LAK-19 and SNC34 Alliance collide in a shared thermal

Two gliders sharing a thermal collided with only light damage, and both landed safely. An instructor and student in a Centrair SNC34C Alliance were thermalling when the instructor radioed a lower LAK-19 to join the lift. The faster single-seater overhauled the two-seater from the rear; despite a FLARM indication, its pilot did not realise he was catching up, and after two turns was inside the circle, converging. Seeing the conflict late, the instructor broke sharply right, but the LAK-19's right wingtip struck the underside of the Alliance's fuselage. Investigators cited the LAK-19 pilot's lack of vigilance as he closed on the glider ahead.

1. Sharing a thermal: Two gliders were thermalling near the airfield; the instructor in the two-seater radioed a lower LAK-19 to join the strong lift.
2. Faster glider overhauls unseen: The LAK-19, faster and better-performing, caught the two-seater from the rear sector, its pilot not realising he was overhauling it.
3. Converging inside the circle: Though FLARM showed the traffic, after about two turns the LAK-19 ended up inside the circle on a path converging with the two-seater's.
4. Late right break: Seeing the conflict late, the instructor broke sharply right to exit the turn, but the LAK-19 was arriving from the rear sector.
5. Wingtip strikes fuselage: The paths crossed and the LAK-19's right wingtip struck the underside of the Alliance's fuselage, tearing off the wing extension.
6. Both land safely: The fuselage skin was gashed about 10 cm; controls stayed functional on both gliders and they landed safely at the airfield.