What happened
On April 11, 2017, a Vans RV-4, registration F-PAUR, was performing a VFR flight from Friedrichshafen to Dijon when the pilot experienced a brief engine cutout. While engine parameters initially appeared normal, intermittent power interruptions continued to occur, prompting the pilot to climb to a higher altitude to prepare for a potential engine failure.
During the flight, the pilot notified air traffic control of the engine issues and requested a modified flight path to avoid the Jura mountains. As the frequency of the interruptions increased, a check of the magnetos revealed that the right magneto had failed. The left magneto subsequently showed increasing engine instability, leading the pilot to declare a 'mayday' distress situation. Eventually, the engine lost all power, leaving the aircraft to descend in a glider configuration.
Seeking the nearest suitable landing site, the pilot targeted Bressaucourt Aerodrome (LSZQ). Upon approaching the field at 2,000 feet, the pilot received radio information regarding runway 07 usage and wind conditions. Following a series of maneuvers, including a tailwind approach and a crosswind approach, the pilot successfully landed on the final approach of runway 07. One person on the ground sustained slight injuries during the event.
The investigation
Because the aircraft had been repaired and returned to service in France before the Swiss Transportation Safety Investigation Board (SUST) was notified, a comprehensive technical investigation into the mechanical origin of the failure could not be performed. The investigation focused on the sequence of events and the reporting process.
Findings
- The primary cause of the engine failure was a failure of the right magneto, which led to progressive engine instability.
- The pilot and the Bressaucourt aerodrome personnel were unaware of the specific regulatory requirements regarding the immediate reporting of serious incidents to the SUST.