Ancient Autopilot

Chrisgoesflying

Chrisgoesflying

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Chrisgoesflying
Apparently, the Comanche I recently bought has an ancient autopilot on board that is still functional. I haven't tested it out yet myself but the broker said it works and he even used it when he ferried the plane for me. To turn it on, apparently all I have to do is push in the knob that is at the bottom of the panel (near the cabin heat, cabin air, etc. knobs). Apparently, the direction is being controlled by the directional gyro (see photo). But, how exactly does that work?

Before takeoff, I align the pictured directional gyro with the compass and runway numbers. I then take off, get into cruise and then what? If I just push the autopilot knob in, will it simply hold that heading? How do I change heading?

I don't think I'll need the autopilot and as I'm upgrading the panel little by little, I'll probably replace the directional gyro and AI with two AV-30s. But, until then, I have a (claimed to be) functional "autopilot" on board so I might as well learn how to use it?

Screen Shot 2023-06-23 at 3.44.44 PM.png
 
I thought maybe you meant a very old First Officer… my bad.

Ya, I have a similar sort of thing on an old Chris Craft cruiser, it’s pretty handy. Really, just experiment with it. It may just hold a heading… old and simple May also mean intuitive.
 
I think it holds heading on 360, so you get stabilized the direction you’re wanting to go, set the DG to 360, and engage the autopilot. Heading changes are made by establishing the appropriate amount of heading “error” so it turns back to 360.

edit: this isn’t the one I’ve flown…the “turn trim” knob didn’t exist on the one I flew, so it’s probably not what I indicated.
 
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Don’t use it until you’ve studied the manual and understand how it works, settings, how it can fail and what to do when it does.
 
Before buying AV30s, I suggest doing a lot of research. We have three airplanes equipped with AV30s and have had numerous problems with the heading indicator functions. So much, that we do not allow them for instrument training. I think there is a software fix coming, but so far they are a huge disappointment.
 
I don't know about a software update, they just released in April, but the external magnetometer has been approved for TC'd aircraft. Buy one of those for your heading indicator.
 
Gilbert Buettner said:
numerous problems with the heading indicator functions
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What about the attitude indicator? Does that work fine? I could also do one AV-30 and one G5. I just really want one AV-30 in there as it can control the Tailbeacon X once I install it when diversified ads-b becomes mandatory in Canada.
 
Chrisgoesflying said:
I just really want one AV-30 in there as it can control the Tailbeacon X once I install it when diversified ads-b becomes mandatory in Canada.
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You might be able to do it with an AV-20. The TailbeaconX install manual mentions that but the AV-20 install manual does not (yet?).
 
They work fine as AI, I've installed a few as back-ups with Aspens. Not sure you're upgrade plans, but 2 G5's require a separate turn rate. You could put the AV-30 there to control the tailbeaconX.
 
I had a Comanche with that autopilot. It would only hold heading of North. Had to set dg to 0 and it would hold that. Make sure your compass is accurate as you will need to reset the dg later when finished using the auto pilot and making turns.
 
Yeah, there are still a few of these vacuum-powered autopilots out there. They were made by Brittain, Tactair and others. I enjoyed mine as kind of a novelty, but when the gyros failed I couldn't get them repaired and had to rip it out. Those 'AN' style DGs and AIs are literally WWII surplus.
 
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