What happened
On April 7, 1973, a Piper Cherokee 140, registration HB-OYH, was conducting a flight from Gruyères to Sion with a pilot and two passengers. Earlier that day, the pilot had resumed flight training after a five-month hiatus, completing several training circuits and a weather reconnaissance flight.
During the approach to runway 26 at Sion, the air traffic controller informed the pilot of a significant wind from 240° at 22 knots. The pilot performed the final approach with full flaps, maintaining an estimated airspeed of 85 mph. Witnesses noted that the aircraft appeared to be traveling at an unusually low speed approximately 1,000 meters before the runway threshold. As the pilot attempted to flare, the aircraft stalled on the right wing and became uncontrollable. The aircraft struck the ground heavily on the nose gear, causing the gear to collapse under the impact. The aircraft came to a stop at the edge of the runway.
The investigation
The investigation focused on the pilot's experience, the aircraft's mechanical condition, and the environmental factors at the time of the accident. The pilot held a valid private pilot license with a restricted radio telephony extension, though his total flight time was only 104 hours, with only 27 hours on this specific type.
Technical inspections confirmed that HB-OYH was airworthy, with the weight and center of gravity within permissible limits. No mechanical defects were identified as a cause for the incident. Meteorological data confirmed visibility of 18 km and a 22-knot wind from 240°. The investigation also reviewed the aircraft's flight manual, which suggests that during high wind or strong crosswind conditions, it may be advisable to approach at higher than normal speeds using partial or no flaps.
Findings
- The primary cause of the accident was a loss of control during the final approach due to insufficient airspeed.
- The aircraft was flying at a speed too low to safely manage the existing wind conditions, which were prone to gusts.
- The pilot had not been instructed to utilize a different flap configuration to compensate for the high winds.
- All occupants remained uninjured following the impact.