What happened
On June 24, 2010, a Glastar GS1, registration HB-YMQ, was performing a flight test at Schaffhausen airfield in Switzerland. The aircraft, a homebuilt single-engine design, was being operated under VFR private flight conditions. After completing a series of flight tests, the pilot returned to the airfield for landing.
During the initial approach, the pilot found the airspeed too high and initiated a go-around. On the second approach, the pilot maintained a speed of approximately 50 knots with full flaps extended. As the aircraft reached the flare stage, the sink rate increased abruptly. In response, the pilot applied full power to execute a go-around. During the climb, the aircraft entered an uncommanded roll and began oscillating around its longitudinal axis. Despite full right aileron input, the aircraft became uncontrollable, banked sharply to the left, and struck the ground in a beet field.
The investigation
Investigators examined the wreckage and the flight history of the aircraft. The investigation confirmed that the aircraft's weight and center of gravity were within permissible limits and that the engine, propeller, and flight controls showed no signs of mechanical failure or prior defects. The fuel analysis confirmed the use of appropriate unleaded aviation gasoline.
The investigation also reviewed the pilot's flight experience and the aircraft's flight manual. The manual specifically warns that approach speeds below 60 knots can lead to a rapid increase in sink rate and that significant power is required to arrest such a descent. The investigation also noted that the pilot was not wearing seatbelts for the upper body during the impact.
Findings
- The primary cause of the accident was the loss of control during a go-around maneuver, which led to the aircraft striking the ground.
- The pilot's approach speed of 50 knots left very little margin for error, as it was below the recommended 60-65 knot range.
- The pilot's relatively low total flight experience and a significant eight-week gap in recent training contributed to the inability to manage the high-angle-of-attack state.
- The aircraft entered a power-on stall condition during the high-power climb phase.