Incident Overview
On June 14, 2014, at approximately 21:45 local time, a Robin DR400-120 with registration F-GCRU was operating a personal flight for an aviation club. The aircraft departed from Nangis (77) bound for Lognes (77), carrying one pilot and two passengers. During the return leg, the engine failed while cruising at approximately 1,150 feet altitude, roughly five minutes south of Lognes.
Flight Sequence and Emergency Landing
Prior to departure, the pilot experienced difficulty starting the engine at Nangis, accompanied by electrical instrument failures. After a club member manually moved the propeller, the engine started successfully. During the flight, the engine RPM dropped suddenly by 250 rpm. Although power briefly recovered, the engine subsequently vibrated and stopped, locking the propeller. The pilot executed a forced landing in a nearby rapeseed field. The tall crops slowed the aircraft, causing it to nose over and roll onto its back. All occupants evacuated safely through a broken rear window without injury.
Technical Findings
The aircraft was equipped with a Lycoming O-235 engine, which had 1,506 hours since its last overhaul in May 2011. Post-accident examination revealed that the number 3 connecting rod cap had separated from the crankshaft and perforated the right crankcase half. The nuts on the connecting rod bolts were found to have unscrewed and been torn out. Additionally, the central main bearing shells were damaged, with oil holes blocked and positioning tabs destroyed. No anomalies were found in the lubrication system or oil quality.
Conclusion
The investigation determined that the engine failure resulted from the separation of the number 3 connecting rod head from the crankshaft and damage to the central main bearing shells. The specific origin of these mechanical failures could not be established. The report notes that the pilot decided to depart despite unresolved starting issues, potentially influenced by the late hour and approaching sunset. The high crops in the chosen field contributed to the aircraft overturning.