Altimeter

The altimeter is a barometric flight instrument that measures static pressure to indicate the aircraft's height above a selected datum. The subscale must be set correctly to ensure accurate height readings, as changes in atmospheric temperature and pressure affect its accuracy. A blocked static source will cause the altimeter to read a constant height regardless of actual climbs or descents.

Key Points

• •Setting a <strong>QNH higher than actual</strong> causes the altimeter to <strong>overread</strong> the aircraft's true height.
• •A blocked static source causes the altimeter to read a constant height regardless of actual climbs or descents.
• •Used to determine pressure height, elevation, and altitude depending on the subscale setting selected.
• •Temperature and pressure variations affect altimeter accuracy — the instrument assumes a standard atmosphere.

Related Terms