Loss of radio control

I had my first loss of control crash today, I'm running 2.91 on an APM2.5 quad.

I'm using a frsky module in a turnigy 9x radio running er9x, and the receiver is a D8RII+ running the new 27ms firmware in PPM mode. I have had about 10 hours of trouble free flight with this rig until now.

I was in alt hold mode, when I noticed that it had stopped responding to my yaw input, so I tried switching back into stab mode, but it didn't do anything. I then tried flipping the RTL switch, and that didn't work, so I finally turned the radio off, which put the rx into failsafe mode and output a throttle value of 990us which triggered the throttle failsafe and initiated RTL. The tlog shows that at 74.7% basically all of the channels stopped updating, and it switched me into loiter mode. At 82.1% the throttle failsafe RTL was enabled by the TX being powered off.

Unfortunately when I powered it on, I was about two metres from the house, and so when it RTLd, it ended up coming down very close to the house and hitting a wooden beam on the way down, which bumped it into the side of the house and broke all the props. Luckily it seems like that's the only damage!

I have my tlog uploaded here: http://www.droneshare.com/view/dobyrdz

My suspicion is that the tx stopped sending valid data somehow, but I'm not 100% sure. Can someone in the know please take a quick look at the tlog. I'm grounding this quad until I can get to the bottom of it.


You need to be a member of diydrones to add comments!

Join diydrones

Email me when people reply –


  • I think I had a similar issue. I've been looking at channel inputs to try and determine if the transmitter failed.http://diydrones.com/forum/topics/fly-away-crash-during-alt-hold

    See attached file. Channel 1 = roll.

    Having the radio off produces the same result as pushing hard left on the roll.

    But I am hoping there is another metric to give me certainty about the signal strength at the time.

    Log Graph - RX Signal.gif

  • Does anyone else have any ideas about how to determine where the failure was? I need to get this thing back in the air safely!

  • Hmm, there's only one wire from the apm to the rx for the ppm signal. I'm pretty sure it was still connected since turning the tx off made the rx output the failsafe signal like it was supposed to.
  • T3

    sounds like maybe one or two wires came disconnected from the receiver to the APM. Probably the mode switch wire, which happens to be right next to the yaw wire. When you turned off the transmitter, the failsafe was detected over the throttle wire, bypassing the mode switch wire. Just a guess...

This reply was deleted.


Laurie J. Troy liked Jasper Kueppers's profile
Apr 1
Timothy Miller liked Joseph Udofia's profile
Mar 18
Joseph Udofia liked Joseph Udofia's profile
Mar 3