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Possible Crash Smoking Gun

Discussion in 'Inspire 1 Discussion' started by damoncooper, Feb 13, 2016.

  1. damoncooper

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    We *may* have a smoking gun in one case of "falling out of the sky" in a case reported by Daryl Watkins.

    In that case it appears there was an erroneous detection of "motors obstructed" error that resulted in the invocation of a ESC FW "safety" feature introduced in recent firmware where the Inspire will shut off its motors if it thinks it detects an obstruction with the motors.

    This feature was added in the firmware release after Myth Busters show premiered that showed the dangerous effects of drone propellor contact with the human body.

    I myself have witnessed the "motor obstructed" error, even while the aircraft was sitting in the ground before motors were even armed.

    I think we may have ourselves a case of erroneous "motor obstructed" errors causing Inspires to shut off their motors and fall from the sky.

    More to come and we need more DAT log files from fallen Inspires but at least in throne case there was no power outage, just the "motor obstructed" error 1 second before the Inspire began tumbling from the sky, all the while being powered and transmitting its telemetry.

    Note that in at least this case the aircraft remained powered as the telemetry continues to come in that the gimbal angle exceeds max etc.

    In other reported "fall from the sky" cases the aircraft apparently looses all power (hinting at a possible separate issue(s) related to the battery shutting down.
     
    #1 damoncooper, Feb 13, 2016
    Last edited: Feb 13, 2016
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  2. ATU

    ATU

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    Ouch.. this error is something even external battery mods won't help. Scary if this error can potentially cause our birds to fall out of the sky at ANY time.
     
  3. damoncooper

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  4. Alastair

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    This is getting rediculous! I know that I'm flying a buzz saw, that's why I don't do it near or over people. Now a knee jerk reaction to a tv show? So now, besides worrying about batteries that shut down to protect themselves causing the AC to fall out of the sky, I have to worry about erroneous faults causing motors to shut off causing the AC to fall from the sky. Isn't THAT dangerous too?? I'm seriously considering selling this pain in the butt.
     
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  5. damoncooper

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    Digging a little more, Reading the release notes it appears this feature was added in FW 1.3, released Aug 4, 2015.

    It could be a later update introduced the bug though as I'd never seen it before FW 1.5 or 1.6 if I recall.

    The Mythbusters episode aired in July 2015, for the record. Given its production lead time and DJI's relationship with Adam Savage, it's entirely possible DJI had advance notice of the episode and made the decision to add the ESC cutoff feature anticipating widespread criticism of the effects of a drone's propellers coming into contact with humans.
     
    #5 damoncooper, Feb 14, 2016
    Last edited: Feb 14, 2016
  6. Mad_angler1

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    What about hitting a bird ? Is that over water as can't quite tell from the image

    Perhaps motor bearing failure, do we know the flight hours ?

    I feel for the Pilot in all these cases but the numbers of failing in general is still massively low compared to sales, but that's not to say it's good in any case. With the modern social media age we hear about every single thing that happens and things can look far worse than the actually are especially when on things like Facebook. There are just so many variables with these things, may folks will be getting up the flight hours now as well and that's going to have an impact on things.

    These are still flying mobile phones with giant batteries strapped to them, what goes up might come down and I don't think we are anywhere near the stage of not seeing failures of some sort, these are consumer toys for the most part, yes some are aimed at the ProSumer level but the Inspire is no different from smaller craft and people should understand that, unless you have multiple FC and battery redundancy(I'm sure you have mentioned that once ;) ) then craft will fail regardless due to natural failure.

    DJI is suffering a little from its own success here, trust me I know all about this specifically and when your the market leader and you have huge sales figures failure rates that are still well within the normal number look huge.

    I don't think we are seeing a sudden surge just perhaps more after the holiday season, not saying every one is new pilots because it's clearly not.

    Again do feel for anyone this happens to and I hope DJI look after them as they generally are but you do need the craft to give them to inspect.


    Sent from my iPhone using Tapatalk
     
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  7. damoncooper

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    Negative. Two witnesses to the flight claim there was no collision with a bird.

    The aircraft was lost in water, yes.

    They said the aircraft fell out of the sky, so motors stopped but not a power failure as telemetry was still being transmitted as you can see
     
  8. damoncooper

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    Here's a sample of what this warning looks like ImageUploadedByTapatalk1455440581.299590.jpg
     
  9. ianwood

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    Can you post logs? DAT files?

