ASK 13 outlanding wire strike — sector change into unanticipated lee subsidence

An ASK 13 on an instructional ridge flight near Claviers (Var) struck a medium-voltage power line on outlanding; the instructor and student were seriously injured. Easterly wind was 40-50 km/h at 1,000 m. The briefing required staying above 1,000 m on the ridge and not crossing Saint Arnoux col. After weak climb on the east face, a move to the south face met unanticipated lee subsidence; the glider passed the col below 1,000 m, no return possible. The instructor took controls, followed the Riou valley, and selected a field. On final turn the right wing struck the line. BEA cited the sector change into unanticipated subsidence.

1. Instructional ridge flight: Aerotow takeoff at 10:53 from Fayence (LFMF) for an instructional ridge flight on the south-east face of the Canjuers plateau, with the student initially flying. Cable release at 10:58 at 1,225 m altitude near the ridge. Initial east-face passes produced only weak climb (mean +0.15 m/s) to 1,250 m maximum.
2. Unusual east-wind for the region: Strong easterly wind 40-50 km/h at 1,000 m altitude with moderate turbulence — rare for Fayence, which usually sees wave or thermal conditions. Météo-France: surface east wind 24 km/h gusts to 55 km/h; storms approaching from the south-west by ~noon. The instructor stated he had never previously encountered east-wind conditions at Fayence, despite ~3,200 h glider experience predominantly in mountain flying.
3. Morning briefing limits: Chief pilot's briefing required: stay on the ridge, return to the airfield if altitude reached 1,000 m on descent (L/D of ~10 to Fayence from the ridge), do not cross the col de Saint Arnoux into terrain with no registered emergency fields, do not penetrate a downwind sector. The chief pilot had intended to brief each crew individually on the day's wind risks but did not reach this crew before they launched first.
4. Sector change met unexpected sink: After the weak east-face climb, the instructor directed a move to the south face of the ridge. The glider began descending at a mean -2.8 m/s — east-wind subsidence and rotors on this lee face — degrading climb performance significantly. The instructor took controls at 11:01:40 at 1,100 m, 2.7 km east of the col du Bel Homme.
5. Crossed col below 1,000 m: At 11:02:36 the glider reached 1,000 m, 400 m south of col du Bel Homme — across the col de Saint Arnoux limit set in the briefing. Return to Fayence was no longer possible. No registered emergency landing fields existed in this sector.
6. Riou valley search for outlanding: The instructor turned south and followed the Riou valley searching for a suitable outlanding site. With assistance from the student, an apparently clear field was selected — a non-registered field. The instructor flew one complete circle around the chosen field before joining the approach.
7. Right wing strikes power line: On the final low-altitude turn, the right wing struck a medium-voltage power line stretched across the approach. The line detached from its supports without breaking; the impact abruptly decelerated the glider and caused a hard ground impact. The student later said the field would have been usable without the unseen line.
8. Hard landing, glider destroyed: Glider destroyed. Both instructor and student seriously injured. Neither the glider nor the occupants carried an ELT/PLB. BEA-cited contributing factors: instructor's limited familiarity with east-wind aerology despite extensive regional experience (contributed to leaving the airfield's local); low height of the outlanding approach (contributed to the wire strike).