I just converted my quad from the HobbyKing v3 board to APM2, and I'm having a problem:
when I increase the throttle to where it actually starts to lift off, the quad starts to wobble, and this wobbling very quickly becomes stronger and stronger and I have to cut the throttle to keep it from burying itself sideways into the ground. It takes under a second for it to get out of control.
When I keep the throttle low and move the elevator/aileron stick, it seems to do all the right things (e.g. move the stick right, the left motor spins up, move the stick forward, the rear motor spins up, etc).
When I hook it up to APM, everything seems OK too: tilting/rotating the quad shows the flight data display updating as expected, so at least the various orientation sensors appear to be working.
I downloaded APM planner and flashed the firmware today, so I should have the latest.
Any pointers as to what might be wrong or what I need to tweak?
See this part of the troubleshooting guide.
Apparently I had it set to X configuration instead of plus. Looks like X is the default, which is a but confusing since the icon you select when picking the firmware shows a plus configuration. After setting it to plus it flew OK, a little bit wobbly still, but that might have just been the wind and a slightly loose motor mount.
You can turn the stabilize P term down by 10% or so, and that should calm it down.