Arduplane 3.9 flyaway with bad compass

Has anybody had the experience with a fly-away on v3.9, when there is a compass problem?  I tried RTL and my plane flew in the wrong direction, even with a good GPS lock, and I was unable to recover because it went out of range of my transmitter before I could switch to manual.   Plane GONE!  Have no idea where it went.   Shouldn't EKF realize the plane was going the wrong way and drop the compass?  I thought that was the entire point of EKF.   Bad inputs are ignored.   It should be pretty obvious if the plane is GOING AWAY from the home position and make an adjustment to it's flight path  and ignore the compass.  Any ideas?  Unfortunately, I don't have a log - plane is probably sitting in a field somewhere when the battery died.  

P. Duffy

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  • You could test your theory by temporarily shutting off GPS during flight. With the EKF in Arduplane, it is unlikely you will notice much change in course if flying straight, so long as your compass is working reasonably well. Same is true with degraded GPS. Unless you are carefully comparing actual flight with planned flight, the difference is hard to spot for some time. One exception would be if you did not have a working airspeed sensor (or alternative speed sensor). Anyway lots of fun testing failure modes before they actually occur so you know how to recognize when they do occur.

    If you loaded a saved mission prior to flight, you might have over written HOME.Think about where HOME might have been in a saved mission an plot a course from launch to HOME to narrow your search pattern.

  • I'm pretty sure it had GPS lock at arm, but who knows?  I'm having to wait to do the grid search until I have time.  It's more about solving the mystery at this point, rather than just recovering the model.  My other theory is that the weather caused the GPS to lose position, it was foggy and it did take longer that usual to obtain a lock, and the GPS module I was using was a cheap one I got on amazon, so perhaps it just lost it's position.

    Andreas Gazis said:

    It sounds very odd that it would fly to a false home since home is set to the arming location by default unless you had done some fairly surreal changes to the params. The only other way I can think of that this might have happened is if you armed before proper GPS lock had been established.

    Arduplane 3.9 flyaway with bad compass
    Has anybody had the experience with a fly-away on v3.9, when there is a compass problem?  I tried RTL and my plane flew in the wrong direction, even…
  • It sounds very odd that it would fly to a false home since home is set to the arming location by default unless you had done some fairly surreal changes to the params. The only other way I can think of that this might have happened is if you armed before proper GPS lock had been established.

  • Hello Ronald,

        I can't say it flew straight away, but it did switch to RTL, as I could see the flight mode change on the display.  Another possible theory is that the home position was incorrect and it flew to a false home.  I'm going to try another grid search this weekend to see if I can find it. I would like to recover the model, just to find out what happened.  

    Ronald Pandolfi said:

    Hi Patrick,

    We have experienced (too many) GPS glitches and compass failures, and none have caused straight and level fly away. Only times we have experienced straight and level fly away was with RC failure. Depending on the type of RC transceiver on board, you might have experienced a failure that was not detected as such by the Flight Controller. This could be caused by a failure of the hardware, or some type of on board interference. The most severe problem occurs when an RC transceiver fails in such a manner that the Flight Controller does not perceive the failure. Unfortunately such a problem is more likely to occur with more advanced RC transceivers with more complex fail safe settings. Under such circumstances, the Flight Controller continues to "believe" it is getting valid signals from the RC transceiver. Even if you trip another FC failsafe or GeoFence, the FC continues to "believe" it is getting "guidance."  

    Ron

    Arduplane 3.9 flyaway with bad compass
    Has anybody had the experience with a fly-away on v3.9, when there is a compass problem?  I tried RTL and my plane flew in the wrong direction, even…
  • Hi Patrick,

    We have experienced (too many) GPS glitches and compass failures, and none have caused straight and level fly away. Only times we have experienced straight and level fly away was with RC failure. Depending on the type of RC transceiver on board, you might have experienced a failure that was not detected as such by the Flight Controller. This could be caused by a failure of the hardware, or some type of on board interference. The most severe problem occurs when an RC transceiver fails in such a manner that the Flight Controller does not perceive the failure. Unfortunately such a problem is more likely to occur with more advanced RC transceivers with more complex fail safe settings. Under such circumstances, the Flight Controller continues to "believe" it is getting valid signals from the RC transceiver. Even if you trip another FC failsafe or GeoFence, the FC continues to "believe" it is getting "guidance."  

    Ron

  • Chris,

    FBWA worked perfectly.  I think the GPS glitched.  But I may never know.

    Chris Anderson said:

    Probably not the compass. Did you try any other auto mode before the RTL, such as fly by wire or stabilize? 

    Arduplane 3.9 flyaway with bad compass
    Has anybody had the experience with a fly-away on v3.9, when there is a compass problem?  I tried RTL and my plane flew in the wrong direction, even…
  • Hey Darrell,

       Yes, I've used aerial photos before to recover a lost model.  Unfortunately, I don't know exactly which direction it was flying, I couldn't see the ground through the video, it was foggy and I lost vision.   I did a survey in one direction, but I need to try more I suppose.  Not sure it's worth the effort, it's only a $300 model.  The time to recover it will be more than it's worth.



    Darrell Burkey said:

    Sorry that this happened. I know what a sick feeling it is to watch all your hard work go totally out of control. 

    If you were flying with a ground station then there will be TLogs available that might help in finding out what went wrong and where it is. Also, if you can calculate even a general idea of where the plane went I have seen several planes recovered by doing a mapping type grid flight over the area and then inspecting the photos. If you know anyone who knows how to do that it really is worth a try.

    Arduplane 3.9 flyaway with bad compass
    Has anybody had the experience with a fly-away on v3.9, when there is a compass problem?  I tried RTL and my plane flew in the wrong direction, even…
  • Andreas, I left the defaults alone with the compass so I don't think compass-learn was enabled.  I'll certainly do so in the future.   I had one fly-away years ago, but that was when Arduplane was first released.   It's possible there was a GPS glitch that caused it, as I don't exactly know what went wrong.  On my larger planes, I have telemetry, but this model didn't, but I had OCR on video.  Unfortunately, I wasn't recording.   

    Its' possible I lost GPS lock, as it was very foggy, and it took a while to acquire the satellites on the ground.  In truth, I shouldn't have been flying in the fog, I was a little over confident!  I had not tested RTL yet.   

  • Sorry that this happened. I know what a sick feeling it is to watch all your hard work go totally out of control. 

    If you were flying with a ground station then there will be TLogs available that might help in finding out what went wrong and where it is. Also, if you can calculate even a general idea of where the plane went I have seen several planes recovered by doing a mapping type grid flight over the area and then inspecting the photos. If you know anyone who knows how to do that it really is worth a try.

  • Do you have a telemetry log? I agree with Chris, sounds rather odd. I routinely ignore compass whining in planes but have COMPASS_LEARN switched on. In many of my flights, the compass is pointing totally wrong when on the ground, then I take off, switch to RTL, leave it for a few circles and the compass points correctly. I have never had even the slightest hint of a plane not heading where it should (yet).

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