What happened
On April 29, 1962, a Weihe 50 glider, registration HB-577, was engaged in a distance flight attempt from Sisseln, Switzerland, with the objective of reaching Grenoble, France. The pilot was navigating through the Jura mountains and following the Chat massif before reaching the Chartreuse massif. While attempting to regain altitude over the Isère valley, the aircraft entered a spiral dive.
During the maneuver, the aircraft struck trees in a right-hand turn near the hamlet of Langelet. The impact caused significant damage, including the separation of a wing from the fuselage and structural failure of the tail section. The pilot sustained a fractured vertebra during the crash.
The investigation
Investigators examined the wreckage and the flight path, noting that barograph data showed the aircraft had descended from 1,800 meters to approximately 500 meters in the fifteen minutes preceding the crash. The investigation focused on the mechanical state of the control systems and the flight dynamics during the final moments of the flight.
Findings
- The primary cause of the accident was the rupture of the left rudder control cable at the level of the corresponding pedal.
- The failure of the cable resulted in a total loss of directional control, preventing the pilot from correcting the aircraft's path.
- The investigation suggested the breakage was caused by an abnormal degradation of the cable's mechanical properties.
- The pilot was unable to prevent the aircraft from converging toward the slope, leading to the collision with trees.