PHAK Glossary

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Alternating current.

Absolute accuracy

The ability to determine present position in space independently, and is most often used by pilots.

Absolute altitude

The actual distance between an aircraft and the terrain over which it is flying.

Absolute pressure

Pressure measured from the reference of zero pressure, or a vacuum.


Force involved in overcoming inertia, and which may be defined as a change in velocity per unit of time.

Acceleration error

A magnetic compass error apparent when the aircraft accelerates while flying on an easterly or westerly heading, causing the compass card to rotate toward North.