Plane always stall in Auto Mode

Please help to review attached log. Plane suddenly spin and stall while in auto mode. It always happen and I have no idea what’s the problem…

Thanks in advance

Are you using a speed sensor (pitot tube) to measure the velocity of the airplane or relying on the GPS?

I have the same problem.

No airspeed sensor.
How to prevent this without airspeed sensor ?

No, I don’t use airspeed sensor. I am using 3DR GPS and Pixhawk with latest arduplane firmware. This morning, it happen again after around 12km flight mission when plane RTL…

Make sure your CG is correct so that the autopilot is not being asked to fly an otherwise un flyable aircraft. Also knock the cruise speed up and make sure you are not doing tight turns when coming home.

Its all in your setup of the airframe.

Thanks Gary,
I’ll try your advice today to make sure the CG is correct and increasing throttle cut. Yesterday, plane flight on straight path between WP with 17 m/s speed, then suddenly roll and crashed.

Today plane crashed again. From log analysis… I found ch1out > rc1_max when plane roll until Lim_roll_cd (5500). In ground test, when roll to right ch1out around 1400, roll to left ch1out 2400.

Please help ho to reduce ch1out… thx

It would be great if you could post the tlog and dataflash log from the most recent flight with the crash.
I had a quick look at your original file you posted (dataflash is better then tlog if possible - both ideal). If you look at the graph (green bit is auto ,mode) I can see when you put it into auto you then adjust the ailerons and elevator (red and green line - this is what the pixhawk sees coming from the receiver) and then you throttle up part way through. The black line at the bottom is the altitude error and its quite high and comes down and then goes up again and I’m not sure why - the barometer looks ok.
Post the next logs and we will have a look.
Thanks, Grant.