The private pilot departed with two passengers for a personal, local flight in a Wheeler Express amateur-built airplane. Air traffic control data indicate that, after departing the airport, the airplane climbed and performed several maneuvers.
A review of onboard flight data revealed that the airplane then maneuvered into a nose-high attitude while in a steep, right turn. As the airspeed decelerated below stall speed and the turn steepened, the airplane pitched nose down and entered a prolonged, right-turning spin until hitting the ground near in Holland, Minn. All three souls aboard were killed.
Examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.
Previous flight testing of a Wheeler Express kit airplane similar to the accident airplane revealed that it had poor yaw stability at low airspeed due to the aerodynamic design of the tail section. The testing also revealed that, during post-stall and high-yaw maneuvering, the horizontal tail and elevators appeared to have an inadequate effect.
Following bankruptcy of the original kit manufacturer, a variant of the Wheeler Express kit airplane was developed using the same wing and fuselage as the accident model, but with a larger tail that had 40% more wetted area to provide additional yaw stability at low airspeed.
Probable cause: The pilot’s failure to maintain adequate airspeed during a high-pitch, steep right turn, which resulted in the exceedance of the airplane’s critical angle-of-attack and a subsequent aerodynamic stall, loss of control, and impact with terrain. Contributing to the accident was the airplane’s design, which resulted in poor yaw stability at low airspeed.
NTSB Identification: CEN15FA321
This July 2015 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.