sch performance

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SCHEDULED PERFORMANCE OF MULTI-ENGINE TRANSPORT AIRCRAFT

INTRODUCTION

1. The basic requirement of a transport aircraft is to proceed safely fromdeparture to destination. For this it should have sufficient power and carrysufficient fuel to fulfil this purpose.

2. Time and fuel required for a manoeuvre are relatively unimportant as faras performance planning is concerned. The whole object of performanceplanning is to ensure in advance of any flight that the space required is nevergreater than the space available.

3. The space required by an aircraft for a particular manoeuvre dependsupon, and increases with, weight. Performance planning consists of fitting thespace required into the space available. Since weight is the main controllablevariable in the problem, the principle end product of performance plan is themaximum permissible take-off weight. It is therefore, evident that theperformance plan is the dominant feature and must be carried out first.

PERFORMANCE PLANNING

4. It is the duty of the licensing authority to ensure that no transport aircraftflies without a Certificate of Airworthiness (C of A) until it has been shown topossess the minimum performance standards defined in Air NavigationRegulations (General) and technically prescribed in the AirworthinessRequirement Publication.

5. Demonstration of performance capability allows the certification of anaircraft type into one of the performance groups A, C, D, E, X and No Group.

6. Situations of urgency may arise that, in order to utilise Military aircraft totheir maximum potential, reduced safety margins are both necessary andacceptable. These are known as Military Operating Standards. An element ofrisk is acceptable in he operation of these aircraft and it is an IAF responsibility todefine and apply appropriate safety margins.

The Performance group System.

7. The civil airworthiness requirements distinguish by groups betweenaircraft performance levels as follows:


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( a ) Performance group A. Aircraft with MTOW greater than5700kgs and performance such that, at whatever time a power unit fails ,a forced landing should not be necessary.

(b) Performance of group B. Aircraft with MTOW less than 5700

kgs(small commuter propellor aircraft with passenger capacity upto 19only) and performance such that engine failure at any stage of flight willnot necessitate a forced landing.

(c) Performance of group C. Aircraft with MTOW less than 5700 kgsand performance such that a forced landing should not be necessary if apower unit fails after take-off and initial climb, or after flight on instrumentshas commenced.

(d) Performance group D. Single or multi-engine aircraft withMTOW less than 5700 kgs which may not be able to maintain height after

an engine failure.

(e) Performance group E. Aircraft with performance similar tothose in Group C and D but whose weight does not exceed 5700 kgs.

(f) Performance group F. Single engine aircraft of MTOW lessthan 5700kg and passenger capacity upto 9.

(g) Performance group X. Large multi-engine aircraft, which havebeen, certificated to American Federal Air Regulations, Part 25 and onlyhave performance data in their flight manuals.

(h) Performance No Group. Aircraft in this group have to comply withrequirements based on information contained in the performance scheduleassociated with the Certificate of Airworthiness, except that where thesedocuments do not contain the required information, the best possibleinformation should be used.

8. For the purpose of performance planning , a flight is divided into fourstages:

(a) Take- Off. This stage is from the commencement of the take-offrun, and initial climb upto a screen height of 35 (this can be 50 in someaircraft).

(b) Net Take-off Flight Path. This is from the 35/50 point to a heightof 1500

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( c ) En Route. This stage is from a height of 1500 over thedeparture airfield to a height of 1500 over the destination or alternateairfield.

( d ) Landing. This is from a height of 1500 at the destination oralternate airfield to the aircraft coming to a stop after completing thelanding run.

9. The minimum standard of performance is known as Net Performance. Itis a legal requirement that all performance planning should be conducted to " netperformance considerations with the exception of military operating standardsdata which is gross performance.

Defination of Terms.

10. The definations given below cover the terms used in this section ofscheduled performance:

Field Lengths.

11. ( a ) Take-off Run Available(TORA). This is the actual length of therunway available for take-off.

( b ) Stopway. This is the area on ground in the direction of take-offdesignated and prepared by a competent authority, where an aircraft can

de-accelarate in the event of an abort take-off.

( c ) Accelarate Stop Distance Available(ASDA). This is thetotal length of the runway plus the stopway. This is further explained withthe help of Fig 1.

RECOGNITIONDECISIONACTION

ACCELERATING BRAKING

RUNWAY

V1

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GROSS ACCELERATE STOP DISTANCE REQUIRED

Fig1.Accelerate Stop Distance Required-Jet and Piston

( d ) Clearway. It is a defined rectangular area on ground or water atthe end of the runway in the direction of take-off and under the control of acompetent authority, over which an aircraft may make a portion of its initialclimb to a specified height. The minimum specifications it must meet are:

(i) Not less than 500 in width.

(ii) Slope not greater than + 1.25%.

(iii) Height not exceeding 26 ft

( e ) Take-off Distance Available(TODA). This is the sum of theTake-off Run Available and the Clearway( if any). It is limited to amaximum of 1.5 times TORA. e. g. when clearway is over water andTORA is 6000 ft , TODA is limited to 9000 ft only.

