GPS keyboards or controlpanels, functions anddisplaysis a factor that significantly increases the potential for pilots to make errors.The proliferation of GPS types contributes to the problem, making it difficultfor pilots to transfer from one type to another ‐ hence the regulatory require‑men t for GPS‐type training for IFR pilots. Clearly, some form of standarddesign code for controls and displays of advanced avionics would be desirable,but is unlikely to be realised. With some GPS receivers, it would appear that

246 Night Flight

marketing and engineering considerations have taken precedence over theoperating needs of the user. What looks neat and nice in the glossy brochurescan end up having many shortcomings when situated in an aircraft cockpit ‑i.e. ergonomic (man‐machine interface) considerations have n o t beenproperlyaddressed. Some GPS receivers are n o t user‐friendly. A further important fac‑t o r is the placement of the equipment in the cockpit. Poor design combinedwith poor placement canmake it extremely difficult for pilots to interfacewiththe equipment with confidence. A few of the considerations that are causingconcern are described below.Size. As is the trend in mobile telephone and computer markets, we are toldby the marketeer that small is good, tiny is better. Consequently, some GPSequipment is unsuitable for aircraft. Tiny keyboards and miniature displays ina cockpit might look good but are quite impractical, contributing in a largemeasure to data entry error.Control Knobs and Switches. This is asignificant area of non‐standardisation.There is also considerable variation in the types of knobs and switches, theirsize, the direction in which they operate and their functions. To aggravatethe problem, there is a growing trend towards providing multi‐functionalcontrols in the interests of neatness and compactness ‐ i.e. providing knobsthat control more than one function, depending on the mode selected. Thetrade‐off is usually added complexity. Therefore, the potential for mistakesincreases correspondingly, especially whenworkload ishigh. A GPS receiverwith simple, unambiguous controls and switches is clearly the best Choice, allelse being equal.Data Display. The problems here have already been touched on . Screen sizecan be critical, particularly having regard to the placement of the unit in thecockpit. However, the size and definition of characters and symbols are alsoimportant issues. The data mus t be clearly discernible within the general cock‑pit scan, but n o t t oo prominent so asto be a distraction, diverting the pilot’sattention from the primary task of flying the aircraft. Generally, with mono ‑chrome displays, CRTs are superior to liquid crystal, especially under varyingcockpit lightingconditions. However, the technology in this area is improvingrapidly and colour displays are becoming more common, highlighting aneedfor standard colour codes aswell asstandard symbology.Position in the Cockpit. This consideration can be influenced by the previousthree. Ideally, the GPS should be located within the NAV/C O M group onthe main instrument panel or centre pedestal panel, depending on the aircrafttype and the information displayed. For example, some receivers can display a


C D I on the data screen. The position mus t ensure that parallax errors andpotential physiological effects, such asspatial disorientation, are avoided.

Human InformationProcessing and SituationalAwarenessHuman information processing and situational awareness are complex humanbehavioural issues that have challenged academics, psychologists, and human‑factor experts over the years. It is extremely relevant to GPS operation andmonitoring. Literally hundreds of technicalpapers, study references andbookshave been written on these matters. Some of these are available in technicallibraries for the keen‐minded to pursue. For o u r purposes, abriefand simpleoverview will suffice.Information Processing. The human brain can be likened to an informationprocessor or computer. The brain has evolved to act logically to incomingstimuli and, like the computer, follows a programmed path to a programmedresult (often this means a decision). The process can be influenced by pastexperiences, training and knowledge (stored data). Under certain circum‑stances, these influences can be very compelling.Any stimulus first has to be sensed by one or more of o u r sensory organs,

such asthe eyes, ears, skin and soon. Our interpretationof what issensed willeither be related directly to the stimuli, or mo re often than no t , modifiedsignificantly by past experiences and knowledge. For example, everyone hasexperiencedan odd sensation of stepping up or downanescalator which is n o tworking, and mo s t of us understand that the command ‘right engine’ meansthe one on the right, n o t the one that is n o t wrong.Generally, the brain is a serial processor, or single‐channel system, in which

information passes through sequentially. In other words, we cannot concentrateonmore than one thing at a time. This iswhy we have information displays inthe cockpit, and warning and caution systems with lights and bells to shift o u rattention immediately should the needarise.The final part of the process is to conver t the stimuli that have been interpreted

