Dart 15 stalls and spins in low slow turn off ridge

The pilot of a Slingsby T.51 Dart 15 was fatally injured after the glider departed controlled flight at low height while ridge soaring at Sutton Bank; aircraft destroyed. As lift weakened the glider descended through progressively lower passes along the ridge. Earlier chances to land on the secondary long-run field were not taken; air-to-air photography in the latter passes likely drew attention from the shrinking margin. From just above the ridge and near stalling speed, the pilot turned left for separation, then reversed right toward the airfield. The inner right wing stalled first and the glider rolled into a spin from too low to recover.

1. Local ridge soaring flight: The pilot of a Slingsby T.51 Dart 15 was on a local flight from Sutton Bank during a vintage-glider visiting event. After aerotow release the glider remained close to the airfield. Surface wind was westerly at ~20 km/h; weather was generally fine.
2. Limited hill-soaring and type time: The pilot had ~412 h total but only 1 h 17 min on the Dart 15 across three flights (two in mid-2005, one earlier the same day). The logbook recorded 17 hill-soaring flights over 10 years, of which only two (43 min total) were solo; the previous day's dual site check at Sutton Bank had been flown in a more docile two-seat trainer. The Dart 15's Pilot's Notes warn that in a 30 degree banked turn at 70-75 km/h, additional bottom rudder drops the inner wing and a spiral dive follows.
3. Ridge lift weakened; height bled off: Wind strength or direction may have shifted subtly during the flight, reducing ridge lift. The glider descended in a series of traverses along the ridge, with witnesses reporting it ~30 to 90 m above the ridge initially and dropping with each pass. On the penultimate southbound traverse it flew along the secondary long-run landing area at ~30 to 45 m; on the final northbound traverse it was less than ~15 m above the ridge, nose-high and unusually slow.
4. Air-to-air photography in low passes: The pilot's digital camera was found switched on at impact. Time-stamps showed 27 photographs taken during the flight, several of other gliders soaring higher on the ridge during the same period that onlookers were already concerned about the accident glider's height. Sustained photography in the latter passes was a plausible source of distraction from the deteriorating margin.
5. Low slow reverse turn back to airfield: From a position only just above the ridge line and at minimal flying speed, the pilot turned left away from the ridge - probably to gain separation from the steep slope - then reversed into a right turn back toward the gliding site, apparently attempting a late return to the airfield rather than committing to the valley fields below.
6. Right wing stalls; rapid roll right: As the right turn developed, the inner right wing stalled first. The glider rolled rapidly to the right, the nose pitched down and it departed controlled flight, entering a spin or spiral dive. Recovery would have required forward control input to unstall the wing; from the height available the departure was unrecoverable.
7. Pilot fatally injured; glider destroyed: The glider struck birch trees on the steep slope ~15 m below the ridge line, west of the gliding site, with the forward fuselage pitched nearly vertical. A branch penetrated the canopy during the impact sequence; the pilot was extricated unconscious and died 20 days later. Engineering examination found no pre-impact failure of structure or flight controls and confirmed the ASI was working normally.