( f ) Balanced field Length. This is the condition when the take offdistance available is equal to the accelarate distance required. Some earlyODMs had simplified graphs for calculation of the takeoff performance incase of balanced field.

Speeds.

12. (a) Decision Speed (V1). This is the speed at or belowwhich, in the event of an engine failure on the takeoff role, takeoff is to beaborted and above which takeoff can be continued. V1 depends on theweight and the airfield dimensions. V1 should not be:

(i) Less than Vmcg

(ii) Should be between Vmcg and Vr.

(iii) Can be same as Vr provided that sufficient accelerate stopdistance is available.

(b) Rotation Speed (V r). This is the speed at which the pilotinitiates a change in attitude of the aircraft in order to leave the ground. Vris a function of the aircraft weight and the flap setting. It should be suchthat rotation at this speed will result in the aircraft getting airbourne andrapidly climbing to V2. Vr should not be less than:

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(i) 1.05 times Vmca

(ii) 1.10 times Vms1

(iii) Such that Vlof (lift off) is 1.10 times the minimum measuredunstick speed.

(c) Take-off safety speed (V2). This speed is a legal requirementthat at least this speed should be attained on one power unit inoperativeperformance by the time the aircraft has reached a height of 35 ft. This isa function of weight and flap setting. V2 shall not be less than:

(i) 1.10 times Vmca.

(ii) 1.20 times Vms1.

(d) All Engine Screen speed (V3). V3 is the speed at which theaircraft is assumed to pass through the screen height with all the enginesoperating on take-off power.

(e) Steady Initial Climb Speed (V4). V4 is the speed, with all powerunits operating; used in the scheduled take-off climb technique (it shouldbe attained between 35- 400 ft).

(f) Target Threshold Speed (Vat). Vat is the speed at which the pilot

aims to cross the runway threshold when crossing.

(g) Vmc. Minimum control speed with critical power unit inoperative.

(h) Vmca. Minimum control speed, take-off climb.

Definition- This should be the speed at which, when the critical powerunit is suddenly made inoperative at that speed, it is possible to recovercontrol of the aircraft with the engine remaining inoperative and the beingmaintained in a straight flight path at that speed. The bank angle in thefinal steady condition may be chosen by the applicant for airworthiness butmay not exceed 5 deg. It should not be necessary to reduce power on thelive engines, and the rudder force required to maintain flight control shouldnot be greater than 670 N. during recovery from the manoeuvre, theaircraft should not assume any dangerous attitude, not should it requireexceptional skill, strength or alertness on part of the pilot to prevent achange in heading in excess of 20 deg before recovery is complete.

(j) Vmcg. Minimum control speed, approach and landing.

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Defination- It should be the minimum speed at which, with the criticalengine being made suddenly inoperative and having been recognised bythe pilot, it is possible to maintain control of the aircraft during take-off with

the engine remaining inoperative, using primary aerodynamic controlsalone to maintain a path parallel to the originally intended path. Indemonstrating the Vmcg, the rudder force required to maintain controlshall not exceed 670 N and it should not be necessary to reduce power onthe remaining power units. During manoeuvre, the aircraft should notassume any dangerous attitude, nor should it require exceptional skill,strength and alertness on the part of the pilot to prevent excessive yawand lateral displacement before the necessary recovery.

(k) Vmcl. Minimum control speed approach and landing.

(l) Vs 1. Stalling speed with the aircraft in the configurationappropriate to the case under consideration.

(m) Vso. Stalling speed with flaps in the landing setting.

(n) Vms1. Minimum speed in a stall with the aircraft in the configurationappropriate to he case under consideration.

(p) Vmso. Minimum speed in a stall with flaps in the landing setting.

Performance.

13. (a) Measured Performance. This is the average performance of anaircraft or a group of aircraft.

(b) Gross Performance.It is such that there is at least 50% probabilityof its being exceeded by the performance of any aircraft measured at anytime.

(c) Net Performance. This represents the gross performancediminished by the amount considered necessary to allow for variouscontingencies which cannot be directly accounted for operationally.

(d) Gradient and Slope.Gradient is the tangent of the angle of climbexpressed as a percentage. Slope is used in place of gradientwhenreferring to airfield surfaces and obstacle profiles.

Miscellaneous.

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14. (a) Screen Height. This is the height of the imaginary screenwhich the aircraft will just clear when taking-off or landing, in an unbankedattitude and with the landing gear extended.

(b) Critical Power Unit. This is the power unit, or units, failure of whichgive the most adverse effect on the aircraft characteristics.

(c) Power Unit Failure Point. It is that point at which sudden completefailure of a power unit is assumed to occur.

(d) Decision point. It is that latest point at which on failure of thecritical engine, the pilot decides to abort take-off.

