Hex decided to leave and never come back

I was flying my hex today, as I was headed toward my current position it decided to not respond to my controls and keep going over me. It was about 100 feet up then looked to increase altitude a bit and kept going away.  It seemed to level off and head the standard direction it would go with no input.  Eventually it was out of sight and long gone.

Does anyone know what could have happened.  I was in stabilized flight mode and the copter was within 200 feet of me when I lost control.  Also any ideas how to get it back, I had my Gopro attached to it recording the flight.

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  • I'm using the stock motors and ESC's from diydrones. Should I be able to kill the motors, tumble and recover? I've tried it twice, unintentionally and both times resulted in a crash. I give throttle again as its falling but all I hear are whistling sounds as it tumbles. I'm using apm2.
  • I think this issue is closed.  I spoke with Randy about it, and if you look at the release notes for 2.8, you'll notice that he implemented a watchdog timer.  If the main code doesn't run for 2 seconds, then it shuts down the PPM stream to the motors.  He tested this by hacking a delay in the code on Ch6, and was able to test it, and it works.

    If you find a hole in it, let us know.

    We also talked about the idea about having the motors go to disarm if the quad goes upsidedown in stabilize.  This one is a bit trickier.  There are a number of pitfalls, such as when people take the copter to altitude, shut it down, watch it tumble, and then throttle up to right itself.  Obviously they couldn't do that anymore.

    But we talked about the possibility, such as, if the copter is past 90°, and altitude is below 2m, then obviously things are not going well in any case, and it's safe to disarm.  This has the hole where, what if you are doing the flip trick, and you are somewhere else other than home altitude, so it's ok to be below 2m.  But at some point we have to decide when to stop protecting for these weird scenarios.

  • I know this is not entirely related but one way to cause an unrecoverable crash is to shot off motors while in the air and after a second or more, try to give throttle. With the current diydrones ESC's and motors they will not spin back up and the copter just falls. I suspect it's because the props start spinning backwards and the ESC's get locked up or confused. I don't think it's a fault of apm but fault of ESC's.
  • How NOT to test failsafe....a short story...

    Today I was ready to fly my Octocopter for the first time. I spend the whole week converting my OctaQuad and spending special attention to electrical noise, weight, etc. 

    Then I read the above story and immediately followed the fail safe setup procedures for my DX8. I then wondered how to test this safely on the ground. APM did show the decrease in throttle, but did not show a change in mode to RTL when turning off the transmitter.

    I all forgot about it when I did my first test flight today. In my back yard....close to my house....

    All excited and knowing that I had to take my daughter to gymnastic lessons, I turned off the laptop and shutdown the transmitter. I know it's wrong, but have done it before....well....this time after 2 seconds, the Octo jumped back to life, jumped to 15 meters (that is what RTL was set too) and before I realized it was so close to my house that it scared the living cr*p out of me. Quickly turned on my transmitter waiting two loooonnnng seconds, regained control and landed....

    I guess my fail safe was setup correctly.....

    Lesson learned: always disconnect the main batteries before turning the transmitter off....

  • I have this very dumb question, that I'm too embarrased to make a thread for, and since it's somehow related to the discussion, I'll post it here.

    I'm using a FrSky TX/RX and I've set failsafe on the RX with all sticks centered and CH7 on, and I have CH7 set for RTL.

    I want to try a mission out to 2 Km away, and I'm afraid that's beyond my TX range.

    Will my APM just ignore the failsafe and carry on the preprogrammed mission, or will it stop and RTL once RX RSSI is below 13 dB and failsafe kicks in ?

  • Seems to me like we've come to the end of the OPs question, with some good lessons learned.

    Set a failsafe, use telemetry, use a locating device, put your name and number on the aircraft.  Try plotting a line in GE in the last known good direction, and start walking.  Post some signs.

    We likely will not know what happened, as there are no logs to look at.  In a rare instance I think I can speak for everyone who has felt this pain that we seriously hope you find it.

    I think the rest of this conversation is valuable for other reasons (code improvements, etc...) but it seems that it would be best had in a dedicated thread so it would minimize redundancy and be easier for everyone to leverage in the future.

  • I had a Trex500 heli go down once in a swampy area with very high grass (taller than me). It had a Quanum battery monitor system from HK that has an LCD display on my TX. As I was heading out to try and track down the heli I decided to try and locate it using the signal strength indicator on the Quanum display. I put the antenna parallel to the ground so that it would be directional and turned around to see where the strength was greatest. Not very exact, but it did give me sufficient guidance to track it down. I was right on top of it when I finally saw it, so I suspect that if I hadn't had the display the heli would still be out there rusting away. If I had a directional antenna available to replace the standard antenna it would be easier. 

  • I read through about half of these comments, but so far I hadn't seen it mentioned, but if you know someone with an FPV setup fixed wing, see if they'll help you out with an aerial search. Ive heard of quite a few guys lucking out and finding their aircraft this way.

  • @Drone Savant; you know that you could always clone a branch of the APM code and add it yourself right?  I'd be interested in seeing how you went with it.  I would however point out that introducing a WDT into the code would likely cause more instability, and that instability would more likely than not crater your copter.  Given a choice I'd rather not crater mine, especially unpredictably and beyond my control, as WDT would without a doubt trigger and reboot the system before you even knew that something was wrong; this however would not have prevented Colin's fly away as the APM sounds like it was working just fine and it was the receiver that was not working, thereby leaving the APM open to other "return home" commands via telemetry, and a much safer alternative than a reboot triggered crash.

    as for the ground-station; it was mine, I created it and wrote the code for it.  it's not geofencing as such and could work in combination with the existing geofencing setup, I did it as a 'last line defense' to work in conjunction with other failsafes for just such an event as this...

  • Hmmm, I've been reading all the comments about the Turnigy 9x, and shortcomings of various techniques to avoid a fly-away and want to throw my 2 cents in if I may;  having had something similar happen to me, I decided to add a 'boundary' function into my ground-station where if it measures more than 'X' meters from the GS coordinates to the APM coordinates it will send a command to put the APM into 'RTL' mode thereby bringing it back home for just such an event...

    I would also consider raising the concept of using the RSSI data from the xbee to designate "out of range" and enact a similar failsafe, this would work nicely in combination with a standard throttle failsafe, and provide redundancy in the event of "pilot error" 

    lastly, I would always advise taking your laptop to the field with you and at least leaving it running in the car with the link to the APM active that way if you crash you can at least have a dot on a map where it was last seen... I know that the copter can outfly the xbee, but it'd be a lot more helpful than nothing at all...

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