What does a tachometer measure in an aircraft?

• A. Fuel quantity in the tanks
• B. Engine's RPM (Revolutions Per Minute)
• C. Aircraft's heading
• D. Pressure of the air-fuel mixture

Answer: (B)

A tachometer measures the engine's RPM (Revolutions Per Minute) in an aircraft. This instrument provides essential information about the engine's performance, indicating how fast the engine is running. Since the performance and efficiency of the engine are critical for flight operations, knowing the RPM helps pilots manage engine power and ensure safe operation.

For instance, a properly functioning tachometer allows pilots to monitor engine speed during takeoff, climb, cruise, and landing phases, aiding in adjusting the throttle effectively. While options such as fuel quantity, aircraft heading, and air-fuel mixture pressure are also important aspects of aircraft operation, they are measured by different instruments and are not the function of a tachometer. Understanding the role of each instrument contributes to a pilot’s ability to operate the aircraft safely and efficiently.