2017 Schweizer 269C accident at Bonvilliers (F-GHAF)

Overview and flight details On 5 July 2017, a Schweizer 269C helicopter, registration F-GHAF, was involved in an accident at Bonvilliers (91), France. The aircraft was operating a private general aviation flight for training/instruction with dual controls. The flight was a proficiency check in preparation for the student pilot's type rating renewal. The helicopter departed from La Ferté-Alais aerodrome. ## Accident sequence After approximately ten minutes of flight, while over wheat fields, the instructor announced a simulated engine failure exercise. The student pilot initiated the appropriate maneuver to reach the recommended autorotation speed and reduced the engine to idle. The engine stopped. The instructor took control while the student attempted to restart the engine, but the attempts were unsuccessful. The instructor decided to land by autorotation on a path bordering the wheat fields. During landing, the right skid struck a mound of earth hidden by vegetation, and the helicopter overturned onto its right side. ## Aircraft and maintenance The F-GHAF was a Schweizer 269C, built in 1981, a light helicopter with a three-blade main rotor, equipped with a Lycoming HIO-360-D1A piston engine. Maintenance was performed by an approved workshop. The investigation found no maintenance defect that could explain the engine failure. ## Engine examination The engine was tested on a test bench with the parameters of the day of the event. It produced the expected power. Several slow and rapid reductions in engine speed were performed. No engine stoppage was observed. The tests also showed that the starter had significant aging and could no longer start the engine when hot. The right magneto also showed significant aging, and the spark plug electrode gap was beyond acceptable tolerances. ## Meteorological conditions The estimated meteorological conditions at the accident site were: CAVOK; surface wind from East to South-East at 5 to 7 knots; temperature: 31 °C at the surface. ## Site and airframe examination The wreckage was located at the edge of a country road bordered by wheat fields. The helicopter was resting on its right side. The tail boom was separated from the fuselage and was found a few meters away. The damage observed was the result of the overturning on the ground. No pre-accident damage was found. ## Pilot information The instructor, aged 65, held a private pilot license for helicopters (PPL(H)), a commercial pilot license for helicopters (CPL(H)), and an instructor qualification since 2013. He also held a private pilot license for airplanes (PPL(A)) with 1,400 hours of flight experience on airplanes. On the day of the accident, he had a total of 1,060 hours of flight on helicopters, including approximately 500 on the Schweizer 269C and 450 as an instructor. The student, aged 67, was the owner of the accident helicopter and held a private pilot license for helicopters (PPL(H)) since 2008. He also held a private pilot license for airplanes (PPL(A)) since 1989. On the day of the accident, he had a total of 135 hours of flight on helicopters, including three in the previous three months. The F-GHAF was the only helicopter he flew. ## Flight manual The version of the flight manual used by the pilots and kept on board the aircraft was a French edition dated 1975. It contained only one instruction applicable to the event considered: in the event of an engine failure at more than 400 ft from the ground, a 'normal autorotation' was recommended. More recent editions describe several procedures and warnings related to this issue. The student, owner of the helicopter, had a recent edition of the flight manual (reissued on 7 December 2012, revised on 19 November 2014). However, this document was published only in English, and the student did not consider it relevant to use. ## Conclusion After the engine stoppage was noted, the instructor took control in an emergency situation. Considerations regarding the risk of vegetation fire led to a change of landing site during a dynamic phase, which may have increased the workload. The overturning of the helicopter resulted from striking a ground obstacle during a sliding landing. The pilot did not ensure the suitability of the landing surface when choosing the exercise area. The investigation was not able to determine with certainty the reason for the engine stoppage.