Kollision in der Luft zwischen Elfe S4 und IS-29D nahe Montricher, Schweiz

Am 22. April 1978 kollidierten eine Elfe S4 und eine IS-29D in der Luft nahe Montricher, Schweiz. Die Elfe S4 befand sich im Kreisflug in der Thermik, als die IS-29D, die gerade vom Schleppseil ausgeklinkt hatte, versuchte, in die Thermik einzusteigen. Bei der Kollision verlor die Elfe S4 ihr Höhenleitwerk, was den Piloten zum Fallschirmabsprung zwang, während die IS-29D sicher auf dem Flugplatz Montricher landete. Beide Piloten erlitten leichte Verletzungen, und die Elfe S4 wurde zerstört. Der offizielle Bericht nannte unzureichende Luftraumbeobachtung durch den Piloten der IS-29D als Ursache.

1. Thermaling after aerotow: After an aerotow from Montricher, the Elfe S4 HB-1155 pilot was thermaling in a right-hand climb north of Montricher at about 1550 m AMSL, with a second glider circling 200 m higher to the south.
2. Third glider joins area: IS-29D2 HB-1378 released from tow near Montricher and flew a straight, south–southwest approach intending to position underneath one of the two thermaling gliders while maintaining what the pilot believed was a safe distance.
3. Loss of visual contact: The IS-29D2 pilot likely saw the Elfe S4 at some point but then lost visual contact with it during the straight-in approach toward the thermal.
4. Inadequate lookout on join: While attempting to join the thermal, the IS-29D2 pilot insufficiently monitored the surrounding airspace and converged on the Elfe S4 at nearly the same altitude.
5. Evasive maneuver attempted: Seeing the IS-29D2 approaching very close on his left at about the same altitude, the Elfe S4 pilot tightened his right turn and slightly dived in an attempt to avoid a collision.
6. Mid-air impact and tail loss: The IS-29D2 cockpit structure struck the underside of the Elfe S4 fuselage between the wing trailing edge and tailplane, causing the Elfe’s empennage to break off and the main fuselage to enter an uncontrollable dive.
7. Crash - minor injury: The Elfe S4 pilot bailed out by parachute and suffered minor leg injuries when the glider crashed and was destroyed in a field south of Montricher, while the IS-29D2, lightly damaged and with its pilot concussed, landed back at Montricher airfield.