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All good things come to an end. Epic RTH Fail

Discussion in 'Pro/Adv Discussion' started by KeithS, Mar 27, 2016.

  1. KeithS

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    After many successful and trouble free flights today my good run come to a disastrous end.

    Just after 8am this morning I went down stairs for a quick fly to take advantage of the nice morning light.

    There wasn't a hint of wind and conditions were perfect.

    I flew out over my usual water way for just over 200m then came back to where I was standing to take a clip of a new park that was just finished in a building complex.

    My height was just under 60m, and clearance above the building I flew over was more than ample, not to mention the P3P was still in full sight. At 192m away and 57m up from my location and take off point I lost signal in an area I'd flown numerous times before without any issue what so ever.

    Return to home kicked in and soon after saw the Motor Obstructed Error on my screen I heard the death rattle of my bird hitting the concrete ground below.

    What confuses me is:

    1. I wasn't far from where signal was lost and my bird was still visible - very unusual as my signal strength is normally really good.
    2. When signal was lost and return to home kicked in the drone didnt rise to the preset of 140m.
    3. Instead the drone went from 57m ALT to 27m ALT and crashed into a building (just nipped the corner)

    Here's some info.

    Healthy Drones HealthyDrones.com - Innovative flight data analysis that matters

    Download KML with these notifications
    Flight time Altitude Home Distance Type Notification
    A 00m 00s 0 m 0 m Mode Mode changed to GPS_Atti
    B 00m 00s 0 m 0 m Tip Home Point Recorded
    C 00m 02s 0 m 0 m Mode Mode changed to AssitedTakeoff
    D 00m 02s 0 m 0 m Tip Return-to-Home Altitude:140M
    E 00m 03s 0 m 0 m Mode Mode changed to GPS_Atti
    F 03m 24s 57.6 m 262 m Data Loss Downlink data connection lost for 7.3 seconds
    G 03m 24s 57.6 m 262 m Mode Mode changed to GoHome
    H 03m 25s 58.1 m 262 m Warning Signal Lost. Aircraft is returning home.
    I 03m 36s 26.6 m 178 m Data Loss Downlink data connection lost for 10.5 seconds
    J 03m 36s 22.8 m 178 m Warning Motor Obstructed
     

    Attached Files:

    #1 KeithS, Mar 27, 2016
    Last edited: Mar 27, 2016
  2. NormanNormal

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    Wow so sorry to hear. Whay the heck happened? I hope someone can explain this. I feel like one of these days my luck will run out, too. No way this was operator error.
     
  3. mikeve

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    Sorry for your loss.

    Is the bird well enough to recover the DAT file. That would tell a more complete story.
     
  4. KeithS

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    I've got the Micro SD Card, and it's OK, there is a 1.41gb MP4 file but I can't play it. When I power on the P3P it just beeps. I'll try and connect it via usb tomorrow.

    Here's the end result.

    I'd like to think it wasn't pilot error, very unusual.
     

    Attached Files:

  5. DroneDestination

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  6. KeithS

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    Sadly I think I'll be needing a little more. But thanks for the tip. I'll be buying some decent tools so I can pull it apart and inspect for internal damage.
     
  7. Trackman1

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  8. Meta4

    Meta4 Moderator
    Staff Member

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    Failure to climb to RTH is a mystery but the rest of the story isn't.
    Signal was lost after flying behind a 20 storey building that was higher than the level the Phantom was flying at.
    If it lost some satellites, it was only after crashing with the 20 story building.
    [​IMG]
     
    hali_pilot likes this.
  9. NormanNormal

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    That was operator error but RTH altitude should have kicked in. In normal circumstances this situation would have easily been resolved. So strange.
     
  10. ferraript

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    without DAT log we can only speculate about what happened in those 10 seconds between 8:18:55.565 and 8:19:05.051
    but I have one possible explanation:
    I can see several throttle inputs from RC in your TXT log in that time 8:18:55.565 and in the 2-seconds period before this time (while Phantom was already returning home)
    maybe this interrupted the bird from ascending and it then started to fly directly to you (at this moment it was at 58.9 m height) and crashed directly into that building

    in the user manual, there is written:
    "Aircraft will stop ascending and immediately return to the Home Point if you move the throttle stick if the aircraft reaches 20 meters (65 feet) altitudes or beyond during Failsafe."
    that would confirm my explanation
     
  11. Dacon Productions

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    This is the reason I always (before fly) get familiar with the area to be flown and adjust RTH altitude accordingly. Never fly behind any thing that is not LOS.
     
    Squirrel! and snowghost like this.
  12. HVDV

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    I am concerned about the "Warning Motor Obstructed" since that indicates that either a prop is obstructed or the motor has seized up. That could cause a voltage drop causing the loss of transmission starting the RTH followed by the loss of height during the RTH
     
  13. ferraript

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    actually this is just the result of the crash into the building
     
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  14. KeithS

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    Thanks for all the contributions. All goes towards the learning process.
     
    NormanNormal likes this.
  15. NormanNormal

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    Wow looks like this is the explanantion. I had no idea this was the case. Yet another thing to watch out for.
     
  16. That Drone Guy

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    Really dumb question but did you check your settings in the DJI Go app after doing the last update? After I did the update, my RTH altitude was set back to the default value which is way too low.
     
  17. KeithS

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    Yep. I thought that myself too and was the first think i checked.
    If you see the log on my HealthyDrones link youll see RTH set to 140m. So that wasnt it.
     
    grottoli likes this.
  18. peterepeat69

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    Answer to this accident is make sure you fly much higher than any building if you were flying at say 100 feet higher your bird would be safe and sound.


    Sent from my iPhone using PhantomPilots mobile app
     
  19. fastsmiles

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    Sorry for your loss. It is easy to lose GPS when flying between buildings.
     
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  20. Meta4

    Meta4 Moderator
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    There's no indication that GPS issues had anything to do with crashing into the building.
    But the loss of signal when behind the building and RTH into the building is obvious.