(and modified) into a decision and some kind of action. The importantconsideration here is that the quality or correctness of the decisionwill depend toagreat extent on the amount of informationobtained (thenumber of stimuli) andthe extent to which past knowledge and experience have been used in making it.The implementationof the decision ‐ the action ‐ also requires the pilot to adoptthe correct response and, importantly, to perceive and interpret the feedback tovalidate the process that led to the decision andaction in the first place.Accident statistics show how easy it can be for pilots to rush into decisions

based on insufficient information. There is also a condition known asfalse

248 Night Flight

hypothesis whereby in relation to processing stimuli, the pilot’s past knowledgeand experience become so dominant that the expectancy of a particularoutcome is unduly raised. Usually, information is either incomplete ormisinterpreted and false conclusions are drawn. For example, a pilot reportsthat apiston engine aircraft’s cruise performance is down by around 10 kt. Thecylinder head temperatures (CHTs) are low, therefore the engines m u s t berunning rich affecting power. But, after landing, the cowl gill circuit breaker(CB) is found popped. Both cowls had been fully open for the entire flightcausing extra drag, low C H Ts and lower than expected cruise performance.The message from this simple example is that m o r e information should havebeen sought. Therefore, the keyword in the whole process is information. Togain information, the pilot m u s t be in asituation to receive it. This means thatthe pilot must be situationally aware.

Compulsive Fiddling. It is appropriate to have a final word about a diseasewith which many pilots are afflicted. It is called compulsivefiddling. It is espe‑cially c o m m o n whenever n e w technology is introduced into the cockpit.The compulsion to fiddle with n e w equipment is, for some, overwhelming.The symptoms include excessive tapping, switching and adjusting, usuallywith the pilot’s head down and eyes focused on the n e w toy and little regardfor how the aircraft isperforming or what ishappening in the realworld o u t ‑side the cockpit.

As we have mentioned, the potential for collision has increased markedlywith the advent of GPS. Clearly, compulsive fiddling is a danger that must berecognised and avoided. The importance of maintaining situational awarenesswhen operating GPS c a n n o t be overemphasised.

Airworthiness RequirementsPilot TrainingIt is a requirement that, prior to operating GPS equipment for primary navi‑gation, the pilot m u s t undertake training with an approved organisation and inaccordance with a syllabus set down in the CAOs. Satisfactory completion ofthe course and competence m u s t be demonstrated and certified in the pilot’slogbook by an approved person (aF O I or chiefpilot, or the CPI of the organ‑isation or their representative).

Aircraft EquipmentUnder current policies, GPS receivers approved for IFR primary‐navigation pur‑poses must have the US FAA Technical Standards Order (TSO) C‐129authorisation or its approved equivalent. Installationm u s t mee t CASA airworthi‑


ness requirements, demonstrate accuracy and reliability and must include theconnection of the automatic barometric aiding function.

Airborne GPSAircraft EquipmentThe GPS aircraft equipment consists of the following:° receiver unit;- antenna;° barometric and heading inputs;0 external CD1 and mode switch; and° annunciator.Receiver Unit. The receiver unit is much more than just a receiver. It usuallyhouses a twelve‐channel receiver, a very capable processor, a keypad, a displaysystem and has aslot for the data card. For aircraft use, the receiver m u s t complywith the US FAA TSO C‐129 specification. This specification states that theGPS unit mus t be panel‐mounted and have permanent power and antenna fit‑tings, mus t provide certain functions and have an up‐to‐date database.Antenna. The antenna ispermanently mounted, usually on top of the aircraft,and hard‐wired into the receiver. The top mounting is important asthe GPSsignals are very low power transmissions, and shielding of the antenna willreduce satellite reception.Barometric and Heading Inputs. To facilitate barometric aiding, a compatibledigital altitude signal isprovidedfrom aservo altimeter or anair data computer.Similarly, amodern remote compass system can supply adigital input of aircraftheading.External CDI. The GPS can be coupled to the H81and displayed on the CDI.This makes GPS tracking similar to that of aVOR. A mode switch isprovidedso the GPS or N AV l can be selected to the CDI. This means that the GPScan be coupled to the autopilot, which is very helpful for en rou te flying if theGPS is delivering accurate information.Annunciator. As the CD1 can be provided with N AV l or GPS tracking infor‑mation, amode annunciator is provided, including failure indications.

