What happened
On July 4, 1968, at approximately 17:30 CEST, a Piper PA-28-180 Cherokee, registration HB-OLS, was performing a short passenger flight lasting six minutes when it attempted to land at Grenchen airfield. The pilot was conducting an approach to grass runway 07 using flaps in position 3.
In an effort to touch down at the minimum possible speed due to irregularities on the grass surface, the pilot allowed the aircraft to lose too much airspeed. This resulted in a significant sink rate during the final approach. Although the pilot attempted to correct the power settings, the loss of altitude could not be recovered. Consequently, the aircraft failed to maintain the required 5-meter clearance over the public road crossing the airfield boundary. The aircraft's right landing gear struck the pavement of the road, which was elevated by approximately 20 cm, causing the aircraft to decelerate violently. The impact resulted in no injuries to the pilot or the passenger, but caused extensive damage to the right wing, landing gear, and engine mount.
The investigation
The investigation examined the aircraft's airworthiness, the pilot's credentials, and the environmental conditions. The Piper PA-28-180 Cherokee was found to be properly registered, with the center of gravity and loading within permissible limits. Weather conditions at the time were characterized by a moderate high-pressure system with cloudy skies and light winds, which were determined to have no significant impact on the accident.
Investigators also reviewed the pilot's experience. At the time of the accident, the pilot's private pilot license had expired. The pilot had approximately 46 hours of total flight time, with only about 7.5 hours logged in the specific PA-28 model.
Findings
- The primary cause of the accident was insufficient monitoring of the aircraft's airspeed by the pilot during the final approach.
- The pilot's attempt to minimize touchdown speed led to an excessive sink rate that could not be corrected before reaching the airfield boundary.
- The pilot's lack of experience in the specific aircraft type contributed to the inability to manage the flight state during a critical phase of flight.