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.
Plain English
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.
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.
Why Pilots Care
Allows pilots to monitor structural loads during maneuvers and remain within the aircraft's certified limits.
Intuition Check
An accelerometer does not simply measure speed. It measures a change in motion, such as the aircraft beginning to climb, descend, slow, speed up, or change direction.
Example Sentence 1
The instantaneous vertical speed indicator uses a small accelerometer to show a climb or descent the moment the pitch attitude changes.
Example Sentence 2
During aerobatic training the accelerometer recorded the peak forces reached in each maneuver.