Need expert eyes - Unknown crash!


  • 25kg X8 multirotor
  • Pixhawk 2.0
  • Taranis and x8R FrSky on RC
  • RFD 900+ on telemetry

5th flight of the day and everything is going well until the UAV drop from 20m up in what looked like a complete power failure, but the logs show that power was still flowing… I’m stumped.

I attach the .bin file for review. I hope your joint experiences will help shed light on what happened.

Thx in advance

00000183.BIN (278.1 KB)

Yeah, something cut your motor power. The current draw suddenly goes from 60A to 0A (CURR.Cur) while the drone is ascending. This was not commanded by the FC, so it is likely a hardware problem.

(Probably) unrelated to the crash: your battery sags by 2.5V, which seems a bit excessive even for 8S. The battery seems a bit overstressed.

Yeah, it’s hardware. What were you using for current sensing ?

Rick, check that 4A spike before takeoff (probably a gimbal working towards default position) and the voltage sag it created.

To answer some of the prior questions:

  • The 8S batteries should be performing right within their operating margin. I’m flying two 10,000mAH (in parallel) with a 20C rating, motors run under 75% load. Even if one of the batteries did fail, wouldn’t the secondary at least try to keep it airborne?

  • The current sensing is fed from the power distribution board (didn’t install myself so can’t actually give you a reference for it)

  • The current draw (4A) before take-off should be the motors hitting idle before spinning to full speed as I don’t carry a gimbal.

Yeah the battery thing is unrelated to the crash, I was just mentioning it because I also use 20C 10Ah 8S batteries with a similar load, and only see 1-1.5V sag.

I would suggest examining your power distribution and cabling, because your motors all lost power in flight at the same time.