Display

1. What are flight instruments?Flight instruments are the instruments in the cockpit of an aircraft that provide the pilot with information about the flight situation of that aircraft, such as altitude, speed and direction. Altimeter, Attitude Indicator, Airspeed Indicator, Magnetic compass, heading indicator,vertical speed indicator, course deviation indicator, radio magnetic indicator.

2. Name the power plant instruments.Aircraft power-plant instruments include tachometers, engine thermometers,pressure gages, fuel-quantity gages, fuel flow meters and indicators, and manifold pressure gage.

3. Name the instrument panels that are normally available in a typical airline (e.g. 737). On what panel the flight instruments and power plant instruments are located? Briefly provide the reasons.

Display Control Panel, Primary Flight Display (PFD), Navigation Display (ND), Flight Data Recorder (FDR), Electronic Flight Bag (EFB), Flight Management System (FMS), Engine Indication and Crew Alerting System (EICAS), Mode Control Panel (MCP), Back-up instruments. Flight instrument at PFD, power plant instrument at

4. Name the flight instruments that comprise the basic ‘6’ layout and state their respective positions.

5. Name the flight instruments that comparise the basic ‘T’ layout and state their respective positions. Does this lay-out also apply to electronic displays?

Yes. The lay-out is also apply to electronic displays.

6. What are the differences between the basic ‘6’ and the basic ‘T’ layout.

7. What is the “glass cockpit”?A glass cockpit is an aircraft cockpit that features electronic (digital) instrument displays rather than mechanical gauges (analog).

8. What are the differences between the “glass cockpit” and the basic ‘T’ layout?

9. What do you understand by the term ‘head-up’ display? With the aid of a diagram describe how the required basic flight data are displayed.

10. Name other types of the flight instrument displays and briefly state what they are.

Chapter 2 Air Data Instrument & Air Data Computer

1. What are the principal components and instrument which comprise a basic air data

system?

Pitot-static probe (airspeed indicator, altimeter, and vertical speed indicator),

pipelines, and drains interconnected to each other.

2. What techniques are used to measure airspeed, altitude and vertical speed?

Airspeed- measure speed in terms of the difference between the pitot and static

pressures detected by either (i) a combined pitot static probes or (ii) a pitot probe

and static vents.

Altitude- operate based on aneroid barometer principle with appropriate

calibration law of which the altimeter respond to changes in atmospheric pressure,

and these changes are indicated in terms of equivalent altitude values.

Vertical airspeed indicator- indicates the rate of altitude change from variations in

static-pressure alone. A time factor is introduced as a pressure function since

vertical speed is determine by the rate at which static pressure change. A special

air meter unit is incorporated in the sensing system to create a lag in static

pressure across the system, in order to establish the required pressure differences.

3. Name and explain what are the pressures that measured by the pitot static probe and

derive P=1/2 * (density) * (Velocity x Velocity)

Pitot pressure- additional pressure produced on the surface when a flowing fluid is

brought to rest at stagnation point at the surface.

1/2 * (density) * (Velocity x Velocity) is the dynamics pressure – additional to the

static pressure in the region of the fluid flow.

Upon reach stagnation point, fluid with velocity V is brought to rest. Kinetic

energy is converted to pressure energy.

Work done in raise an equal volume above the level of steam = kinetic energy of

the fluid before it brought to rest. Prove :

4. What are the errors associated with airspeed terminologies: IAS, CAS, EAS, TAS ?

IAS (indicated airspeed)- reading of airspeed indicator corrected only for

instrument error (difference between the true and indicated value)

Computed airspeed- indicated airspeed with correction of PE applied to an

airspeed sensing module via an electrical correction network.

CAS (calibrated airspeed)- the computed airspeed compensated for the non-linear,

square-raw, response of the airspeed sensing module associated with air data

computer systems.

EAS (equivalent airspeed)- airspeed calculated from the measured pressure

difference when using the constant sea-level value of density.

TAS (true airspeed)- EAS compensated for changes in temperature and density of

various flight level.

5. Define the term Mach number and explain how it is indicated by measurement in terms

of the ratio (Pt – Ps) / Ps?

Mach number is the ratio of an aircraft speed, V to the speed of sound, C that can

be computed from the pressure measurement and is indicated in the Machmeter.

Machmeter utilized 2 variables to compute the ratio for the Mach number:

A) airspeed- which measured in terms of pressure difference Pt – Ps by

airspeed indicator. Airspeed cannot be measured but is governed by static

pressure condition, altimeter is used to measure Ps and feed it into the indicating

system.

B) altitude- measured by means of an aneroid capsule sensitive to Ps.

Deflection of the capsule of both mechanisms is transmitted to the indicator

pointer by rocking the shafts and levers.

6. What is the difference between “pressure altitude” and “indicated altitude”?

Pressure altitude- the value indicated by the altimeters under International

Standard Atmosphere condition which is based on the basic of the calibration of

air data instruments with regard to its ISA and assumed values.

