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My First Crash and post crash checks.

Discussion in 'Phantom 2 Vision + Discussion' started by Emeye, Feb 7, 2015.

  1. Emeye

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    Hi, this is my first post, unfortunately following depressing circumstances.

    I've had my Vision 2 plus quite a few weeks now and every weekend, apart from the one just gone when I had a sickness bug, I have had lots of successful, careful flights.

    Today, I updated the camera firmware to v1.3.0 and probably feeling a bit overconfident following so many successful flights, I launched by phantom in a smaller clearing than normal following calibration.

    As soon as it was in the air I realised that it was not stabilising in one spot - I manually tried to keep it steady, preparing to land, but it shot sideways and into a tree about 15 metres away.

    I'm still wearing the prop guards - the one that impacted the tree completely shattered and it fell down to the ground side on - luckily this saved the camera. Another prop guard split, and the battery had been ejected!! :shock:

    I tried a couple of small test flights after the accident, very low, and again it was not stabilised and I had a couple of minor downs onto soft ground before I gave up.

    One thing I was thinking was that I carried the Phantom in the boot of my car for the first time, rather than my wife's car, and I have a large subwoofer in the boot - could this have affected anything - as I said I did calibrate before taking off as I usually do!

    After the accident the Vision app was warning that Transmitted Calibration was required. I will run through the routines.

    Is there any way to try and diagnose what could be the issue before I attempt another flight tomorrow?

    Also, what checks should I go through on the phantom tonight to check nothing is damaged - the rotors were on very tight when I removed them?

    I plan to fly in a large open playing field tomorrow.

    Cheers.
     
  2. Fplvert

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    Location:
    Southern Idaho USA
    :D
    Welcome to the forum!
    Sorry about you crash, but I think you already figured the big magnetic speaker was the culprit.
    Before you fly again, you should do an advanced IMU calibration. Make sure the bird is cool and on a level spot when you hook it up to your computer.

    MHL
     
  3. Emeye

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    I feel pretty dumb as I did wonder about the speaker, but thought a standard preflight calibration would do the job!

    The calibration is the one thing I am struggling to get my head around! I've read quite a few threads but still not sure.

    The note in the PC app for the compass say the mod value should be -500~500 which I takes means between -500 and +500, but then mentions values of 750 and 2250.... Moving the Phantom around on my dining table attached to my PC results in large variation in the mod value.

    At risk of looking even dumber, can I run the advance Cali with the Phantom sat on my dining table at home, or does it have to be outside? IIRC you can not run advanced Cali from the android or iOS app?
     
  4. rbhamilton

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    You don't need to feel dumb. Nobody is born knowing any of this stuff.

    You can do the IMU calibration inside just fine. IMU stands for Inertial Measurement Unit. It's the device inside the drone that tells it which way it's accelerating and how quickly it's changing speeds based on changes in inertia.

    Imagine a weight on the end of a string hanging inside a box you are holding. You run forward. The weight would swing backwards. You come to a sudden stop and the weight will swing forward. If you were sealed inside an amusement ride and couldn't see out, you could watch your little box and observe changes in direction. The drone needs to be level and not moving in order for the device to find it's Zero point. I doubt the drone uses a lead weight on a string but that's the basic idea anyway.

    I think the poster's suggestion is a good one and you should do it for sure after a crash but it won't fix a compass that's off kilter from sitting on a magnet. That's done with the compass calibration. If the compass stays out of wack it's a fairly inexpensive thing to replace.

    Back to your issues in the small clearing - are you sure you had enough satellites for a good lock? You need at least 6 and trees eat up GPS signal for breakfast. Even if you start with 6 it's easy enough to drop down to 3 or 4 passing near a tree. Remember your GPS sats are all over the place - sometimes just barely over the horizon and they move around fairly quickly too. They aren't all directly above you. Once you are under 6 sats, all bets are off. If you are a bit unsteady on the stick it's game over.

    A big open clearing is really important. And the more sats the better.
     
  5. knowonecares

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    Location:
    Long Beach, CA
    "Back to your issues in the small clearing - are you sure you had enough satellites for a good lock? You need at least 6 and trees eat up GPS signal for breakfast. Even if you start with 6 it's easy enough to drop down to 3 or 4 passing near a tree. Remember your GPS sats are all over the place - sometimes just barely over the horizon and they move around fairly quickly too. They aren't all directly above you. Once you are under 6 sats, all bets are off. If you are a bit unsteady on the stick it's game over."

    I do test flights in a small area surrounded by trees about 20 feet apart, while in flight I constantly see the LEDs going from Green to Red indicating loss of a satellite or two, but its a local park and i'm very careful until I can go the big field. The last time I had a similar crash as Emeye, I had not successfully calibrated the compass, later on with forum help I realized it was doing the "Toilet Bowl Effect" circling in about a 10 foot circle instead of hovering solid.

    After a crash, I take off the shell top and inspect the motor wires to the ESC boards, and look for any sort of burning or melting on the boards, push down on any plugs that may be unseated, clean any dirt i see, rotate the motors to feel for debris (they have magnets inside that will attract all kinds of stuff, not quite sure myself how to get the dirt out, but a little lung power seems to work for me so far), also check your Motor mount screws for looseness, and then inspect the camera gimbal for unplugged ribbons above it, and any separation of the gimbal motors. Thanks for the speaker info, tho, never thought about that. Let the forum know the results of your next flight.
     
  6. Emeye

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    I suspect it could have been GPS related. I did have 6 satellites to start with.

    How does the Phantom cope with dropping satellites during flight? Does it go into Alti mode as soon as it has less than 6 or does it just get confused and try to cope with 5 satellites?

    I had been practicing flying in Alti mode so either I wasn't good enough or the Phantom had a mind of its own! In hindsight the clearing really was too tight for Alti mode, but I'd assumed to be able to fly in GPS mode.
     
  7. BioTeq

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    It switches to Atti and what happened to you sounds like a classic wind drift after sattelite loss.
     
  8. Emeye

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    Good news. My Phantom Lives to fly another day!

    I had to attack the compass with a magnet though as it would not calibrate.

    Yesterday, I think I had the perfect storm of borderline GPS, scrambled compass thank to subwoofer in the car boot Ms overconfidence!

    Thanks for everyone's feedback. :)