Do you remember the infamous Link Trainers?
I restored one, for my CAP squadron, back in my college days. WWII model, type was, I believe, C4 rather than the wartime AN-T-18.
Absolutely fascinating devices. Basically an analog computer...in vacuum. Roll and pitch used vacuum bellows, yaw had a huge vacuum motor up front with a big belt going to a pulley at the balance point. Small vacuum tank stored attitude (at half the rate of real life), and a separate vacuum manifold "stored" the airspeed. The vacuum in the airspeed manifold held a valve forward. If the vacuum got too low, the pendulum would drop, breaking the vacuum and applying vacuum to one side or the other of the yaw motor to make you spin.
One negative: They didn't fly like an actual airplane. Roll too far, and the bellows wouldn't have enough effect to bring you upright...you had to dive to increase speed, and roll level using a rocker underneath the fuselage. Maybe ours was just old, and we didn't have enough RTV on the bellows. But I've heard the same story from others. You learned NOT to use ailerons in turns, just rudder. Often, photos showing Link Trainers in actual operation (as opposed to posed shots) have the strap installed on the left side that locked it in roll. Didn't really need it for instrument training.
Came with a wheel, like a transport, and an optional stick, like a fighter. The stick gave horrible leverage. Wheel worked better.
It flew in other weird ways, too, but didn't realize what was going on until I re-read "Stick and Rudder." Langewiesche describes how non-fliers THINK airplanes work. And that's exactly how the early Links operate. Remember, it was originally designed as a carnival ride.
The Link itself used early electronics, but not for the fundamental flying. Fans, lights, remote-reading instruments for the instructor's table as well as the "bug" that drew the lines on maps.
I've told this story before, but it's a good one. I have one unique record.
Was working on the Link late one evening. Popped the think into a left spin. While it whirled around, I started smelling smoke. Popped the side-opening canopy a bit, and as the Link whirled around, I saw smoke coming from the electrical box in the base. Shoved the wheel forward, and kicked the right rudder pedal.
The rudder cable popped off the pedal. No way to stop the spin. So I fully threw open the canopy. stood in the door, and dived out when a clear spot of floor appeared.
I'm the only person ever to successfully bail out of a burning Link Trainer in an unrecoverable spin.
Ron Wanttaja