Incident Overview
On 18 May 2019 at 15:14 local time, a pilot departed on a Cessna 152 (registration SP-FZK) for a flight from EPLU to EDCQ. This was the pilot's second flight in the aircraft that day. During the first flight, while performing a circuit, the engine power dropped during the second turn. The pilot shortened the pattern and landed back at the departure airfield. A technical inspection and engine run-up revealed no abnormalities, and all engine parameters were normal. The pilot then decided to take off again and continue the planned cross-country flight. During the second turn of the circuit, just before departing on route, another detectable engine power loss occurred, which resolved after a few seconds. After 7–8 minutes of flight, the engine began to vibrate for about 15 seconds, and RPM dropped to 2000. Oil pressure and temperature remained normal. Approximately two minutes later, strong airframe vibrations set in, RPM fell to 1700–1800, and metallic sounds were heard until the engine shut down. The pilot turned toward the airfield (at 1500 ft altitude, 13 km distance) but assessed he would not make it and immediately selected a meadow visible under the left wing for an emergency landing. While searching for a landing site, the pilot did not monitor oil pressure or temperature. At about 500 ft, the engine stopped completely. The landing was without consequences. After landing, a female witness who had observed the final minutes of the flight approached the pilot and reported that when the aircraft approached Polkowice, a white trail was visible behind it. The pilot correlated this with the onset of the first engine vibrations.
Engine Examination
Post-accident inspection of the airframe and engine revealed a significant amount of oil on the lower fuselage and horizontal stabilizer. A rupture was found in the lower crankcase near cylinder #1 of the Lycoming O-235-L2C engine. Disassembly of the engine disclosed a broken connecting rod at the big end in cylinder #1. The bearing shells were missing from the damaged connecting rod end, and no oil traces were found. One of the bolts securing the connecting rod cap had sheared off midway along its length. The absence of larger fragments of the big-end bearing shells, heavy wear on the crankshaft journal, and numerous metal particles in the oil filter indicated that the journal-bearing system operated under conditions of increased friction. The significantly greater wear on this journal compared to others (e.g., cylinder #3) suggested that the bearings had seized on the crankshaft, increasing rotational friction. The considerable overheating of the journal pointed to inadequate or absent lubrication. Similar instances of bearing seizing, rotation, and insufficient lubrication have been documented in these engines.
Probable Cause
The probable cause of the incident was a malfunction in the crankshaft journal-bearing system during operation under conditions of unstable cooperation (seizing of the bearings on the crankshaft) and insufficient lubrication.