What happened
On June 26, 1973, at approximately 19:30 CEST, a pilot conducted a one-hour solo flight departing from Grenchen Airport in a Piper PA-18-150 Super-Cub, registration HB-OLR. During the return to the airfield, the pilot attempted an approach to grass runway 25 but found the aircraft too high, resulting in a touchdown only 140 meters from the end of the runway. The pilot initiated a go-around following this first attempt.
The second approach followed a similar trajectory. The aircraft touched down on its main wheels in a nearly horizontal attitude, approximately 125 meters before the runway end. In an effort to stop the aircraft, the pilot applied heavy braking while the tailwheel remained airborne. After crossing the threshold of the paved section of runway 07, the aircraft pitched forward and overturned. The aircraft came to rest on its back roughly 30 meters from the end of the runway; no fire occurred. The pilot sustained no injuries, though the aircraft was heavily damaged.
The investigation
The investigation examined the pilot's credentials, the aircraft's airworthiness, and the environmental conditions at the time of the accident. The pilot held a valid private pilot license with radio telephony privileges and had 112 hours of total flight time. No medical issues or prior incidents were noted in the pilot's records. The Piper PA-18-150 was found to be airworthy, with weight and balance within legal limits.
Weather conditions were clear with visibility exceeding 10 km. While the sun had set behind the Jura mountains, lighting remained sufficient despite some diffuse haze. Notably, a portion of the grass runway 25 had been shifted slightly south due to a wet patch in the center, marked by red pennants. The investigation found that the pilot did not take this displacement into account.
Findings
- The pilot misjudged the glide slope, resulting in two excessively high approaches.
- A lack of decisiveness prevented the pilot from executing a second go-around after the first long landing.
- The pilot applied excessive braking while the aircraft was still in a nearly horizontal attitude.
- The transition from grass to the paved runway surface increased braking effectiveness, creating a forward torque that caused the aircraft to nose over.