FAA Powerplant Written Practice Test

What is the primary purpose of the tachometer on an axial-compressor turbine engine?

1. Measure fuel flow

2. Monitor speed during starting

3. Check oil pressure

4. Indicate temperature variances

The correct answer is: Monitor speed during starting

The primary purpose of the tachometer on an axial-compressor turbine engine is to monitor the rotational speed of the engine's components, particularly the compressor and turbine sections. During the starting process, it is crucial to keep track of the engine speed to ensure that the engine is spooling up correctly and reaching the desired operational limits. Monitoring the tachometer allows operators to verify that the engine is starting properly and can help identify any issues early in the start sequence. A tachometer's readings are vital for ensuring the engine does not exceed its limits during start-up, as excessive speeds can lead to engine failures or damage. Thus, the tachometer plays a critical role in the safe operation of the engine by providing real-time feedback on speed during the crucial starting phase.