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.
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.
