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Professional Compass Error Crash

Discussion in 'Phantom 3 Help' started by TomP3P, May 24, 2016.

  1. TomP3P

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    Hi,

    I've just experienced an issue with the compass, this has happened twice over the past 3 days in two separate locations. Each time the P3P has turned to its side, and flown straight into the ground.

    I've done the compass calibration prior to flying and no errors were reported prior to take off. It also had good strong GPS signal with 17-20 satellites on the second crash.

    If anyone could give some guidance on what might have caused this, the first crash was an open field. The second crash was above my house, where I've flown multiple times before without issue. It happened twice on this second crash, once it was mid air and managed to recover - the second time it was closer to the ground and happened to quick for me to do anything.

    First Crash:
    HealthyDrones.com - Innovative flight data analysis that matters
    Phantom Log Viewer - PhantomHelp.com

    Second Crash:
    HealthyDrones.com - Innovative flight data analysis that matters
    Phantom Log Viewer - PhantomHelp.com

    Any info from the logs is appreciated, and if you can offer guidance on getting it fixed that would be great.

    Thanks
     
  2. msinger

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    Please attach your DAT flight logs here too. If needed, you can find instructions for locating that file here.
     
  3. TomP3P

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    The file was too large to attach here so I've uploaded it to Dropbox:

    Dropbox - FLY151.zip

    Thanks
     
  4. Meta4

    Meta4 Moderator
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    Both flight records show plenty of Speed Error notifications and in the first, the only compass error shows after it has crashed.
    Usually this is bad news regarding a problem in the propulsion system ... maybe an ESC.
    I'd recommend going straight to DJI over this one.
    I've just seen DJI replace someone's lost Phantom where the flight record was full of speed errors.
     
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  5. msinger

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  6. BudWalker

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    Looking now.
     
  7. BudWalker

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    I'm looking at FLY151.DAT that corresponds to the second flight. There is something very odd about the height data in this flight; it's saying the flight ended approx 50 meters higher than the beginning. Ignoring that, for now, I looked at other data to see what happened.

    The COMPASS_ERROR_LARGE and SPEED_ERROR_LARGE indications occurred after the P3 hit the ground and aren't relevant to the cause of the incident. Looking at accelerometer and roll data
    upload_2016-5-25_6-25-7.png
    At time 672.7 the P3 rolled from +3.5 to -25.0. At the same time there was acceleration spike. I think this when the pilot saw the abrupt roll and impact with the ground. The data at 674 shows the P3 tipping over and bouncing while the props are hitting the ground.

    As for the cause I looked at control inputs, roll and yaw
    upload_2016-5-25_6-44-15.png
    At 671.4 full left rudder was applied until 672.1. In response the P3 rotated from a 81 degree heading to a -26 degrees heading. Yaw data isn't shown. I'll speculate that the increase in roll was in response to a right crosswind. At 672.1 the full left rudder was removed and replaced with full throttle. Then the acceleration spike came shortly thereafter at 672.7.

    I wasn't there and didn't see it firsthand, but it looks to me like the P3 was rotated into a crosswind close to the ground and then rolled (to compensate for the crosswind) just enough to catch a prop.

    @TomP3P I appreciate that you've taken the time to post this data. Every time I look at an incident I learn a little more about the P3. I'm hoping that others share this view.
     

    Attached Files:

  8. TomP3P

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    Thanks for taking the time to look at this.

    There wasn't any concerning wind that I could feel, the healthydrones log shows 5-6mph winds towards the end of the flight. The acceleration at 672.7 was more than likely my response to the phantom swapping to atti mode after the compass error message, at this stage it was already on its side. It happened so quickly and out of nowhere that I don't think I had any real control/effect at this stage.

    What is the best method for liaising with DJI on this? Email?

    Thanks
     
  9. TomP3P

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    Sorry I've just re-read this line, and I am 100% confident that the compass error showed on my iPhone DJI Go App and I was alerted that it switched to Atti mode before the crash. I heard the error, looked at the phone, looked back at the drone ant it was shooting down like a meteor.
     
  10. BudWalker

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    IMHO, the acceleration spike at 672.7 is too narrow to have been caused by any control input. It takes time for motor speeds to change. If it were caused by pilot input it would be "smoothed out" some.

    When you say shooting down like a meteor, what height did you see it roll over and start down. There still is the unresolved issue of the flight data saying the last known altitude was 50 meters above the Home Point. Was the battery still seated in the battery compartment?
     

