Amateur-built Sopwith Baby N41LR accident near Lee'S Summit, Missouri

Probable cause

The airplane builder's improper installation of the lower right wing which resulted in an uncommanded left roll and the subsequent loss of control.

NTSB analysis

The pilot departed on the airplane's initial test flight in a tailwheel-equipped biplane. At the speed when the tailwheel lifted from the runway, the airplane began an uncommanded left roll. The pilot attempted to arrest the roll moment but was unsuccessful. He aborted the takeoff but lost control of the airplane as it settled down in a crab. The airplane exited the side of the runway and resulted in the failure of the left landing gear, and subsequent nose over of the airplane. The lower left wing sustained substantial damage.

The airplane builder conducted a post-accident examination and reported that the right wing had a different "angle-of-attack" then the other wings, due to a construction error. This difference likely resulted in the uncommanded left roll during takeoff. This rolling tendency was not detected during the previous four high-speed taxi tests..

Text from the NTSB. Open the NTSB docket for CEN20CA184 for the full record.