HEXA almost crash

Today will go down in my flight history. One of the six motors burnt out while flying over a residential area. I only avoided the crash because I am flying an X6 drone. If it were a quad, it would definitely crash into the ground, or worse, it would do property damage.

I am asking for help in finding the cause of the engine burning out during the flight. I have never faced a similar situation.

Motors: 6x Gartt ML5008 400KV
Propellers: 6x Tarot 17 "TL100D10
ESC: 6x Hobbywing XRotor Pro 40A
Battery: 1x LiPo Tattu 16000mAh 6s 15C
Drone weight: 7.3 kg

I post the log:
https://drive.google.com/file/d/1Z98WaQ6otl4bX30iCRuoT7tgKkzqFMbi/view?usp=sharing

PID:

Photos:


It was going well but that bad motor (or ESC) got worse and worse during the flight, losing thrust over time.
The output of the opposite motor is reduced to compensate.

I would use MissionPlanner motor test to run some tests and see if the motor or the ESC get hot.Without temperature data it’s hard to tell whether it was the motor or ESC. It could even be an ESC fault that has now ruined the motor - or the other way around :frowning:
Could be as simple as bearings in the motor - if so replace all bearings in all motors.

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I dismantled the burnt motor, the bearings rotate smoothly, but I’m not sure if they will behave the same at high speed. This is a guessing game.

Motor coils not shorted? It happened to me with an Octo, the motor burned, the coils closed short and consequently the entire power system collapsed, completely shutting down the equipment.

This is what the coils of a burnt engine look like:

Oh yeah! In your original picture you can see that in the motor coils, I missed it earlier.
You’ll still need to test if that ESC is OK, or dont take the chance and just replace it.

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I did a test of the motor temperature with a pyrometer in a home condition 27° C. I used the motor test in Mission Planner for this. During 2 minutes at 50% throttle consumes 11A and heats up to 78 ° C. I made measurements in the area of bearings.

It’s getting really hot, usually no more than 70ºC with payload.

Scorpion motors need regular oiling of the bearings. I wonder if other brands should recommend the same.