Quad tilted to the left and hit ground

Hi all,

I was hovering my quad indoors and all of sudden it tilted to the left and hit floor.I flew this quad before on 4S and never had issue since i built it last month.But now i tested on 6S @ storage level. Motors are genuine DJI phantom 4 pro motors and ESCs are Tekko32 F3.

I tried to review the log but i could spot anything except Motor no.2 RPMs are shooting up.I don’t have expertise to review it properly. Still learning.

Could anyone please have a look at my log? Thanks.


Edit: I found that ATT roll is changing abruptly and deviating from desired roll . So one motor desyncing ??

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Do not use 6S batteries on a copter parameterized for 4S.

You will need to fully redo all the tuning procedures after doing such a drastic change!!

Thanks Lucas.I won’t use 6S.

So did it happen due to using 6S?I just want to make sure that it didn’t happen due to any ESC issue.If that’s the case then I can send ESCs back for warranty.

Hi @ninja_zx11,

I had a quick look at your logs but your analysis that something went wrong with motor 2 seems correct to me. It shows the classic symptoms of a motor/esc failure for motor2:

  • motor 2 (back left) spikes to maximum and its opposite (motor 1) goes to minimum
  • the vehicle leans towards the suspect motor with the high output (motor2). In this case the vehicle rolls left and pitches back.
  • desired and actual attitude angles are find an then suddenly diverge at the moment the motor output goes high

From the MOT_PWM_TYPE parameter (4) it looks like this vehicle is using DShot 150 and the board is a KakuteF7.

If this was 4.0.7 I would definitely conclude that this is a motor/ESC failure especially considering this is the first time you’re testing with 6S (I assume the ESCs and motors can handle this?) but I will check with the other developers before making that conclusion.

@andyp1per, FYI.

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Thanks Randy for looking into my log. Yes its 4.0.7 and board is KakuteF7 and ESCs are Holybro Tekko32 F3.Escs on Dshot150. ESCs are rated up to 6S.

I will try to run hard on 4S to check if problem still occurs.

What’s the voltage rating on the electrolytic caps you have on ESC voltage inputs ?

Actually I have a single 1000uf 25V Low esr cap at the battery input. But I was running 6S @ storage level. So batt volts were 22.5 when this incident happened.

This was just a 6S test and this quad is intended to run on 4S.I just tested to get a feel on 6S as my electronics support 6S except this 25V cap. That’s why i was running at storage charge.

I having the same issue i think today.

I using 4S.

log https://www.dropbox.com/s/6q1720fee591sd7/2021-05-03%2009-29-26.bin?dl=0

tail end of video: https://www.dropbox.com/s/wtwsf0pvznrrm3y/crash.mp4?dl=0 After 7 min of testing and flying well i heard a pitch change " high" the tail moved up like a cat and i lost control of the craft.

Few min before fling well: https://www.dropbox.com/s/0rbzrms8mbsmwl0/rotation01.mp4?dl=0
a friend thinks its a esc issue.

Pitch and roll depart at about 2:36:57

Motor outputs change at the same time, not exactly like a failure, they still seem to be responding but outputs 9 and 10 are affected the most - maybe a desync??

What BLHELI settings are you using?
Outputs are generally a touch on the low side when operating normally, you might need to add a bit of dummy payload.
And plug in those MOT_BAT settings :slight_smile:

will do, I have a bigger battery i can fit a 5000 mAh. Dshot 600 but just the passthrough option set to auto.

Yeah I saw DSHOT600 in params.
I meant the settings in the ESCs like Low RPM Power Protect and so on:

I can get that for ya, basically i just used the rotate direction. coming up.

Definitely turn off Low RPM Power Protect and Low Voltage Protection, just ensure your other forms of voltage monitoring and failsafe actions are accurate and configured correctly.

I think with that size craft you’d be able to strap it down and play around with MissionPlanner motor test, or especially the BLHELI motor test function where you can set high/low throttle cycles. See if you get any desyncs.

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Thank you very much.

Brandon, what flight controller is this?

X2.1 777 mRo It’s been a fantastic controller overall.

Did a few changes as suggested and a few more settings like powerup.

Turned off Low RPM Power Protect and Low Voltage Protection.
changed demag to high, changed power up to 13
will use bigger battery or install the gopro 9
setup battery monitor and fencing.

Thank you will test it ASAP.

As belt and braces it might be worth changing SERVO_DSHOT_RATE = 4 or even 5, this will run the dshot output rate at 4xloop rate = 1.6Khz which on an F7 is fine (assuming your loop rate is 400Hz).

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Sounds good will do.