Mosquito stalls near a ridge crest in strong bise turbulence
The pilot of a Mosquito was killed when the glider stalled near a ridge in strong turbulence and dropped almost vertically into forest at Gruyères; aircraft destroyed. On his first flight of the season, the pilot was soaring the Fribourg Prealps in a gusty bise. The wind funnelled and sheared through the steep valley in strong up- and down-drafts. Near the crest at about 1600 m MSL — barely 100 m above the trees — the glider most likely stalled on a vertical gust, too low to recover before hitting the wooded slope. The probable causes were a stall too low to recover, strong local turbulence in rugged terrain, and a possible pilot malaise.
- Aerotow local flight: The pilot departed Gruyères at 14:21 on an aerotow for his first local training flight of the season in his Mosquito glider.
- Mountain turbulence area: The flight took place in a steep, complex pre‑Alpine valley with strong bise-induced turbulence and significant vertical air accelerations reported by other pilots and the rescue helicopter.
- Low height near ridge: Shortly before the accident the glider was flying near ridge height around 1600 m MSL, leaving only about 100 m above the treetops, insufficient margin to recover from a stall.
- Sudden stall event: In the turbulent valley flow, the glider most likely entered an uncommanded stall, probably induced by a vertical gust and possibly compounded by pilot malaise.
- Unrecovered nose drop: With inadequate height to complete a recovery, the stalled glider transitioned into a near-vertical descent without returning to normal flight.
- Crash - fatal: Around 16:20 the glider impacted a steep, wooded west slope of the Dent du Chamois in a near-vertical attitude, destroying the aircraft and killing the pilot instantly.