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Unusual P3A Stability Problem Today

Discussion in 'Pro/Adv Discussion' started by Zzyzx, Apr 2, 2016.

  1. Zzyzx

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    Location:
    Beaverton, OR, USA
    Finally getting some good weather up in the Portland, Oregon area, yay.

    P3A, DJI Go Android 2.7.1, P3 firmware 1.7.60, RC firmware 1.5.80.

    I flew four batteries last weekend with no issues whatsoever.

    Today I took it out, did the usual pre-flight, and took off. I usually take off manually (P-GPS) and hover at about 5-10 feet just to check things out before heading out. It typically might move around an inch or two in any direction at first, but usually quickly establishes a steady hover and maintains position.

    Today, however, it did not. It went into a horizontal orbit. It maintained level facing the same direction, but moved in an approx. 2 foot circle around the home point.

    I took it up a little higher, about 15 feet or so, and gave it a little forward pitch. Rather than moving straight ahead, it moved ahead and a bit aggressively to the right. It was very difficult to control directionally with pitch and roll. The yaw seemed fine. If I tried to stop and hover, it either drifted a lot to the right or went into the same orbit pattern.

    Since I was in a clearing surrounded by trees I got a little spooked and landed right away, power cycled everything, and recalibrated the remote and the compass. Took off again with the same issues. It seemed have a great GPS lock and everything.

    I moved to a different location (a big open field about 0.5 miles away) just in case there were some buried power lines or something throwing the compass off. I recalibrated the RC and compass at the new location.

    At first it did the same thing at the new location. But after flying around slowly for a minute or two it stabilized and hovered in position. I flew around higher and further and it was mostly stable. A couple of times it veered off to the right again, but it didn't feel like the controller inputs were getting the same response as usual (especially pitch and roll) and when I landed it was not as positionally stable as usual for the last few feet down to the ground.

    Nothing has happened to the P3 since last weekend, it was just stored normally, not dropped or bumped around or anything. I keep it and transport it in the DJI hard shell case, and put the case on the back seat in the truck so it's not rattled around when transported.

    Any ideas how to best debug what's happening? I'm going to take it out again tomorrow morning to a different location, so if you have any tests or things I can try to figure out what's up, that would be most appreciated.
     
  2. Fat City

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    Try recalibrating the IMU - I suspect it could be the source of the symptoms you're seeing.
     
  3. Zzyzx

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    Hmm, I'm noticing something on the bench here at home...

    I have it sitting here with no props on. I start up the motors (CSC). When I apply forward pitch or left roll, I hear a different sound to the motors than when I apply back pitch or right roll. The right rear motor has a different sound, hard to describe but it's a bit raspier. The other three motors all sound the same and have that smooth whoosh sound to them. I could record an audio file if that would help anyone diagnose it.

    Maybe I have a motor going bad? Could that be causing stability issues?
     
    #3 Zzyzx, Apr 2, 2016
    Last edited: Apr 2, 2016
  4. Zzyzx

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    Thanks, that's one calibration I didn't do over. I'll try that tomorrow morning.
     
    No Lemon likes this.
  5. Zzyzx

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    Yes, the IMU calibration seems to have fixed the instability issues, thanks @Fat City ! No more orbit on hover, it's now locked on position with minimal normal drift, and no more drift to the right on forward pitch. I also calibrated the compass and RC again, and the gimbal just while I was at it. :)

    Maybe this is a bigger question, but how would the IMU calibration go off like that? I guess I assumed once it was set I'd have to replace components before it would become invalid?

    I still have that one right rear motor that sounds noticeably different than the other three, but it didn't seem to affect flying four full batteries on both Saturday and Sunday (nice weather in the Pacific Northwest US over the weekend -- it waited to rain until this morning).
     
  6. dexter82

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    Hi i have exactly your problem in same your conditions aircraft, but imu calibrating didn't help me however, i dont know what also try to fix
     
  7. The Springs

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    I have a P3S that is doing similar things. It hovered rock solid when I first got it but I flipped on landing once and now there is a whistle I think it is in one motor but it is hard to tell and is exaggerated with full up .Something just sound different I have calibrated the IMU twice because it will not stay steady now .In hover it climbs a bit moves to the left moves to the right descends all in a sort of square about 10"x10" I might put on the other set of props to see if that helps.It could be a bit of grit in the motor but I dont know what you can do about that.
     
  8. xbrute

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    Location:
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    Toilet bowl effect..


    Sent from my iPhone using PhantomPilots mobile app
     
  9. The Springs

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    Not a very comfortable shaped toilet then