What happened
On April 19, 2015, during the second day of the AZ CUP 2015 gliding competition, two gliders collided while circling in a shared thermal near Jablonná, Czech Republic. The first aircraft, an ASW-19B, registration OK-0019, was flying in a left-hand turn at approximately 1,300 m AGL. Simultaneously, an ASW-19, registration OK-0310, was also circling in the same thermal.
As the two aircraft were maneuvering, the ASW-19 (WT) was climbing more rapidly and began to fly inside the turn of the ASW-19B (KX). During the second turn, the lower part of the left wing of the ASW-19 struck the horizontal stabilizer of the ASW-19B. The impact caused the ASW-19B to lose control, entering a violent nose-down pitch and subsequent spiral dive. The pilot of the ASW-19B was forced to abandon the cockpit and deploy a parachute, landing safely in a meadow with only a minor injury to a lower limb. The ASW-19B subsequently struck the ground and was destroyed. The pilot of the ASW-19 continued the flight and landed safely at Zbraslavice.
The investigation
The ÚZPLN investigation examined flight data recorders from both gliders, which allowed for a synchronized analysis of their positions and flight parameters. The investigation established that both pilots were qualified and the aircraft were airworthy. The committee analyzed the flight paths, noting that while the pilots were aware of other aircraft in the vicinity, the specific geometry of the converging paths was not recognized in time. The investigation also reviewed the meteorological conditions, which were found to be clear with good visibility, and therefore did not impede the pilots' ability to observe the other aircraft.
Findings
- The collision occurred because neither pilot recognized the danger of intersecting flight paths during the turn in time to take evasive action.
- The ASW-19 was climbing at a higher rate, which caused it to move from a lower position to a higher position relative to the ASW-19B during the maneuver.
- The aerodynamic forces generated by the impact caused the ASW-19B to become uncontrollable, leading to the pilot's decision to bail out.
- Meteorological conditions were favorable and provided sufficient visibility for avoidance maneuvers.