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Strange behavior during sub-zero temperature flight

Discussion in 'Standard/4k Discussion' started by P.Lindblom, Nov 22, 2015.

  1. P.Lindblom

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    During a flight earlier today I got a bit worried when my P3S started behaving weirdly. Before the flight I calibrated the compass, as always, and I took off where I've taken off many times before. The temperature was -6°C (21,2°F) and there was pretty much no wind.

    Here's a one minute video of what happened.



    The first odd thing I noticed was that the drone didn't really go straight. It started to turn slightly by itself and at the same time the gimbal started to tilt. Suddenly the DJI GO lady told me the flight mode was changed to Atti. Looking at the log, though, the drone was in contact with at least 10 satellites during most of the flight and it was only in Atti mode for one second. I decided to turn back and on the way back I thought the drone started to dive. I was slightly less worried when I saw that the altitude didn't change. For some reason the gimbal had tilted down, so I brought the camera back up again and it tilted itself left and right. I finally reached my landing zone, so I pointed the camera down and started the descent. Before landing I flew around for a while at an altitude of 3m to check for any odd behavior, but nothing else happened that was out of the ordinary.

    Here's the flight log: HealthyDrones.com - Innovative flight data analysis that matters

    Any ideas what could have caused this?
     
  2. Mario_SB

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    It sounds like you may have experienced a compass error. You may have had good GPS but I believe the compass works independent of that. I believe the wobbly flight occurs when the compass and GPS aren't "in sync". You may have experienced some kind interference or a bad compass calibration.
     
  3. Meta4

    Meta4 Moderator
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    You haven't given many details to work with and it's not clear exactly what problem you are concerned about but if your Phantom isn't flying straight, the obvious suspect is your compass.
    When someone says Before the flight I calibrated the compass, as always, I am always suspicious of the potential for a bad compass calibration.
    If you have a good compass calibration why introduce the possibility of a bad calibration with unnecessary recalibration?
     
    dirkclod likes this.
  4. P.Lindblom

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    Well, there were three things that concerned me. I mentioned them all in my first post.
    1. A few minutes into flight the Phantom stopped flying straight and started to turn slightly by itself.
    2. The gimbal started moving around, tilting up and down, side to side.
    3. The flight mode was changed to Atti for one second. I suppose that could be unrelated, but since it hasn't happened to me before and it did this time I thought I'd mention it as well.
    The main reason is because it says I should do so in the manual. I usually don't do it if my previous successful flight was in the same location, but my last flight before this one was in another country.

    The turning because of a bad compass calibration makes sense, but could the compass also make the gimbal go haywire and change the flight mode to Atti?
     
  5. Mario_SB

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    No. In my opinion you most likely experienced a compass error in which the Phantom experienced a lot of instability in flight which then affected the stability and performance of your gimble. I've have experienced this twice already and I have seen how unstable the Phantom looks in the air when the compass goes haywire.