Definition
Devices that detect motion of the aircraft itself — specifically rotation rates and linear accelerations — without reference to anything outside the aircraft. In an Attitude and Heading Reference System (AHRS), inertial sensors typically consist of three rate gyros (or gyro equivalents such as MEMS or ring-laser units) measuring pitch, roll, and yaw rates, and three accelerometers measuring acceleration along the aircraft's longitudinal, lateral, and vertical axes.
Plain English
Small sensors built into the AHRS that feel how the aircraft is turning and how it is being pushed around. They sense the motion from inside the aircraft, without looking at the ground, the sky, or any signal from outside.
Context Anchor
Seen in discussions of attitude and heading reference systems, especially the equipment behind an electronic attitude display.
Derivation
From Latin 'inertia' meaning 'inactivity' or 'resistance to change in motion.' Inertial sensors work by detecting a body's resistance to changes in motion — that resistance is what the sensor measures and converts into rotation rates and accelerations.
Why Pilots Care
They supply continuous attitude and heading data to AHRS when GPS or magnetic references are unavailable or unreliable.
Analogy
They work a little like your inner ear: they do not look outside, but they can feel turning and acceleration. Unlike your inner ear, they are designed to feed that motion information to flight instruments in a measured way.
Intuition Check
Inertial sensors do not see the horizon or look outside the airplane. They measure motion and turning inside the aircraft, and the system uses that information to build the instrument display.
Example Sentence 1
The AHRS uses inertial sensors to continuously track the aircraft's pitch, roll, and yaw without needing input from outside the aircraft.
Example Sentence 2
If inertial sensors detect a sudden change in acceleration, the system updates the attitude display without waiting for external input.