After more than two hundred flights with my APM2 equipped quad, today, in the remotest of possible locations my quad failed to respond and attempted to fly away by itself! All I can say is thank goodness for Knobthorn trees.

I wanted to get some video of the area but didn't have my small cam with me so I attached my Galaxy Smartphone to the front of the quad, I have done this before and know that the video won't be that great (lots of jello) but will at least give an idea of the scenery. I waited for satellite lock and then hand launched (too much dust on the ground) just in front of where I was standing, I went slowly up to about 20m, hoverered then did a 180deg pirouette and slowly started descending back towards my position.

When the quad was about 3m from me and 2m off the ground I throttled up to stop the descent which was fine but now the quad was drifting forward slowly so I tried to tilt it backwards... suddenly I had that sickening realization that it wasn't responding, I wiggled the sticks...NOTHING!. I ran towards it but it was still drifting forward and climbing very slowly, now at about 2.5m. It continued very calmly and smoothly and I briefly considered throwing the only thing in hand (my transmitter) at it to try bring it down, but it flew on until it collided with a Knobthron tree at about 4m high.

3 motors were jammed by branches but one was still spinning away calmly. I wasn't... I was able to run to the nearby parked pickup and drive under the tree, reach up to unplug the battery and then get the quad down.

I have read the horror stories of fly-aways but one naturally never expects it to 'happen to me'.

- My radio is a tried and tested two year old Hitec Aurora 9 which has one of the most robust AFHSS 2.4GHz systems. The quad was 3m from me when it happened!

- My failsafe is setup correctly and double-tested, with the throttle channel going to 900ms on event of signal loss.

- All four my SS 30A ESC's (2A BEC) power the APM2 (each tested 0.09v of each other) effectively quadrupling the current capacity. I've never had a suggestion of a brownout.

So what happened? I don't know, I can't see anything definative in the logs (attached). If someone has any ideas I'd be very grateful!

As for now my faith in APM2 has been shattered, like an old friend you can no longer trust.

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Yikes graham, i had a problem with GPS lock this morning - turned out it was my new crappy camera interfering badly, I still maintained control though - sort of, and obviously it was fine in stab mode as the interference was related only to the GPS.

good luck finding your problem!

Graham, sorry to hear that! I've asked the dev team to analyze your logs and try to get to the bottom of it. Is it at all possible that the RC cable shook loose or that there was otherwise a connection failure? The failsafe only works if the RC receiver is still connected and can send a signal-loss value to APM.

Could wifi on the smartphone have jammed the radio link ? 

I realize that the RC frequency hopping should prevent that from happening...

When a cell phone attempts to contact a cell tower it output a very high power pulse..... place you cell phone next to a cheap am/fm radio....does not need to be plugged in or have batts.  every 10 to 15 min. you will hear the speaker start making noise a cherp type sound.

That is the high power output inducing current on the speaker wires. setting next to an un-shielded APM could very easy lock up the APM 

Depending on the distance to the cell tower that pulse can be a full 5 watts

Logs would help..
Its probably just the Mobile pages of this forum that hides the logs from Mr

I agree with Kevin, the interview with the cells nearby can screw up a few watts of power, this can definitely send haywire APM2 or your receiver.
Dear Graham, Chris showed your crash on the dev list, but you would need to have the various logs for help the developer, cool thanks!
In the future and for security (I've done) put your smartphone in "Aero" mode... :-)

The logs are at the bottom of his post. The dev team is analyzing them now. We can see that PWM signals stopped coming about ten seconds before the crash, but can't tell if that was due to a wire/connection failure or something else. 

Thanks Chris appreciate that.

Hi Kevin, when I say remote it is very remote, in a wildlife reserve 100's of kilometers from the nearest town in South Africa, there are no cell towers nearby. The phone was on however, so I thought maybe that was the culprit but the furtherest point that I flew from me was perhaps 40m (20-25m high) where my RC signal should've been blanketed by the carbon frame and yet the loss of control occured at no further than 3m from me.
The phone was attached to the front of an H-frame quad which is 600mm long, the APM2 is in the middle so would be min 260mm away from the phone at it's nearest point. I have also flown with the phone before both on the quad and obviously on my belt with no problems, so I discounted that.
I'm now very nervous to fly again because if I had been in my usual open flying area the quad and the phone would be gone. Will probably only do it again with the quad tethered, I can't afford to lose it.
Re: the failsafe, the logs don't show it going into Loiter, rather it just stayed in Stabilize so the slow climb and drift will cause any 'copter in the same situation to fly away, I may want to fundimentally change my failsafe behaviour.

Actually not having any cell towers is worse !  It causes the phone to repeatedly beacon at Max output power to find a site.

There are documented cases where cell phones have caused problems in SCADA systems resulting in power outages. 

does not mean it was the cause, but a possibility 

Analog or digital phone ?

Analog is much worse.....much higher power output

a solution would be to put phone in airplane mode turning off all emitters 

Hi Graham,

Did you happen to have Mission Planner connected via a telemetry radio at the time? If so you should have a tlog on the computer for the flight. That may give us some additional clues as to what went wrong if you can post it.

Cheers, Tridge

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