Using Airborne GPS for NavigationThere are many different types of GPS units that meet the T 3 0 C‐129 standard.While many of the modes and functions of each unit are similar, terminology andkeying sequences vary. You will have to spend some time on your particular unitto gain confidence with the system. Some manufacturers also produce some c o m ‑

250 Night Flight

puter‐based trainers that allow you to explore the receiver modes and functions inyour o w n home and in your o w n time.

Tracking Accuracy and Collision AvoidanceHigh‐accuracy tracking is testimony to the precision of GPS. The drawbackis that, asmentioned, this very quality of precision track‐keeping increases thepotential for collision, particularly head‐on collision, with other GPS‑equipped aircraft operating on the same track or approaching the same pointfrom the same direction. This highlights again the need for good communi‑cations and the correct maintenance of cruising levels.

Index

Aabove ground level 19above mean sea level 4acceleration 68, 73ADF 202‐216

accuracy of 210errors with 205‐210in flight use of 210‐216and radio magnetic indicator 202, 204and relative bearing indicator 202‐204

advection 39advection fog 39aerodrome beacons 104aerodrome elevation 11aerodrome frequency response unit 106aerodrome lighting 100‐108

approach lighting 103‐104apron lighting 103failure of 160lane of entry strobe lights 105night VFR requirements 109obstacle lighting 104pilot‐activated lighting 105‐106runway lighting 100‐102taxiway lighting 102‐103visual approach slope indicator system106‐108Wind direction indicator lighting 106

aerodrome QNH 4aerodrome reference point 5AFRU. See aerodrome frequency

response unitAGL. See above ground levelAI. See attitude indicatorair mass 29aircraft lights 57, 87, 137airsickness 79‐80airspeed indicator 3‐4, 115

errors with 4andpitot‐static system 3, 12preflight check of 11

257

speed indications on 3airwork 83, 89alternate aerodrome suitability 110alternator 14altimeter 3, 4‐5, 115

accuracy check of 5errors with 5and pitot‐static system 4, 12and QNH setting 4, 11unserviceablity of 5

AMSL. See above mean sea levelapproach lighting 103‐104apron lighting 103area QNH 4artificial horizon 113A81. See airspeed indicatorATIS. See automatic terminal

information serviceatmospheric perspective. See

environmental perspectiveatmospheric pressure 4attitude indicator 3, 6‐7, 114

errors with 7failure 0f7, 161‐162preflight Checks of 11

auricle 69autokinesis 58automatic direction finder. See ADFautomatic terminal information service

1 1autopilot 3, 15‐18

rotary roll switch 18wings‐leveller autopilot 15

AVFAX 179

Bbalance 68, 70‐77balance ball 7, 11balance indicator 7balanced static system 12bank attitude 6

252

barometric aiding 239barometric subscale 5

See also QNHbarotitis 69battery 15beginning of daylight 43binocular vision 53‐54black‐hole approach 64‐66blackout 55blind spot 54, 54‐55BOD. See beginning of daylightbroadcasting stations 202bus bar 14

Ccalibrated airspeed 4CAS. See calibrated airspeedCDI . See course deviation indicatorcharter flights 88, 89, 91, 92civil twilight 42, 83clear ice 31‐32clock 10‐11

night VFR requirements 94preflight check of 11

clouds 19‐22abbreviations for 19grouping of19‐20heights of 19inadvertent entry of 146nomenclature 19

coastal fog. See advection fogcochlea 69cockpit lighting 127

failure of 159night VFR requirements 88‐89

cold front 29‐30colour blindness 55colour vision 55compass correction card. See deviation

cardcompass instruments 3, 9‐10cones 53configuration 116control instruments 115control‐wheel steering 17convection 21

Night Flight

convective clouds 19coordinated universal time 10, 178cornea 51course deviation indicator 222crew resource management 49C R M . See c r e w resource managementcruising levels 4, 95cumulus cloud 20, 22, 33‐34cupula 70, 73CWS. See control‐wheel steering

DDALR. See dry adiabatic lapse ratedatum 4daylight 42, 43‐44deceleration 78decision making 45‐46, 48‐51departure aerodrome suitability 108destination aerodrome suitability 108‑

