ACM 2 Quad Loses All Radio Control


I have a peculiar incident to report, where by my quad running the latest software from MP (3.0.1), appeared to lose radio contact with the TX on at least 3 occasions. I flew a total of 3 batteries and all flights experienced the same issue. The issue is where the quad at a random point stops taking any input from the TX (even at distances of only 20 - 50 m and less) and appeared to enter a self-leveling mode, where I have no control. The faults all happened in stabilise mode and the first two were recoverable (the copter moved slowly and held an altitude and I was able to pull it from the sky), but the last flight resulted in a complete loss of control and now the quad is stuck in tree quite high up. Even turning my TX off and on again didn't help establish radio control while the quad was drifting out of control (only power cycling the controller gets rid of the issue when it's on the ground).

What could be causing this? I was hoping to find particular conditions/circumstances to replicate the issue, but it just seems to intermittently occur.

I upgraded to the latest PPM encoder, and I am using a 9X with custom firmware and FrSky 2.4 GHz modules. I'm also using V2 hardware.    


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  • Hi,

    Had same issue a couple of weeks ago but I managed to recover.

    Using 9x with ER9x firmware, frsky D8R-XP with DCPPM 27 ms firmware, 1.2 video, minimosd and 433 telem.

    Did not upgrade to the latest PPM encoder, no compassmot.

    I thought that it was a problem with signals overlapping and havent flied since then.

    It was the first flight after updating, tried autotune with no success and continue with flight

    Happened during stab mode. 

    Can anyone check my log in order to see if there is something strange in the first 5 mins of flight?

    I had control after RTL.



    2013-10-20 13-57 1.log
  • I don't have my micro usb with me at the moment. I'll be able to get it in 3 days, but for the time being I don't think I can get the logs. I've been using my 3DR radios to tweak settings for the past few flights.

  • Thanks for the ideas. I've since managed to rescue my quad before any rain got to it, and have flown it since. I've also taken it for a few test flights out in the country and this issue hasn't occurred again. I did discover that by enabling simple mode and super simple mode at the same time caused similar symptoms to what I described caused my initial crash. I had one of my flight modes set to be both simple and super simple just to see what it was like, and although I never changed into this mode (intentionally) when I crashed there may have been some glitch in the radio/pot used to select flight modes that then caused the loss the control.


    On maybe a related note (?), I flew two independent flights in alt hold mode today and after a few minutes of normal behaviour the quad suddenly accelerated upwards with no response from the sticks on the radio. This happened on both flights. I managed to regain control both times by switching to normal stabilise mode. What could be causing this?  

  • Take a look here

    best regards Lukacs

  • MR60

    It could also be caused by vibrations on APM. it happened to me once on a quad where I did not use any vibration dampening techniques under APM.

    Here is how I got the quad out of the tree:

  • Maybe, is there a way to test it? It's strange that the issue is intermittent. I though that the ACM enters loiter or something to hold position when the radio link fails, and the quad wan't holding position after I lost control of it.

  • Moderator

    faulty Rx?

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