What happened
On May 16, 1965, a Piper J3C aircraft, registration HB-ONH, was performing a flight from Bex Aerodrome toward the Col des Mosses. During the flight, the pilot encountered turbulence and downdrafts near Leysin, prompting a decision to return to the airfield.
The aircraft touched down on runway 33 approximately 35 meters from the threshold with an approach speed of 55 mph. The landing was described as a short but normal three-point touchdown. However, as the aircraft continued its landing roll at a speed between 30 and 40 km/h, the nose pitched forward, causing the aircraft to flip onto its back. While the occupants sustained no injuries, the aircraft suffered significant damage, including a deformed engine mount, a broken carburetor support, and a damaged wing strut.
The investigation
The investigation examined the mechanical condition of the aircraft, the pilot's experience, and the physical characteristics of the landing. Technical inspections conducted by the Federal Office of Civil Aviation (OFA) and maintenance records confirmed that the braking system was in perfect working order and showed no tendency to lock up.
To understand the physics of the event, the investigator performed reconstruction tests using a similar aircraft (HB-ONV) under nearly identical wind and weight conditions. These tests demonstrated that without the use of brakes, the aircraft would have required much more runway than was available before reaching the intended stopping point (the airfield refreshment stand). The investigation also noted that while the pilot claimed not to have applied the brakes, the physical necessity of braking to stop short of the obstacle suggested otherwise.
Findings
- The aircraft's weight and balance were within prescribed limits, though it was noted that the aircraft was somewhat "tail-light."
- The pilot had not flown this specific type of aircraft for seven months prior to the accident.
- The mechanical components, specifically the brakes, were functioning normally.
- The investigation concluded that the pilot likely applied the brakes with excessive force, leading to the sudden deceleration and subsequent nose-over.