TAKE-OFF PERFORMANCE

15. In the planning for take-off it is assumed that, although the aircraft has allpower units operating at the start point, one power unit will fail aftercommencement of the take-off run and before the take-off is complete. Inthe event of an actual power unit failure during take-of it becomesnecessary for the captain to decide whether to abandon or continue withthe take-off.

Take-off Planning Consideration.

16. Maximum permissible take-off weight for any flight will be the least weightobtained after considering:

(a) C of A limit.

(b) WAT limit for take-off.

(c) Field length requirement.

(d) Take-off net flight path.

(e) En-route terrain clearance.

(f) WAT limit for landing.

(g) Landing distance requirements.

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17. C of A Limit. The Certificate of Airworthiness specifies maximumstructural take-off weight for the type of aircraft. This weight is absolute andshould not be exceeded.

18. WAT limit for Take-off . The maximum weight for take-off shall not

exceed that weight imposed by the altitude and temperature conditions of the

airfield under consideration. This limit is designed to ensure compliance with positive

gradient of climb with one power unit inoperative. The WAT limit graph takes noaccount of the runway length.

19. Field Length Requirement. This works on the basic premise that therequirement should not be more that what is available i.e. the take-off run,accelerate distance and take-off distance required should not be more than that

available. The following considerations are taken into account:

(a) Take-off weight.

(b) Altitude of airfield.

(c) Air temperature at the airfield.

(d) Slope of the airfield.

(e) Retardation effects of any measurable amount of slush, snow or

water on the runway surface.

(f) The reported wind component.

20. Decision Speed (Wet). Some ODMs will in future contain additionaldecision speed information scheduled for the use when emergency distance iswet. This speed is on an average some 5-10 kts less than the decision speedused in case of a dry runway.

Take-off Field Length Requirement.

21. The Regulations specify distinct requirements for field lengthrequirements. The take-off weight and V1 speed must be such that the mostsevere of these requirements are met:

(a) Take-off run required All power units operating. This is 1.15times the gross distance from the starting point to the point where theaircraft becomes airbourne, and one-third of the distance between the

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point at which the aircraft gets airbourne and the point at which it attains ascreen height of 35 feet.

1/3 rd 1/3rd 1/3rd

35START V1 Vr Vus

a bTORR=1.15 x (a+b)

TORA

Fig 2. TAKE-OFF RUN REQUIRED-ALL POWER UNITSOPERATING

(b) Take-off run required-One power unit inoperative. This is thedistance from the starting point to the point where the aircraft getsairbourne, plus one-third of the distance between the point at which it

attains a screen height of 35 ft. this has been further explained with thehelp of Fig 3.

1/3 rd 1/3rd 1/3rd

35START V1 Vr Vus

a b

TORR

TORA

Fig 3. TAKE-OFF RUN REQUIRED ONE POWER UNIT INOPERATIVE

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(c) Take-off Run Required One Power Unit Inoperative Wet Runway.This is the distance from the starting point to the point where the

aircraft becomes airbourne to effect a transition to attain a height of 35 ft,

in a manner consistent with the achievement of a speed not less than V2at 35 ft. The power unit failure should be recognised at V1 appropriate tothe wet runway.

22. In order to comply with the Air Navigation Regulation the take-off runrequired should be the greatest figure of the sub-para(a), (b) and (c).

23. In the take-off run analysis there are two variables, V1 and aircraft weight.

If he aircraft is light, then it is possible to lose a power unit earlier during the take-off run than when the aircraft is heavy. Thus ignoring other considerations, V1depends on aircraft weight and increases as the weight increases. Further, if allthe power unis continue to operate throughout the whole of the take-off run, thenthat will be the upper limit of the take-off run.

24. The Emergency distance requiredshould be the greater off:

(a) The gross distance from the starting point to the point where theaircraft comes to a rest after abandoning take-off following an enginefailure at V1 on a dry surface using all possible modes of deceleration.

(b) The gross distance from the start to the point where the aircraftcomes to rest after abandoning take-off following a power unit failure at V1appropriate to a wet runway and using all possible modes of deceleration.

25.Emergency distance required must not exceed emergency distance available.Again, there are two variables, V1 and aircraft weight, but this time, if theaircraft is light, then the power unit can be lost later during the take-off runthan when the aircraft is heavy. We see again that ignoring otherconsiderations in the emergency distance, V1 depends on the aircraft weightand decreases as the aircraft weight increases.

26. The take-off distance required for various conditions is derived as follows:

(a) Take-off distance required-All power units operating. This is 1.15times the gross distance to accelerate with all power units operating fromthe starting point to the rotation speed, to effect a transition to climbingflight and attain V2 by 35 ft and should be consistent with achievement of

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a smooth transition to a steady initial climb speed (V4) at a height of 400ft.Refer to Fig 4 for diagrammatic explanation.

