Bad desired angles lead to a flip during take-off


I would like to have your help with this investigation.

The case- my drone flipped over on take-off in Loiter mode.

  • X4 copter
  • Ver 4.1.1
  • DataFlash log & TLog & Parameters list- Sign in to your account
  • Time tag of flip in logs: 08:37:12
  • This is not the first flight of the drone

My findings so far-

  • [08:28:06] After the pixhawk boot, the NAV desired angles are set up with an abnormal value of roll +39 deg; pitch -38 deg.
  • [08:37:07] Drone arming- the NAV desired angles are changed to (still abnormal) roll -8 deg; pitch +32 deg. all motors are spinning at the same rate.
  • [08:37:12] Take-off attempted- Drone pitched up and flipped on the back
  • No messages or warnings at all.

I have never seen this kind of behavior before and I would appreciate any help

I have a heli user that experienced a similar behavior posted here where the desired pitch and roll angles were very high before takeoff. The user was also using version 4.1.1.
I would recommend that you upgrade your version to the latest stable version which is 4.1.5. Then before you takeoff verify in your ground control station that your desired lean angles are at appropriate values which should be zero. If you see this same behavior in 4.1.5 please post a log file in this thread.

1 Like

Dear Bill
Thanks for your reply and help.
What do you think will be better? to downgrade to V3.6.12 or upgrade to V4.1.5?

Upgrade to 4.1.5. There could be patches that fixed this issue but I never heard anyone having this kind of problem. Nonetheless, monitor the desired angles through mission planner prior to launching. I don’t remember the exact signal names in mavlink but I’m fairly positive they are there. If you are able to reproduce this, then use the log_disarmed parameter to log all of the data even prior to arming. Then post it here. It will help determine if it is unique to your setup or a true bug.

Hi Bill
Thanks for your reply.

The relevant fields are nav_pitch and nav_roll.

You can see their values in the Tlog I attached, you can see that they have incorrect values since the pixhawk boot-up [log time- 08:28:06].

Do you think there is a bug here?

Thanks for your attention, I’m looking forward to your reply!

Before I do anymore troubleshooting, I would like you to upgrade to the latest stable version. See if you are still experiencing this issue with the latest stable and we can go from there.