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Nearly lost a Phantom!!

Discussion in 'General Discussion' started by DomKane, Apr 29, 2013.

  1. DomKane

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    OK, so prepare for a bit of a rant here... Gonna try and include as much info as possible, because although this wasn't a fly-away, and is most likely either a one-off ghost in the machine, or even more likely user-error, the info may be of some use...

    So I bought a 2-axis Gimbal for my Phantom over the weekend and tried installing it yesterday, so got it built and connected the servos, then booted up the DJI Naza M Assistant to enable the servos, only to find out one of my servos was faulty, so I took off the gimbal and called it a day.... While I was in the Naza M Assistant software, I also enabled the IOC. This may all be irrelevant. :s

    Today, I took it outside for a quick flight outside my apartment, waited for it to warm up and get 6+ satellites in GPS, and everything ran fine for a couple minutes... I then decided to walk a bit further down the road, and setup again there... Again, got the single green light, took off fine, had about 1 or 2 minutes of flight before I noticed something wasn't quite right... It started to wobble a bit so I brought it towards me as it was currently over a lake about 20m out and 10m high. As it got over my head it suddenly started banking a hard left, which is where I started to panic and made the split decision to crash land it as it was veering towards the lake... It kept drifting a hard left, but luckily smashed into a small metal post at the edge of the lake and bounced off on dry land(!), as the GoPro mount and anti-jello plates tore apart and went flying in the air (again luckily on the side of dry land!).

    BAD NEWS: The Phantom shell has a big dent in it, and I lost the four little rubber grommets from the anti-jello plates.
    GOOD NEWS: Hell, that could have been a LOT worse!

    I brought the Phantom back home and booted up the NAZA M Assistant software to take a look and see... Everything looked fine... Started up the motors, and they run fine... :D

    Points of note:
    ** I noticed I left the Gimbal tick-box activated in the software.
    ** I had activated the IOC before this flight.
    ** I had flown for 2 or 3 minutes in a flight about 5 minutes previous to this one.
    ** Although second nature, I can't now recall double-checking the Switch-1 and Switch-2 positions pre-flight.
    ** The GoPro was recording, WiFi was OFF.
    ** Watching the GoPro footage back, the recording stops around the time the Phantom began to wobble.

    Now my first guess was that the battery might have been lower than I thought on my second take-off maybe running on low voltage... It had been charged 48hrs ago so should have had plenty of juice, but if I know LiPo's then this may have been the culprit.

    HOWEVER... The GoPro leaves a couple of questions... The SD card popped out on impact, so when I saw the footage stop (about 10-15 secs before impact) I assumed that the GoPro just didn't get a chance to render the last 10 secs or so to the SD card... I'm not sure if that's how it works, so my test for that was to hit record on the GoPro at home, wait for 30secs, then eject the SD card and see what happens... Did I lose the last 10secs? No... The video file was corrupt... I have done this twice now, so perhaps someone else can confirm this?

    If we can confirm that ejecting the SD card mid-recording definitely corrupts the file every time, then this means the GoPro definitely stopped recording at what seems like the exact moment the Phantom seemed to lose control. (Mine is a GoPro Hero 3 running v2.39 software).
     
  2. FangsCPO

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    Possibly activating the gimble control and IOC at the same time is not a recommended action. Just a guess since everything was good prior to this. Then again maybe you left the gimble control on when there was no gimble installed since you say you took it off because one of the servos wasn't working. Hopefully, you can figure it out. Good Luck!
     
  3. Gizmo3000

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    Are you sure that you didn't accidentally have it in HL or CL while flying?
    when the Phantom comes within a 10m range while doing so, it will act like it hit a virtual wall and start flying totally different than expected.
    that's just one possibility.

    things get dicey when Phantoms start flying unexpectedly in the wrong direction ..
    the general rule (which is hard to remember while frantically trying to regain control) is to put it into ATTI mode will help you recover when GPS mode is off.

    sorry to hear about your busted shell. hopefully you can get a new one (if you can find one in stock) for $50,.and then it only takes an hour or so to swap everything out and into a new shell.
     
  4. pwright

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    Off the top of my head I seem to recall there being a couple of directories that the GoPro creates on the SD card. Perhaps there is a log file or something in one of them?
     
  5. DomKane

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    The .LRV is a Low Resolution Video and the .THM is a Thumbnail.

    The more I think about it the more it comes down to two possible things....

    1) Simple battery dying and it trying to land and me fighting that.

    2) GoPro went nuts and caused WiFi interference (even though WiFi was switched off, the recording stops at exactly the moment the Phantom started playing up).
     
  6. DomKane

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    Yeah this is a possibility (albeit remote) as I can't remember 100% double-checking the switch locations upon take-off because I tend to do that without even thinking these days.

    Yeah I'll be getting a new shell as soon as I see one in stock, but probably won't change it over just yet as the current one shouldn't affect the flying as it is with a couple very small dents.
     
  7. DomKane

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    Yeah the Gimbal was still enabled, although I can't see this having any effect in theory, especially as the first flight was error-free.
     
  8. TickTock

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    My money is on #2 (GoPro went nuts). Hard to believe it was just a coincidence that the video stopped simultaneously. Their firmware is buggy (mine would lock up periodically until they published the recent firmware update so it's easy to believe there are more bugs in there). What was the state of the GoPro battery? Maybe low GoPro battery voltage contributed to the failure.
     
  9. jumanoc

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    A simple way to detect if it was low voltage issue:
    Turn On TX, and connect the battery as when normal to start a flight. Let it warm and just start props without taking off.
    If led shows GREEN- RED- GREEN - RED, definitively battery ran out voltage.
     
  10. DomKane

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    The GoPro had a fresh battery so definitely wasn't that, and it was on the latest firmware (released yesterday or the day before).

    The Phantom battery was a stock one, and about 30 secs before losing control it had given a little flicker of the red LED during a high-throtle move, so I know it was starting to run low, but it hadn't given me any real warnings and I wasn't doing anything fancy in the final 30 secs that would have used much battery at all.

    All very strange... I'm going to disable the gimbal and the IOC in the Naza M Assistant tomorrow before I try and take it out again... I'll run a couple of low-level flights in a field without the GoPro before trying again with the GoPro.

    Small steps...
     
  11. DomKane

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    Took it out for a flight test today... Obviously don't need to mention I waited for IMU to warm up, GPS to lock home position and find 6+ satellites etc etc...

    At first it was drifting a bit when hovering at 2m, but after a few minutes of really gentle flight at 2m height, it eventually started to lock on to position. So this was probably me being hyper-sensitive to anything from the crash. :)

    I did also notice that an average speed descent caused more wobble than usual. I'm fully aware of the physics of turbulence (prop wash), but it seemed to be a lot more unsteady than usual... But again, that could have been me being hyper-sensitive.

    TBH, things could be a lot worse... Took me 4 batteries to start building my confidence back up to flying anything over 7m or 8m height, lol.