MCQ questions

Question 1

Answer 1

Low pressure turbine

Question 2

A by-pass engine LP compressor

a) supplies less air than is required for combustion
b) supplies more air than is required for combustion
c) supplies only the required quantity of combustion

Answer 2

b) supplies more air than is required for combustion

Question 3

A turbo jet engine gives

a) small acceleration to a large mass of air
b) large acceleration to a small mass of air
c) large acceleration to a large weight of air

Answer 3

b) large acceleration to a small mass of air

Question 4

A jet engine derives thrust by

a) drawing air into the compressor
b) impingement of the propelling gases on the outside air
c) reaction of the propelling gases

Answer 4

c) reaction of the propelling gases

Question 5

In a reverse flow system the last stage of an axial flow compressor is often centrifugal, this is to

a) provide initial turning of the airflow
b) prevent compressor surge
c) increase the temperature rise

Answer 5

a) provide initial turning of the airflow

Question 6

In a free turbine

a) there is a clutch between compressor and power output shaft
b) there is no mechanical connection with the compressor
c) there is a direct drive with a free-wheel unit

Answer 6

b) there is no mechanical connection with the compressor

Question 7

If an electrical de-icing system is operating, thrust will

a) decrease
b) increase
c) remain constant

Answer 7

a) decrease

Question 8

A method of comparing engine efficiencies is by comparing

a) thrust to weight ratio
b) fuel consumption
c) specific fuel consumption

Answer 8

c) specific fuel consumption

(Specific fuel consumption = is the amount of fuel burned in one hour in order to produce one unit of thrust)

Question 9

'’Ram effect’’ due to aircraft forward speed will cause the efficiency of the engine to

a) remain constant
b) increase
c) decrease

Answer 9

b) increase

Question 10

Bernoulli’s Theorem states that at any point in a flow of gas

a) the static pressure is less than the dynamic pressure
b) the static pressure and dynamic pressure are equal
c) the total energy remains constant

Answer 10

c) the total energy remains constant

Question 11

A bypass ratio of 5:1 indicates that the bypass flow is

a) equal to 1/5 of the hot stream
b) five times the cold stream
c) five times the hot stream

Answer 11

c) five times the hot stream

Question 12

In a turbo jet engine, combustion occurs at

a) constant velocity
b) constant volume
c) constant pressure

Answer 12

c) constant pressure

Question 13

The working fluid of a gas turbine engine is

a) air
b) gasoline
c) kerosene

Answer 13

a) air

Question 14

As subsonic air flows through a convergent nozzle the velocity

a) increases
b) decreases
c) remains constant

Answer 14

a) increases

Question 15

The stator vanes in an axial-flow compressor

a) convert velocity energy into pressure energy
b) convert pressure energy into velocity energy
c) direct air into the first stage rotor vanes at the proper angle

Answer 15

a) convert velocity energy into pressure energy

Principle of Operation of compressor stator vanes:

'’The pressure rise results from the energy imparted to the air in the rotor which increases the air velocity. The air is then decelerated (diffused) in the following stator passage and the kinetic energy translated into pressure’’

Question 16

What units in a gas turbine engine aid in stabilisation of the compressor during low thrust engine operations?

a) bleed air valves
b) Stator vanes
c) Inlet guide vanes

Answer 16

a) bleed air valves

Note:

Bleed air valves are a method of Airflow control.

They achieve bleed-off of surplus low-pressure air supply at speeds below ‘‘design speed’’

They close usually, just as the engine reaches idle speed.

At low engine RPM the air passing through the compressor is not being compressed enough, which means that the volume of the air becomes too great for the aft end of the compressor to handle. This can lead to a compressor surge. Installing bleed valves to vent the excess volume of air from the compressor can prevent this. (The most common method in use today is to use inlet guide vanes to vary the amount of air entering the compressor - dodgy qeustion)

Question 17

A nozzle is ‘‘choked’’ when the gas flow or air flow at the throat is

a) subsonic
b) sonic
c) supersonic

Answer 17

b) sonic

Question 18

In the dual axial-flow or twin spool compressor system, the first stage turbine drives the

a) N1 and N2 compressors
b) N2 compressor
c) N1 compressor

Answer 18

b) N2 compressor

Question 19

During the high RPM range on an axial flow gas turbine engine, in what position are the variable intake guide vanes and bleed valves

a) at maximum swirl position, bleed valves open
b) at maximum swirl position, bleed valves closed
c) at minimum swirl position, bleed valves closed

Answer 19

c) at minimum swirl position, bleed valves closed

(swirl position??)

