Well I maidened my vtail and doing fine...some slow circuits and such when I tried a quick forward and back pitch movement and the copter wouldn't stop oscillating front to back. I didn't have time to switch out of self level mode but did cut the throttle to try to minimize the impact. Broke one front boom and motor mount and one rear motor mount. All props and motors are ok. But what would have caused the copter to pitch back and forth uncontrollably like that? Any help is appreciated. Robert
Sounds like the board was getting attacked by vibe -- something I'm wringing out of my V-tail, too, with some success.
Once the v-tail picks up some speed, both the motor load and turbulence from the craft's prop wash increases, with them, the vibe goes up. The vibe confuses a sensor to think a motor is rising when it's actually falling, so it throttles it down, which causes the sensor see a real sudden dramatic drop on that corner, so back up it goes, likely in time to be confused again -- as long as the vibe keeps knocking it off, the error will only get worse.
I've had a badly nicked set of props do this at low speed, replacing them settled it out all the way to a very high speed (1/2 throttle to hiover -> 3/4 throttle Fast Forward Flight). I've also had one of my shock mounts get loose -- the board started to flex because of it, and the craft couldn't even lift out of ground effect without the throttle oscillating.
three things you can do:
- balance the props
- balance the motors
- isolate the control board from vibe
If you haven't done the third well, the other two will only marginally help -- just make sure there's nothing hard physically touching the board -- if it's hard, it's a channel for vibe to be transferred to the board. .