What happened
On January 17, 1998, a Robin DR 300-108 aircraft, registered F-BSJK, was conducting a local flight from the Vitry-en-Artois aerodrome. Following a period of engine testing where no anomalies were detected, the pilot commenced takeoff. The flight parameters initially remained normal; however, approximately one minute after departure, the pilot experienced a significant drop in engine power accompanied by noticeable vibrations.
In response to the engine malfunction, the pilot executed a return to the airfield. The aircraft landed safely, and the engine was shut down once the aircraft had cleared the runway. There were no injuries and no damage to the aircraft resulting from the event.
The investigation
During the subsequent inspection of the Lycoming O-235-C2A engine, maintenance personnel identified a mechanical failure within the valve train. Specifically, the exhaust valve of one cylinder remained in the closed position. The investigation revealed that a rocker arm adjustment screw had become loose, and its associated locknut had fallen into the rocker cover.
Upon further inspection of the engine, it was determined that all adjustment screws required re-tightening. At the time of the incident, the engine had completed only 40 hours of operation following a major overhaul by the manufacturer.