FAA Powerplant Written Practice Test

In a gas turbine engine, when does the starter stop cranking?

1. When the ignition is engaged

2. After self-accelerating speed is reached

3. Immediately after engine shutdown

4. When the fuel flow is initiated

The correct answer is: After self-accelerating speed is reached

In a gas turbine engine, the starter stops cranking after the engine reaches self-accelerating speed. This self-accelerating speed is the point at which the engine can maintain combustion on its own without the assistance of the starter. It is critical for the starter to engage the engine sufficiently to allow it to reach this speed. Once the engine is self-sustaining, the power of the combustion process takes over, and there is no need for the starter to continue running. Continuing beyond this point could potentially lead to unnecessary wear or damage to the starter. After reaching self-accelerating speed, the various processes in the engine – including centrifugal forces and the energy being generated from combustion – take control, allowing the engine to operate independently. Understanding this transition is vital for proper engine operation and maintenance practices.