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My P3P crashed, DJI not cooperating

Discussion in 'Pro/Adv Discussion' started by Chris_P, Jun 11, 2016.

  1. Chris_P

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    Hello everyone,
    I've been reading and learning on this forum since I purchased my P3P in November 2015. I hoped to never have to post this message but here I go ....

    I put about 50 flights on my bird, all of them went perfectly. Ive read and followed all the suggestions shared on this forum and I fly very carefully. I read many posts about RTH crashes and I set my RTH altitude to 50M to avoid issues in this area.

    3 weeks ago, I was up north on my friends boat filming some ariel shots. i was riding in the boat with the P3P flying above us. We started in one area and drove approximately 1.5 km. As we moved along, I periodically updated my RTH location. We turned around within this bay and I was bringing her in for landing, usually I have her hover and I grab the landing gear while shutting the motors down. As I brought her in, she was about 40 from me at an altitude of appox 15 feet. Suddenly, the drone just flew off at full speed away from me, crossed the bay and smashed into a rock before falling into the water. The camera was smashed right off the bottom and three props broken. Luckily my friend and his family were standing near that rock and recovered it within seconds of it falling in the water. It was fully submerged for a few seconds however.

    I was totally perplexed as to what happened as I totally lost control and had no user input when it took off and crashed. I reviewed the logs on my iPad and then it was clear what happened. Apparently, my RTH location wasn't updated properly and my battery was at the point where I just had enough power to return to the perceived incorrect RTH location (1km away). Evidently this triggered an auto RTH sequence that took control away from me, flying the drone into the rock which stood between my location and the RTH point.

    The other crazy part is I had previously set my RTH altitude to 50M. This didn't happen.... when the auto RTH started, it just flew off at the same landing altitude without rising to 50M as I had initially programmed.

    I went through the whole DJI warranty procedure, they took over 2 weeks to review my flight logs and eventually said, they would like to assist me by offering me 15% off a new P3P !!!! I responded saying that it was a malfunction in their software that caused the crash and they just responded yesterday saying they will offer 20% off a new P3P and thats their final offer. They didn't explain what their 2 week investigation revealed or what their position was regarding the reason for the crash. I find this totally unacceptable.

    I mentioned to the customer service rep when I called that it was very lucky that this happened in a rural area away from people. An auto RTH like this happening within a populated area could cause serious injury or damage to property ! They need to address this by a dialog box confirming RTH requiring the user to press OK before initiating the RTH. I still have no idea why it ignored my setting of 50M for the RTH altitude.

    If anyone has any thoughts or advice in dealing with DJI I would be very happy to hear it. I plan to call them again on Monday to argue this further.
     
  2. Chris_P

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    Here is the flight log if anyone can assist making sense out of this mess
     

    Attached Files:

  3. Meta4

    Meta4 Moderator
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    DJI aren't good at explaining things.
    If you are wanting to deal with DJI, it would be to your advantage to have some understanding of what went wrong.

    Your app has a "black box" data recorder that can probably explain what happened.
    If you want to learn from the experience and be able to avoid similar occurrences:
    Go to http://www.phantomhelp.com/LogViewer/Upload/
    Follow the instructions to upload your flight record.
    Come back and post a link to the report it provides and some of the experienced people here might be able to analyse it and give you an understanding of the cause of the incident.
     
  4. Meta4

    Meta4 Moderator
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    I see you've just posted the flight record ... that's enough to go on.
    Thanks
     
  5. Meta4

    Meta4 Moderator
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    I haven't got time for a full assessment right now but a few things I notice are that:
    The home point was not updated at all during the flight.
    The home point at the end is the same as it was in the beginning.
    The Phantom reached a point at 16:09 where it calculated that it had to RTH or it would not have enough battery to RTH (5900 feet away) if it kept flying.
    RTH commenced and the Phantom flew for 200 feet toward the original home point at normal RTH speed without climbing.
    (I can't see what RTH height was set at)
    At 16:22, the Phantom appears to hit something about 55 ft above home point and after that it's all over.
     
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  6. RocketBrew

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    Did you upgrade firmware since setting RTH height? It resets every time I do an upgrade.
     
  7. msinger

    Approved Vendor

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    Chris_P, I uploaded your flight log here.

    According to your flight log, it appears the following occurred:
    • Your RTH altitude was set to 30 meters.
    • At 16m 9.4s, your Phantom started returning home due to low power (this occurs when the "Smart Return-to-Home" feature is enabled in DJI GO).
    • The home point at that time was the original home point since the home point was never reset after takeoff.
    • Your Phantom climbed to 65 feet (above the takeoff point) before it started returning to the home point (the takeoff point).
    • During the ascent to 65 feet, you hit the throttle stick a few times.
    • Your Phantom crashed at 55 feet above the home point.
    The Phantom manual notes the following in the RTH section:

    "If you move the throttle stick after the aircraft rises above 65 feet (20m) but below the pre-set Failsafe RTH altitude, the aircraft will stop ascending and immediately return to the Home Point."

