Pixhawk Flyaway

I had a disturbing experience yesterday. I was test flying my Hex and after a few successful hovers, a little PID tuning, and running through a few flight modes, I decided to let it stretch it's wings a little more.

On a fresh charge, I put it into Loiter, took it up a couple hundred feet, did a slow 360 and then slowly moved it forward.

Then, All of a sudden, the Hex sped up, headed toward the river, then banked to the right, spun around and put itself into a field about a quarter mile away.

Fortunately, no-one was hurt, and the Hex itself only suffered a couple broken arms and a prop - but needless to say, I'm quite concerned and want to get to the bottom of this before taking it out again.

I've uploaded the flight video to youtube at http://youtu.be/sc4UqOOiUUQ

I'm also attaching the flight log files.

I don't doubt it's related to something I did (or failed to do) and any insight would be greatly appreciated.



In case it helps - here the vehicle specs


Tarot 680 (Carbon) Hex frame.

Sunnysky V3508 380KV motors

5S 4000mah Zippy Lipo

3DR Pixhawk, 3DR 915Mhz Telemetry & 3DR GPS unit

Futaba 14GS Radio

Mavlink connection to Droidplanner 2 on a Nexus 7


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      • is that a genuine pix?

        • Yep, Pixhawk, GPS, Power Unit and Telemetry are all direct from 3DR

  • What version firmware?

    What's strange is when you lose control TH_OUT is pinned max.. 

    Did you have fence enabled? What was the setting?

    • Per the log file it was Arducopter version 3.1.3.

    • 1) I'll check on the firmware version when I get home, it was installed via APM Planner as the latest stable version about 2.5 weeks ago.

      2) Nope, no fence enabled (I haven't started playing with those features yet) 

  • I've had a similar event happen to me while in Loiter. I discovered my GoPro 3 was interfering with the GPS. I too had very little input. The only thing kept from hitting the ground was I got it out of loiter and into stabilize mode. If loiter isn't working right chances are RTL won't work either.

    I'm no expert looking at the log files but at first there doesn't seem to be the normal GPS fail that most people encounter. Also mapping you GPS track it looks nice and stable. At one point the HDOP went up to 6.94 but this is when you where just hovering low to the ground.. It is best when this is below 2. But it looks like at that point you were just hovering in one spot. When . By chance do you have the TLOG file on are tablet. Having the TLOG allows you to replay the flight on Mission Planner.

    I also looked at your RCIN channels and see the inputs were being received by the pixhawk but in loiter or RTL your inputs will cause minimal reactions.

    BTW where are your speed controllers located? Also is there a chance the pixhawk came loose from the frame?

    Here is a quick synopsis of your log file provided by Mission Planner

    Log File C:/Program Files (x86)/Mission Planner/logs/HEXAROTOR/1/9.log
    Size (kb) 2614.5185546875
    No of lines 35566
    Duration 0:03:58
    Vehicletype ArduCopter
    Firmware Version ArduCopter
    Firmware Hash
    Hardware Type
    Free Mem 0
    Skipped Lines 0

    Test: Brownout = PASS -
    Test: Compass = FAIL - Large change in mag_field (38.29%)
    Max mag field length (723.70) > recommended (550.00)

    Test: Dupe Log Data = PASS -
    Test: Empty = PASS -
    Test: Event/Failsafe = PASS -
    Test: GPS = WARN - Min satellites: 7, Max HDop: 6.94
    Test: Parameters = PASS -
    Test: PM = PASS -
    Test: Pitch/Roll = PASS -
    Test: Underpowered = PASS -
    Test: VCC = PASS -

  • Oh, one thing I forgot to mention - once things went haywire - there seemed to be no apparent response to any control inputs from the radio control unit (as well as my attempt to hit the "go home" button on droidplanner)

    • quick question, were you monitoring telemetry with a phone/tablet or a laptop, and did you use the telemetry to find it on the ground? I'm looking at moving to the APM ecosystem from Immersion telemetry, but I really like having the flight path on my phone on a map in case something goes wrong... thanks!

      • If you use a computer running Mission planner, APM Planner or an android tablet/phone running Droid Planner or Andropilot along with the 3dr Radio you can track your crafts position as long as you have reception. People say the telemetry is usually good up to a mile with the stock antennas. When I fly I use my Samsung Note 3 and the radio. I like it because I can put the phone in my pocket and have the radio hang out using an OTG cable. It also gives me another log file to look at if I need to review. If by chance I lost my aircraft I could locate the last position the ground station received using the Droid Planner or Andropilot.

        I also like using these because it tells me how good my GPS reception is by reporting the HDOP. With a HDOP greater than 2 I would not put it in any flightmode that requires GPS. 

        • thanks, just what I needed to know :) the more I read about ArduPilot/Copter and get into the community the more excited I am, just wish I hadn't spent 3k on a custom Naza build before discovering you guys! I think I'm gonna do a scratch build now following one of the guides, but completely built with the APM ecosystem in mind. I want to run long-range missions in remote areas (fence checking, livestock monitoring etc), and I need a rock-solid telemetry link and monitoring that it looks like I can get from this ecosystem for a fraction of the price for equivalent from DJI. thanks!

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