V2 35

V1 Vr Vus Clearway

TORA STOPWAY

TODR

TODR x1.15 TODR(4 ENGINES)

TODA

Fig 4. TAKE-OFF DISTANCE REQUIRED ALL POWER UNITSOPERATING

(b) Take-off distance required One power unit Inoperative. This isthe gross distance from the starting point through the rotation speed, andthereafter to effect a transition to climbing flight and attain a screen heightof 35 ft at V2 with one power unit inoperative the failure of the power unit

being recognised at V1 appropriate to a dry runway. Refer to Fig5 fordiagrammatic explanation.

V2

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35

V1 V2 Vus

CLEARWAY

TORASTOPWAY

TODR

TODA

Fig 5. TAKE-OFF DISTANCE REQUIRED-ONE POWER UNITINOPERATIVE

(c) Take-off distance required- One power unit inoperative-Wetrunway. This is the gross distance from the starting point through rotation

speed, and thereafter to effect a transition to climbing flight and attaining aheight of 15 ft in a manner consistent with achievement of V2 at 35 ft, thefailure of the power unit recognised at V1 appropriate to wet runway.

27. In order to comply with the Air Navigation Regulations, the take-offdistance required should be the greatest of sub para (a), (b) and (c) mentionedabove and should not exceed the take-off distance available.

28. In the take-off distance analysis there are the same two variables asbefore, i,e V1 and weight. If the aircraft is light, a power can be lost earlier than ifthe aircraft was heavy. Thus ignoring other considerations, V1 depends on

weight, and increases as the weight increases. Further, as in the case of take-offrun, in case all power units continue to operate throughout the whole take-offdistance, it simply places an upper limit on the aircraft weight.

29. When field lengths are unbalanced it is necessary to consider individuallytake-off run, emergency distance and take-off distance available. If, however,emergency distance available and the take-off distance available is of the samelength, then the field is said to be balanced. From the balanced field chart it ispossible in one step to determine:

(a) Maximum take-off weight to comply with emergency distance withone power unit inoperative.

(b) The V1/V2 ratio appropriate to this weight and common to the twodistances.

30. Performance planning for take-off stage is now complete by selection ofthe most limiting weight from the factors considered so far, i.e.:

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(a) C of A limit.

(b) WAT limit (take-off).


(d) Brake heating limiting limitation, tyre speed, cross wind limitation,use of anti-icers, reduced performance due to slush or standing water onrunway, Noise abatement procedure Runway LCN, Anti-skid systeminoperative, use of water methanol and Flap setting.

NET TAKE-OFF FLIGHT PATH

31. Air Navigation Regulation requires aircraft to clear all obstacles by not less

than 35 ft within a defined area from the end of take-off distance available. Thenet take-off flight path with one power unit inoperative is plotted from35/50height points as appropriate, above the end of take-off distance required,to a height of 1500.

32. In determining the net take-off flight with one power unit inoperative, thefollowing factors must be taken into account:

(a) Take-off weight.

(b) The altitude of the airfield.

(c) The temperature at the airfield.

(d) Average slope of the take-off distance available.

(e) The reported wind component.

Flight Path Profile.

33. The net take-off flight path is divided into a maximum of six segments.These segments are explained diagrammatically in Fig 5. These six

segments, together with the other information necessary for understandingthe net take-off flight path, are defined below:

(a) Reference Zero. This is a point 35 ft or 50 ft directly below theaircraft at the end of TODR. It is the origin for the scale plot of the aircraftheight against horizontal distance.

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(b) Five Minute Point. This is the point at which the take-off powertime limitation is reached (normally five minutes from the start of the take-off, but, if different, this will be stated in the aircraft ODM).

(c) First Segment. This is from 35 ft to the point at which on one

power unit inoperative net performance, the landing gear is fully retractedand (if applicable) the propeller of the failed unit is feathered.

(d) Second Segment. This extends from the end of first segment tothe height selected for the initiation of retraction of flaps (generally from400 ft to not more than 1500 ft).

(e) Third Segment. The aircraft is flown level at the height selectedfor flap retraction and accelerated to flaps up safety speed. At this speed

the flaps are retracted.

(f) Forth Segment. This extends from the end of the third segmentto the five minutes point or 1500-ft whichever is earlier.

(g) Fifth Segment. At the five minutes point (or 1500 ft) power isreduced to maximum continuous rating, and the aircraft is flown level andaccelerated to the one power unit inoperative en-route climbing speed.

(h) Sixth Segment. If 1500 ft has not been reached by theend of the fourth segment, the sixth segment extends from the end of the

fifth segment until a height of 1500 ft is attained.

1500

NOT BELOW 400

1st SEG 2nd SEG 3rd SEG 4th SEG 5th SEG6th SEG

FROM HT LEVEL TILL 5 MIN PT. LEVEL CLIMBING35 TO FLAP FLAP UP OR 1500 TO 1500UC UP RETR

V2 ACC FLAP FLAP UP ACC ENROUTE EN-ROUTE

UP SPEED SAFE SPEED CLIMB SPEED CLIMB SPEED

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MAX TAKE-OFF POWER MAX CONT PWR

Fig 6. NET TAKE-OFF FLIGHT PATH

34. It is pointed out that the foregoing describes a typical plot but one which isby no means mandatory. It is, therefore, possible to find aircraft that have three,four or five segments in their net flight paths and whose speeds in the varioussegments from those illustrated above.