Question 20

When reheat is used EPR

a) is reduced
b) is increased
c) Remains constant

Answer 20

c) remains constant

Note:

'’Reheat’’ = Afterburning

Question 21

Which of the following units are generally used to measure aircraft noise?

a) decibels (dB)
b) Effective perceived noise decibels (EPNdB)
c) sound pressure

Answer 21

b) Effective perceived noise decibels (EPNdB)

(pitch as well as noise pressure)

Question 22

What is the maximum practical angle through which the gas flow can be turned during thrust reversal?

a) 180 ^
b) 135 ^
c) 50 ^

Answer 22

b) 135 ^

Question 23

A carbon seal has which type of sealing arrangement?

a) full contact with race
b) full contact with labyrinth
c) full contact with casing

Answer 23

c) full contact with casing

Carbon seals 21. Carbon seals (fig. 9-7) consist of a static ring of carbon which constantly rubs against a collar on a rotating shaft. Several springs are used to maintain contact between the carbon and the collar. This type of seal relies upon a high degree of contact and does not allow oil or air leakage across it. The heat caused by friction is dissipated by the oil system.

Question 24

On a FADEC engine

a) A and B channel use the same phases of the motor
b) A channel uses control alternator and B channel uses aircraft bus power
c) A channel uses a separate winding of the control alternator to B channel

Answer 24

c) A channel uses a separate winding of the control alternator to B channel

Question 25

A bellmouth compressor inlet is used on

a) aircraft with low ground clearance
b) helicopters
c) supersonic aircraft

Answer 25

b) helicopters

Question 26

Electrical de-icing operates

a) cyclicly independent of ambient air temperature
b) cyclicly dependent on ambient air temperature
c) operates continuously

Answer 26

b) cyclicly dependent on ambient air temperature

Question 27

The inlet door on a variable geometry intake is open at

a) subsonic speeds
b) supersonic speeds
c) idle speeds

Answer 27

a) subsonic speeds

Question 28

The compensation device on an EGT system must be re-calibrated after

a) manufacture and overhaul
b) each time a part of the system is replaced
c) does not need calibration

Answer 28

c) does not need calibration

'’Compensation device on EGT system is automatic and therefore does not need to be calibrated’’

'’To prevent variations of cold junction temperature affecting the indicated temperature, an automatic temperature compensating device is incorporated in the indicator or in the thermocouple circuit’’

Question 29

During start the ‘starter light’ remains on after light up

a) this should be neglected
b) it should be monitored for 30 seconds and if still illuminated the engine should be shut down
c) the engine should be shut down immediately

Answer 29

c) the engine should be shut down immediately

The starter has not disengaged and damage to the starter/gearbox will result

Question 30

Noise from the jet wake when untreated by suppression is

a) low frequency, high decibel
b) high frequency, high decibel
c) low frequency, low decibel

Answer 30

a) low frequency, high decibel

Question 31

When testing an EGT system

a) the OAT is neglected
b) the OAT is always taken into consideration
c) OAT is only taken into consideration when over 20^

Answer 31

c) OAT is only taken into consideration when over 20^

OAT = Outside Air Temperature

Question 32

A free turbine is usually found on a

a) Turbo-fan
b) Turbo-jet
c) Turbo prop

Answer 32

c) Turbo prop

Question 33

If the LP shaft shears

a) turbine runaway occurs
b) compressor overspeed occurs
c) compressor underspeed occurs

Answer 33

a) turbine runaway occurs

The turbine drives the LP compressor or fan

Question 34

A turbo-shaft engine has

a) a mechanical connection between compressor and turbine
b) the power shaft is not connected to the compressor
c) none of the above

Answer 34

b) the power shaft is not connected to the compressor

Question 35

Normal fuel/air ratio for successful combustion is?

a) 15:1
b) 10:1
c) 25:!

Answer 35

a) 15:1

'’The ideal proportion of air and
jet fuels is 15:1. This is called the stoichiometric ratio.’’

