What does the Tachometer (RPM) Indicator signify?

• A. Engine temperature
• B. Fuel levels
• C. Engine compressor rotor RPM in percent
• D. Oil pressure

Answer: (C)

The correct choice provides insight into the specific function of the tachometer within aviation machinery. A tachometer (RPM) indicator specifically measures the rotational speed of the engine compressor rotor in terms of percentage of its maximum RPM. This measurement is crucial for monitoring engine performance and ensuring that the engine operates within safe limits during various phases of flight.

Understanding this metric is essential for pilots and maintenance personnel, as it allows for the monitoring of engine health and performance, ensuring that the engine is functioning optimally and not exceeding its design limits. While engine temperature, fuel levels, and oil pressure are also critical aspects of engine operation, they are monitored by separate indicators and gauges and do not relate directly to the tachometer's specific role.