FAA Powerplant Written Practice Test

When does the drive coupling of a turbine engine air starter stop turning?

1. During the starting phase

2. When engine shutdown occurs

3. Immediately after start-up

4. When the throttle is adjusted

The correct answer is: When engine shutdown occurs

The drive coupling of a turbine engine air starter stops turning when engine shutdown occurs because it is directly linked to the operation of the engine. During the starting process, the air starter engages and drives the engine to initiate its operation. Once the engine successfully starts and reaches its operational speed, the air starter is disengaged, but it can also stop when the engine is turned off or shut down. At this point, the engine is no longer producing power, and the need for the starter is eliminated, hence the drive coupling comes to a stop as the airflow ceases and the connection to the engine is cut. This association is critical for the efficient operation of the starter system, ensuring that the starter only drives the engine when it is required. The other options describe scenarios that do not align with this operational logic, as the drive coupling continues to function during the starting phase and does not immediately stop after start-up or when the throttle is adjusted.