Complete loss of control after takeoff


I would appreciate any help finding the cause of crash of my hexacopter, running 4.3.6 (on Matek F405 miniTE).

Here is the story:
First flight of the day, flew normally, mix of ACRO, LOIT, STAB, did the test of RC Failsafe - it returned to land, but decided to slam in the ground a bit too hard, damaging one arm…
Replaced the arm.
Took it out for a quick test flight. After arming in STAB, gave a bit of a throttle to lift off, the motors spun fast, uncontrolled yaw/rotation, and copter rapidly moving towards parked car. To avoid collision, gave it max throttle, it overflew the car and slammed into a brick wall behind.
Surprisingly, the system was still powered up, so was able to retrieve uncorrupted log.

I’m not that good at analyzing, so would appreciate any clues as to what caused uncontrolled behaviour.

log_1_UnknownDate.bin (142.6 KB)

The log ends abruptly at ~3m in altitude probably when it hit the wall but you can clearly see the Yaw on Take-off. Perhaps a motor was damaged in the previous crash.

This craft should not have been flying at all, it’s on default parameters w/o even the Initial Tune Parameters set which are for pre-maiden flight. Best to start at the Tuning section of the Wiki and work thru it starting in Mission Planner with Setup>MANDATORY hardware>Initial Tune Parameters

Just reading the text and not looking in the log, my bet is when the arm was replaced the motor direction was reversed via the bullet connectors - causing the uncontrolled yaw on the next flight.

MissionPlanner Motor Test

i’m not THAT stupid. Motors are soldered, wiring was not affected during arm swap, as motor bolts on the pad and wires are cable-tied along the arm.

Seems to be large yaw-imbalance after takeoff.

Airscrew size = 9 inch - yes, I’m on DJI 2312 motors and 9450 props !
Battery Cellcount = 4 - yes, 4S battery at 4.2 max voltage, 3.3 is good for minimum. LiPo.

That frame done 24.5 hours/133 flights. So maybe the previous crash somehow zeroized the tuning…

Thanks, was that commanded by RC ? (do I have a glitchy gimbal perhaps?)

Actually looks like the expected yaw and desired yaw track well (so the autopilot was actively commanding fast CW yaw). Maybe the compass got damaged during the crash?

Thank you, probably should have run recalibration…

Yeah I thought about it last night too and guessed you probably didnt need to disconnect the motor or ESC since it may have been soldered anyway. I apologise - I didn’t think you were stupid.

You can forgive me for assuming the motor direction issue though since NOT running the motor test is a mistake we commonly see way too often. And the number of times we see “I’ve definitely run the motor test and everything is perfect but it still flips over…
If I’m going to use a copter that hasnt flown in a while I’ll run some motor tests and do a quick scan over parameters to ensure nothing has been changed by cosmic rays or long-forgotten tests.

haha been there, done that, back in 2018, when I’ve assembled my first DIY quad :slight_smile: Lucky i did test flights attempts tethered with a bit of a rope, so no damage to the surrounds :slight_smile: Then my friend explained me the whole “front props scooping inwards” layout for motor direction.

I’ve rebuilt it (replaced two “tight” motors that were damaged in crash), flashed 4.3.7, did ground runs to check smooth motor operation and correct direction.
On the test flight, after about 10 metres, it started jerking, and then one (front right) motor just stopped ! Thankfully being hexacopter, it remained surprisingly controllable, even directional control was ok. I managed to gently bring it to land without damage !
When disarmed, motors were beeping “down tones” (kinda like ESC recalibration sound ?). Buggy / damaged ESCs ??? (i use two 4-in-1 Diatone Mamba’s)

Just an idea: Check all your battery voltage monitoring and failsafe levels in arducopter, and check in BLHELI settings that low voltage protect is OFF
Could also be a bad connection somewhere??

battery voltage monitoring is a bit weird with this frame: QGC shows red 100% all the time, but if i click on it, shows real voltage state, and low battery failsafes work (it’ll attempt to RTL at 13.2v for 4S). Also on OSD (looking through FPV goggles) it shows correct voltage.

I may re-run ESC cals, and double check the wiring, and maybe swap the motor to be sure.

ESC had it. On initial power up, it runs all motors, but if I keep throttle high for 5-10 seconds, that motor starts jerking then shuts down… repeated twice. I wonder if that what caused the original uncontrolled yaw crash ?

Good thing its a hex with two 4-in-1 ESCs so hopefully I can remap one of the two unused channels.

Interesting. I also used a Diatone Mamba and experienced uncontrolled yaw. @xfacta remember that? I wonder if there’s an issue with these ESCs. I was just about to wire up a new one but am now reconsidering.

well that frame flown for 25 hours and numerous crashes/rebuilds, before experiencing that yaw issue.

The full model of ESC is “Diatone Mamba F40 MK2 40A Dshot600 4-in-1 ESC”.


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Ahh gotcha. I was and am running the F45_128k

I am also facing the same issue… did the problem solved? If yes kindly provide the solution

I suspected and changed ESC and motor, but I think in the end it was the ribbon cable between FC and ESC. What is your setup ?