Accident Details
On May 25, 2024, at approximately 15:45 local time, a glider accident occurred at Rapla Airfield (Kuusiku) involving a Blanik L-13 glider (registration ES-2010, year of manufacture 1977). The glider was operated by the Tallinn Aeroclub, which was conducting introductory flights using a winch launch system.
Sequence of Events
The winch launch day began with favorable weather, but conditions worsened during the afternoon. By the fifth flight, the wind had shifted to the northwest and thunderclouds were forming. The glider captain, after landing, noted the wind change. For the sixth and final flight, the crew decided not to reposition the winch despite the shifting wind, resulting in a downwind launch. The towing vehicle (winch car) was parked on the service road to the east of the runway, approximately 15 meters ahead of the glider and a few meters laterally from the wingtip.
During the final flight, the glider captain allowed the person who had been driving the towing vehicle to take the front seat, leaving the vehicle unattended. The wing runner for the launch was an inexperienced individual from an earlier sightseeing flight. After the winch cable was attached and pre-flight checks completed, the launch commenced with a faster initial acceleration as agreed with the winch operator due to the tailwind.
Shortly after the start of the takeoff run, the glider began to veer left, and the left wing dropped. The captain attempted to correct with right rudder and aileron, but the glider's left wing struck the parked towing vehicle, and the right wing contacted the ground. The glider then veered sharply right, the captain released the winch cable, and the glider came to a stop after irregular ground movement, facing the takeoff direction. The accident resulted in damage to the left wingtip and a lateral tear in the fuselage behind the wing.
Analysis
The investigation determined that weather conditions changed rapidly: wind direction shifted approximately 200 degrees between 13:00 and 16:00, with increasing gusts up to 9.3 m/s. The decision to launch downwind without moving the winch contributed to reduced control effectiveness at low airspeed due to the tailwind component. The glider's starting position was offset to the left side of the runway. The wing runner's lack of experience may have exacerbated the leftward veer. The parked towing vehicle was too close to the takeoff path.
Conclusions
The accident was caused by the glider captain not ensuring that obstacles (the towing vehicle) were safely positioned relative to the glider before commanding the winch launch. The relative positions led to the leftward veering glider colliding with the vehicle, causing extensive damage. Contributing factors included the glider's offset starting position, absence of procedures in the club manual for vehicle placement during winching, the decision to launch downwind without repositioning the winch, performance pressure to complete flights, and the inexperienced wing runner.