Copter - 3.4.6: RTL Land At Wrong Location After Battery FS

I loaded Copter 3.4.6 on my Pixhawk this weekend to do some flying in auto mission. I wanted to test out some of the FS options. I experienced a behavior I cannot explain with battery failsafe.

I purposely left the battery failsafe voltage higher than I normally would so the event would trigger in the middle of the auto mission. I have battery failsafe set to RTL. As I had planned, about 3-4 minutes into my auto mission the battery failsafe triggered and the pixhawk quad entered failsafe and went into RTL mode. (All expected behaviors at this point).

The quad turned and started to fly straight towards home. It flew for about 30 seconds along its course toward home until it stopped, and started to descend and land (unfortunately it was still above a woods). It was not a crash but a controlled land by the quad. The quad was still about 1240 ft from home location when it decided to land. (The quad did end up crashing as the land happened above a woods and into trees.)

I double checked the FS parameters and looked at the data flash logs. The FS parameters for the battery look correct and are set to RTL. I cannot find any additional errors in the data flash logs. Does anyone have an idea of what and where I should look next to understand what might have caused this behavior?

Did you take off in Stabilize or Alt Hold without a complete GPS fix? If you did that, it probably got its first GPS fix while airborne, which sets the home location for wherever you happened to be at the time.

I had believe I had GPS fix as the quad followed the mission plan for about 3 minutes tracking perfectly. I am thinking that it would not have been able to change and execute on auto mission mode without the GPS fix. Is there another place I should check on why it choose the location it did for landing?

So the mission began with takeoff? In that case it would definitely have had a valid GPS fix, or it wouldn’t have begun. Post the logs for folks to look at.

I armed the motors, lifted off the ground, and triggered auto. The copter flew the mission for about 3 minutes until my FS Battery triggered (as I expected since I set the value higher than normal to test the FS battery RTL functionality). RTL did trigger but the copter did not RTL.

Thank you for the help.

Just wanted to bump this to see if anyone might be able to help explain why the Quad unexpectedly landed where it did on a Battery FS RTL. Help anyone?

Hello , I can see in your log an error 16 2 ( line 117275) which means Bad Variance , immediatly followed by an error 17 1 (Failsafe_EKF line 112276) an a Land (line 112277). The FAISAFE_BATT arrives later and is not a priority (line 131058).Bad Variance is frequently due to interferences on the compass , maybe not distant enough of the electronics , motors …