What happened
On January 19, 2013, a Cessna 152, registration PR-EJB, was conducting a visual flight rules (VFR) navigation flight with an instructor and a student pilot on board. The flight originated from Itápolis, SP, and included a full landing at Presidente Prudente, SP, followed by a touch-and-go maneuver at Londrina, PR.
While cruising at 5,500 feet, the crew noticed a drop in engine oil pressure. As the aircraft climbed to 6,500 feet, the engine began to vibrate heavily, accompanied by the smell of burning oil. To prevent further damage or an in-flight fire, the crew shut down the engine and performed an emergency landing in a soybean plantation located in the rural area of Cornélio Procópio, PR. Both occupants of the Cessna 152 escaped the crash uninjured, though the aircraft sustained damage to the engine and propeller.
The investigation
The investigation focused on the mechanical failure of the engine. Investigators found that the aircraft had recently undergone a general overhaul. During this maintenance process, two piston plugs (P/N LW11625) were not installed on the piston pin of cylinder number 4. This omission led to significant piston wear and the generation of metal shavings (swarf) within the engine.
Findings
- The primary cause of the engine failure was improper maintenance during the engine overhaul, specifically the failure to install necessary piston plugs.
- The resulting metal shavings compromised the engine's internal lubrication system.
- The loss of lubrication led to the breakage of internal engine components, causing the observed oil pressure drop and severe vibration.