Introduction
On 2 June 2016, at approximately 13:05 local time, two gliders collided in a thermal updraft near the town of Długie Nowe, about 6 km southwest of Strzyżewice airfield (EPLS). The aircraft involved were an Arcus M (registration D-KKKO) and a Jantar 2B (registration SP-3371). The collision occurred during the third task of the 6th Polish Gliding Championships in the 15-meter class.
Flight History
Both gliders had departed from EPLS earlier that day. The Jantar 2B launched behind a tow aircraft at 12:21, while the Arcus M, equipped with a self-launching engine, took off under its own power at 12:22. The pilots spent the subsequent hour thermalling and evaluating conditions in the area. By around 13:00, a large number of gliders were circling in a thermal between Długie Nowe and Przybyszewo, waiting for the start of the racing window.
The Arcus M initially flew south of Leszno, then moved west toward Długie Stare. At about 12:50, its pilot decided to head to a thermal about 2 km south of that village, where several gliders were climbing. After several minutes, the glider reached an altitude of approximately 1380 m near cloud base.
The Jantar 2B first thermalled near Długie Stare, then flew west to Osowa Sień, where it reached 1402 m. Finding the lift weak, the pilot decided to return toward the airfield and flew to an area south of Długie Stare where most gliders were circling.
Collision
At about 13:05, the Arcus M pilot, concerned about being too close to the cloud base, decided to descend while continuing to circle in the same thermal. He stated that he counted the gliders below, saw no immediate threat, and then partially opened the airbrakes to increase descent rate. The glider began descending with a sink rate gradually increasing to about 5 m/s.
Meanwhile, the Jantar 2B entered the same thermal from the west at an altitude of about 1270 m, beginning to center the lift with a left turn. After turning approximately 180°, the pilot heard a FLARM warning and saw a glider approaching rapidly from above, behind, and to the left. He immediately pushed the control stick forward and turned right to dive away. However, a loud crash was heard, and the Jantar entered a near-vertical dive. GPS data from both gliders indicated a closing speed of about 50 km/h.
Aftermath
The loud impact and momentary loss of control prompted the Jantar pilot to release the canopy and unbuckle his harness, preparing to bail out. Realizing the glider remained controllable, he resumed gliding flight and landed safely at the departure airfield. The Arcus M sustained serious damage to its left wing torsion box but also remained controllable, allowing its pilot to return safely to EPLS. Neither pilot was injured.
Investigation Findings
The Polish State Commission for Aircraft Accident Investigation (PKBWL) determined the probable cause to be the Arcus M's circling in close proximity to cloud base within a thermal containing many gliders, followed by its descent using airbrakes at a high vertical speed while circling. This led to a collision with the Jantar 2B, which was entering the same thermal and beginning to center it. The PKBWL issued no safety recommendations.
Damage
- Arcus M (D-KKKO): Serious damage to the left wing torsion box.
- Jantar 2B (SP-3371): Damage to the left wing leading edge.