M15.13 Start and Ignition Flashcards
How are gas turbine engines started?
By rotating the high pressure compressor
When does the starter stop assisting with the engine?
When the engine reaches a self sustaining speed
The torque supplied by the starter must be what?
In the excess of the torque required to overcome compressor inertia and friction loads of compressor
What would happen if the starter was turned off before the engine reached idle speeds?
Fail to reach self acceleration
Cause deceleration
What is a cartridge starter?
A small impulse type turbine drive by a high velocity gases from a burning cartridge
What is the most commonly used starter in commercial jet engines?
Air Starting
When does the sprag clutch assembly engage?
Automatically as soon as the rotor starts to turn but disengages as soon as the drive coupling turns more rapidly than the rotor side
Two subassemblies of pressure regulating valves?
Pressure regulating valve
Pressure regulating valve control
The regulating valve assembly consists of a valve housing containing what type of valve?
Butterfly- Type valve
Two types of electric starter systems?
Direct cranking electrical systems
Starter generator systems
The direct cranking electric starter is usually what type of current?
Direct current (DC)
Direct cranking electric systems are moused mostly on what engines?
Small turbine engines such as APU and small turbo shaft engines
What is a starter generator starting system?
Also like direct cranking electrical systems except that after functioning as a starter, they switch to a generator after the engine has reached a self sustaining speed
Positives of starter generators?
More economical since one unit functions both starter and generator
Total weight of units are reduced
Fewer parts required
How many volts and ampereres are usually required of the starter generator to start?
24 volts
1500 amperes
A starter generators internal circuit has what four windlings?
A series field (C field)
A shunt field
A compensating field
An inter pole or commutating windling
To start an engine equipped with an undercurrent relay, what is first necessary?
Close the engine master switch
In a starter generator, when the battery and start switch is turned on what relays close?
Motor relay
Ignition relay
Battery cut out relay
When would continuous ignition be used?
If there is a possibility of engine flame out
What is an example of when to use continuous ignition?
Abnormal and emergency situations such as hailstorm or volcanic clouds
How is the complete exciter sealed?
Hermetically sealed
In a capacitor type system how is the voltage stepped up?
Transformer units
What is a typical annular gap igniter plug also known as?
Long reach igniter
Why does a long reach igniter project into the combustion chamber liner?
To produce a more effective spark
How does a constrained gap plug work?
Operates at cooler temperatures
Possible as spark does not remain close to the plug, arcs beyond the face of the combustion chamber limer
How long should you wait after shutdown before removing components on the high voltage components?
Wait at least 20 minutes
How can you test or check the igniter?
Listening for a clicking noise as the engine begins to turn, driven by the starter
Removing it and activating the start cycle to see a visible spark across igniter
Starting system Safety precautions?
Observe engine intake and exhaust hazard zones when carrying out tests
Use correct hand gloves when handling hot psrts
To perform igniter maintenance what should occur?
Standard procedure calls for disconnection of the igniter lead coupling nuts at the exciter end first
What types of tools should be used when dealing with the ignition system?
Insulated tools
When starting an engine which rotor starts rotating first?
The high pressure compressor
Air pressure required to start an engine?
30-50 Psi
