Chapter 12: Starting System

Question 1

4 sub system that needs to be started almsot simultaneously to start engine

Answer 1

air, fuel, oil, ignition supply

Question 2

what are the soruces of supply to start engine

Answer 2

APU
GPU
other running engine

Question 3

what power is needed to start an engine

Answer 3

pneumatic, electric

Question 4

how long is the starting process?

Answer 4

10 seconds

Question 5

how does the starter motor help start the engine?

Answer 5

starter motor runs main gear box > rotates HP shaft

Question 5

what is the self-sustaining speed for twin spool engine?

Answer 5

40-50% N2 RPM

Question 6

what is a hung start?

Answer 6

engine not reaching self sustaining speed

Question 7

requirements of ignition system

Answer 7

1) igniting low temp lean fuel/air mixture which is at high speeds
2) in-flight relighting
3) prevent engine flameout
4) operate even when spark plug foul
5) safety (prevent electrocution)

Question 8

what is spark plug fouling?

Answer 8

foreign material accumulating at tip of igniter

Question 9

what are the pneumatic and electrical supply for?

Answer 9

pneumatic: spin starter motor

electrical: powering EEC and ignition units

Question 10

types of gas turbine engine starter

Answer 10

1) Air turbine starter (turbofan)
2) cartridge (fighter)
3) electric motor starter (turboshaft/prop)

Question 11

how does cartridge air starter work?

Answer 11

cartridge ignited by applying voltage > cartridge generate gas > rotation done by gas

Question 12

what is a starter control valve?

Answer 12

on/off valve allowing air supply to starter motor

manual overridden switch to open valve for troubleshooting

controlled by EEC

Question 13

components of ignition system

Answer 13

1) ignition unit
2) igniter plug
3) high tension leads
4) circuit breakers
5) air cooling tubes

Question 14

safety precautions when handling ignition problem

Answer 14

1) shut down engine and let it cool for 10 mins
2) pull all relevant circuit breakers
3) wear high temp resistant gloves
4) ground tension ignition leads

Question 15

common starting problems

Answer 15

1) low duct pressure
2) no rotation (no rpm)
3) start valve solenoid failure
4) no ignition/fuel flow/oil pressure
5) hung start
6) hot start

Question 16

what is a hung start?

Answer 16

engine accelerates to some intermediate RPM below self sustaining speed without increasing or decreasing

Question 17

reason for hung start

Answer 17

not enough energy or power to accelerate the engine

Question 18

troubleshooting hung start

Answer 18

engine shut down, restart from beginning after letting it cool down

Question 19

what is hot start?

Answer 19

when EGT goes above limit as a result of rich fuel/air ratio

Question 20

how can hot start be anticipated?

Answer 20

greater than normal initial fuel flow

Question 21

how to troubleshoot hot start?

Answer 21

dry motor till EGT is below 100degC and retry

Question 22

what is dry motoring?

Answer 22

starting engine without fuel