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. Investigators cited the sector change into unanticipated subsidence.

1. Instructional ridge flight: Aerotow takeoff from Fayence for an instructional ridge flight on the south-east face of the Canjuers plateau, student flying; initial east-face passes produced only weak climb to 1,250 m.
2. Unusual east-wind for the region: A strong easterly wind of 40-50 km/h at 1,000 m brought moderate turbulence, unusual for Fayence, which typically has wave or thermal conditions instead.
3. Morning briefing limits: Briefed limits required staying on the ridge, returning to the airfield if altitude reached 1,000 m on descent, not crossing the col de Saint Arnoux, and not entering a downwind sector.
4. Sector change met unexpected sink: After the weak east-face climb, the instructor moved to the ridge's south face, where the glider began sinking at a mean 2.8 m/s in lee subsidence and rotors, degrading climb performance.
5. Crossed col below 1,000 m: The glider reached 1,000 m south of the col du Bel Homme, beyond the col de Saint Arnoux limit set in the briefing, after which return to Fayence was no longer possible.
6. Riou valley search for outlanding: The instructor turned south down the Riou valley seeking an outlanding site and, with the student's help, chose an apparently clear unregistered field, circling it once before the approach.
7. Right wing strikes power line: On the final low turn the right wing struck a medium-voltage power line across the approach; the line detached without breaking, abruptly decelerating the glider into a hard impact.
8. Hard landing, glider destroyed: The glider was destroyed and both instructor and student seriously injured; neither carried an emergency locator beacon, and the outlanding approach's low height led to the wire strike.