If you’ve ever seen the cockpit of an airplane, you’ve probably noticed the round ball that shows your attitude, and if you are like us, you’ve wondered exactly how the Attitude Direction Indicator (ADI) works. Well, [msylvain59] is tearing one apart in the video below, so you can satisfy your curiosity in less than 30 minutes.

Like most things on an airplane, it is built solidly and compactly. With the lid open, it reminded us of a tiny CRT oscilloscope, except the CRT is really the ball display. It also has gears, which is something we don’t expect to see in a scope.

Getting to the ball mechanism was fairly difficult. It is nearly the end of the video before the ball comes apart, revealing a pair of hefty but tiny autosyn units and a clockwork full of gears. Bendix equipment often used the autosyn to transmit positions over wire similar to a selsyn but using AC instead of DC.

Next time you peek into a cockpit, you’ll know what’s driving that eyeball or, at least, what might be driving it since not every one of these is identical, of course.

These cool devices show up in our feed every so often. If you can cram a CPU, a screen, and an accelerometer into a Lego, you could build one for your next block model.