35. The aircraft weight used for the initial scale plot is the maximumpermissible take-off weight determined by the take-off plan. If, on using thisweight, the required legal obstacle clearance (i.e. 35 ft for a straight climb and50ft whilst the heading is changed by more than 15 deg) is obtained, then theNet Take-off Flight Path imposes no limitation. If the required obstacleclearance is not obtained, then the take-off weight must be reduced, and afurther plot be constructed with reference zero redefined at the end of thetake-off distance required. Having repositioned reference zero, it will also benecessary to re-adjust obstacles horizontally and vertically as applicable. Thisenables a graph to be drawn for two or three flight paths for various weights,the axis of the graph showing take-off weight against clearance. This willenable the maximum take-off weight which will achieve the desired clearanceto be established. This is further explained with the help of a graph (Fig 6), inwhich it is seen that to achieve a vertical clearance of 35 the take-off weightshould be less than 166000 lbs.

REQUIRED CLEARANCE=35 FT

+ 40

CLEARANCE+20

0

-20

-40TOW FOR 35 CLEARANCE

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160 162 164 166 168 170

TAKE-OFF WEIGHT (X 1000 LBS)

Fig 7. Take-off Weight for Clearance by 35.

36. The following specifications are laid down by the Air NavigationRegulations regarding the Net take-off flight path and the various segments ofclimb:

(a) The net take-off flight path will be the gross take-off flight path, withthe critical unit inoperative diminished by a gradient of climb of :

(i) 0.8% for aircraft with 2 power units.

(ii) 0.9% for aircraft with 3 power units.

(iii) 1.0% for aircraft with 4 power units.

(b) The gross gradient of climb in the first segment shall not be less than:

(i) 0% for aircraft with 2 power units.

(ii) 0.3 % for aircraft with 3 power units.


(c) The gross gradient of climb in the second segment shall not be lessthan:




(d) The gross gradient of climb in the fourth and final segment shall notbe less than:

(i) 1.2% aircraft with 2 power units.


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(iii ) 1.5% for aircraft with 4 power units.

(e) The gross gradient of climb on approach for an aircraft having onepower unit inoperative is:



(iii) 2.4 % for aircraft with 4 power units.

En-route Performance

37. En-route performance planning concerns that portion of the flight whichstarts at 1500 ft,i.e. , at the end of the net take-off flight path , and ends at 1500 ftover the landing airfield.

En-route Terrain Clearance.

38. En-route, aircraft must clear all obstacles within 10 nm(5 nm under certaincircumstances) on either side of the intended track by a vertical interval of atleast 2000 ftusing one(or two) power units inoperative net performance. Further, when theaircraft arrives over the airfield, it must have at least a zero gradient of climb on

net performance at 1500 ft above the airfield. The navigational aids available onthe route under consideration will determine whether obstacles within 5 nm or 10nm of the track are to be considered.

39. In assessing the ability of the aeroplane to comply with the terrainclearance requirement, account must be taken of the meteorological conditions(including temperature) expected for the flight, and the aircrafts ice-protectionsystem must be assumed to be in use when appropriate.

40. While calculating the drift Down Altitude, the maximum possible altitudethat can be assumed at the start of the drift down is the least of:

(a) Maximum re-light altitude.

(b) The planned altitude to fly.

41. Once the maximum permissible altitude is established, the drift down ofthe aircraft is calculated using the en-route net gradient of climb. The drift downis calculated and a vertical clearance of 2000 ft is checked against all obstacles.

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If this clearance is not achieved, either the aircraft weight must be adjusted untilthe required clearance exists or, alternatively the aircraft must be re-routed toavoid critical obstacles. It should be noted that in some cases it is possible for theaircraft to drift up. Fig 7 explains the profile of an aircraft drifting down from theenroute altitude and clearing the enroute obstacles.

42. The method for calculation of the drift down altitude after a power failureis:

(a) Determine the maximum height from which the drift down willcommence.

(b) Determine the required terrain clearance.

(c) Select the vertical spacing to be used for calculations(1000,2000or

5000).

(d) For the mean height and temperature obtain from the graph theenroute net gradient.

(e) Calculate the horizontal distance traveled during descend.

MAX RELIGHTINGALTITUDE

1ST OBSTACLE

ALTITUDE (FT) 2ND OBSTACLE STABILIZING ALT

HORIZONTAL DISTANCE FROMENGINE FAILURE (NM)

Fig 8. Drift Down Profile with Obstacle Clearance.

43. Effect of Wind on Drift Down Path. To obtain the true distancegradient the forecast wind component must be applied; a head wind component

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decreases the distance traveled (increases the gradient), whilst a tail windcomponent will give an increased horizontal distance (decreased gradient).

