Tachometer

A tachometer is an instrument that measures the rotational speed of the engine crankshaft (on piston aircraft) in revolutions per minute (RPM). On fixed-pitch propeller aircraft, it is the primary engine power instrument. On constant-speed propeller aircraft, it indicates the propeller RPM set by the governor.

Tachometer and Engine Management

On fixed-pitch aircraft: higher throttle = higher RPM = more power. Monitor tachometer against redline (maximum RPM) during run-up and take-off. On constant-speed aircraft: the propeller governor automatically maintains selected RPM; the tachometer confirms the governor is functioning and that RPM is within limits.

Related Terms

See also: Manifold Pressure Gauge, BHP.