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Advanced P3 Incident and Crash

Discussion in 'Phantom 3 Help' started by BudWalker, Jun 1, 2016.

  1. BudWalker

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  2. Droneflyer06

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    Hi Budwalker. I did post that .DAT file but ill go ahead and add it here in this new thread. I didn't have a video recording and i really appreciate all your help. Please let me know what you find.Dropbox - FLY065.DAT
     
  3. BudWalker

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    @Droneflyer06 you stated that "Drone tilted sideways and headed to the ground.". The .DAT shows that the P3 started descending from a height of 25M to 20M and then the .DAT file ends. Is it possible that it hit that structure between third base and home at a height of 20M and fell to the ground after that? Was the battery still seated when you recovered the P3?
     
  4. Droneflyer06

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    It went straight in the ground and the battery flew out it on impact! Didn't respond to any input


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  5. Droneflyer06

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    It sounded like three of the motors was at full rev. What are you seeing on the motors ?


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  6. BudWalker

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    I looked some more at this flight. Although there was a "compass error" at 9.4 it was not caused by a bad calibration or the AC coming near ferrous material. Although I had raised the possibility of a propulsion issue and the pilot stated that "sounded like three of the motors was at full rev " there were no propulsion issues evident in the .DAT data.

    The pilot stated that the AC went straight into the ground and that the battery came out on impact.. However, the .DAT ended at 12.063 secs showing a speed of 15 M/S and 20 Meters above the home point. This shows that the battery came out before the AC hit the ground. The descent rate was 6 M/S implying the AC impacted 2 or 3 secs after the battery came out.

    The interesting part of this flight is the incident at 8.8 secs. Leading up to this full elevator had been applied at 6 secs and then removed at 8 secs. The AC pitched up in response and just about slowed to 0 M/S when there was an acceleration spike along the Z axis at 8.8 secs.
    upload_2016-6-2_6-45-46.png
    The acceleration was -2 G spiked to -4 G then resumed at -2 G. This data was extracted at 200 HZ instead of the default 30 HZ. The spike is not a 1 sample spike; there were 14 samples in this interval. I.e., this is not some data glitch. Looking at the other two acceleration axes.
    upload_2016-6-2_6-56-30.png
    This implies that if the AC were hit with a projectile then it would've come from below and to the left of the AC.

    Following this event the AC finished braking at about the same time the data says the AC pitched down, rolled left, and yawed CCW. I compared the rate at which it pitched down to a flight I had where I was getting data about braking maneuvers just like this. In comparison this flight was more aggressive in it's pitching down. There doesn't seem to be any reason for the AC to roll left.

    The compass error came 9.4 secs with a switch to ATTI mode. Normally, the AC will just hover but in this case it flew backwards. The Yaw is always suspect when there is a compass error so the direction of travel from the Google Earth display and the thrustAngle was used to determine that the AC was flying backwards. thrustAngle is a diagnostic that uses motor speed data to determine the direction relative the AC.

    magYaw is a DatCon diagnostic that computes yaw independent of what the AC's flight controller thinks the yaw is. It's been used several times to explain the cause of a compass error. In these cases Yaw (from the FC) will become different from magYaw with one being correct and the other incorrect. In this flight Yaw and magYaw become different but both appear to be incorrect.
    upload_2016-6-2_7-58-30.png
    At 8.9 secs Yaw is 32 degrees, magYaw is 157 degrees, but the heading (from the direction of travel and thrustAngle above) is 116 degrees. Note that 9.4 secs the FC declared a compass error and switched to ATTI mode.
     
    #6 BudWalker, Jun 2, 2016
    Last edited: Jun 2, 2016
  7. Droneflyer06

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    Thanks for all the time out your taking to help me figure out what happen. So from all the data that you have gone through what conclusion have you come to?


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  8. Droneflyer06

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    I'm a bit confuse about the information that's it's showing about the battery


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  9. Eagle1

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    Hey Budwalker
    What software you used to translate all this info?
     
  10. BudWalker

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    The software I like to use can be found here. It converts the .DAT into a .csv and then I use the Excel plot capability to make the plots you see in my posts. You can also use Dashware to visualize the .csv. If you want to use Dashware that site has a page with the stuff you'll need to use Dashware.
     
  11. BudWalker

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    The battery info comes from the fact that the .DAT terminated abruptly with the AC still in midflight; i.e the cause being that the battery was disconnected. I didn't think about this earlier but a likely scenario was that the battery slid enough to disconnect but was still lodged in the battery compartment. Then it came out on impact.

    I'm not comfortable making any further conclusions beyond what I've posted. Are you sending it to DJI repair?
     
  12. Droneflyer06

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    That's what I'm planning on doing. The battery was full secured in the AC before it was airborne. Reason for my concern is that I didn't see it hit anything before hitting the ground. And it was still under power until impact. Just seem strange how that happen. I really do appreciate your time and effort in trying to figure out what went wrong with the AC. Still a mystery


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  13. Eagle1

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    Thanks Bud
     
  14. Eagle1

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    Good luck Droneflyer06
    Hopefully DJI deal with you right
     
  15. BudWalker

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    There was another flight that I looked at recently where the recording stopped 2 or 3 secs before impact. From that flight and yours I was starting to think that there may be a 2 or 3 second delay in the recording. I did an experiment with my P3 where I knocked the side of the P3 at 5 second intervals. Then after the last knock waited 4 secs and removed the battery. Not real precise measuring but it seems there is data up until the battery is removed. I.e., there is no 2 or 3 sec recording delay as I was speculating.

    Is it possible that it just appeared to be under power in those last 2 or 3 secs? It was descending at 6 M/S when the recording stopped and would've continued at that rate.
     
  16. Droneflyer06

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    I'm still wondering what could have cause it to lose control like that and not responding to any inputs from controller. I don't really know what to say about that time gap that is there between final data reading and impact. The AC must have some how power itself down, because the battery seem to have suffered damage as well to were it won't power the AC.
     
  17. Luap

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    Below is the flight payed back in Dashware. First part in real time, second part slowed down by 90%
    From what you said in POST15
    The click would probably be where the Chart accel X/Y/Zms2 spikes at Flight Time 8.70 seconds.
    The motors start Revving all the way up starting at Flight Time 10.30 seconds. Both Motors Left and Right Front rev up to 10000RPM right before logging stops. This is close to max RPM.

    A few things that I see. Right before the spikes in chart accel X/Y/Zms2 volts are around 15.20. Past the spikes volt goes down to 14.52 V. For a battery that indicates 96% left and only 10 seconds flight time this is unusually low.
    Amp draw is quite high. In hover its usually around 10A. Your short flight is around 20A. A strange reading is 10 seconds into flight Amp goes down to 1.52.
    Maybe a data error.

    My initial thought is there was a mechanical issue right from start of flight, maybe bad motor bearings, and it got worse at the accel X/Y/Zms2 spike.
    The spike also happens during motor braking.
    All the the error messages and motors revving up happen after that.
    The battery might have shut down due to volts going below 12-13v which is why logging does not record up to impact.

     
    BudWalker likes this.
  18. Droneflyer06

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    Thank you Luap for taking the timeout and reviewing the data


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