Plain English Meaning

A device that senses how quickly the aircraft is speeding up, slowing down, or changing direction. Where a regular VSI waits for pressure to change before showing a climb or descent, an accelerometer feels the movement straight away.

Full Definition

An instrument that measures the rate of change of velocity, typically expressed as a g-load (multiples of the acceleration due to gravity). In aircraft, it senses changes in speed or direction and is used inside other instruments, such as the inertial reference system or certain vertical speed indicators, to detect motion almost instantly.

Context Anchor

Seen in discussions of vertical speed indicators, especially designs that reduce the normal delay before a climb or descent is shown.

Derivation

From Latin accelerare, 'to hasten,' combined with the Greek metron, 'measure.' Literally a 'hastening-measurer' — a device that measures changes in speed.