What happened
On July 5, 1963, a Jodel D-II, registration HB-SOL, departed from Ascona airport for a flight to Biel. The pilot was accompanied by one passenger. Although the weather in the Ticino region was initially favorable, the flight path through the Alps presented uncertain conditions. The pilot, who was not trained or equipped for instrument flight, proceeded with the flight despite reports of thunderstorms and heavy cloud cover in the Alpine regions.
As the aircraft approached the area near Giswil, it emerged from a thick cloud layer at approximately 1,600 meters. Witnesses on the ground observed the aircraft in a steep, descending flight, noting an increase in engine noise that suggested high power settings. As the pilot attempted a recovery maneuver to level the aircraft, the structural integrity of the plane failed. Witnesses reported seeing a wing detach, followed by the aircraft spinning and breaking into multiple pieces across a debris field spanning roughly 900 meters.
The investigation
Investigators examined the wreckage near Giswil-Grossteil and analyzed the flight conditions. The investigation focused on the structural failure of the wing and the flight maneuvers performed immediately before the breakup. Technical inspections of the Jodel D-II confirmed that the engine and airframe were in good condition, with no evidence of mechanical failure or prior defects. The investigation also reviewed the pilot's flight experience and the meteorological data for the route between Ascona and Biel.
Findings
- The aircraft was subjected to structural overstress during the recovery maneuver.
- The pilot entered a weather situation that prevented safe continued flight under visual flight rules (VFR).
- The aircraft emerged from the clouds in an abnormal flight attitude, likely a steep dive.
- The high aerodynamic loads generated during the pull-out maneuver caused the right wing spar to fail under bending stress, which subsequently led to a torsional failure of the left wing spar.
- Both occupants of the aircraft were killed upon impact.