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Crashed doing Waypoint in Litchi, battery drained but never got warning

Discussion in 'Pro/Adv Discussion' started by Digdat0, Apr 21, 2016.

  1. Digdat0

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    So today i was out flying the P3P, doing some Waypoint missions in Litchi by the local sporting stadium. I ended up running out of battery and the bird fell to the ground from 269 feet while going 30.4mph. Smashed one of the arms, smashed the battery, broke the gimbal vibration absorption board, two props down and two motors damaged. Luckily, the gimbal and camera survived which is nice. Looks like i need to replace the shell, the absorption board and two motors to get her flying again.
    • Litchi on Android (Litchi_3.2.1)
    • Android 6.0.1 (just updated yesterday) on Nexus 7
    • DJI Go 2.7.2
    • Firmware 1.08 (updated 2 days ago)
    Litchi stopped properly reading the battery properly at 2m 47.9s into the flight. It kept telling me that i had 86% left and was at 15.276V. I should have caught this as a red flag and landed and swapped batteries, but i didn't. As a result, the app wasn't properly telling me how much battery or time left, and i wasn't paying attention and it ran out. About the 21 min mark i hear "BEEP BEEP BEEP BEEP" and then NO SIGNAL pops up on the screen and the video is completely dead. I had to find the last known GPS spot to hunt it down and found it in grass, looks like it may have hit a metal fence.

    In the logs, i can see that Auto Landing kicked in at the 21m 21.3s mark. Since I was flying a way point, I think the default fail safe is to auto land and thats what it tried to do. Few weird things here:
    1. Why didn't it alert me about battery low level at 30%, which is how DJI Go is set? I thought Litchi did this?
    2. Why didn't RTH kick in at that point? Thats the behaviour in DJI Go, i assumed Litchi would use this.
    3. Why did the app wait for it to be critically low and then initiate the autoland? Why not do it earlier based on available battery left? Logs show nothing about battery warnings otherwise.
    4. Why didn't it land safely? Shouldn't auto land kick-in, with enough battery to be able to land? It dropped from 269 feet to the ground, it did not autoland . In the video I have, the power cuts clean while video was going like i turned it off, doesn't show the fall or crash at all. I think this is when i heard the BEEP BEEP BEEP and it stopped recording.
    5. Why significant increase in speed and altitude at the very end? Once it hits the auto land it slows down to 0-2 mph (from 17mph), then at the end suddenly increases in altitude and speed (speed goes from 0 to 30mph).
    Anyone else have issues with Litchi reporting wrong battery time?

    I also have the detailed Litchi log, but cannot attach for some reason.

    Pics below:

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    #1 Digdat0, Apr 21, 2016
    Last edited: Apr 25, 2016
  2. sacooke

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    I am sorry for your misfortune. I have no help to offer unfortunately but having read so many of these unfortunate crashes, those that can help and will make their way here shortly, are going to ask you to post your flight logs so they can pick it apart. Maybe you can do that while you wait....good luck.
     
    Royr1957 likes this.
  3. Avocet

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    Thanks for the photos. I'll bet posting them was difficult - so thank you again. A cursory look indicates that perhaps it struck multiple items at some point. The battery damage seems like it would have had to of happened after it separated from the bird body???

    Also, I'm wondering about the cause of the wound to the metallic motor housing. Grass? doubtful; a prop at high RPMs? I suppose ... From 300 feet, forces begin to mount exponentially ... Think about what is salvageable and ponder a rebuild? It can be wonderfully satisfying (emotionally and financially) to bring her back to life again. It could also be more prudent to keep her for parts sales and move into another unit. :) Thanks again for your generous postings.
     
  4. Phantom751874

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    Did you take off with 100% battery?

    If not then that's probably why.
     
  5. Phantom751874

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    Sorry didn't see you noted "at the 21 minute mark". So that was probably a full battery then at the beginning. 21+ minutes is a bit longer than what I have come to expect from a Phantom 3. I usually see 18-19 minutes or so.
     
  6. Digdat0

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    yeah it was fully charged, logs show 95% at takeoff. I assume below 100% from the imu warmup.
     
  7. Digdat0

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    The only thing near/above where I found the drone is a metal fence and a tree. I hypothesize that it hit the metal fence and then Landed in the grass. It's a black metal spikey fence, so it could explain the damage to both the shell and battery. One hits the cross post while the other hit a upright post. But at that point, there was no juice left so no specific record of it. I dunno, but I'm gonna try and rebuild it. All the electronics still work fine, except the two motors, so I'm hopeful of a rebuild.
     
  8. shockwave199

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    Which flight? You mention you were flying 'missions', which implies more than one. Which mission did this problem happen? Were you flying only one battery for multiple missions?

    You're vague on the details about your flights and so it's hard to say, only, no one should ever program a single mission that puts the bird out for that long, warnings be damned. A low battery warning may have failed, but you should have had your own bells going off in your head to bring it back in long about the 14 minute mark. Have you checked what your low battery and critical battery percentage settings are in the dji app? For starters, confirm low battery is at least at 25-30% and critical is at the normal 10%.
     