44. Net gradient of climb for enroute obstacle clearance with the critical powerunit inoperative shall be the gross gradient of climb diminished by:

(a) 1.1% for aircraft with 2 power units.

(b) 1.4% for aircraft with 3 power units.

(c) 1.6% for aircraft with 4 power units.

LANDING REQUIREMENTS

45. There now remains one further set of requirements, which needsinvestigation and this concerns landing distance criteria that deal with destinationand alternate airfields separately. As with take-off requirements, landingrequirements can be treated under similar headings, i.e.,

(a) C of A limit (landing).

(b) WAT limit (landing).


46. C of A limit (landing). The certificate of airworthiness limit is absolute andmust not be exceeded except in emergency.

47. WAT limit (landing). The landing WAT limit ensures a positive gradient ofclimb in the overshoot configuration, with one power inoperative.

48. Arbitrary Landing Distance. This is the gross horizontal distancerequired to land on a dry hard surface, from a screen height of 50 ft, and come toa complete stop, at agradient of descend not greater than 5%(3 deg glide path), and a constant speedof not less than the greatest of:

(a) 1.3 times the minimum stalling speed with flaps in the landingconfiguration.

(b) The all power units operating threshold speed (Vat).

(c) The one power inoperative target threshold speed minus 5 kts.

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49. Destination Airfield -Arbitrary Landing Distance. The landingdistance required appropriate to Destination Airfield shall be the ArbitraryLanding Distance determined inaccordance with para 48, times 1.82 for aircraft having turbo-jet power units andnot fitted with effective reverse thrust; 1.67 for all other aircraft. All the landing

distances are further explained with the help of Fig 9.

GRADIENT5% SPEED AT THRESHOLD

AS PER PARA 48

50 FT STOP

LANDING DISTANCE

DEST LANDING DIST REQD=LANDING DIST x (1.67 OR 1.82)

ALTERNATE LANDING DIST. REQD= DETINATION LANDING DIST x 0.95

Fig 9. ARBITRARY DISTANCE REQUIRED DESTINATION AND ALTERNATEAIRFIELD

50. Reference Landing Distance. This is the gross horizontal distancerequired to land on a reference wet hard surface from a height of 30 ft and cometo a complete stop. The speed at the height of 30 ft is the maximum thresholdspeed; touchdown is at the reference touchdown speed attainment of which isunder limiting operational conditions of ceiling and visibility.

51. Landing Distance Alternate Airfield. The landing distance required atan alternate airfield will be the landing distance at the destination airfieldmultiplied be 0.95. In case of Propeller driven aircraft the factor to be multiplied is0.86. However, the new factor 0.95 has made retrospect in the case of jet aircraft.The reason for making the regulations more restrictive is because there is less

justification for a marked differential between the destination and alternatelanding distance. A modern aircraft is less susceptible to variation in landing

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techniques and its scheduled distances are subject to fairly tight control ofapproach and touch down speeds.

52. Multiple Runways. If airfields have multiple runways then each runwaywill need to be treated individually, unless the best runway can be determined by

inspection.

53. Having now decided on the maximum permissible landing weight, thiscould impose a restriction on take-off weight since maximum take-off weight cannever exceed maximum landing weight plus burn off fuel from departure to thedestination or alternate airfield.

54. The following specifications are laid down by the Air NavigationRegulations regarding the gross gradient of climb on approach for an aircraft

having one power unit inoperative:

a (a) 2.1% for aircraft with 2 power units.bc (b) 2.3% for aircraft with 3 power units.

(c) 2.4 % for aircraft with 4 power units.

55. Having gone into the details of calculating the TORR, TODR and ASDRthe basics to be kept in mind while decreasing/increasing the decision speed(V1) are that it causes:

(a) Increases/decreases the TORR.

(b) Increases/decreases the TODR.

(c) Decreases/increases the ASDR.

Weight and Balance.

56. The principles of weight and balance are applicable to all aircraft. Aircraftcarrying standard loads, e.g. training and air defence aircraft are normally flownunder a pre-computed weight and balance clearance, but transport aircraft, dueto their variable load capacity, require a separate clearance for each sortie.

Aircraft Weight Limitation.

57. A limitation is imposed on the AUW at which any aircraft is permitted tooperate. This limitation depends on the strength of the structural components ofthe aircraft and the operational requirements it is designed to meet. If these

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limitations are exceeded, the safety of the aircraft may be jeopardized and itsoperational efficiency impaired.

Effect of Increased All Up Weight on Aircraft Performance.

58. The effect on the aircrafts performance due to increasing the AUW is to :

(a) Increasing the stalling speed, thereby increasing the take-off andlanding speeds.

(b) Increase the aircrafts inertia, thereby reducing the acceleration ontake-off and deceleration on landing.

(c) Reduce the rate of climb.

(d) Lower the absolute ceiling and optimum range altitude.

(e) Reduce the range and endurance.

