What happened
On July 15, 1962, a Piper Super Cub HB-OPX was involved in a fatal accident near Disentis, Switzerland. The flight was part of a mission for the Swiss Air Rescue (SRFW) to replenish fuel supplies for a helicopter-based search and recovery operation following a previous aircraft crash at Oberalpstock.
After arriving from Kloten, the pilot attempted to drop several 5-liter fuel canisters using parachutes. The first drop failed as the canisters detached from the chutes upon impact, and the second package drifted into a ravine. Following these unsuccessful attempts, the pilot decided to land on a triangular meadow near the helicopter base to deliver the remaining fuel.
During the landing approach, the pilot encountered tailwinds and turbulence. While attempting a go-around (aborted landing) by applying full power just before touchdown, the aircraft struck a boundary stone. The impact caused the plane to roll toward the Vorderrhein gorge, where it subsequently collided with the lightning protection cable of a high-voltage power line. The aircraft crashed into the gorge, caught fire, and the pilot was killed in the wreckage.
The investigation
SUST investigators examined the pilot's experience, the aircraft's mechanical state, and the operational procedures used during the mission. The investigation noted that the pilot had not performed cargo drop training since 1960 and was not fully familiar with the specific equipment being used.
Technical examination of the HB-OPX revealed that the engine was still operating at high power at the moment of impact, evidenced by the propeller being found separated from the engine with sheared mounting bolts. The investigation also reviewed the cargo configuration, noting that the canisters were secured with copper wire rather than more stable steel strips, and that the pilot had failed to properly retract the parachute release lines.