Background
On 11 June 2005, the Oldtimer Segelflugvereinigung Schweiz (OSV) held its 17th meeting at Schaffhausen airfield (Schmerlat), attracting 37 pilots with 24 vintage gliders. The Segelfluggruppe Schaffhausen, which operated the airfield, granted hospitality. The event was publicized locally. Among the participants was the owner and pilot of a L-Spatz 55 (HB-737), accompanied by his wife and family. The glider was assembled and prepared for flight.
Two towing aircraft were used: a Robin DR400-180 (HB-EXT) for faster gliders and a Piper J-3C-65/L-4 (HB-OIO) for slower ones. At about 13:00, two gliders were ready at the start of runway 25: HB-737 in front and Moswey III HB-485 behind.
Accident Sequence
Minutes before the HB-737 was ready for departure, the pilot's wife left the aircraft's side to take photographs. She moved from the runway toward the southern edge. At the same time, the Piper HB-OIO was taxiing along the southern runway edge towards the starting point to tow the next glider. The pilot was alone, seated in the rear seat (as per the aircraft's single-pilot configuration); the front seat was empty.
The woman, about 150 m away, saw the HB-OIO approaching. She turned her back to the taxiing aircraft to photograph the HB-737's takeoff. She stood about 30 m down the runway from the start and 30 m south of the runway centerline. She took several photos as the glider passed. Meanwhile, the HB-OIO had stopped or was barely moving near her.
Seconds after the HB-737 passed her, the propeller of the HB-OIO contacted her backpack. She was thrown forward several meters. The backpack and its contents were shredded. The woman sustained back injuries and shock. The pilot, unaware of her presence until the collision, stopped the engine and exited the aircraft. He stated he never saw a person in front of the aircraft.
Airfield Situation
The investigator arrived about an hour after the accident. Dozens of spectators were present with no barriers separating them from the flight operations area. Spectators, families with strollers and children, and cyclists were moving in the southern part of the operations area where gliders were positioned and tow planes taxied. A mobile platform with information about flight operations and the flight director was located south of runway threshold 25, manned by a start list keeper. Neither the start list keeper nor the flight director intervened with spectators. A fixed sign reading "Caution: airfield begins here. Beware when entering the runway!" was nearby. About 150 m from the accident site, an open-air restaurant operated with no separation between its tables and the taxiway.
Aircraft and Pilot Information
The Piper J-3C-65/L-4 (HB-OIO) was manufactured in 1944. It is a high-wing taildragger with tandem seating. It was equipped with a Continental C-90-8F engine (90 HP). At the time, it was used by the Segelfluggruppe Schaffhausen for towing older, lighter gliders.
The pilot, born in 1932, held a Private Pilot License (PPL(A)). He had 1580:40 total flight hours, with 10:45 hours in the last 90 days (including 1:33 hours on the accident type). He had performed over 9000 landings.