1 1Odestination obsession 46‐48deviation card 10

preflight check of 11dewpoint 20DC. See directional gyrodirect indicating compass 10directional gyro 8distance measuring equipment. See D M Ediurnal effect 125D M E 232‐235

D M E indicators 232‐233D M E station information 233‐234in flight use of 234‐235night VFR requirements 94range of 234rated coverage of 234

doppler V O R 219double vision 53downbursts 24‐25dry adiabatic lapse rate 31dynamic pressure 12

Eeardrum 69ears 68‐70

inner ear 69‐70

Index

middle ear 69o u t e r ear 6 9

EFIS. See electronic flightinstrumentation system

electric tr im 18electrical system 3, 14‐15

failure of158‐159electronic flight instrumentationsystem 9BLT. See emergency locator transmitteremergencies 148

declaring 149emergency equipment 90‐91emergency light signals 153emergency locator transmitter 91, 153,

155empty field myopia 55empty field short‐sightedness. See emptyfield myopia

empty sky myopia. See empty fieldmyopia

end of daylight 43, 177engine failure 156‐158

in single‐engine aircraft 156‐157in twin‐engine aircraft 157‐158

environmental perspective 58EOD. See end of daylightEustachian tube 69evening civil twilight 42eyes 51‐53

adaptation to darkness 128

Ffalse expectations 58false horizons 60false verticals 71, 75flight instruments 3‐11

compass instruments 3, 9‐10control instruments 115gyroscopic instruments 3, 6‐8night VFR requirements 89‐90performance instruments 116and pitot‐static system 12preflight checks of 11pressure instruments 3‐6

flight levels 4

253

flight notification 125, 186‐190flight tolerances

for avoiding controlled airspace 95for night VFR 86

fluX valve 9PM (from) 99focal point 66‐68fog 37‐41forecast QNH 5foveal region 53freezing level 31frontal fog 40‐41frost 33

GGDOP. See geometric dilution ofprecision

geometric dilution of precision 238global navigation satellite system 235global positioning system. See GPSGN SS. See global navigation satellite

systemGPS 235‐250

airworthiness requirements 248barometric aiding 239and collision avoidance 241error magnitudes for 242errors with 240‐241and geometric dilution of precision238and human factor considerations 243‑248masking function of 239requirements for night VFR 92operation of 236‐240and position dilution of precision 238and R A I M 238Without R A I M 242receiver design 238, 240use in flight 249‐250

greyout 55gust front 23gyroscopic instruments 3, 6‐8

254

Hhailstones 24heading indicator 3, 8, 115

alignment with magnetic compass 8checks of 8errors with 8alignment with magnetic compass 11preflight check of 11

hearing 68, 69H I . See heading indicatorhoar frost 33horizontal situation indicator 9H51. See horizontal situation indicatorhuman factors 45‐80

crew resource management 49decision making 45‐46, 48‐51destination obsession 46‐48and GPS use 2437248

hypoxia 55

IIAS. See indicated airspeedicing 30‐37

and anti‐icing equipment 35avoiding 35combatting in‐flight accumulation of36and de‐icing equipment 35

indicated airspeed 3instrument flight 113‐122

attitude instrument flying 120‐122flightpath references 122and instrument scanning 114‐120on limited panel 161‐165

instrument scanning 114‐120abbreviated scans 119‐120selective radial scan 117‐119vertical scan 120

INTER 98iris 52

Llag 6landing lights 131, 141

failure of 159lane of entry 105

Night Flight

lane of entry strobe lights 105lapse rate 30the leans 77‐78, 143lens 51, 51‐52lighting

aerodrome lighting 100‐108, 160aircraft lights 57, 87approach lighting 103‐104apron lighting 103cockpit lighting 88‐89, 127lane of entry strobe lights 105obstacle lighting 104pilot‐activated lighting 105‐106runway lighting 100~102taxiway lighting 102‐103Visual approach slope indicator system106‐108Wind direction indicator lighting 106

limited‐panel flight 161‐165and bank attitude interpretation 163,164control during 164in the descent 165and pitch attitude interpretation 162‑163i n a t u r n 165in the climb 165

line squall 27linear acceleration 73, 74LMT. See local m e a n timelocal mean time 178localiser 94locator 200LOE. See lane of entrylubber line 10