(f) Reduce maneuverability and assymetric performance.

59. There is an optimum position of the CG of any loaded aircraft that willchange with the AUW of the aircraft. Even if the CG of a loaded aircraft is at theoptimum position at the time of take-off, in-flight changes in the AUW cause theCG to move and such a movement may cause a progressive loss of efficiency,leading, as the distance increases from the optimum position, to a state of

serious and even dangerous unbalance.

Effect of Unbalanced Loading.

60. Incorrect loading of the aircraft can move the CG near the normal fore-and-aft limits and this can have the following effects in the aircrafts performance:

(a) CG too far forward.

(i) Necessitates a large stick force per g, making the aircraftdifficult to manoeuvre and heavy to handle.

(ii) Necessitates a large elevator movement for landing.

(iii) Requires the use of excessive nose up trim to maintainstraight and level flight, resulting in increased drag and aconsequent decrease in range and endurance.

(b) CG Too Aft.

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(i) The aircraft becomes less stable and may become unstable,possibly leading to loss of control.

(ii) In some aircraft the increased load on the tail-plane may

cause flutter.

(iii) Requires excessive use of nose down trim to maintainstraight and level flight, resulting in increased drag and aconsequent decrease in range and endurance.

Cargo Restraint.

61. All cargo carried in the aircraft must be secured against forces that maytend to move it from its allotted position in the aircraft. These forces may becaused by the acceleration or deceleration of the aircraft when taking-off orlanding, by air turbulence, by control surface movements, or by the inertia of thecargo item should the aircraft crash-land or ditch.

62. If an item of cargo is not properly secured it may move, with one or moreof the following results:

(i) Injury to personnel in the aircraft.

(ii) Movement of the CG outside the permissible limits.

(iii) Structural damage to the aircraft.

(iv) Blockage of emergency exits.

(v) Damage to other cargo items.

FUEL PLANNING

63. The fuel plan is an essential part of flight planning. Accurate calculation ofthe fuel required for a particular operation is important to safety, economicaloperation, and the maximum utilization of the available payload.

Variables Affecting Fuel Consumption.

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64. In general terms fuel consumption is a function of the followingparameters:

(a) Pressure altitude.

(b) Air temperature.

(c) Speed.

(d) All Up Weight.

(e) Engine RPM.

65. The significance of the individual parameters depends on the type of

aircraft engine being considered and is summarised in the following paragraphs:

(a) Piston Aircraft. These aircraft operate in that part of theatmosphere that has the greatest rate of change of density with altitude (0-15000 ft). A wide range of pressure altitudes and temperatures isencountered and the fuel planning method must be capable of takingaccount of these variations. Furthermore the piston engine is a veryversatile power unit the required output can be achieved by variouscombinations of RPM and intake manifold pressures. Thus all variablesmust be considered when studying piston aircraft fuel consumption.

(b) Turbo Prop Aircraft. The normal operating altitude range of theturbo prop aircraft is 15000-30000, where the density gradient is lessmarked than in the 0-15000 range, thus pressure altitude is a lesssignificant factor.As far as the RPM is concerned, a turbo prop engine isoperated at optimum RPM and changes in power output are achieved byvarying the pitch of the propellor.

(c) Pure Jet Aircraft. Jet aircraft operate in the region of thetropopause in order to obtain the best combination of engine and airframeefficiency. Thus fuel consumption data can be presented in terms ofoptimum operating heights. As with the turbo-prop engines, jet engineRPM ranges are small and are not used as entering arguments.

Calculating the Fuel Plan.

66. When the route and time portion of the flight plan has been completed thefuel requirements are then calculated as follows:

(a) Determine the AUW at take-off.

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(b) Calculate the fuel needed for the climb.

(c) Calculate the fuel needed for each leg.

(d) Calculate the descend fuel.

(e) Calculate the fuel required for a planned diversion.

(f) Calculate a contingency reserve (this is generally 5% of the fuelrequired for climb, cruise and descend).

(g) Make an additional allowance for unusable fuel and that requiredfor taxying, holding and approach.

67. Leg Fuel Calculations. Since fuel consumption during cruise flightdepends on the aircraft weight, the mean AUW must be determined for each leg

of the flight and the fuel flow for the weight extracted from the appropriate graphor table. The method of determining the mean AUW for each leg depends on thetype of the aircraft being considered; for a jet aircraft, the calculation must beexact since fuel flow varies considerably with the change in weight; for pistonaircraft, the calculation is less critical.

MATO Fuel Calculation.

68. IAP-3314 Manual of Air Transport Operations lays down the method ofcalculating fuel in transport aircraft while on a cross-country flight. The total fuelcarried for the flight is to be based on the following requirement:-

(a) Fuel for flight time from departure to destination.

(b) Fuel for flight time from destination to terminal diversion.

(c) Fuel for 10% of (a) and (b) above to cater for variation in aircraftperformance, meteorological inaccuracies and errors in navigation.

