Harmon Technologies, Inc.

Tachometer

The tachometer displays the speed of the engine (and propeller) in revolutions per minute.  Typically, the RPM as between 2400 and 2600 RPM except when very low power settings are used.  The pilot looks at this gauge when setting the propeller pitch to properly load the engine.  Once set, the propeller governor will automatically vary the pitch to maintain the same RPM.  This changing of the pitch is very much like changing gears in a car with a standard transmission.  Higher RPM settings (like low gear) are used during climbs while lower settings (high gear) are used when cruising.  After the initial full-power take-off, a setting of 2,500 is normally used for climbs and 2,400 is commonly used for cruise.

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