Indicated altitude- the error value read by the altimeters under non-standard

condition due to the constant changing of atmosphere pressure and temperature.

7. Explain why ADC systems are used in aircraft.

The ADC circuit is integrated with their principal data modules that automatically

applied the correction for PE, barometric pressure changes, compressibility effect

and provision can be made for the calculation of true airspeed (TAS) from the air

temperature data inputs.

8. What are TAT, SAT, RAM RISE and RECOVERY FACTOR?

SAT (static air temperature)- the ideal temperature of air under pure static

condition at flight levels, compatible with the operating range of any particular

type of aircraft concerned.

TAT (total air temperature)- the possible maximum temperature rise that can be

derived when air is brought to rest without further addition or removal of heat.

RAM RISE- the value of temperature rise higher than the SAT due to the result of

changes in boundary layer behavior and the effects of friction.

RECOVERY FACTOR- the sensitivity of the sensor that expressed in terms of

percentage.

Chapter 4 Gyroscopic Flight Instrument

1. What are the properties of gyroscope that are being applied in the flight instruments?

i. Rigidity- the property which resists any force tending to change the plane of rotor

rotation depends on: speed of rotation, mass of rotor, distance at which mass acts

from the centre.

ii. Precession- angular change in direction of the plane of rotation under the

influence of an applied force. Rate of precession depend on: strength & direction

of applied force, moment of inertia of rotor, and angular velocity of rotor.

2. How the gyroscope is used to indicate pitch and roll attitudes in the gyro horizon?

By its displacement with respect to each appropriates gyroscope of which

each has three degrees of freedom and consequently three mutual axes

facing to each other.

3. How are the spin axes of gyroscope arranged for the detection of pitch and roll attitude

changes and for establishing directional reference. Explain in detail.

The spin axes of gyroscope are arranged both in horizontal and vertical

manner so that it can utilize their rigidity property that provides a

stabilized references unaffected by movement of the supporting body, and

precession property which controls the effects of apparent and real drift,

thus maintaining the stabilized gyroscope.

4. What are “real drift” and “apparent drift”?

A) Apparent drift- The corrected drift of gyroscope with respect to

earth`s rotation where the attitudes of the gyroscope in the aircraft is being

referenced with respect to the earth`s surface.

B) Real drift- Result from the bearing friction and gimbal system

unbalanced of which these imperfections causes unwanted precession.

5. What is “transport wonder”?

Transport wonder is the apparent tilt of the gyroscope of which its spin axis has

tilted in a vertical plane during the transport period when its input axis is aligned

with the local vertical component of earth`s angular velocity.

6. What do you understand by the terms “gimbal lock” and “gimbal error”?

A) Gimbal Lock- The loss of the stable roll attitude reference which causes

the gimbal system to precess or topple as the gyroscope were to be turned when it

is in the lock condition. This happen when the spin axis in the gimbal orientation

becomes coincident with one or other axes of freedom that serves as the attitude

displacement references.

B) Gimbal Error- Error due to gimbal system orientation where the gimbal

rings are not mutually at right angles to each other when the gyroscope is

displaced from one point to the other point.

7. Describe how the rate gyroscope principle is applied to indicate the rate at which an

aircraft turns.

Gimbal ring has a calibrated spring connected between the gimbal ring and the

casing to restrain movement about the longitudinal axis YY1. In normal operating

position, the rotor spin axis which due to the spring restraint will always be

horizontal and the turn pointer will be at zero datum mark.

When the rotor spinning, its rigidity will increased further ensuring that

equilibrium is maintained.

As the indicator were to turn in F direction about a vertical input axis, the rigidity

of the rotor will resist the turning movement since it detects an equivalent force

being applied to its rim at point F.

The gimbal ring and rotor will be tilted about the longitudinal axis as a result of

precession at point p. The gimbal ring stretches the calibrated spring as it tilts

until the force it exerts prevents further deflection of the gimbal ring.

The spring force is a measure of the rate of turn since:

Precession = constant * angular momentum * rate of turn

The measure of turn rate, can thus be taken from the measurement of actual

movement of the gimbal ring from the zero position.

8. What are the types of gyroscopes used in flight instrument? (Answer: NOT COMPLETE)

Motor-driven gyroscope of electric type.

Gyroscope that is either vacuum or pressure of pneumatic type.

9. What are the advantages of rate gyros compared to displacement gyros?

Require no erecting device or correction for random precession.

The turn pointer will respond to a faster rate of turn changes, at the same times

respond to a definite turn rate instantly since a system for damping out the

oscillation is incorporated in the gyro.

Not necessary to rotate at high speed because the rotor is always at centre,

maintained in constant stable horizontal axis that control by both of the restraint

springs.

10. What are the parameters being presented by the following flight instruments and what

type of gyroscopes are used:

i. Artificial Horizon

ii. Turn and Slip Indicator

iii. Director Indicator