C6/2006L Collision of two glider aircraft in Orimattila on 15 July 2006

On Saturday 15 July 2006 at 14:37 local time, a collision of two glider aircraft occurred above the Heinämaa village of Orimattila city, in which a privately owned LAK-17AT type glider aircraft, competition sign AC, and a Rolladen-Schneider LS8-t owned by Pernun Pilotit ry, competition sign T8, were damaged. The pilots of both aircraft were
unharmed. On 18 July 2006 the Accident Investigation Board Finland (AIBF) appointed in its decision no. C 6/2006 L an investigation commission with accident investigator Reijo Mäkeläinen as chairman and investigator Tuukka Takala as a member of the commission.

The pilots of both gliders AC and T8 were taking part in the Jannen Kisat gliding competition held at Räyskälä aerodrome. Both gliders took off by aeroplane towing from Räyskälä aerodrome. AC reached the Heinämaa waypoint from the west and after passing the waypoint turned back towards a lift it had left earlier. The pilot of AC did not see T8, which was approaching from the opposite direction. The left wings of the aircraft hit each other at an altitude of 1490 m above ground level. The closing speed of the two aircraft was approximately 250 km/h at the time of collision. Both aircraft remained airworthy after the collision. T8 made an uneventful landing at Lahti-Vesivehmaa aerodrome at 15:00 hours and AC at Räyskälä aerodrome at 15:47 hours.

Due to the small angle between the inbound and outbound routes to Heinämaa waypoint given in the competition task, the inbound and outbound traffic were close to each other. When examining the emergency canopy jettison mechanism of AC it was found that the canopy of the aircraft had not separated in spite of the pilot carrying out the correct canopy jettison procedure. The locking handle of the spring-type jettison mechanism had been left in an incorrect position and it did not operate in the intended manner. The LAK-17AT instructions concerning the canopy jettison mechanism are inadequate and do not give a clear indication of the correct position of the spring locking handle. There are no markings of the correct position for the red locking handle on the locking system in the aircraft.

The pilots did not see each other in time to avoid the collision. Contributing factors to the accident were the routing of the competition task, which caused the inbound and outbound traffic at the waypoint to pass near each other, and the poor visibility of a glider approaching from a directly opposite direction.

The investigation commission issued two safety recommendations. The commission recommends that the manufacturer of the LAK-17AT specify the instructions in the flight manual and markings in the aircraft concerned with the canopy jettison mechanism in such a way that the correct position of the spring locking handle is evident and unambiguous. The commission also recommends that the organisers of gliding competitions investigate the possibility of requiring the use of collision warning systems in competitions.

C6/2006L Report (pdf, 0.32 Mt)