Bad crash of my Hexa

[chschmid]

I spent the afternoon at the flying field and we where taking some videos. I had two perfect flights. Then I took off for the 3rd flight. Took her to 5m, engaged PH, set heading, switch to HF. I usually test if HF works fine then. I yawed 90° left and found that HF is not set right. I try setting heading again with no success. I reset home position and then set heading again. This time the system works in HF as expected. I pass the cam control to my buddy. He switches on the cam and a the same moment the Hexa tilts to the left and crasehes more or less upside down. (some cables off, GPS wire in two parts, one arm broken, two props broken, gimbal .... ect)

Going thru my logs I find that the logs stop at a maybe 30°tilt to the left @ PH altitude.
I have no clue what the tilt and crash caused, but what makes me even more nervous is that the logging stopped midair. Does that imply that the CPU stopped working?
After the crash, the board plug was not connected. But I guess it unconnected at the crash. If it would have unconnected in flight, the log would stop @ nice level flight.

I really could use some hints for doing the aftermath and isolating the problem. Unfortunately I have no ground or air Video of the Crash.

Log and KML

Cheers
Christof

[Cookiemonsta]

Which firmware version did you use?
Greetings,
Monsta

[chschmid]

Sorry I forgot to mention that.
FW r198 mod (two channels passthrough in gimbal.*). No changes since the maker fair.

Cheers
Christof

[Kisssys]

I wonder why the battery voltage prior to the disturbance was discharging normally to a nice 15.4, during the next 850ms it dropped to 13.6 and going down fast.

Well I guess it could be that the battery can't handle the current, it was asking a lot.

[Max]

Oh no! Sorry to see that Christof!

As Bill explained to me once, the logging process has a buffer, so it may not log the last second or two before impact. That it was still logging during the tilt suggests that the system was still running OK. The one time I experienced a system shutdown in mid-air due to fw bug, all motors quit at once and the 'copter came straight down. Could you tell if the motors were still powered before the impact? Is the chopper well balanced, or would it tilt to one side in a free-fall?

The voltage does look suspicious! Hope you get to the bottom of it.

-Max

[chschmid]

Thats very interesting. I was looking at the current log. Here are the logs of the flight. I cut 0-374 sec because the AQ was sitting battery connected for a while before take off. The flightpack was disconnected at the crash.

My best guess is the volage drop due to the current drawn. The logger can not read more than 60Amps max. The System draws 6x20Amps at full trottle. I use 25C batts. Given that the current went up to some 100+ Amps, 3.4V per cell is ok.
Checking the used Pack I have only .02V celldrift. (4.01,3.99,4.01,3.99).

It looks like the AQ shut down the motors while going down. Before disconnecting the main battery, the current log is 1.38A only.

New Session,88,940.5,HEXA,162,6000
Timestamp (s) Voltage (V) Current (A) Consumed mAh
374.2 16.59 1.62 0.11
374.4 16.59 1.62 0.11
374.6 16.53 4.16 0.11
375 16.49 8.5 0.11
375.2 16.49 8.5 0.11
-> Liftoff
375.4 16.37 31.56 0.11
375.8 16.13 36.78 0.11
376 16.13 36.78 0.12
376.2 16.05 30.72 0.12
376.6 16.08 30.6 0.12

-> Hover @ ca 30A

497.4 15.28 28.11 1.11
497.9 15.28 29.99 1.11
498 15.28 29.99 1.12
498.2 15.27 29.73 1.12
498.6 15.27 29.06 1.12
498.8 15.27 29.06 1.13
499.1 15.27 28.09 1.13
499.4 15.29 29.04 1.13
499.6 15.29 29.04 1.13
499.9 15.29 27.21 1.13
500.3 15.27 26.16 1.13
500.5 15.27 26.16 1.14
500.6 15.27 30.37 1.14
501.1 15.28 30.05 1.14
501.3 15.28 30.05 1.15

-> here the current jumps to a lot of A. My logger can not read more than 60A. The System draws 120A @ full throttle.

501.4 15.04 61.04 1.15
501.8 14.3 61.11 1.15
502.2 13.69 61.1 1.15
502.5 13.69 61.1 1.17
502.6 13.56 61.14 1.17
503 13.66 48.14 1.17
503.2 13.66 48.14 1.18
503.4 14.54 1.38 1.18


Cheers
Christof

[chschmid]

[chschmid]

Maybe I had a motorfaillure. I will check that tomorrow.

[bluuu]

bad crash :/

Can You compare this with my crash ?
It was similar ?

[LPR]

Christof

It's really sad to see your beautiful copter looking like it does now. I hope you get an answer to how it happened.

The Dewalt quad is still flying well but I had a little crash due to a change I made in DIP settings. Always looking to find the limits.

Larry