  9. alokbhargava

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    We used to hear last year about sudden crashes of P3s due to battery failures and finally it was concluded that starting a flight with partial charged batteries could result into such sudden crashes. This case also looks very similar. OP will know if there were many flights on the same battery and the last one was with not fully charged.
     
    peterepeat69 likes this.
  10. peterepeat69

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    As a rule I take the bird home at 40% battery, it's all about risk management.


    Sent from my iPad using PhantomPilots mobile app
     
    Lifted Chevy and n6vmo like this.
  11. movius

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    Gosh, you guys are brave. Longest flight I've had is 12 minutes and I'm watching the battery indicators and fly time remaining like a hawk.

    Sent from my SHIELD Tablet K1 using Tapatalk
     
    Peio64270 likes this.
  12. Mark The Droner

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    1. If you lose your telemetry, your app will continue to report the last known telemetry. So you'll be getting bad reports, but it will be apparent since the telemetry isn't changing.

    2. Not sure. It could be that Litchi does not RTH but instead hovers when it sees a low battery and awaits your command. I am not positive on this.

    3. The app does not do anything. It's your aircraft that's doing what it's programmed to do. If I'm correct on #2 above, then it would auto-land at critical battery.

    4. If your cells aren't balanced, your battery can shut off mid flight when the battery is at a critical low.

    5. Yeah this is a puzzle. I will guess you had a motor or prop failure. The aircraft rises and falls rapidly the last 15 secs while accelerating. So a motor/prop failure would account for the drop combined with the acceleration in speed. Just guessing.

    Sorry for your loss.
     
  13. BigAl07

    BigAl07 Moderator
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    I'd say the mission was a bit excessive and something happened during the AutoLand aspect. Looks painful and I bet it sucked big time. Sorry for the damage but hopefully it's an easy and successful rebuild.
     
  14. alokbhargava

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    It appears that during the last few moments your bird's legs got entangled into fence when it was still flying. To overcome/ correct the situation, internal controls raised the speed/ power to make it follow desired path. That's what logs showed.

    Anytime bird is hovering and you try to pull it down with holding legs, you will notice, blades try to run faster at that moment.
     
    Squirrel!, fred_lefevre and BigAl07 like this.
  15. BigAl07

    BigAl07 Moderator
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    Yes definitely something happened to cause the aircraft to "attempt" to climb out (possibly damaged by that point) yet it was still descending for whatever reason. See where the "speed" increased while the altitude decreased. Something bad happened which we may never know for sure.
     
  16. BudWalker

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    I'm not sure I understand. The speed in the plot is A/C speed and isn't related to power. I.e. it isn't motor speed. This plot doesn't show that the A/C was caught and trying to power it's way free.

    If the speed(MPH) data in the plot comes from horizontal and vertical speeds then the plot doesn't say much. The sudden drop in altitude starting at 4:29:56 would cause an increase in speed. But, the slope of that descent looks straight and the speed, while increasing, varies. I think there's more to the story here.

    If the speed(MPH) data in the plot comes from just horizontal speed then this very unusual. In normal flight horizontal speed is controlled by elevator and aileron inputs. Altitude is controlled by throttle. In the last 10 seconds or so the pilot would've had to do some sophisticated, coordinated stick inputs to achieve the results shown in the plot. As that seems unlikely there must be some other explanation.

    @Digdat0 would it be possible to get the .DAT for this flight? To see how to retrieve the .DAT go here. It'll be large so you'll have to Dropbox or GoogleDrive it.
     
  17. Digdat0

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    I might as well show some of the pics i took while filming (mission pics below as well):

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    I've a new rule, i stop watch flights in case the app doesn't show battery levels properly. At 15 mins, we head home.

    I was flying 3 separate missions one after another, no landings between. The first was circling local stadium (.7m, 3 min), the second was circling the block (1.4m, 6min) and the third was re-running the first one with tweaked camera angles. I did brief 'ad-hoc' flying after mission 1 and 2 and also the small distance to fly over there.

    These were the missions from Litchi (i crashed at position #17 in the 'Autzen Circle' mission the second time I ran it.

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    Except, i was at 270 feet up when this happened. The fence is about 10 feet up :) I'm starting to think that i had my thumbs on the controls and i made it go up/forward in my panic to get signal back. The crash/landing spot was about 10-20 feet from spot #17 on my first mission, so I'm thinking it was my thumbs here as the mission was not intended to fly that close to the stadium.

    I'll see if i can get it later today or tomorrow, may not have time to get this as work is crazy.

    I appreciate the inputs!
     
    #17 Digdat0, Apr 22, 2016
    Last edited: Apr 25, 2016
    BigAl07 likes this.
  18. BigAl07

    BigAl07 Moderator
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    Well said. Spoken like a true professional.

    I would have thought the Lit Ap would have given several warnings but that's a huge assumption because I have yet to give it a try.
     
  19. BudWalker

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    Lemme amend my request for the .DAT. Sounds like you've pretty much figured out what happened. The .DAT probably won't add much and it's a hassle to retrieve and post. But, if you're curious I'll be glad to look at it.
     
  20. alokbhargava

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    It becomes difficult to analyze in absence of logs.