Loss of Engine Power in a Cessna 185 B During a Parachute Jump Operation (F-BNLC)

Accident Overview and Flight Profile, On August 20, 2011, at approximately 14:44 local time, a Cessna 185 B with the registration F-BNLC was engaged in an aerial work flight for parachute jumps near the aerodrome of Vesoul (70), France. The pilot was conducting his third rotation of the day, carrying four passengers consisting of one tandem pair and two individual parachutists. During the climb, when reaching 2,700 feet approximately 8 nautical miles from the aerodrome, the pilot heard an explosion from the engine. He observed slight oil projections on the windshield and noticed a reduction in the engine's revolutions per minute to around 1,500, even though the power control was set to full throttle. In response, the pilot executed a turnback and informed the air traffic controller of the issue and his intention to return to Vesoul. Recognizing the continuous degradation of engine parameters, the pilot decided to evacuate the passengers. However, due to the aircraft's low altitude (around 900 meters), only two of the parachutists were able to safely jump, leaving the tandem pair behind. The pilot determined that reaching the runway was impossible and made a forced landing in a maize field approximately 3.3 nautical miles from the runway. During the landing rollout, damage occurred to the leading edge of the left half-wing. The aircraft was damaged as a result of the impact and rollout. Maintenance and Technical Findings, The F-BNLC was powered by a Continental IO 520 D engine, which was installed new on March 14, 2006, and had accumulated 798 hours of operation before the accident. The most recent 50-hour maintenance inspection was carried out on August 9, 2011. Following this service, the engine ran for 12 hours and 20 minutes, including approximately 1 hour and 10 minutes on the day of the accident. Post-accident observations on the aircraft revealed a hole in the engine crankcase at the location of cylinder number 4. The piston of this cylinder was not recovered. The connecting rod remained in place but was found to be fractured at its crankshaft attachment. In April 2011, with the BEA's agreement, the engine was sent to the manufacturer, Continental, in the United States for examination. However, by September 2013, the manufacturer had provided no information regarding the results of this examination. The event exhibited similarities with an incident involving a Cessna 206, registered F-GDAA, on June 18, 2011. Nevertheless, because the engine examination could not be completed, it was not possible to confirm the similarity. Conclusion, Due to the lack of response from the manufacturer to the BEA's inquiries, the cause of the connecting rod failure in the F-BNLC's engine could not be determined. The BEA's investigation is solely aimed at improving aviation safety and does not seek to establish faults or responsibilities.