What happened
On June 6, 1970, a Piper PA-18 Super Cub, registration HB-OYM, was engaged in glider towing operations at the Courtelary airfield. After completing its 25th towing flight of the day, the pilot transitioned to the final approach for runway 06. Because the aircraft was still too high, the pilot initiated a sideslip maneuver to lose altitude.
During the approach, the pilot had deployed the flaps to 15 degrees. The aircraft was flying at an estimated speed of 60 mph, which was below the manufacturer's recommended approach speed of 70 mph. As the aircraft descended to approximately 2 or 3 feet above the ground, the pilot attempted to level out the sideslip, but reported that the flight controls failed to respond despite pulling the control column fully aft. The aircraft subsequently struck the ground with its left wheel a few meters before the start of the grass runway, resulting in a slight rightward skid and significant damage to the landing gear and fuselage.
The investigation
The investigation examined the pilot's experience, the aircraft's maintenance history, and the environmental conditions at the time of the accident. The pilot was highly experienced with the Piper PA-18 Super Cub, having completed 90 hours of flight time and 520 landings in this specific model. The aircraft was fully airworthy and within weight and center-of-gravity limits.
Investigators analyzed the flight controls and found that while the control cables appeared slack, this was a direct result of the fuselage deformation caused by the impact. The investigation also noted that the pilot had been performing towing operations all day in moderate to heavy turbulence, which may have contributed to pilot fatigue.
Findings
- The pilot was flying at 60 mph, which was significantly below the 70 mph recommended approach speed.
- The use of a sideslip maneuver with flaps extended is generally reserved for emergency situations; however, the pilot only used the first notch (15 degrees) of flap.
- The combination of low airspeed and existing turbulence caused the aircraft to lose control effectiveness at low altitude.
- The pilot likely attempted an extremely short landing to reach the glider park located at the runway threshold, leading to the late correction attempt.