Crash du Pilatus B4 lors d'un vol d'entraînement près d'Ulrichen, Suisse
Le 29 juillet 1987, un Pilatus B4-PC11AF a été impliqué dans un crash près d'Ulrichen, Suisse, lors d'un vol d'entraînement. Le pilote, qui volait en solo dans le cadre d'un camp de vol à voile alpin, a largué le câble de remorquage à une altitude insuffisante de 2100 mètres. Bien qu'il ait réalisé l'erreur, le pilote a poursuivi le vol pour éviter de retourner à Münster en raison de contraintes d'horaire. Le planeur a décroché lors d'un virage et a percuté une pente raide. Le pilote a subi de graves blessures et l'appareil a été détruit.
- Aerotow to ridge: During an alpine gliding camp, the pilot departed Münster in aerotow in a Pilatus B4 for a solo training flight along the Goms valley.
- Premature tow release: After a 180° turn near the Oberwaldergrimsel/Chietal area, the pilot released from tow at about 2100 m MSL, already below local ridge height contrary to prior instruction.
- Desire to avoid landing: Realizing she had released too low, the pilot nevertheless decided to continue the flight to avoid an early landing at Münster that would prevent another launch due to reservations.
- Low, slow ridge flying: In pure thermal conditions and with shallow local slopes, the pilot flew slow figure‑eight patterns close to the hillside, reducing height margin for corrections.
- Poor speed monitoring: The pilot flew mainly by feel and paid little attention to the airspeed indicator while maneuvering near the slope.
- Stall and loss of control: During a turn toward the valley at low height, the glider dropped below minimum flying speed, stopped responding properly to control inputs, and departed controlled flight.
- Crash - serious injury: The glider impacted a steep slope near Flieli, 1.5 km northwest of Ulrichen, seriously injuring the pilot and destroying the aircraft.