Definition
An instrument that senses and measures acceleration along a single straight-line axis. In aircraft inertial systems, three linear accelerometers are mounted at right angles to one another to detect acceleration in all directions, and their outputs are integrated over time to produce velocity and position information.
Plain English
A sensor that measures how quickly the aircraft is speeding up or slowing down in one specific direction. Combine three of them (one for each direction) and you can track every change in motion.
Context Anchor
Seen in aircraft instrument, navigation, autopilot, and flight data systems that need to sense motion.
Derivation
Linear means 'along a straight line' (from Latin linea, a line). Accelerometer combines accelerate with the suffix -meter, meaning 'measuring device.' So the name describes exactly what it does: it measures acceleration along a straight line, as opposed to rotational acceleration, which is measured by a different device (a gyroscope or rotational accelerometer).
Why Pilots Care
Linear accelerometers are the heart of inertial navigation. If they drift or fail, the system's computed position and velocity will drift with them — which is why modern systems cross-check accelerometer data against GPS and other references.
Analogy
It is like a very sensitive motion sensor that can feel a push in one direction and report how strong that push is.
Grounding Statement
If the aircraft surges forward during takeoff, a forward-facing linear accelerometer can sense that forward acceleration.
Intuition Check
Linear does not mean “simple” here. It means the acceleration is measured along one straight axis, not as a turning or rotating motion.
Example Sentence 1
The inertial reference unit uses three linear accelerometers, one for each axis, to track the aircraft's motion through space.
Example Sentence 2
Three linear accelerometers mounted at right angles supply the acceleration data needed for dead-reckoning navigation.