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Thread: AFS Autopilot

  1. #1

    AFS Autopilot

    Hi. Two questions regarding the autopilot use:

    1. When in heading bug mode. I change the heading bug to call a new heading. Plane turns to the new heading, but will not roll out early enough so the plane ends up 2- - 30 deg off heading. Then, the autopilot hunts back. Is there a setting to adjust to reduce this error?

    2. When in altitude bug mode. The autopilot hold the altitude well. On two occasions over the past couple weeks, the plan starts a climb (once) or a decent (once) from the altitude selected by the bug. In both cases, the plane was tracking the altitude well, then just decides to begin a climb or decent. On one occasion, I noticed that the AP module display was showing a rolling set of lines. I disconnected and then reset the altitude. Is there something I should do in the case? Or a setting?

    Thanks

  2. #2
    1. When in heading bug mode. I change the heading bug to call a new heading. Plane turns to the new heading, but will not roll out early enough so the plane ends up 2- - 30 deg off heading. Then, the autopilot hunts back. Is there a setting to adjust to reduce this error?

    Lower the AP roll gain in the EFIS, you might also need to raise the LAT Activity in the AP. Try the Roll Gain first.


    2. When in altitude bug mode. The autopilot hold the altitude well. On two occasions over the past couple weeks, the plan starts a climb (once) or a decent (once) from the altitude selected by the bug. In both cases, the plane was tracking the altitude well, then just decides to begin a climb or decent. On one occasion, I noticed that the AP module display was showing a rolling set of lines. I disconnected and then reset the altitude. Is there something I should do in the case? Or a setting?

    The rolling lines on the AP head are telling you it needs trim. Sounds like you had it way out of trim and the servos did not have enough torque and started to slip.
    Rob Hickman
    Advanced Flight Systems Inc.

  3. #3

    Lost heading

    2. When in altitude bug mode. The autopilot hold the altitude well. On two occasions over the past couple weeks, the plan starts a climb (once) or a decent (once) from the altitude selected by the bug. In both cases, the plane was tracking the altitude well, then just decides to begin a climb or decent. On one occasion, I noticed that the AP module display was showing a rolling set of lines. I disconnected and then reset the altitude. Is there something I should do in the case? Or a setting?

    The rolling lines on the AP head are telling you it needs trim. Sounds like you had it way out of trim and the servos did not have enough torque and started to slip.[/QUOTE]

    Rob, I've had a similar situation but when following a heading and then the airplane will suddenly just veer off course. I'm not aware of any indication on the autopilot for the roll trim needing retriming. Times that I have checked the trim when it occurs, the trim seems to be pretty good. It gives no indication (that I'm aware of) that the autopilot has given up following the course and it continues to following the altitude just fine.

    1) Is there a roll trim required indication
    2) Is there any ability to notify when the roll servo has "given up".
    3) Shouldn't it try to recapture the assigned course?

    Thanks,
    Nick

  4. #4
    I have never had the Roll Servo slip in my RV-10, it should have lots of torque.

    I have never seen it veer off course , does it try and come back to the heading bug?

    If you press CHECK it will show you the current commanded ROLL and Vertical speed that the EFIS is sending to the AP.
    Rob Hickman
    Advanced Flight Systems Inc.

  5. #5
    It has happened on many occasions but not on every flight. On a recent two hour round trip, it didn't do it on the way down but did once on the way back. It might happen once in every two to three hours of flight time. No, it does not ever try to recapture the heading. I can't say for sure but I believe that it happens regardless of whether I'm in the AP or EFIS mode.

    Next time I'll try to remember to look at the commands. Has anyone else ever experienced this problem?
    Nick

  6. #6
    Not that I know of, you might talk to Lucas at Trutrak about it. Do you usually have it in Heading mode?
    Rob Hickman
    Advanced Flight Systems Inc.

  7. #7
    Quote Originally Posted by Rob Hickman View Post
    Not that I know of, you might talk to Lucas at Trutrak about it. Do you usually have it in Heading mode?
    I use it in both and I'm pretty sure that the problem happens in both AP and EFIS modes. The last time it was in EFIS mode.

  8. #8
    Call Lucas, this sounds like an AP problem.
    Rob Hickman
    Advanced Flight Systems Inc.

  9. #9
    First try a gyro set. With the aircraft stationary (not flying) hold the knob of the autopilot in for about 45 seconds. Let me know if the problem repeats.
    Lucas
    Trutrak Tech Support

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