What happened
On June 12, 1965, a pilot was conducting a cross-country flight in a Hütter H-28 glider, registration HB-223, traveling from Spreitenbach toward Chasseral. During the flight, the pilot encountered significant downdrafts while attempting to cross the Moutier valley. These sinking air currents prevented the pilot from reaching the intended destination and eventually made a landing elsewhere unavoidable.
After failing to find further rising thermals, the pilot selected a landing field near the main road between Moutier and Gänsbrunnen. During the final approach, the aircraft flew over an orchard containing a telephone line supported by wooden poles. In an attempt to gain enough airspeed to clear the wires, the pilot applied back pressure, which caused the left wingtip to strike a wooden utility pole. The impact snapped the pole and caused the aircraft to spin. Approximately 20 meters later, the glider came to a halt in a meadow, having struck the ground with its fuselage and right wing. The pilot sustained light injuries, including a concussion and minor lacerations.
The investigation
The investigation focused on the pilot's decision-making process and the flight parameters during the final approach. Investigators examined the aircraft's condition, finding no technical defects or maintenance issues; the weight and balance were within legal limits. The investigation also reviewed the meteorological conditions, noting that while the day offered good flying weather, localized moderate turbulence and downdrafts were present in the Jura region.
Findings
- The primary cause of the accident was the pilot's decision to delay the landing in an attempt to continue searching for thermals despite encountering heavy downdrafts.
- The landing approach was executed improperly, likely due to the pilot focusing on minimizing the rate of descent via the variometer rather than maintaining the optimal glide speed required to clear obstacles.
- The collision with the telephone pole was a direct result of insufficient airspeed during the final segment of the flight.