What information does a tachometer provide for a reciprocating engine?

A tachometer is an instrument specifically designed to measure the rotational speed of an engine's crankshaft, which is typically displayed in revolutions per minute (RPM). In a reciprocating engine, the RPM indicates how fast the engine is running and is crucial for monitoring performance, determining power output, and preventing engine damage due to excessive speeds.

The tachometer allows pilots and operators to maintain the engine within its optimal RPM range for various flight conditions, ensuring efficient fuel consumption and preventing engine strain. By providing real-time feedback on the engine's RPM, the tachometer plays an essential role in flight safety and operational efficiency.