Flyaway with no manual control

#1

I’m not sure where this post belongs, so I will start here.

Situation: I was flying a F550 hexacopter with Pixhawk 1 running PX4 v1.8.2. It was checked out on the bench for all flight modes and everything was working. When I went outside to fly it, I checked out all functionality on QGroundControl, and watched the screen as I switched between all flight modes and they all appeared on the screen. GPS had 20 satellites. The Pixhawk light was green. Everything appeared to be good. I powered up, armed it in MANUAL mode, and I made a short flight to confirm everything was airworthy.

On the ground, I put it in ALTITUDE mode, took off and let it hover at 20 meters. Then I switched to POSITION mode. Instead of hovering in place, it started to move away from me and started climbing. Immediately I changed to MANUAL mode and tried to regain control. Nothing happened. Changed to STABILIZED mode. No help. Tried ALTITUDE mode. Nothing. Then I hit the RTL switch. No response. It kept moving steadily away. Then I tried all the flight modes many times but there was absolutely no response from the drone. I watched helplessly as it went out of sight. I watched the path on QGC. It was traveling towards a highway and a highly populated area, so I put the throttle in max position hoping that would keep it high. Altitude eventually went to 800 meters, yet nothing I did with RC control did anything to get it to come back.

Eventually I lost telemetry and data stopped. It was then at about 120 meters and coming down slowly, and the battery was very low so I knew it would be on the ground soon. The last known position was noted and we went to the area to look for the drone. This is a heavily wooded area, and after looking for it for a few hours, we have not found it, and may never get it back. Hence no log files are available.

One thing I remembered from the pre-flight checks was that I could not arm the drone in POSITION mode, but I thought that was not allowed, so I ignored it. In retrospect , maybe that indicated a problem.

Can anyone offer any ideas as to why this drone ignored MANUAL RC control?

Thanks,
Joe

#2

UPDATE: We found the missing drone three days after it crash landed. The log file has been downloaded but its too large to be uploaded to Flight Review (325 MB).

We’re analyzing the ulg file and trying to find the cause, but it would be great to be able to see all the graphs and flight modes. I posted this issue in another forum. But I’d still like to know under what circumstances PX4 will not respond to MANUAL RC control??

Joe