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TruTrak Autopilot issue

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I have the TruTrak autopilot shown in the attachment and have a problem. It wanders 10 degrees either direction. It's installed in an experimental Maule, but a friend told me that this old unit used to be quite popular in the RV community and that maybe someone here would have an idea.

You can see the problem clearly in a video I made here: https://youtu.be/b-ds_jEp5LM?t=83

Any help would be greatly appreciated. Maybe it's just a bad unit, but thought it was worth asking.
 

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Download the instructions, go back to square 1, re align everything from scratch.

When you turn it on, always allow it to erect itself when you are absolutely still on the ground.

This was sage advice from Andrew at whoever Trutrak are now and worked for us.
 
Download the instructions, go back to square 1, re align everything from scratch.

When you turn it on, always allow it to erect itself when you are absolutely still on the ground.

This was sage advice from Andrew at whoever Trutrak are now and worked for us.

I didn't do the installation on this, so probably good advise in any case to verify that everything was done correctly. I'll give it a try. Thanks for the tips.
 
I’ll second the comment to not move the airplane until you see it finish its boot-up cycle - you’ll know that when it says “autopilot Off” (at least on our TT’s - not absolutely sure what you’ll see, but it takes about 30 seconds). If you power it up while you’re moving, it’ll never settle down….
 
The advice given here is great!
1. Check control/autopilot system for lost motion.
2. Don’t move until boot is complete.
3. Make sure you have a good GPS signal to the AP for best performance.
4. Look at AP settings (the advice to start again from base settings and adjust one thing at a time is perfect).
5. As always, shoot me an email…while I may not be the fastest to respond, I do try to help everyone that has a TruTrak make it fly as it should! :)
 
The advice given here is great!
1. Check control/autopilot system for lost motion.
2. Don’t move until boot is complete.
3. Make sure you have a good GPS signal to the AP for best performance.
4. Look at AP settings (the advice to start again from base settings and adjust one thing at a time is perfect).
5. As always, shoot me an email…while I may not be the fastest to respond, I do try to help everyone that has a TruTrak make it fly as it should! :)

1: I don't know what that means.
2: Wilco
3: No GPS. Heading only on this one.
4: Wilco
5: Thanks!
 
1: I don't know what that means.
2: Wilco
3: No GPS. Heading only on this one.
4: Wilco
5: Thanks!

1. Check for any free play between autopilot servo and ailerons/elevator. This includes prior suggestion that maybe the shear screw is sheared.
3. Andrew: my recollection, maybe faulty, was that ‘heading’ was actually gps track?? If so I don’t know what happens with no gps.
OP: mid-continent instruments now provides service, although this unit is pretty old, I’m not sure.
 
If not using a GPS input I would try real hard to arrange one - it is only 1 wire.
If not available read the instructions on how to align the internal sensor, it may never work that well depending on the interference from other systems in the aircraft, and may be worse of some headings than others.
 
again, the responses here are perfect.

on the GPS front, agreed that you really should have one (even a handheld is just fine).
 
again, the responses here are perfect.

on the GPS front, agreed that you really should have one (even a handheld is just fine).

My AFS TruTrak Digiflight works very, very well…precise and reliable…but I have to turn the AP master on after start-up and best not move the airplane until the AP tells me it’s got satellites.

Question for Andrew…the perennial question is whether or not modern avionics can be on when the plane is started or when the main Master is turned off. I my AP is on the avionics Master, but also has its own power switch. What’s the verdict on the TruTrak Digiflight II? Should it be off at start-up and shutdown, or does is it surge and voltage-drop protected enough to matter?
 
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lol, I think there are lots of opinions on this one...but...

I will say that modern avionics (TruTrak products included) have robust power supplies and shouldn't have any issues with potential spikes during engine start.

I also still have a master switch and basically all of my stuff is off at startup anyway. The voltage is going to drop enough that most everything will reset, so I just leave it off until after the fan is turning.

As far as the autopilot goes, you are fine either way.

Also, to be noted...most of the time when I answer a question here it is because the amazing ROY THOMA has let me know there is a question. If any of you meet up with him, buy him a drink. He's just simply the best!
 
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Thank you. Having kind of a “legacy” autopilot that, for me, works great and does everything I want it to…I appreciate your presence here and ready willingness to share. I’d buy both you AND Roy a beer anytime.
 
1: I don't know what that means.
2: Wilco
3: No GPS. Heading only on this one.
4: Wilco
5: Thanks!

I have a similar TT unit to yours, and if no gps is connected, it only flies by the bank angle you dial in, from zero to 30 degrees left or right.
 
Got back in the air over the weekend after an extended time walking. Flew from San Diego to Chicago. Lots of time to re-test the autopilot. Without the manual all I could really do is make sure that the thing was completely booted up before moving the plane. Despite doing this, it was still wandering quite a bit, so I don't think that's the solution.

However, in 10 or so hours of flying, I did have some legs where it worked just fine. Including the longest leg of almost three hours where it flew nicely almost the entire time.

Very strange.
 
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