Help! BF 3.5 quad yawing twitching and falling out of the sky

Christian L.

Junior Member
Many thanks to whoever can solve this one

I recently built a QAV-Skitzo:

BFF4 fc
dys aria 35a blheli_32 esc's
emax rs2306 2750kv motors
frsky xsr rx
BF 3.5.1 flashed using the BETAFLIGHTF4 target
DAL 5046 CYCLONE props

fc used for pdb, sbus, taranis qx-7 tattu fpv line 4s 1300mah 95c lipo, ALL BF settings stock except airmode on and anti gravity on

i took this quad out for its maiden flight, and i noticed that the motors seemed to be twitching, but i didnt really pay attention. after about 2 min of flying, the quad dropped out of the sky. i presumed it was just a desync, so i took it out for another flight the next day. this time, the number 1 motor appeared to have significant trouble spooling up, almost as if there was a rock stuck between the stator and the bell. i picked it up, and spun the motor. it provided no resistance at all and spun normally. i armed it again, the motor had the same issue, but after a few seconds, it spun normally. i gave it some throttle, and it lifted off. i instantly noticed that it was yawing hard right. if i didnt correct for it, it would spin 180 degrees in just a few seconds. i trimmed it out using my radio, and kept flying. i now noticed that the motors, (im not sure what one, but i think it is one of the front ones) would twitch. it was almost like they desynced for a split second and then recovered. the quad would lurch forward when this would happen, and it happened at a pretty short interval, a few times per minute at least. after a few minutes of this, the quad tipped toward the number 1 motor, all the motors stopped (i know this because i saw it and even though it was still armed when it hit the ground, it did not continue to spin or twitch and there was no prop damage) and the quad fell out of the sky. there was no damage, this is the same failure that has happened twice in a row. i never went above 40% throttle, as it was the maiden flight and i just wanted to feel it out. the battery and ALL of the components are BRAND NEW. i know for a fact that it is not the wifi at the location, as i have flown at this location with similarly equipped quads in the past, and it has worked out fine. if you would like some pictures of video of the issue, then let me know and i will post it. please help, as i really want to get it flying, and i am completely puzzled as to what the issue is.

thanks so much,
christian L.

update: i have some more investigating in the BF motors tab, and it appears to be a desync, most severe on motor 1, but occurs on all 4 motors to varying degrees. HOWEVER the way the motors react (in the motors tab w/no props) seems extremely similar to the noise issue on the original lumenier lux. but this may be incorrect and not the issue, as i have never had to troubleshoot an issue even remotely similar to this.


Wake up! Time to fly!
Check out Joshua Bardwells setup video.

All them fancy filters and features in beta flight dont always play well with each other on certain builds.

The drifting and the statement you "trimmed" yaw makes me also wonder if you overlooked radio set up for channel centers and end points. A quad NEVER needs "trim" if radio set up is done properly.