24 Gas Turbines Auxiliary Power Units (APU) and Engine Starting – LMS

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📄 Notes ⚡ Cheat Sheet

Q1. What is the correct sequence during the start of a turbine engine on theground?

Starter, ignition, rotation, fuel

Rotation, ignition, fuel

Starter, rotation, ignition, fuel

Rotation, fuel, ignition

Q2. On the ground, the Auxiliary Power Unit (APU) can provide: 1. Electricity 2. air for starting system 3. hydraulic pressure 4. air for air conditioning The combination which regroups all of the correct statements is:

1, 2, 4

1, 2, 3, 4

2, 3, 4

Q3. The most important oil system instrument indication during gas turbine engine start is:

oil pressure.

oil temperature.

oil quantity.

oil filter clogged warning signal.

Q4. After a successful start of a high bypass turbofan engine, the air starter:

is disengaged by the coupling between engine N1 spool and starter by the use of centrifugal forces.

remains engaged and rotates continuously with the N2 spool.

is disengaged by the coupling between engine N2 spool and starter by the use of centrifugal forces.

is disengaged by using a clutch that is controlled by the main engine control.

Q5. A modern Auxiliary Power Unit (APU) is designed to provide power- for ground starting of an engine. It also supplies both in the air (subject to certification limitations) and on the ground :

Air conditioning and electrical services

Air conditioning and thrust in the event of engine failure

Either air conditioning or electrical services, but never both at the same time

Air conditioning and electrical services (on the ground) electrical and hydraulic back-up services (in the air)

Q6. With regard to a twin spool turbofan, an abortive start (hung start) will result in:

N2 speed stabilising at a higher than normal rpm and a subsequent decrease in EGT.

N2 speed stabilising at a lower than normal rpm and a subsequent decrease in EGT.

N2 speed stabilising at a lower than normal rpm and a subsequent increase in EGT.

N2 speed stabilising at a higher than normal rpm and a subsequent increase in EGT.

Q7. An abortive start (hung start) occurs when starting a gas turbine engine, the correct action is to:

select the other igniter system.

shut down the engine.

move the thrust lever forward to increase fuel flow.

activate both igniter systems.

Q8. An abortive (hung) start is the term used to describe an attempt to start in which the engine:

will not rotate.

commences initial rotation, but fails to receive any fuel.

lights up, but fails to accelerate sufficiently.

fails to light up.

Q9. An abortive (hung) start is the term used to describle an attempt to start in which the engine:

Will not rotate.

Commences initial rotation, but fails to receive any fuel.

Fails to light up.

Lights up, but fails to accelerate sufficiently.

Q10. A “hung start” is the failure of an engine to accelerate to its normal idle speed. It may be caused by:

failure of the fuel to ignite in the starting sequence after the engine has been accelerated to the required rpm by the starter

the starter cutting out early in the starting sequence before the engine has accelerated to the required rpm for ignition

an attempt to ignite the fuel before the engine has been accelerated sufficiently by the starter

compressor surging

Q11. A hung (abortive) start of a gas turbine engine may be caused by:

failure of the fuel to ignite in the starting sequence after the engine has been accelerated to the required rpm by the starter

compressor surging

the starter cutting out early in the starting sequence before the engine has accelerated to the required rpm for ignition

a too low pneumatic starter pressure

Q12. One of the advantages of multiple-spool jet engine designs is that:

engine length can be reduced.

if one spool seizes, the remaining spool(s) will continue to operate normally.

a smaller air starter driving only a single spool can be used.

a compressor stall cannot occur under any condition.

Q13. For a turbine engine, the term self-sustaining speed relates to the speed at which the engine :

is designed to idle after starting

will enable the generators to supply bus-bar voltage

will run without any external assistance

operates most efficiently in the cruise

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