Motors stopped after RTL Off during the descent

ArduCopter Copter 4.3
1

Hi all.

I crashed my quadcopter today and would appreciate help understanding the exact reason behind the crash.

First I took off and ran AutoTune which took around 15 minutes. Then switched to PosHold and did a couple of runs back and forth to test the new PIDs (it indeed performed better than before). Then, while in PosHold, I switched RTL On, the quadcopter successfully returned and started descending. At around 5 meters altitude I flicked the RTL switch Off like I did many times before and expected the quadcopter to stay in place in PosHold, but instead it stopped the motors and dropped down like a rock. Luckily I was able to recover the log from the FC. I believe the FC got shorted due to the impact so the log ends abruptly. You can still see the AccZ spike right near the end though.

I have my flight mode switch on CH5, arm/disarm switch on CH6 and RTL switch on CH7. I am sure I did not flick the arm/disarm switch during the descent and the log confirms that.

Is there some setting such as “drop on RTL Off when below N meters” I missed? It feels like I’ve read about something like that. Or what else could be the issue?

Log file: Proton Drive

2

I cant see exactly why everything stopped and it fell - it doesnt look like it was disarmed BUT you do have a disarm/flight mode issue anyway.

The Flight mode channel is set to 5 → FLTMODE_CH,5
but channel 5 is also set to arm/disarm, same as channel 6
RC5_OPTION,153
so set that to 0

Vibrations are a little higher that ideal, so keep an eye on that.

1 Like
3

That’s why it shows this:
Chan5
Had never seen that before. The Arm State did go low Arm>ArmState

4

Thanks for looking into my crash and pointing out the issue with CH5! I will make sure to remove it from the configuration.

I have further analyzed the text log myself. The motors stopped 497334 microseconds, roughly 0.5 sec after flicking the RTL switch Off (CH7 LOW) which is A LOT of time from the FC’s perspective.

There are 5 RCIN entries in the log with CH7 LOW before the first
RCOU, 1930076740, 1000, 1000, 1000, 1000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
(when motors actually stopped)

Additionally, most of the time CH5 (flight mode switch(+ArmDisarm as it turns out)) was LOW and I was flying just fine. Also it turns out I was flying in AltHold, not PosHold as I said previously.

I am concerned about the following events right before the motors stopped:

RCIN, 1929976718, 1498, 1495, 1511, 1490, 981, 2006, 982, 1495, 1495, 1495, 1495, 1495, 1495, 1495 -- CH5 LOW, CH7 LOW, still hovering
RCOU, 1929976734, 1683, 1652, 1693, 1713, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 -- still hovering
IMU, 1930033817, 1, -0.03420993, 0.03389969, -0.003666854, 0.1133321, -0.6048949, -10.11778, 0, 0, 31.24371, 1, 1, 8026, 1003 -- still hovering
ARM, 1930074030, 0, 0, 0, 2 -- disarmed
EV, 1930074033, 11 -- DISARMED
EV, 1930074038, 18 -- LAND_COMPLETE
EV, 1930074043, 17 -- LAND_COMPLETE_MAYBE
AUXF, 1930074064, 153, 0, 1, 1 -- ARMDISARM
RCIN, 1930074091, 1498, 1495, 1511, 1491, 981, 2006, 982, 1495, 1495, 1495, 1495, 1495, 1495, 1495
IMU, 1930074133, 0, -0.03785662, -0.01811079, -0.001043019, 0.06309134, -0.05056441, -9.777349, 0, 0, 31.29408, 1, 1, 8013, 1001
IMU, 1930074133, 1, -0.03903559, -0.01423263, 0.009299725, -0.007442152, -0.2231734, -9.994185, 0, 0, 31.24668, 1, 1, 8026, 1003
EV, 1930075897, 56 -- MOTORS_INTERLOCK_DISABLED ???
ERR, 1930076320, 24, 0
MSG, 1930076356, EKF primary changed:0
RCIN, 1930076700, 1498, 1495, 1511, 1491, 981, 2006, 982, 1495, 1495, 1495, 1495, 1495, 1495, 1495
RCOU, 1930076740, 1000, 1000, 1000, 1000, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0  -- motors off
IMU, 1930113982, 0, -0.07790092, -0.05334528, 0.0118871, 0.005556145, -0.1037423, -4.952807, 0, 0, 31.29859, 1, 1, 8013, 1001 -- rapid acceleration towards the ground, accZ -4.95 vs -10 in hover

Might the disarm have happened due to the AP assuming it successfully landed, not because of the switch?

Text log: Proton Drive

5

Still hoping to hear an opinion on that…