Mmagnetic bearing 196magnetic compass 9, 10

errors with 10and heading indicator 8, 11and magnetic dip 10preflight check of 11

magnetic dip 1Omagnetic flux detector 9mammatus 25

Index

manoeuvring speed 28mask angle 239mayday 149‐150METAR 37, 41meteorological visibility 41microbursts 24‐25morning civil twilight 42motion sickness 79‐80mud map 183‐184

NNAIPS 180navaids 116

night VFR requirements 92, 93‐94,1 10orientation principles 195‐198

navigation aids. See navaidsNDB 199‐202

broadcasting stations 202errors with 205‐210locators 200NDB identification 200‐201night VFR requirements 93range of 93, 199rated coverage of 94, 199‐200

night 83night effect 205‐207night flight 130‐144

and aerodrome lighting 100‐108approach 138‐140arrival 137avoiding controlled airspace during 95circuit 142‐144cruising levels 95departure 133descent 136en rou te 134‐136engine start 130flight tolerances 86, 95go‐around 142landing 141‐142preflight checks for 124‐125preflight inspection 126‐127and sunrise 124and sunset 123‐124take‐off 132‐133

255

taxiing 130‐132and thunderstorms 98‐99touch-and‐go landing 141‐142traffic separation 95and turbulence 98‐99turning 124

night flight planning 124‐129, 177aerodrome availability 126aircraft considerations 126airfield planning 129AVFAX 179cockpit lighting 127cockpit organisation 128escape routes 191example flight 177‐186flight notification 125, 186‐190front seat passengers 128mud map for 183‐184NAIPS 180and point of no r e t u r n 192‐194radio procedures 125SARTIME 188, 191time zone conversions 178‐179weather considerations 126

night navigation 134‐136night VFR 83

aerodrome lighting requirements 109aerodrome navaid requirements 109aerodrome weather requirements 109‑1 10aeronautical requirements 86aircraft lighting requirements 87‐89airwork requirements 83, 89alternate aerodrome suitability 110charter requirements 88, 89, 91, 92circuit requirements 99cockpit instrumentationrequirements89‐90controlled airspace requirements 94departure aerodrome suitability 108destination aerodrome suitability 108‑1 10emergency equipment requirements90‐91handlingrequirements 84, 85lateral navigation requirements 92‐95

256

navaid requirements 92, 93‐94operational requirements 83‐84, 85passenger requirements 85, 88, 91provisional forecast requirements 99radio equipment requirements 91‐92recency requirements 84, 85testing requirements 86‐87transponder requirements 92vertical navigation requirements 96 ‑97weather requirements 97‐100

night VFR rating 83, 123night Vision 56‐57, 129non‐directional beacon. See N D Bnose‐down pitch illusion 78‐79nose‐up pitch illusion 78NVFR. See night VFR

0OAT. See outside air temperatureOBI. See omni‐bearing indicatorOBS. See omni‐bearing selectorobstacle lighting 104omni‐bearing indicator 222omni‐bearing selector 222optic nerve 51orographic lift 21, 34ossicles 69otolithic organs 69, 71, 72otoliths 71outside air temperature 4over‐water flight 90‐91

pPAL. See pilot‐activated lightingpan-pan 151PAPI. See precision approach path

indicatorpartial‐panel flight. See limited‐panel

flightpassengers 85, 88, 91, 128PDOP. See position dilution of precisionPEC. See pressure error correctionperformance 121performance instruments 116peripheral vision 53, 57

Night Flight

pilot‐activated lighting 105‐106piloting 45pinna 69pitch attitude 6, 8pitot pressure 12pitot‐static system 3, 12‐13

errors with 4pitot tube blockage 13, 159preflight check of 11static vent blockage 12, 12‐13, 160

PNR. See point o f n o r e t u r npoint of no r e t u r n 192‐194position dilution of precision 238position uncertainty 147precipitation 21‐22, 35

intermittent precipitation 22showers 22

precipitation‐induced fog 40, 41precision approach path indicator 106,

108preflight checks 11, 124‐125

of cockpit 128of flight instruments 11of pitot‐static system 11of vacuum system 11

preflight inspection 126‐127presbyopia 52pressure error correction 4pressure instruments 3‐6provisional forecasts 99pupil 52

