CHRISTENSEN STEVE WHEELER EXPRESS — Holland, MN, 2015

CHRISTENSEN STEVE WHEELER EXPRESS — Holland, MN

3 fatal High-time pilotLow altitude

Date	July 28, 2015
Location	Holland, MN
Aircraft	CHRISTENSEN STEVE WHEELER EXPRESS (amateur-built)
Purpose of flight	Personal
Conditions	Day · Visual Meteorological Cond
Phase / occurrence	Maneuvering Loss of control in flight
Pilot age	59
Pilot total time	1,204 hrs · Experienced
Time in type	475 hrs
Fatalities	3

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 findings

Personnel issues-Task performance-Use of equip/info-Aircraft control-Pilot - C
Aircraft-Aircraft oper/perf/capability-Performance/control parameters-Airspeed-Not attained/maintained - C
Aircraft-Aircraft oper/perf/capability-Performance/control parameters-Angle of attack-Not attained/maintained - C
Aircraft-Aircraft oper/perf/capability-Performance/control parameters-Yaw control-Related operating info - F

What happened

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 ground impact. 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 poststall 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 percent more wetted area to provide additional yaw stability at low airspeed.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.