Log analysis after hard crash


I have some trouble figuring out what was the cause of the crash for one of my 690 size quadcopters.
7.4kg AUW
Quadcopter using tarot x680 Frame
T-Motor mn501s 360kv motors
17 inch carbon props
Tmotor alpha ESC 40A LV
CUAV x7 PRO with dual GPS (CUAV neo V3 PRO and CUAV neo 3)
Turnigy Graphene 6s 12000 Mah Battery

Summary: Mid flight oscilations out of the sudden follower by control loss and falling out of the sky. Mission Planned did not display any message during the flight except for the normal WP reached.

Link containing the log: Crash 1 - Google Drive

Firmware 4.0.7.

Any help is appreciated.

Thank you,


looks like motor 2 failed. it didnt fail right away it looked like it started working intermittently before it failed. could be a loose propeller or wire.

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It did actually but much too late. Potential Thrust Loss when it was about 9m from hitting the ground.

I will test it on the bench to see if it works or not. To think that even “the safer propulsion system” can fail mid air is a scary thought…
Can you by any chance take a look at the desired pitch/roll vs actual pitch/roll?
I can’t figure out if there are any red flags I might have missed (before motor 2 started acting up)
Tuning was done manually on this quad.

Thank you for your reply.

This is why all my future builds have ESC telemetry, that way I know what the motor was doing when it failed Instead of only knowing what the flight controller is asking from it.

your des pitch and roll look fine.

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T-Motor Flame :fire: - the name gives it away.
Change to Hobbywing X Rotor or something reputable with BLHELI32.
Or APD if you need high-end and reliable.

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I heard some horror stories with the flame esc-s, that’s why I went for the alpha.

Will look into APD, thank you!

Yeah sorry I thought you wrote Flame but I see it was Alpha. Same story though…

We have been flying alphas for a long time. What we learned was that you have to open the aluminum case and check the wires, capacitor, and soldering. Sometimes they come broken, specially the capacitor leg in the circuit board. Hope APD is more reliable, we are also looking forward to test it.

I have tested all motors on the bench before disassembling the quad. Sadly they work fine, both the motors and ESC-S. And when I say sadly I mean I still have no clue what happened on that flight that lead to the crash.
I took the esc apart and it seems to me that there is a fine solder job.
Pictures attached.

It’s possible it just desynced, it’s common when trying to run really low kv motors. Shortening the motor wires can help but its something I have seen a few times with tmotor escs. I can’t say if they are bad or they are just common and I just hear about them more often but its known to happen.

I wonder what changes are made in their firmware when you select different Motor options? This is from a T-motor seller.
Flame firmware

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That’s interesting I have never seen motor specific firmware for an ESC, If this is the case for Tmotor escs then it would explain a lot.

Yea, actually I hadn’t either until I google searched those ESC’s. That retailer also says this:

What firmware do you prefer?
T-Motor factory can flash the firmware to work best with your motor (in the ALPHA ESC Recommendations list above), you can write down your motor model in the comment box when you checkout, we’ll tell T-motor factory.

Kind of skeptical that actually happens…

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Do they list different firmwares on the Tmotor site for the escs?

In my case, I bought the motors from a different vendor. When I ordered the ESC-s from the other vendor they asked what motors I intend to use with that specific esc. Then they flashed the correct firmware.

I was curious about this as well so I bought an esc flasher and indeed, when you connect them to the PC and run the software it was showing firmware for mn501s 360kv (the motors I was using).

So yes, apparently they do flash them, but i have no idea what changes inside the firmware with each different motor. Another interesting fact that I haven’t got a chance to test is that they said the alpha esc-s work only with specific tmotor motors.

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Firmware is selectable in the software used for flashing the esc after all the connections are done.
Search for Tmotor Data Link for more info.

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Can you see the settings used from the flasher software? Like BLHeliSuite shows.

Hi. I’ve had crash 3 times with MN501S . I believe there is problem on ESCs . Now ı am using MN6007II

This is my last crash : https://drive.google.com/file/d/1ZcC9rP2rlU5u-DnDr2m5UM3wQAagcUa-/view?usp=sharing

Yes, similar situation.