10 Questions
During a normal engine start cycle, at what approximate rotational speed does the engine reach self-sustaining operation?
30% of maximum RPM
What is the purpose of the blowout cycle during an unsuccessful start attempt?
To prevent potential damage by allowing unburnt fuel to drain or evaporate
What is the typical duty cycle (maximum operating time) of an air turbine starter motor in modern turbofan engines?
3-5 minutes
If the engine fails to start within the starter motor's duty cycle, what action is typically taken?
The fuel and ignition are switched off, but the starter motor continues to run
During engine start, which two key instruments should be closely monitored?
Exhaust Gas Temperature (EGT) gauge and High-Pressure (HP) compressor rotational speed gauge
What is the initial event that occurs during a normal engine start cycle?
The ignition system is activated, and the igniters begin to glow
What event causes the second rise in Exhaust Gas Temperature (EGT) during a normal start cycle?
The Fuel Control Unit progressively increasing fuel flow
What is the purpose of the automatic cancellation of the starter motor and igniters during a normal start cycle?
To allow for a smooth transition to idle RPM
Which component is responsible for regulating fuel flow during the engine start cycle?
The Fuel Control Unit
What is the purpose of the starter motor during the engine start cycle?
To rotate the compressor until the engine reaches self-sustaining speed
Learn about the electric starter motor and sprag clutch in gas turbine engines. Understand how the sprag clutch disengages at idle speed to prevent damage to the starter motor. Explore its use in smaller jets and helicopters.
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