Accidente del Piper PA-18-150 cerca de Vilan tras fallo del cable de remolque con Pilatus B4-PC 11AF
El 5 de agosto de 1977, un Piper PA-18-150 que remolcaba un Pilatus B4-PC 11AF despegó del aeródromo de Bad Ragaz. Durante el vuelo cerca de Vilan, el cable de remolque se aflojó y luego se rompió, causando que el Piper perdiera el control y se estrellara contra una pendiente pronunciada. El piloto del Piper murió en el accidente y la aeronave fue destruida. El piloto del planeador logró regresar al aeródromo de manera segura. El incidente ocurrió en Suiza, sin daños a terceros reportados.
- Aerotow ridge climb: During an aerotow from Bad Ragaz toward the Vilan area, the tow combination climbed along the ridge after passing the Sadreinegg ridge in rising air.
- Tight turn near slope: After crossing the Sadreinegg ridge, the towplane initiated a relatively sharp right turn toward the mountainside and then abruptly reversed into a sharp left turn in close proximity to the slope.
- Low height and clearance: The tow was being flown with low height above ground and small horizontal distance from the slope, below prescribed minima, leaving little margin to recover from upset.
- Slack tow rope: During the right turn the glider climbed slightly above the towplane, causing the tow rope to slacken and hang through.
- Glider fails to release: When the towplane disappeared from his field of view in the steep left turn and turbulence, the glider pilot took the release handle in hand but did not immediately jettison the tow.
- Rope snatch and break: As the towplane reversed into the sharp left turn in turbulence, the slack rope suddenly came taut, abruptly lifting the towplane’s tail toward the slope and then failing at the glider-side splice instead of at the weaker intended weak link.
- Crash - fatal: At very low height the towplane, upset by the rope snatch and close to the steep terrain, entered a near-vertical descent and impacted the slope fatally injuring the tow pilot, while the glider released and later landed safely back at Bad Ragaz.