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  11. TomP3P

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    I would estimate it was at around 10-12 meters in the air and yes the battery was still seated - my partner confirmed it was slightly out, by around 1cm but still powering the phantom. I lost the camera feed, as the cable got damaged.
     
    #11 TomP3P, May 25, 2016
    Last edited: May 25, 2016
  12. BudWalker

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    Well, this theory isn't that compelling. How about another theory that's also not compelling, only in a different way. Then we can vote:)

    The battery being out by 1 cm is a lot. Is it possible that the battery became disconnected and then reconnected when the P3 hit the ground. This would explain the recording stopping at 50 meters. It doesn't explain the incident at the end of the recording.

    Is there a FLY152.DAT, probably with the same date-time stamp as FLY151.DAT. Either that or 675 seconds after the FLY151.DAT date-time stamp.
     
  13. BudWalker

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    @TomP3P no need to get the other .DAT. I took a closer look and think there is some kind of ESC issue. I don't remember if you sent it to DJI for repair. If not you should. Definitely don't fly it.

    I do think that the battery came loose and that's why the recording stops 50 meters above the Home Point. That's a separate issue though.

    Instead of the default 30 Hz sampling rate 200 Hz was used. There is another incident at time 389 just like the one at the end of the recording. Here is the accelerometer data for that incident.
    upload_2016-5-25_16-59-47.png
    And here is the motor data for the left front.The other three motors look the same.
    upload_2016-5-25_17-0-47.png
    The excursions are motor commanded, not motor speed. I don't understand the relationship between the motor commanded and the acceleration spike. You'd expect there to be a relationship between the motor speed and the acceleration spike. But, this pattern is the same for the other motors and all 4 motors in the incident at the end of the flight. I suspect there is an ESC issue that causes the acceleration spike.

    Note that motor load goes to 0 during most of the incident. @Luap observed this in one motor in another flight we looked at and we were speculating this could be due to a bad solder joint or a loose connection in the circuit supplying current to the motor. After that flight the conditioned worsened to the point where the P3 would attempt a motorStart and then shutdown with an ESC error. That P3 was repaired under warranty.

    Both of these incidents were followed with a compass error. This one had a .5 second switch to ATTI. Maybe the last incident would've had the switch to ATTI if the recording hadn't stopped.
     
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  14. TomP3P

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    Thank you @BudWalker, I appreciate you taking the time to review the data.

    I have sent a submission in to DJI. I will look if there was a second DAT file when I get home tonight.
     
  15. Droneflyer06

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    Hi, I'm hoping somebody can help me. My drone had taken off, then went crazy and flew sideways straight in the ground. Not sure what could have caused it to happen. Any help appreciated


    Sent from my iPhone using PhantomPilots mobile app
     
  16. msinger

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    Droneflyer06, it would be best to start a new thread, explain the scenario in great detail, and attach your TXT and DAT flight logs.
     
  17. Droneflyer06

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    Thanks msinger. I'm new on here and not sure how everything works on here. I did everything as I always do before flying. I have a DJI phantom 3 professional. Was getting 14 satellites and showed that it was safe to fly. Took off and at about 78ft I heard a click and the and the motors sounded like they were revved all the way up. Drone tilted sideways and headed to the ground. I tried to to control it and nothing! It all happened in 12 seconds. From take off to crash


    Sent from my iPhone using PhantomPilots mobile app
     
  18. Droneflyer06

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    Here is my flight record.
     

    Attached Files:

  19. Meta4

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  20. BudWalker

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    The best guess is that there was some propulsion issue. But the certainty is very weak. Without more data from the .DAT it's difficult to be more certain.

    I used @ferraript 's .txt converter to get this plot
    upload_2016-5-31_6-46-30.png
    At 8.8 secs the AC pitched up, rolled left, and yawed CCW.

    With no other cause apparent we're left a propulsion issue being the cause. If one of the motors stopped or there was broken prop you'd expect to see the AC spin. If there was a momentary motor issue you'd expect to see the AC recover instead of flying into the ground.

    Yawing like this is always suspect when coincident with compass problems. I.e., the yawing data may not be correct. But, those compass problems didn't start until .5 secs later.
    upload_2016-5-31_6-55-13.png
    I.e., the compass problems were a result and not a cause. Having the .DAT would help to figure this out.