Accident Overview
On December 8, 1970, at approximately 15:00 local time, a Piper PA-18 Super Cub, registration HB-OPW, was involved in an accident at Les Eplatures airfield. The aircraft was owned and operated by the Aé.C.S. Section des Montagnes neuchâteloises. The pilot, born in 1949, held a valid private pilot license issued on August 26, 1968, and had accumulated 74 hours and 24 minutes of flight time, with about 40 hours on the Piper Super Cub. The passenger, born in 1914, had no aviation experience but had flown with the pilot before.
Events Leading to the Accident
Shortly before 15:00, the pilot removed the aircraft from its hangar and positioned it on the tarmac parallel to runway 06 for a pleasure flight with the passenger, who sat in the rear seat. The pilot did not place wheel chocks and asked the passenger to apply the brakes during the hand-starting of the engine. After verifying the brakes, the pilot started the engine. The aircraft began rolling and turning right toward the hangar, approximately 10 meters away. The pilot moved away, passed under the right wing, and rushed to the cockpit to cut the ignition, but the left wingtip struck a doorpost of the hangar. The aircraft pivoted left, and the still-turning propeller damaged the hangar door.
Witness and Mechanical Observations
No eyewitnesses directly observed the accident. Two mechanics in a nearby workshop heard the engine running at an estimated 1500 rpm (note: idle was about 800 rpm) and heard the impact, then found the aircraft against the hangar door. Examination of the wreckage confirmed the brakes were in good working order. The next day, an investigator asked the passenger to simulate the braking action as done during the accident. The passenger placed the soles of his shoes flat on the brake pedals, but the toe of his shoes contacted the front seat support structure, limiting braking effectiveness. The passenger had not been instructed on proper braking technique (using heels).
Damage Assessment
Neither the pilot nor the passenger was injured. The aircraft was severely damaged, approximately 70% of its value at the time. The engine required disassembly and inspection, its mount was deformed. The propeller was damaged. The left wingtip was crushed, the leading edge deformed, the fuselage structure near the left wing root deformed, and the canopy plexiglass shattered. The hangar door was also damaged.
Runway and Weather Conditions
The accident occurred on the tarmac in front of the old hangar near the airport office. The tarmac had a slight slope toward the hangar. At the time, the ground was covered with a uniform layer of ice and, in places, up to 5 cm of snow. Weather was fine with a temperature of +2°C.
Investigation Findings
The pilot had valid licenses for the intended flight, and the aircraft had valid certificates of airworthiness and was well-maintained. The check-list for the aircraft explicitly instructed that chocks must be placed under the wheels before starting. The pilot was aware of this requirement. The absence of wheel chocks and relying on an inexperienced passenger for braking, combined with the engine running at higher than idle rpm due to an advanced throttle position and the tarmac slope, were contributing circumstances. The pilot's pre-start check of the brakes was insufficient to ensure effective braking throughout the start.
Conclusion
The accident occurred because the pilot elected to start the engine by hand without placing wheel chocks and relied on braking by the passenger, who lacked aviation experience.