Dan Thomas
Touchdown! Greaser!
- Joined
- Jun 16, 2008
- Messages
- 12,389
- Display Name
- Dan Thomas
In the flight school our first simulator was an older electromechanical Frasca. It was naturally unstable and would wander off heading and attitude if you took your eyes off the panel for more than a couple of seconds. Great scan trainer. It used a bunch of motors and a confusing array of mechanical linkages and wheels.Ah, analog. Always reminds me of the original Link Trainer...an analog computer, using vacuum as the computational media.
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View attachment 140458
Ron Wanttaja
The next two sims were digital, but they used potentiometers for the flight and engine control inputs. Potentiometers are a really troublesome doodad, as their carbon tracks get worn and make carbon dust that gets under the runner and causes sudden and severe resistance excursions, leading to loss of control. I had to regularly replace those pots. Potentiometers caused throttle runaway problems in the earlier throttle-by-wire cars, too. My 2006 Hyundai has a custom-made dual throttle potentiometer, and the computer looks for agreement between them. If one starts acting up, the car goes into a low-power limp mode. Mine acted up and I paid $300 for a new one and installed it. Opened the old one and discovered that I could have simply cleaned it with a bit of isopropyl alcohol.
When we bought the new and expensive Redbird sim, it still had pots in it. I asked their engineers why they hadn't used or created induction or Hall-effect sensors for the inputs so as to eliminate the frustrating potentiometer failures. They had no good answer to that one.



