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Wandering Brittain


cferr59

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I have a Brittain Accuflite and Accutrak autopilot in my new to me Mooney.  The seller demonstrated using them and tracking the heading bug and VOR without issue (hands off).  However, when I try to use them, they seem to correct about 30 degrees after passing the heading bug, then command a turn in the opposite direction to 30 degrees after passing the heading bug, then continues to wander back and forth in this manner..  It seems like they need some kind of adjustment. Anyone ideas on where to star troubleshooting?

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Which AFCS panel do you have?  There should be a hi and lo switch for nav gain on an Accutrak.  There is another thread going on about hose leaks.  Might be helpful to know exactly which version you have.  Pictures help.  It could be as simple as the disable switch leaking or could require deeper troubleshooting.

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Here are the control panels.  I primarily tested with the Accuflite II ON attempting to use the heading bug and the others in OFF, but I did attempt a few other settings with similar results.  I'm planning on flying tomorrow and can try to get a few more detailed test profiles.

 

cm1.jpg

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To use the Accutrak you should also select the hi or lo with the nav switch. So both switches should be on.  The accuflite should turn on the heading.  I typically have the three switches on and the gain in high to track the GpS.  No wandering when set up right. I recently had the o ring in the yoke disable switch leak, and it wandered a lot.  If it worked on the demo flight and not now, it may be as simple as that.  The button can be removed from the yoke.  Some folks do that to disable the pC.  I stopped doing that because it is what caused the problem I describe.  Start the testing while the airplane is already on a radial.  VOr centered  and heading bug aligned.  Should be steady.  Also, do you have a GPS?  There may be a switch to select between nav aids.

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Thanks, I will try a more thorough test tomorrow and try to get some video.  I have mainly be testing the Accuflite with my (potentially uninformed) opinion of how it should work.   I think a few test profiles with video will be more expository.  I have an IFD440 with GPS/NAV and a KX-155 for secondary NAV.

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Work it one step at a time for the test.  May help to have a safety pilot as its easy to get into a heads down mode.  You are not all that far away, in Mooney miles, if you continue to have problems and want a second opinion.  A working Brittain is a really good autopilot.  

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Ok, I did a bit of testing today.  I think my issue yesterday stemmed from attempting to use the Accuflite without turning on the AccuTrak.  If you do that, it will not correct until it hit 30 degrees on either side of the heading.  I need to take a longer cross country with it to confirm that it is 100% fine, but it turns out that this might just have been user error...

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