VTOL plane crash during hover tuning

Hello guys,
We have been trying to tune a VTOL plane of about 8 kgs. The actual weight of the bird will be about 10 kgs, but we were doing an initial tune and test with the current configuration.

We did some initial tuning manually in some high winds and got a good enough tune to check forward flight. For a better tune in VTOL, we started tuning in less windier conditions yesterday.
However, during the second flight the plane started swinging and we ended up crashing. I did not get the video of the crash unfortunately.

We have been trying to identify the cause of this behavior from the logs. The first flight was very good, and we made very little changes in the PID for the second flight.


  1. There was a decent amount of wind in both flights leading to slight oscillations but well within the capabilities of the system.
  2. The motors and ESCs had become quite hot after the first flight, not sure of the reason because in the current setup, the system is over powered. (Q_M_THST_HOVER ~ 0.17)

Here are the logs for both the flights (FLIGHT 1) (FLIGHT 2). We have been unable to identify the exact reason for the crash, so any ideas will help.
Thanks & regards,

Hello again,
We had another crash with the plane in a similar fashion.
In the first crash, the Motor 2 ESC was burnt, not sure if that caused the crash or happened because of the crash.
We replaced the ESC and repaired the body and tested again. This time the Motor 2 again has not taken the command for correction. However this time, ESC 1 is burnt.
We are using a combination of T motor MN505-S Kv380 and Air 40A Esc (rated for 60A burst).
Are we missing something here?

The LOG for this flight can be found here - FLIGHT 3.

We are stuck in a bind and really appreciate any help you can provide.
Thanks & regards

Hello guys,
This is a bump, we’re really stuck without answers.
The plane is the MFE Fighter VTOL 4+1 that we’re running on a 6s configuration rather than the standard 12s. The plane performed well in the earlier flights, including forward flight without any issues, so an hardware failure after really isn’t adding up.
Any input will be greatly appreciated.
Thank you

Well, there’s your problem!

You cant just cut the input voltage to half without changing motors and ESCs accordingly. Motor kv is one factor and ESC current is another. For same hover power, 6S setup is going to use 2x the current vs 12S. And current causes heat, power electronics do not care about voltage when it comes to heating.

My guess is that your ESCs are burning up because of low voltage and high duty cycle to make up with 6S voltages to 12S motors.

For comparison we are running 420 kv motors and 4x 80 Amp ESCs in 7.5kg 6S powered Vtol and it will happily pull 200 Amps from battery if you really hammer it in Qstabilize.

Hey @tkoivuro, thanks for your reply.
These MN505 motors are rated for 6s. We chose the electronics for the 6s config - motors, ESCs, everything. The Air 40A ESCs are rated for 40A continuous and 60A peak. The recommended ESCs also have a similar rating.

Yeah, looked at specs a bit later.

But in my mind your lift motor ESCs have far too low current rating for such a heavy vtol operating at 6S battery voltage. Original configuration with 12S battery is using 40 Amp ESCs and that is propably just fine.