An interesting failure

Hi all, I am new to this forum so hello all.

Saturday morning, usual flying site, good weather. I performed a manual takeoff, slightly crosswind, climbed to around 40m and selected RTL as I normally do to check the autopilot and rtl functionality. Immediately on selecting RTL the gcs (missionplanner on windows 10) lost connection. The plane (Skywalker x8) performed a graceful climbing turn back to the RTL location and started to circle. Satisfied with this but a little confused about the datalink loss I switched to manual and my plane continued circling. I could get no response from the plane at all. After about 10 minutes of circling above the home location my X8 took off south like a scalded greyhound maintaining altitude quite nicely. 60m gives around 10m clearance of the highest point within 5 miles of my flying site. At this point I was thinking that I have lost my model and was heading for the car. About a mile and a half away I saw a small flash of yellow as she turned around and headed back home performing a perfect RTL. While all of this is going on I am trying to reconnect the datalink but noticed that the 3DR has a flashing green LED so no connection. No joy with this and restarting the Taranis was just as effective. I resigned myself to a crash when the battery went flat. Part of the circle on RTL is over a lake and crosses a major road. I heard the motor stop as the SC went into battery protect mode and the plane crossed the road at about 30 feet and landed in the field! The only damage was a winglet snapped off.

On returning to my workshop I found that the 3DR was completely dead, no LEDs at all and on connecting to the APM (2,6) discovered that there were no datalogs saved on the apm and the RX calibration had been wiped so no response from the apm using the RC tx.

No idea what caused any of this and no logs to try to diagnose it. I am guessing that there was some kind of power surge which fried the 3DR and wiped the flash memory for the logs and settings yet it ‘remembered’ the home location and flew (very well) with the default PID settings.

I have replaced the 3DR module with a spare and that works and connects fine. The APM seems to be holding the settings properly now and happily creates log files although I haven’t had the weather to fly again yet.

Total flight time this flight 35 minutes, with just over 34 and 3/4 of them being out of my control.

Total airframe time: 3 hours 37 minutes, all trouble free.
3000mah 3 cell.
I can’t remember the motor but it is about 600 watts on 3s and a 12x7 folding prop.

If anyone has any suggestions as to what may have happened I would be interested. I have now set up a rally point away from the lake and road and an auto landing procedure so hopefully a similar failure in the future will keep the plane away from the road and lake and put the X8 back on the ground without me having to wait for a flat battery.

Looking forward to your responses,


Of course, with no logs we’ll never know for sure.
you mention “fried 3DR” , I guess you don’t mean the 3D Robotics company is/were “fried” but APM ? - or GPS or something.
Dataflash is not easily damaged by electric anomalies.
The removed radio-calibration reminds me of the possibility of

  • at least, you should change the radio link ID, but maybe, like many others - you fly on “25” ?
    Finally - using windows is not a thing I would consider safe, or reliable, even when offline. Check out APM Planner2 and/or mavproxy and run it on Linux like professional users do.
  • Anyway - with no logs, only guessing remain.

I am unsure as to whether the 3DR module is a symptom or the cause of this issue. It is completely dead now. I had one of these units fry on another project, that toasted a pic 16f628a for me (overcurrent as it failed.). I have changed the “25” as I fly several aircraft and it is a reminder to me which is set up on the pc. I do use mission planner but as you observe it is on windows 10. I had considered the hack but it is unlikely, partly through location but mostly because there isn’t anythng a hacker could do that would fry only some of the onboard electronics whilst in flight. The APM appears to be fine, as does the gps. everything is working properly now I have replaced the 3DR module. It looks as though it will be another week before the weather will allow me to test fly. I will have the drone ready with a catch net just in case though.