    I've had the motor obstructed error once. Landed it, changed batteries, took off again and never saw the error again.
     
  10. damoncooper

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    Ian, the aircraft was lost in the water. See above.
     
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  11. Mad_angler1

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    Any idea of flight hours ? Could be FW but just wondering is motor bearing could have seized or failed.

    Hard to tell


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  12. damoncooper

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    Daryl's account is that it was a relatively new Pro with stock props.

    He says,

    "I wanted to share a quick playback video of a flight that I witnessed. This was from a relatively new Inspire Pro with the stock QR props. The pilot is well-seasoned and this aircraft had almost 20 flights on it just in the previous 48 hrs (I was also with him during those flights). The only thing positive that came from this was the fact that it didn't fall onto people, homes or cars AND the awareness of what CAN happen. It's back in DJI's hands now awaiting their action."
     
  13. Mad_angler1

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    If it's a pro then it's not going to have a lot of hours.

    Hope the OP gets it sorted.

    Thinking about it could just be a simple ESC failure, if an FET goes down it would detect an obstruction, it's exactly the same with the stuff I work with when we loose an triac on the a 3ph motor controller, the diagnostics picks up motor jammed error as its assuming the power is reaching the motor.



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    #13 Mad_angler1, Feb 14, 2016
    Last edited: Feb 14, 2016
  14. damoncooper

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    A simple ESC HW failure wouldn't be a big deal. It happens. It's possible.

    But the warning being issued is something I myself and others have seen when the aircraft was simply sitting on the ground powered on, with motors unarmed.

    To summarize:

    A) the motor obstructed condition is documented to be occurring when motors are not obstructed

    B) the feature is designed to shut off all motors if this condition is detected

    C) the motor obstructed condition is documented in this crash to have occurred just seconds prior to the crash

    D) this was not a bird strike as witnesses saw no birds and the video stream showed no birds in view

    E) it is unlikely that dust or debris due to pilot neglect were causal due to the young age and service life of the aircraft and experience of the pilot

    F) ESC failure is unlikely for the same reasons as (E) and the much more likely cause is (A).

    I think unless more evidence becomes available that points to the contrary, all indicators point to this crash most likely being the result of a simple FW bug.

    If we see other cases with similar data points that likelihood would rise.
     
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  15. Mad_angler1

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    #15 Mad_angler1, Feb 14, 2016
    Last edited: Feb 14, 2016
  16. damoncooper

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    Another possibility that would match the evidence is a prop coming off and other prop hitting the one that fell off causing motor obstruction.

    These were the latest prop design and if that were the case that's also concerning since
    they were locked (it's a binary operation with the V2 QR props and clearly they were locked or the aircraft would not have made it this far)
     
  17. damoncooper

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    I'm not sure of the point of your post. Hand waving over the evidence that exists doesn't make it go away.

    It just means you are hand waving over the evidence that exists.
     
  18. damoncooper

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    All theories welcome that match the evidence :)

    And more evidence from this or other similar incidents would be helpful.

    DAT files from crashed aircraft in particular would be helpful. Please post here or PM me if you are able to help in that regard.
     
  19. unyks

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    Maybe it is time for an better organization of this subject. It is good that users report their issues in their own threads but that does not give you a good overview about the incidents. We should maintain a list of all the incidents poeple report hier with some data like date of purchase, date of death, firmware version, cycles, weather conditions and other data that is maybe important. Depending on the outcome and amount of feedback we have maybe something in our hand against DJI to be more cooperative.

    We had a similiar story with Volkswagen (i try to keep it very short). I'm driving a 2011 VW California and I'm running a very big community together with some friends. A few years ago we got the 1st reports about roof corosion and of course, VW rejected repairs if the car was out of the 2 year warranty, with some luck they offered some discount. So we started to collect the incidents and confronted VW with it, after a while VW changed their mind and now they are doing a free repair for up to 7 year old cars and with repair i mean a complete replacement of the roof top!

    I don't know if this works also with DJI but it is worth a try, think about it.

    Chris
     
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  20. Mad_angler1

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    #20 Mad_angler1, Feb 14, 2016
    Last edited: Feb 14, 2016