New build big copter take of problem

hi i just built big quad and was trying to take of first time today. when i raised throttle on stabilize mode. t was about to take of but power simply cut of and there was strange sound. i am really happy that everything happened on the ground and there was no damage. i will upload logs maybe someone could look at them with more experience. also parameters with log uploaded bellow:

does your FC keeps restarting after motor cut off ?
do you hear startup ring tone ?

not sure, will try again tomorrow to test this. its 5k drone so really dont want to crash it

If you can’t afford the loss, then don’t fly it at all :slight_smile: That’s the first rule when flying multicopters.

Now, before I take a look at the logs, can you please list the hardware ? Props, motors and Kv, ESCs, LiPo packs used and FC.

dont tell me about this :slight_smile: i crashed too many models already. and i dont want to crash it due to fc bug.

28props, u8 100kv. kde 75a hv esc, 48v lipo, pixhawk cube black

Tbh, I’ve never seen a log captured with a bitmask like yours. With default bitmask, FC, OS, firmware versions are only reported at boot, not at every arming. At the first glance your log looks like FC rebooting at every arm, and that’s why @hosein_gh asked if boot beeps are heard.

Now, I’m not familiar with the KDE ESCs on 12S. Have you bench-tested your motor/prop/esc combination adequately to check for desynchs ?

My method is - after gauging speeds using a servo-tester with a pot - I put THR on a 3POS switch with a custom curve going 1000-1200-2000. Then I go mid-high mid-high repeteadly for a couple of minutes, judging response speed, stopping now-and-then to measure ESC and motor temperatures.
( by hand, and remembering after every test there’s a radiometric FLIR camera on the shelf, 3 meters away :slight_smile: )
A desynch is hard to spot in these days of 32-bit ESCs. Gone are the days of motors screeching to a halt. They never stall today, but if you see it’s sluggish instead of sharp in reaching max thrust, you’ve had a desynch and recovery. Or, at least one, because you can have many such events during a single acceleration command. Causes are two: over-propping the motor or not-so-smart ESC.

Beware of:


You must have an external BEC connected to the servo rail in order to provide enough current to the ESC electronics.

I know that 5v 7a ubec is plugged into fc

The question is: Where is it plugged? KDE ESC documentation is quite clear. It must be plugged on one of the ESC 1-8 out of the PixHawkCube 2.1 board

surelly not in the a55 :smiley: its in the 8 port