AAD meaning in Electronics ?

In skydiving, an automatic activation device (AAD) is an electronic-pyrotechnic or mechanical device that automatically opens the main or reserve parachute container at a preset altitude or after a preset time.

AADs are typically used to open the reserve parachute container at a preset altitude if the descent rate exceeds a preset activation speed. This indicates that the user has not opened their parachute, or that the parachute is malfunctioning and is not slowing the descent rate sufficiently.

The older style mechanical AADs are falling out of fashion in favour of newer style electronic-pyrotechnic models. These newer models have been proven more reliable as their built-in computers allow for better estimation of altitude and vertical speed. Electronic AADs typically employ a small pyrotechnic charge to sever the reserve container closing loop, allowing the spring-loaded reserve pilot chute to deploy.