RTL -> THR to 100 -> Skywalker Crash

ArduPlane Plane 3.9
1

Hi guys,

I had a strange problem on the last flight that caused my skywalker to crash.
At one point during the flight, I activated RTL and everything went well, when it got to home and started loitering, the throttle went to 100 and when it started to turn, it started to increase the inclination angle and started going towards the ground, at that moment i’ve passed to STAB to try to get it back but it was too late. Can anyone help me analyze the problem and try to find the possible cause?
Log and dvr record https://drive.google.com/drive/folders/1q8QMjBj4n85M8eUgbO_cQE2wdgJEry3X?usp=sharing

Auto analysis result
No of lines 861388
Duration 0:17:17
Vehicletype ArduPlane
Firmware Version V3.9.6
Firmware Hash a8568402
Hardware Type
Free Mem 0
Skipped Lines 0
Test: Autotune = NA -
Test: Brownout = GOOD -
Test: Compass = FAIL - Large change in mag_field (54.53%)
Test: Dupe Log Data = GOOD -
Test: Empty = GOOD -
Test: Event/Failsafe = GOOD -
Test: GPS = GOOD -
Test: IMU Mismatch = GOOD - (Mismatch: 0.50, WARN: 0.75, FAIL: 1.50)
Test: Motor Balance = NA -
Test: NaNs = GOOD -
Test: OpticalFlow = FAIL - FAIL: no optical flow data
Test: Parameters = GOOD -
Test: PM = NA -
Test: Pitch/Roll = NA -
Test: Thrust = NA -
Test: VCC = UNKNOWN - No CURR log data
start the issue thr=80% roll 13º

Screen Shot 2020-09-26 at 16.49.02
Screen Shot 2020-09-26 at 16.49.021340×766 137 KB

thr=100%

Screen Shot 2020-09-26 at 16.49.13
Screen Shot 2020-09-26 at 16.49.131362×806 137 KB

see roll º :crazy_face:

Screen Shot 2020-09-26 at 16.49.23
Screen Shot 2020-09-26 at 16.49.231302×782 119 KB
Screen Shot 2020-09-26 at 16.49.34
Screen Shot 2020-09-26 at 16.49.341348×760 107 KB

Thanks in advance

2

Problem with compass
It seems you had a huge baro drift !

image
image1920×1056 512 KB

3

Thank you very much for taking the time and helping me analyze my problem.
I’ve new questions:

  1. How do you see the graph that way? I have tried in mission planner but I cannot change the layout of the chart
  2. the compass can cause the throttle to change to 100% only when it enters loiter?
  3. how can I correct the problem?

Btw, i think the BARO alt is correct, at least is same as the dvr video… here is where the problem start

crash_analysis
crash_analysis2374×1570 797 KB

compass_config
compass_config1346×954 175 KB

4

Hi @tridge, is there any chance you can help me determine the problem? i was trying to investigate it with my knowledge and with the help of another experimented person but we did not find why the THR went to 100 and the roll to 73º.
Thanks in advance

5

You have problem with your compass and your cog seems tail heavy. For full throttle, ardupilot try to compensate … Check Aileron and Elevator at the same time for tail heavy

image
image1249×974 140 KB

Explanation on roll for tail heavy is available here : Crash - Death Spiral - Arduplane 4.0.1

6

sorry for late response! thank you very much for your help.
For the compass issue, do i need to recalibrate the compass? or i need to something more?
I’m going to check all the servos again and add a little more weight to the nose