History of the Flight
On 8 July 2022, the pilot and a passenger departed from Yverdon-les-Bains aerodrome (Switzerland) at approximately 10:00 local time, bound for Lyon-Bron aerodrome in France. This was the first leg of a multi-day cross-country flight. Shortly before 13:00, while en route at an estimated altitude of 1,000 ft, the pilot sensed abnormal heat in the cockpit. The oil temperature indicator needle was in the red zone. Soon after, the engine shut down. The pilot was unable to restart it and initiated a forced landing. He adopted the recommended maximum glide speed of 145 km/h, configured the aeroplane for landing, and positioned it into the wind. He shut off the fuel supply and switched off the battery. During landing in a corn field, the right wing collided with the ground, causing the aeroplane to tilt over and come to rest inverted. The pilot and passenger, unhurt, evacuated the aeroplane.
Wreckage and Systems Examination
Examination of the wreckage revealed that the aeroplane struck the ground with a shallow nose-down attitude, heading north with a right bank. The nose gear was deformed left rearward. Flaps were extended to the landing position. The nose and rear fuselage were almost completely separated from the main airframe due to impact forces. The propeller damage—one blade intact, the other bent backwards—was consistent with an in-flight engine shutdown. Fuel was present in the single tank.
At the BEA facilities, examination of the instrument panel showed substantial signs of overheating and fusion on the protective sleeves covering the bundle of electrical wires along the back bottom of the panel. These marks indicated an overcurrent in the electrical system. No other overheating marks were found on the wreckage. The melted plastic runs were oriented downward, suggesting the overcurrent began during flight, as the aeroplane later inverted. The exact cause of the overcurrent could not be determined, but it likely occurred on a cable connected to the main electrical bus supplying all electrical devices. The magneto cables were not responsible for the overcurrent. During flight, fusion of the protective sleeves caused electrical continuity, grounding the magneto cables and cutting the engine ignition system, leading to the engine shutdown.
The electrical system had undergone several modifications not meeting the manufacturer's standards. These included a cigarette lighter socket with wiring showing overheating marks (likely pre-existing), use of non-standard cables, obsolete cables left in place, and non-compliance with the cable colour code. The organization responsible for these modifications could not be identified.
Additional Information
The aeroplane, owned by the Yverdon flying club, was purchased second-hand in the 1990s. At the time of the accident, it had 12,270 flight hours and was equipped with a O-320-D2A engine with a two-magneto ignition system. Maintenance since 2011 was performed by Mecanair workshop; prior maintenance was by Aero Nord. No records indicated significant alterations to the electrical system during or after acquisition. The club president and maintenance workshop stated that modifications, including the cigarette lighter socket, predated the club's ownership. The pilot reported not using it, and the president believed other pilots did not use it either.
The 57-year-old pilot held a PPL(A) issued in 1993 by Swiss authorities, with about 465 total flight hours, 350 on the DR400, and one hour in the three months before the accident. The passenger, also a pilot and club member, held an ATPL(A) with about 13,000 flight hours, including 1,500 on single-engine aircraft and 500 on DR400.
Weather conditions at the time and area were estimated by Météo-France: high-pressure pattern, mostly north to north-east wind moderate to strong, causing likely light to moderate turbulence near mountains, with clear sky to few clouds.
Conclusion
The investigation determined that an overcurrent in the electrical system caused fusion of protective sleeves on cables, leading to electrical continuity. This grounded the magneto cables, cutting the engine ignition and causing the engine to shut down. The pilot performed a forced landing, during which the aeroplane overturned. The cause of the overcurrent could not be determined.