O.QNH 4, 5

aerodrome QNH 4area QNH 4forecast QNH 5

Rradial 217radiation fog 38‐39radio 125

call priority 151emergency procedures 148~154failure of 152‐153night VFR requirements 91‐92

Index

radio magnetic indicator 9, 202, 204radio navigation aids. See navaidsRAIM. See receiver autonomousintegrity monitoring

ram air pressure 12rated coverage 94rate‐one turn. See standard‐rate t u r nRBI. See relative bearing indicatorreceiver autonomous integritymonitoring 238

refraction 59relative bearing indicator 202‐204

fixed‐card 202rotatable~card 204

relative movement 58r e m o t e indicating compass 9required navigation performance 235retina 51, 52rime ice 32‐33RMI. See radio magnetic indicatorRNP. See required navigation

performancerods 53rotary roll switch 18runway lighting 100‐102

SSALR. See saturated adiabatic lapse rateSARTIME 188, 191saturated adiabatic lapse rate 31sea fog 40seat of the pants 70, 77selective radial scan 114, 117‐119semicircular canals 70, 73showers 22sideslip 12skid ball. See balance ballslaving 9somatogravic illusion 7, 78SOPs. See standard operating proceduresspatial disorientation 71spatial orientation 70‐71SPECI 41St. Elmo’s fire 27stable atmosphere 21standard operating procedures 130

257

standard pressure 4standard‐rate t u r n 8, 115steaming fog 41stereopsis 54stimuli 21storm hazards 26‐27stratus cloud 20, 22, 34sunrise 42, 44sunset 42, 44supercooled water 32TTAF 41, 99TAS. See true airspeedtaxiway lighting 102‐103TC. See t u r n coordinatorTEMPO 98terminator 44terrain shielding 234thermals 20thunderstorms 22‐24

avoiding 27‐28characteristics of 22‐24effect on ADF/NDB 209hazards to aviation 26‐27mature stage of 23and night VFR 98‐99SIGMET warnings of 26

time zone conversions 178‐179tracking tolerances 92traffic separation 95transition altitude 4transition level 4transponder 92trend type forecast 99true airspeed 3, 4TTF. See trend type forecastturbulence 98‐99turbulence penetration 28turbulence penetration speed 28turn coordinator 3, 8, 11, 13, 115t u r n indicator 3, 8, 11, 13T‐VASIS 107twilight 42‐43

258

Uunplannednight flight 146unusual attitudes 166‐173nose‐high unusual attitude 170, 173nose‐low unusual attitude 167‐170,172on limited panel 171‐173

upslope fog 40UTC . See coordinated universal time

VVA. See manoeuvring speedvacuum system 3, 13failure of 161‐162preflight check of 11

VASI. See visual approach slope indicatorVASIS. See Visual approach slopeindicator systemVB. See turbulence penetration speedvertical scan 120vertical speed indicator 3, 6, 115and pitot‐static system 6, 12preflight check of 11

vertigo 69vestibular apparatus 69, 71, 73Virga 21, 25Visibility 41vision 51‐57accommodation 52binocular vision 53‐54and the blind spot 54, 54‐55and colour blindness 55colour Vision 55double vision 53and empty field myopia 55night vision 56‐57, 129peripheral Vision 53, 57andpresbyopia 52and stereopsis 54and visual acuity 53

Visual approach slope indicator 64Visual approach slope indicator system106‐108precisionapproachpath indicator 106,108T‐VASIS 107

Night Flight

visual illusions 58-68on approach 62‐66autokinesis 58and black‐hole approach 64‐66in the circuit 61, 144environmental perspective 58false expectations 58false horizons 60and focal point 66‐68and night approach 63‐64relative mo v eme n t 58and runway size 63and runway slope 62‐63and white‐out approach 66

visual meteorological conditions 47Visual scanning 57and aircraft lights 57and the blind spot 55and peripheral vision 57

VMC . See visual meteorologicalconditions

VOR 216‐232course deviation indicator 222doppler V O R 219errors with 217‐219identification of 220‐221in flight use of 222‐232night VFR requirements 94omni‐bearing indicator 222omni‐bearing selector 222radials 217range of 219‐220rated coverage of 94, 220

VSI. See vertical speed indicator

Wwhite frost. See hoar frostWhite‐out approach 66wind direction indicator lighting 106windshear 25‐26wings‐leveller autopilot 15

Xx‐height 138

night rating

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