Event Overview
A witness reported that before arriving in the run-up area, the pilot lowered the airplane's flaps. After the right flap fully extended, the flap key on the drive shaft inside the 90-degree drive assembly adapter fractured in overload in the direction of flap extension. Before takeoff, the pilot raised the flaps; however, with the fractured key, the right flap would have remained fully extended.
Pilot Actions and Missed Checks
The pilot could have identified this condition prior to takeoff either visually or by means of the flap indicator, which received its input from the right flap actuator. Despite this, the pilot subsequently took off, and the airplane turned left. It is unknown at what point the pilot would have noted a control problem.
Aerodynamic Stall
The pilot climbed the airplane to 250 to 300 feet and allowed the airspeed to bleed off to where the airplane stalled and subsequently spun into the ground. Airplane manufacturer calculations revealed that the pilot should have been able to maintain control of the airplane at airspeeds over 70 knots. According to the pilot's operating handbook, the best two-engine angle of climb airspeed was 99 knots and the best two-engine rate of climb airspeed was 120 knots.