What happened
On February 16, 2002, a motorized hang gliding flight ended in a fatal accident in Köyliönkylä, Loimaa. The pilot, a 53-year-old male, attempted a takeoff from a field. After an initial failed attempt due to soft snow, a second takeoff was performed on a frozen section of the field.
Shortly after takeoff, the Solarwings Typhoon S4 Plus climbed to a maximum height near the treetops while flying into a headwind. The aircraft then turned left toward the takeoff site, circling at an altitude of approximately 20 to 40 meters. While flying with a tailwind or crosswind, the nose of the glider suddenly pitched up, followed immediately by a violent descent. The glider entered a nose-over spin, rotating approximately one and a half times before impacting the ground at high speed. Despite immediate rescue efforts by helicopter and ambulance, the pilot succumbed to his injuries.
The investigation
The investigation examined the aircraft's condition, the pilot's experience, and the environmental factors. The aircraft was a 1984 Solarwings Typhoon S4 Plus (registration/list number 167) equipped with a custom-built Minimum-type motor. Investigators analyzed the flight path, the engine's performance, and the mechanical state of the glider, including the dive bar and sail fabric. The investigation also reviewed the pilot's medical history, specifically noting reports of numbness in his hands during cold weather, and the regulatory environment regarding motorized hang gliding at the time.
Findings
- The primary cause of the accident was a violent stall at low altitude followed by a nose-over spin.
- The stall was likely triggered by strong, turbulent winds coming from behind the treeline, or by incorrect loading of the glider, which was found to be tail-heavy and approximately 55 kg over the manufacturer's maximum weight limit.
- The nose-over rotation was caused by the propeller's thrust vector being positioned significantly above the center of gravity, a condition exacerbated by a recent change in the propeller's pitch angle.
- Contributing factors included the poor overall condition of the aged glider, specifically the weakness of the sail fabric, and the possibility that the dive bar was left in the transport position.
- The investigation also noted that the motor component was uninspected and unlisted, and that the pilot had experienced hand numbness in cold conditions, which may have led to a loss of control.
Safety action
- All hang glider pilots should monitor wind velocity and turbulence levels above the treetops during pre-flight checks.
- Pilots using older gliders must specifically inspect the strength and dimensions of the sail fabric, as UV radiation and age can cause shrinkage and tearing.
- Operators of motorized gliders must ensure the propeller thrust vector is correctly aligned with the aircraft's center of gravity.
- The Finnish Civil Aviation Authority and the Finnish Aeronautical Association should clarify and update gliding instructions and the division of regulatory duties to ensure all rules are current and accessible to pilots.