Usually a setup problem, many are using AP3.1.1 quite happily on a flying wing. Test on the ground with the aircraft level, If you switch to FBW_A (don't use FBW_B just yet) then the elevons should stay level and move in their correct directions when the aircraft is rolled or pitched. If not your setup is wrong.
I have checked the elevon on ground direction is ok also tested in FBW_A same issue could it be a hardware problem? on flying wing i am not using rudder channel from radio do i have to close yaw gains?
3.1.1 works fine for me on a wing, please post a log file.
Attached find log file
When you say you've checked direction, is that the direction it moves in response to you moving the tx sticks? or the direction the ap moves the elevon in response to you moving the wing up/down left/right?
I have checked both TX and APM moving it in pitch and roll.
And the control surfaces move the opposite way to the way you move the wing by hand in fbwa? ie manually point wing up elevon moves to push the nose down?
Do you have a .log file or just the .tlog file?
yes in right directions i had tested a previous version i cant remember with flawless auto takeoff and landing. in which folder is only .log file?
I regularly fly 3.1.1 on my flying wings... it works nicely.
The failure you describe could be related to a couple of things in your setup.
1) the level for the APM has to be calibrated (set it with a few degrees of up (positive incidence) and wings level) without a little positive incidence in its level reference the wing will descend when in FBWA.
2) The problem you describe sounds like the APM is configured incorrectly. The APM has to move the control surfaces in the correct direction in FBWA... Not just move the right way the Radio input to test this, without any input from the xmtr roll the wing left and right... the aileron on the high wing should come up. with the nose pitched down both ailerons should come up. If it does anything else, you have a config issue.
Best of luck
Looking at your log it is clear your RC calibration is a long way off. When you are flying in manual the zero of your sticks is around 1600 for channel 2 and 1447 for channel 1. Those values need to be in RC2_TRIM and RC1_TRIM so that ardupilot knows when you want the plane to fly level. It also looks like your _MIN and _MAX values are wrong. So start by re-doing your RC calibration. I suspect you may have skipped that step. You may also like to read up on the TRIM_AUTO option (make sure you read the docs carefully to understand how it works).
You should also fly in FBWA or AUTOTUNE before any other mode. Your flight log shows most of the flight is manual, then you skip straight to auto. You do spend a couple of seconds in RTL and FBWB, but not enough to actually tell how it flies.
I'd also highly recommend you read up on AUTOTUNE mode. If you are already comfortable flying the plane in manual then try AUTOTUNE_LEVEL=7.
Are you using the Airspeed sensor. If yes, and it is "enabled" make sure it is reading airspeed, had this issue with my FX-79, found my airspeed sensor was not reading, and was enabled, and in every Auto mode, it thought it was stalling, so it dove to gain airspeed. Also, I just had a crash this saturday that involved "min airspeed" beign set FAR too low, my fault I know, but this created a situation where the airspeed was a bit too low, and turning from down wind to an up wind situation, the aircraft tip stalled into a irrcoverable spin dive. Out of curiousity, which airframe are you flying?