Piper Altimac IIIC issues

cowman

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I went from having no autopilot in my old Archer to now having an old Altimac IIIC in my Lance, this is pretty huge improvement to me but after living with it for a year there are a few quirks... really major ones if I think about it.

The only mode that really works for roll/hdg is heading bug mode. It works fine, other than constantly adjusting for the precessing DG and changing wind conditions. Nav mode doesn't appear to track the GPS course at all(GNS530W). Whenever I've engaged it, it just banks left and turns for a while then banks right like it's hunting. I haven't really tried it with a VOR, I don't normally track those. I did try flying an ILS with it a couple of times under VFR conditions. Once to my surprise it caught the localizer and glideslope and flew the approach perfectly, requiring me only to click off the AP at the decision point and land the airplane. The second time I tried it, it just turned. Not tracking at all. I wouldn't attempt to use this in actual the way it is now.

Then there's the altitude hold. It kind of works, sometimes it works perfectly. However, most of the time when I engage it, it climbs 50-100 and levels off/holds there. Often it will creep up over time but that may just be due to changing barometric pressure along the route, not totally sure. I often get frustrated with it and just turn it off.

Less critical but still annoying is how badly it handles even light turbulence- it tends to over-correct and make the bumps worse for passengers. I usually just turn it off after a few lurches and hand fly until things get smoother.

From my casual research, replacing this system with something newer is probably a $15-20k or more project which I have a hard time justifying. How much can an avionics shop realistically do with this old AP? I could live with the limitations but I would like it to at least hold altitude properly and it would be really nice if it would track the GPS.

I also have a related issue with the DG- on very cold days it just spins for maybe 30-40min until it warms up. Effectively when this is going on I don't have an AP. I've thought about ditching the vacuum unit for something digital but as I understand it, most of those like the Garmin G5 won't drive this old autopilot.
 
Don’t know that system but generally if people have ancient ones that even can be fixed, the big autopilot place in Oklahoma seems the best bet for them from most stories.
 
I have a IIIC in my Aztec and it's a very nice match for my airplane. Might not pass the Cirrus/Garmin/STEC demands of today, but it's still a great autopilot. Mine does drift a wee bit on the altitude hold initially (down 50 ft), but that doesn't bother me enough to put it in the shop just to fix that one thing.

As Nate said above I would get hold of Ralph Stahle at Autopilot Central in Tulsa. imo, the IIIC is a good enough autopilot to be worth repairing, and they know what they are doing, so you aren't paying for someone to learn on your system.
 
From my casual research, replacing this system with something newer is probably a $15-20k or more project
Isn't the TruTrak STC'd for the PA32R? Isn't it like half that money installed?
 
My friend has the AutoControl III (Century IIb) in his Arrow. Basically the same, without the altitude hold. Any way, he has it coupled to his G5s and they provide reasonable GPSS response together now. The key is to use heading to get on your course, then switch to OMNI or NAV.
 
If you're serious about getting the Altimatic IIIc fixed or worked on at all, call Autopilots Central. They are extremely knowledgeable about legacy autopilots, and have helped me out twice with the Altimatic IIIc. Often times certain things can be adjusted, but others they need repaired. They can walk you through it. On one occasion, they diagnosed one of my problems, had me remove the component and ship it to them to fix. On the other occasion, it turned out to be loose electrical connectors (common problem apparently). If you are looking to replace, I believe you have a few different digital options these days, depending on what you want to pay.
 
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