JS1 drops into trees on short final in a sudden wind shear

A JS1 was substantially damaged when it sank rapidly on short final and struck trees short of the runway. The pilot, experienced but on only his third flight on the type, was returning to land after a short local flight; his downwind and approach were normal. On short final at about 65 m the descent steepened sharply and the glider sank fast. He retracted the airbrakes — which barely change speed — yet it kept dropping, hitting the treetops ~350 m short of the threshold, where a wingtip caught a branch and it dove in. Investigators judged a sudden local wind shear near the ground the likely cause; other finals minutes earlier were normal.

1. Return to land, normal approach: After a short local flight the pilot returned to land on runway 20; his downwind and approach were normal down to about 500 m.
2. Descent steepens on short final: On short final at about 65 m, and having chosen to land short of gliders on the runway, he met a sudden steepening of the descent and the glider began sinking fast.
3. Likely wind shear near the ground: The day's gusty valley aerology and terrain north of the field made a sudden, local wind shear the likely cause; nearby finals minutes earlier were normal.
4. Airbrakes retracted, still sinking: He retracted the airbrakes, but these barely change airspeed and the glider kept dropping.
5. Trees short of the runway: A wingtip caught a tree about 350 m short of the threshold; the extension tore off and it dove in, substantially damaged. The pilot was unhurt.