Tuesday, January 31, 2006

My home made NASA autopilot

This is a little note about keeping your building in perspective towards the object of actually getting in the air.

Way back in '82 when I first got my Q-2 kit I was thinking about all the neat things I could do with my plane. Mind you, it didn't look like a plane yet, just a bunch of parts, foam, glass, and bottles.

I went to a forum at Oshkosh given by a sharp NASA guy (I think his name was Don Hewlett) and he was demonstrating how to build an auto pilot using a stream of air blown across a couple of thermistors. The first year I saw him, he used a tiny motor to drive a tiny fan. In later years he used an audio speaker mounted in an empty beer can. The pulse of the oscillating speaker was to produce a puff of air across the thermistors. As the plane shifted position, the air stream would be deflected and one thermistor would be cooler than the other one. This differential would be used to drive the autopilot circuit. I thought this was very cool. He even passed out his plans.

I had a retired Bell Phone Labs engineer willing to help and he carefully milled the housing for the fan and the tiny fan blade. I bet he spent 20 hours on it. I bought all the other components and etched the circuit board.

Meanwhile, my plane was sitting in the garage not going anywhere. I was spending all this time on the autopilot project and wasn't actually building anything.

Fortunately, I somehow realized that spending time on an autopilot was getting me absolutely nowhere towards me getting in the air. I didn't have my priorities on straight.

Now, as I go into my 20th year of flying my Q-200, all of those autopilot parts are still in a box in the hangar. Maybe I can make it work someday - maybe not. But I do know that once I got my priorities straight I started making real progress.

And that is why we urge people to follow the plans, at least as closely as possible. Get it in the air first, then add the autopilot, tip tanks, canard flaps, winglets, retractable gear, or pulse detonation engine in your spare time.