Post-release DG-600 collides with thermalling ASK 21 at cloudbase

A post-release DG-600 collided with a thermalling ASK 21 at ~1150 m MSL (400-500 m AGL) ~40 s after release; both ASK 21 pilots (dual training XC) were fatal, the DG-600 pilot bailed out with a leg fracture, both gliders destroyed. The DG-600 had aerotowed south of the field, released east of Tiersteinberg in low cloudbase, made a left U-turn and tracked toward gliders ~3 km SW; the ASK 21 closed from right-rear in a slight right bank and neither pilot saw the other in time. Suspected contributors: white-on-cloud background, cloud wisps, mutual scan assumptions, and DG-600 post-release scan distraction. No technical or medical findings.

1. Dual XC training; busy low cloudbase: The ASK 21 took off at 11:12 with two pilots on a dual training cross-country; the DG-600 launched solo by aerotow at 11:48, joining ~8 gliders south of Schupfart in weak thermals.
2. DG-600 post-release tasks degrade scan: Pilot released east of Tiersteinberg, made a left U-turn and tracked toward thermalling gliders ~3 km SW; post-release checks and manipulations plausibly degraded scan during the U-turn.
3. ASK 21 thermalling near base: ASK 21 was circling near the cloudbase in roughly the same airspace; the report posits the ASK 21 crew may have assumed the approaching DG-600 had seen them and was joining the thermal.
4. Convergence; neither pilot sees in time: DG-600 pilot reported the ASK 21 silhouette entering peripheral vision from right-rear, slightly low, in a slight right bank — no avoidance possible.
5. DG-600 right wing into ASK 21 fin/stab: The DG-600 pilot reported the ASK 21 silhouette entering peripheral vision from right-rear, slightly low, in a slight right bank, with no avoidance possible.
6. Bailout attempts: The DG-600's right wing first struck the ASK 21's vertical fin; the ASK 21's stabiliser separated and hit the DG-600's forward fuselage, ~40 s after release, at ~1150 m AMSL.
7. ASK 21 inverted into woods; both fatal: ASK 21 fell inverted into forest, severely destroyed; both pilots fatal. DG-600 fell into woods and hung in trees; destroyed. No technical or medical findings; class G airspace.