Question 36

A magnetic chip detector inspection should be carried out

a) within specified time from shut down
b) with engine running
c) with engine cold

Answer 36

c) with engine cold

Question 37

A firewire is installed

a) to withstand inertia, vibration, etc, encountered during normal operation
b) vertically
c) horizontally

Answer 37

a) to withstand inertia, vibration, etc, encountered during normal operation

'’Fire wires can be any shape or position, retained in rubber clips’’

Question 38

APU has

a) automatically controlled thrust and is self contained
b) constant speed and is self contained
c) variable speed and is self contained

Answer 38

a) automatically controlled thrust and is self contained

Question 39

Anti-ice is recommended during:

a) when OAT is below - 10 ^C
b) thunderstorms
c) when OAT is +10 ^C and visible moisture

Question 40

Of the following, which engine type would most likely have a noise suppresser unit installed?

a) Turboprop
b) Turbojet
c) Turboshaft

Answer 40

b) Turbojet

Question 41

Bleed valves are normally spring loaded to the

a) closed position
b) mid-position
c) open position

Answer 41

c) open position

Question 42

Foreign object damage on compressor, when boroscoping is indicated by

a) tip curl
b) nicks and scores
c) flats

Answer 42

b) nicks and scores

Question 43

A magnetic chip detector detects

a) particles held in suspension
b) magnetised particles
c) particles which are too small for the naked eye

Answer 43

b) magnetised particles

Question 44

Resistive and capacitive type firewires are tested with

a) megger/ohmmeter
b) megger/voltmeter
c) multimeter

Answer 44

a) megger/ohmmeter

Question 45

Engine anti-ice is taken from

a) HP compressor
b) LP compressor
c) Turbine

Answer 45

a) HP compressor

Question 46

Fire wire clips have rubber in them to

a) insulate the fire wire electrically
b) stop heat transfer to element
c) support the wire

Answer 46

a) insulate the fire wire electrically

Question 47

The symbol for designating the speed of a single compressor engine is

a) N.G
b) N
c) N1

Answer 47

c) N1

Question 48

APU shut down is initiated by

a) low oil pressure, fire warning
b) low oil pressure, fire warning, hot oil temperature
c) high oil pressure, fire warning, hot oil temperature

Answer 48

b) low oil pressure, fire warning, hot oil temperature

Question 49

What happens when bulb type thermometer resistive element goes open circuit?

a) read less than ambient
b) read more than ambient
c) no reading given

Answer 49

b) read more than ambient

Question 50

A fixed throttle with increased mass airflow

a) EPR goes up
b) EPR goes down
c) EPR remains constant

Answer 50

c) EPR remains constant

EPR (Engine Pressure Ratio) = air pressure at exhaust / air pressure at inlet

Mass airflow will be the same throughout the engine hence no EPR change

Question 51

Fuel heater prevents

a) HP filter icing
b) LP filter icing
c) Neither

Answer 51

b) LP filter icing

Question 52

When a volume of air is compressed

a) no heat is lost or gained
b) heat is lost
c) heat is gained

Answer 52

c) heat is gained

Question 53

On a FADEC engine the EEC

a) has electronic control of the hydro-mechanical fuel control unit in all modes
b) has electronic control of the hydro-mechanical fuel control in some modes
c) has mechanical control of the hydro-mechanical fuel control system

Answer 53

a) has electronic control of the hydro-mechanical fuel control unit in all modes

(EEC = Electronic Engine Control)

Question 54

Fire extinguishers work by

a) combining with remaining oxygen to get rid of it
b) creating more oxygen
c) reducing oxygen

Answer 54

a) combining with remaining oxygen to get rid of it

Question 55

The air used for combustion is

a) Primary
b) Secondary
c) Primary and Secondary

Answer 55

a) Primary

Note:

Secondary air is that part of the air, which is metered into the combustion chamber to complete combustion.

Tertiary air is that air which acts as a cooling agent.This air takes no part in combustion.

Question 56

Compression occurs

a) across rotors
b) across stators
c) across stators and rotors

Answer 56

c) across stators and rotors

Approximately 50% of the total pressure rise occurs in the impeller, and 50% in the vaneless space and diffuser

Question 57

Igniter plugs are cleaned by

a) compressed air and brushing lightly with soft brush
b) light sand blasting
c) steel wool

Answer 57

a) compressed air and brushing lightly with soft brush

Question 58

On a FADEC engine, the channel reset

a) always selects A channel
b) always standby which becomes active on the next start
c) selects B channel

Answer 58

b) always standby which becomes active on the next start

Question 59

HEIU works by

a) a contact breaker
b) a discharging capacitor
c) ac busbar

Answer 59

b) a discharging capacitor

(HEIU = hydraulically activated electronically controlled unit injector. An interesting yet complicated injection system that functions by using pressurized engine oil to fire its fuel injectors)