Flat turn at rotation

One of my twins rotated in two directions at take off but flew well otherwise. It did a flat turn to the left at rotation. Rotation in two directions has been seen about 6 other times on this airplane but in the opposite direction.

Speculation:
1. Balance is forward and nose wheel is effective until rotation starts.
2. Vertical fin is not large enough to be effective at slower speeds.
3. Engines are spaced further apart than necessary.
4. Transition difference between engines, one may be slower than the other or an engine stumbled on transition.
5. Engines have slightly different top RPM.

A flat turn towards the pits would not be good. None of the tendency to flat turn at rotation has been seen on the Cherokee twin. The Cherokee is light on the front wheel.

Bill

All your possible causes seem valid. How about loose rudder surface? Flat turn at the moment of lift off, if I understand this? If all else you proposed and no glitches in the radio, the lack of effective rudder seems like a good one. Got a spare gyro around? Put it on the rudder and see if the problem goes away..it can react faster than you can.
Just a thought.
twinman..
PS...you got that four engine monster ready yet???

I failed to satisfactorily resolve ‘transition after long idle’ on engines that were to be used and parked idea temporarily. After a few weeks of settle time another attempt will be made. “Hurry up and get them all cranked” is objectionable from a safety standpoint. I can screw up without hurry up and really detest blood on the airplane.

Bill

Awhile back Bill Krumel flew a DS Connie that had a history of straying on takeoff. His conclusion was that the plane was just a "TAD" tail heavy. Once in the air the Connie flew great and landed great. (A really beautiful plane) With not enough traction on the nose gear the plane would be hard to control until the rudders were effective. His suggestion was to move the cg a little forward. There were 2 Connies at Bomber Field during that event. The Flying Dutchman took off straight as an arrow. All speculation until we see the next flight but it makes sense.
Edwin

This airplane was balanced quiet nose heavy. The airplane has also tracked very straight on the ground for the last hundred or so flights. Just after rotation it has attempted a 30-degree or so flat turn but only occasionally. Initially I thought it had an affinity for the big shade tree. Recovery from the turn simply required ruder and climbing out closer to the tree than preferred.

The balance has been changed and tomorrow another test flight will be made.

Bill