    You hit the throttle stick about one second after your Phantom reached an altitude of 65 feet, but it appears your Phantom stopped ascending and started returning home as soon as it hit 65 feet. If the log is correct, I cannot explain why that happened. It should have continued to ascend until you hit the throttle stick one second later.

    If you ignore that unexplainable event, your Phantom still would have been at an altitude of about 67 feet (assuming the same rate of climb) when you hit the throttle stick if it had continued to climb. That means it would have then started returning home at 67 feet and I'm assuming it would have crashed at that altitude as well. So, either way, your Phantom was doomed since you did not cancel RTH prior to the time your Phantom reached the point of impact.

    FYI, when using the Smart Return-to-Home feature, DJI GO does display a prompt to allow you to cancel the auto RTH. If you don't see that prompt and/or do not cancel the RTH from that prompt within 10 seconds, your Phantom will start returning home. At that point, you can press the RTH button on your remote controller to cancel RTH.
     
    #7 msinger, Jun 12, 2016
    Last edited: Jun 12, 2016
  8. Chris_P

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    Thank you all for the comprehensive analysis of this incident. I truly appreciate the insight offered. I do have a few questions ....

    1. Im happy there is a record of my pre-set RTH altitude. I was worried that it got reset or erased when I updated the DJI GO app. That said, I don't understand the reasoning behind throttle input cancelling the altitude rise and triggering a RTH at a lower altitude. To be honest, everything happened so quickly, I had no idea that RTH had engaged, I thought there was some interference that caused me to lose control. The throttle inputs were my attempts to regain control of the craft once the RTH commenced.

    I don't understand how DJI calculates altitude, there is no way that rock facing where it crashed is 65 feet. It crashed maybe 5-6' above the water then fell in the water. I have attached a pic taken by the drone just before the crash. The picture shows the exact rock area where it crashed. I was standing on the swim platform of the boat bringing it in then it took off and smashed into the rock directly across from the boat.

    2. Considering these circumstances, is 20% off a new P3P a reasonable offer from DJI? I truly think that these unfortunate circumstances could have been prevented if the drone rose to my 30M height I would at least have had time to realize what was happening and cancel the RTH and regain control of my craft. Looking at the picture, I can assure you there wasn't any noticeable rise in altitude. It just appeared to me to fly directly across and hit the rock. I would expect DJI to take some responsibility and do a little better than their current offer.... Has anyone had them reconsider a "final offer"?
     

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  9. mmtphoto

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    Just a quick question, wouldn't switching to att mode cancel return to home?
     
  10. tytlyf

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    Here's my guess.

    Once RTH was engaged, the drone was flying back to where you started the flight. Which is what the log shows. I don't know why the altitude was so low unless there was throttle input making it go lower. This appears to be a situation where you don't want RTH enabled. Especially when you're changing your location.

    So the question is, did RTH ignore the set altitude or was there throttle input to lower it (user error)?
     
  11. msinger

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    See my comment above. I addressed both of your questions.
     
  12. tytlyf

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    Thanks, I wasn't aware of the 20m activity when hitting the throttle. Can you tell throttle position at all during the flight from the logs?
     
  13. msinger

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    Yes.
     
  14. tytlyf

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    Where in the logs can I find that info? Does the log show decrease throttle during any of this right before the crash?
     
  15. msinger

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    You can find a link to the log in my first comment above.

    Yes. The OP descended a few times after the Phantom started returning to the home point.
     
  16. tytlyf

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    Gotcha. I looked at the log here Phantom Log Viewer - PhantomHelp.com but don't see a throttle input column. Am I missing a different area of the log? This is more for me personally so I can be more informed when viewing my logs and others.
     
  17. henick

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    I'd always assumed the cancel RTH height (via stick input) was to give the pilot the ability to maximize the remaining battery if the extra altitude wasn't needed.

    RTH often causes new pilots to panic when it happens. IMO, all new pilots should practice RTH in a field so they get comfort before relying on it in a real situation.

    I panicked the first time also but luckily it didn't cost me anything.
     
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  18. impilot51

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    Download the CSV. There is a link at the top of the displayed flight log. There is more info in the file than is being displayed.​
     
  19. tytlyf

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    Thank you. In this case it appears to be user error. Which makes sense since the drone is flying back to where it started. Operator tried lowering altitude in panic. This is normal.
     
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  20. Chris_P

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    Personally I think the prudent approach would be an audio warning indicating that RTH will activate in 30 seconds or something like that with a dialog box to cancel or accept. As I stated in my initial thread, having RTH engage without warning has the potential for disaster. Imagine if this scenario occurred in a populated area?

    Looking at the picture I posted of the area, I still don't see how that rock is 65' ? Not sure how those altitude calculations work

    Can someone advise if the offer made by DJI is reasonable or should I fight for more? I have no point of reference dealing with their customer service offers...
     
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