What happened
On May 18, 2019, at 15:14 LMT, a Cessna 152, registration SP-FZK, departed from an airfield for a flight following the EPLU - EDCQ route. This was the pilot's second flight of the day in the aircraft; during the first flight, the pilot had experienced a power loss during a turn, which prompted an immediate return to the departure airfield. After a technical inspection and engine test showed normal parameters, the pilot decided to proceed with the planned route.
During the second flight, a similar power loss occurred during the second turn of the circuit. Approximately seven to eight minutes into the flight, the engine began vibrating for about 15 seconds, accompanied by a drop in RPM to 2000. Two minutes later, severe vibrations and metallic noises occurred as RPM dropped further to between 1700 and 1800, eventually leading to total engine failure. The pilot, positioned 13 km from the airfield at 1500 ft, determined that returning to the airport was not possible and executed an emergency landing in a meadow visible under the left wing. The landing was completed without further incident.
The investigation
The investigation examined the aircraft's airframe and the Lycoming O-235-L2C engine. Post-landing inspections revealed significant oil leakage on the lower fuselage and horizontal stabilizer. A physical inspection of the engine crankcase near cylinder number 1 showed torn material.
Upon disassembly, investigators found that the connecting rod of cylinder number 1 had broken at the big end. The broken big end showed missing bearing shells and traces of oil, and one of the bolts securing the big end to the crankshaft had snapped halfway through its length. Further analysis revealed significant wear on the crankshaft journal, heavy metal debris in the oil filter, and evidence of overheating. The investigation also noted that the engine continued to run for approximately four minutes after the oil leak began, but without lubrication, the remaining journals also showed signs of increased wear and overheating.