(d) Fuel foe 30 minutes of ODR (Overhead Diversion Reserve-It allowsfor holding overhead at the diversionary airfield, an instrument letdown, anovershoot and landing).

(d) Fuel for taxy, run-up and unusable fuel (not to be included in theAUW for take-off).

CONCLUSION

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69. The main end product in performance planning is finding the value of the

maximum permissible regulated take-off weight. It should be clear that thisweight may be determined by the take-off, the net take-off flight path, the en-route terrain clearance, or the landing distance limitation.

70. It is not possible to design an aircraft in which the lift, weight, thrust anddrag forces are always in equilibrium during straight and level flight; the centre ofpressure and the drag line vary with changes of angle of attack and the positionof the Centre ofGravity depends on the total distribution. Operation at weight in excess of themaximum AUW will reduce the safety factor thereby increasing the risk ofstructural failure in manoeuvre or when flying in turbulent conditions. Whilst it isimportant to ensure that the normal maximum AUW of an aircraft is notexceeded, the distribution that weight, i.e., the balance of the aircraft, is equallyimportant.

71. The height and speed at which the aircraft is flown depends on thespecific task and the aircraft type. Generally speaking an aircraft is operated toachieve maximum range during transit flight and for maximum endurance whilston station ass combat air patrol. In other situations, such as penetration of hostiledefences, speed and height will be determined by the tactics in use.

72. A computer programmed to suit individual aircraft performancecharacteristics would give the quickest and most accurate solution to theperformance plan. Such computers are already in use, but at present they arecostly, cumbersome and used mainly by aircraft manufacturers. It is highly likely,

however, that future development will produce a manageable computer for useby operators.

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QUESTIONS

1. State true or false.

(a) Time and fuel are very important considerations in performanceplanning.

(b) The space required by an aircraft to manoeuvre depends on itsweight.

(c) The principle end product of a performance plan is the maximum

permissible take-off weight.

(d) Licencing authority has nothing to do with certifying theairworthiness of an aircraft.

(e) An-32 falls under performance Group A.

(f) TODA for runway 27 in Goa is infinite since sea is available for theinitial climb.

(g) The width of the stopway is twice that of the runway.

(h) Take-off should be continued if you have an engine failure at V1.

( j ) Atleast V3 should be attained on one power unit inoperative aftertake-off by 35.

(k) Power unit failure and the decision point are the same.

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(l) Reference zero is the point directly below the aircraft at the end ofTORR.

(m) When calculating the arbitrary landing distance the glide slopeshould not be more than 5 deg.

2. Fill in the blanks.

(a) Generally all modern multi-engine civil passenger aircraft arecertified to performance __________ standards.

(b) For the purpose of flight planning, a flight is divided into________stages.

(c) The minimum standard of performance is known as

_______________.

(d) A field is said to be balanced when the _____________ is equal tothe ______________.

(e) Stalling speed with flaps in the landing setting is _____________.

(f) Rotation speed (Vr) is a function of __________and ___________.

(g) When the emergency distance is wet then the V1 is _________kts less.

(h) With an increase in the V1 the TORR and TODR __________ and theASDR __________.

(j) Fourth segment starts from the end of the third segment to the________ or __________, whichever is earlier.

(k) Enroute an aircraft must clear all obstacles within ________ nm oneither side by atleast __________ ft with one(two) engines inoperative.

(l) With the CG too forward the aircraft becomes _____________ andwith CG too back the aircraft is ___________.

(m) In the MATO fuel calculation the 10% of the fuel required fromdeparture to destination and to the diversion is to cater for

____________ .

(n) ODR caters for ____________________________________________.

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3. Explain any three.

(a) The various performance groups.

(b) Explain the stages of performance planning along with a diagram.

(c) With the help of a diagram explain the various stages of the NetTake-off Flight Path.

(d) Give the method of calculating fuel for a cross-country flight asgiven in MATO.

LESSON PLAN

QFI COURSE : 112

SUBJECT : SCHEDULED PERFORMANCE OF MULTI-ENGINETRANSPORT AIRCRAFT

DURATION : 1 Hr 30 Min

OBJECTIVE : To introduce the concept of Scheduled Performancefor Transport Aircraft

TRAINING AIDS :

1. PROXIMA

2. WHITE BOARD

3. OHP

BIBLIOGRAPHY

1. BOOK : IAP 3456

2. BOOK : MANUAL FOR AIR TRANSPORT OPERATIONS

METHODOLOGY

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(A) LECTURE (B) LESSON (C) DISCUSSION

PREVIOUS LESSON TIE- IN

NIL

INDEX

Sl. No. Chapter Page No.

1.

2.

3.

4.

5.

6.

7.

8.

9.

Introduction

Brief History

Laws of motion

Orbits of Satellites

Typical launch of a Satellite

Types of Satellites and Launch Vehicles

Use of Satellites

Future trends

Conclusion

01

01

02

05

06

08

09

10

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