Gas Turbne Starting

Question 1

Engine starting first step after start switch set to ON

Answer 1

Opens spar valves and activates starter motor turns the HP compressor

Question 2

After the HP compressor has started running what happens to the the PRSOV

Answer 2

HP shut off valve (PRSOV) opened allowing fuel to enter the combustor

Question 3

Start Sequence

Answer 3

Ignition On/Starter Motor On
HP fuel on/N2 compressor starts to spin
Light up occurs after HP shut off valve opened and fuel introduced
Starter motors continues until self sustaining RPM at 30%
Cut out starter motor
Stabilises at ground idle

Question 4

Dry start

Answer 4

Fuel fails to flow no light up/no EGT rise
Stagnating LOW rpm

Question 5

Hung Start

Answer 5

Low and stagnating RPM
Low fuel flow
High EGT

Too low pneumatic starter pressure before fuel supplied to sustain combustion - engine fails to accelerate

Engine lights but fails to accelerate

Can be a result of compressor stall or surge

Question 6

Hot Start

Answer 6

Rapid rise in EGT must be shut down asap
Continues to accelerate
Could be exceed fuel in combustor

Causes:
Early stare cut out
Fuel mis scheduling
Strong tailwinds
Very low rpm

Question 7

Wet Start

Answer 7

Engine fails to light up but RPM stabilise at low value while unburned fuel is sprayed into combustion chamber

Low/stable RPM
No EGT rise
Some indicated fuel flow

Run a dry run

Question 8

No rotation on start

Answer 8

Most likely failure of engine starting system

Question 9

No FADEC indications

Answer 9

FADEC failure = engine indications blank engines will run wont be controllable with thrust lever

Question 10

Multi Spool Start

Answer 10

N2 compressor starts rotating first

Question 11

Airborne Relighting

Answer 11

Altitude needs to be below 25,000ft and speed needs to be sufficient
Re light envelope

Question 12

Thrust Indications are

Answer 12

Engine pressure ratio
Speed of the fan (N1)
Torque

Question 13

Engine pressure ratio is

Answer 13

Jet pipe pressure to inlet pressure

Question 14

EPR is useful for

Answer 14

Indicating thrust

Question 15

What happens if P1 becomes blocked on EPR

Answer 15

Pressure may overread as inlet pressure will not be registering correctly

Question 16

How is power determines on turbo propeller engine

Answer 16

Torque

Question 17

Engine health parameters

Answer 17

Oil pressure/temp/quantity
Vibration
Fuel flow

Question 18

De Rating

Answer 18

Rated thrust of engine reduced
Via FMS CDU
Apply a lower maximum thrust limit on engine
Increases engine life

• cannot be overridden by thrust levers

Question 19

Flex thrust - assumed temperature method

Answer 19

Artificially inputting high ambient temp on FMS
Does allow max thrust if needed

Question 20

FADEC major functions

Answer 20

Automatic thrust rating control
Engine operation within safe limits
Fully automatic engine starting
Thrust reverser control
Engine over speed/EGT protection function
Engine monitoring and help for maintenance and troubleshooting

Question 21

FADEC power sources

Answer 21

Dedicated FADEC power sources from different bus bars

Question 22

Flat Rated

Answer 22

If OAT exceeds limit thrust is limited

This ensure guaranteed value of thrust up to a certain OAT

Question 23

DC trembler

Answer 23

Generates a higher voltage to the igniters via DC current to the transformer.