What happened
On May 17, 1964, a pilot participating in a national gliding competition at Hausen am Albis took off in an Elfe MN, registration HB-736. While flying in the Sihlbrugg-Menzingen area, the pilot encountered weak thermals and decided around 14:00 to perform an outlanding between Baogly and Kappel.
The pilot selected a field characterized by short terrain and surrounding trees, intending to execute a steep approach using a brake parachute. Upon deploying the parachute, the expected braking effect failed to materialize. The pilot initially believed the parachute had not fully inflated. While attempting a turning maneuver to approach the field from the opposite direction, the pilot observed the parachute's shadow and realized the device had torn away from the aircraft.
Following a second approach attempt that maintained excessive speed, the pilot initiated a third turn. During this final attempt, the pilot was unable to clear the tree line and impacted a tree crown at minimal airspeed.
The investigation
The investigation focused on the mechanical failure of the braking system and the sequence of the landing attempts. Investigators examined the wreckage of the brake parachute attachment point. The inquiry established that the pilot remained uninjured, though the Elfe MN sustained heavy damage.
Findings
- The primary cause of the accident was the failure of the brake parachute attachment, specifically that the wire loop had torn away.
- The failure was attributed to improperly manufactured wire clamps.
- The pilot misjudged the distance to the obstacles during the final approach attempt.
Safety action
- The investigation identified that the wire clamps used for the brake parachute attachment were not correctly executed, leading to the structural failure of the attachment point.