What happened
On 6 January 2005, at approximately 11:25 local time, a weight-shift ultralight aircraft, a HybredR 503 with registration OH-U134, crashed into the ice of Lake Ylistenjärvi in Vammala. The pilot had been performing taxiing exercises using skis on a nearby field but moved the operation to the frozen lake after finding the field too small. The pilot's intention was to perform short take-offs and landings.
During the maneuvers, the pilot noted that the airspeed indicator was non-functional due to snow accumulation in the pitot tube. After completing two large oval-shaped taxiing circuits, the pilot attempted a take-off into a crosswind. The aircraft climbed at a very steep angle, reaching an altitude of between 10 and 30 meters. The combination of the rapid ascent and deteriorating visibility caused the pilot to suddenly reduce the throttle to idle. This action led to an aerodynamic stall, causing the pilot to lose control. The aircraft traveled approximately 300 meters before impacting the ice at a steep 45-degree angle, tilted heavily to the right. The pilot sustained serious injuries.
The investigation
The investigation examined the pilot's training background, the aircraft's technical condition, and the prevailing weather conditions. Investigators found that the pilot had completed training for a Class B ultralight aircraft, which utilizes entirely opposite control inputs compared to the Class A weight-shift aircraft involved in the accident. The investigation also looked into the mechanical state of the aircraft, noting that while the airspeed indicator was inoperative, no other technical failures were found that could have caused the crash. Additionally, the investigation noted that a ski attachment had partially detached prior to the flight, though this was not considered the primary cause of the accident.
Findings
- The pilot was performing taxiing and short flight maneuvers without the necessary flight training for this specific aircraft type.
- The pilot attempted to fly in weather conditions that were clearly below the permitted minimums, specifically regarding visibility and cloud base.
- The pilot lacked prior flight experience in weight-shift ultralight aircraft.
- The sudden increase in vertical speed and the loss of visual reference to the horizon due to poor visibility led to the fatal error of reducing throttle to idle.
- The pilot had not fully mastered the aviation regulations regarding weather minimums and flight privileges during their theoretical course.