What happened
On March 15, 2005, at approximately 10:05 local time, a Piper PA-25-235, registration OB-1231, operated by Alas Agrícolas S.A.C., was performing agricultural spraying operations at the Hacienda Laredo in Trujillo, Peru. While the pilot was executing the final turn of the sixth scheduled flight of the day, the aircraft experienced a sudden loss of engine power.
Due to the low altitude required for the spraying operation, the pilot had limited time to react and searched for a clear area to perform an emergency landing. The aircraft lost lift and struck a sugarcane plantation. The impact caused significant structural damage, including the breakage and compression of the fuselage and wings. The pilot, who was wearing a shoulder harness, evacuated the aircraft without injury.
The investigation
An investigation by the CIAA focused on the mechanical state of the engine and the maintenance history of the aircraft. Investigators examined the Textron Lycoming O-540-B2B5 engine and found extensive internal damage. Specifically, the investigation established that the engine crankcase had been breached due to the rupture of the crankshaft between the number 1 and 2 main bearings, which also caused the separation of the connecting rod from cylinder number 1.
Technical analysis of the crankshaft revealed a wear of 0.015 inches on the rod bearings. The investigation determined that this specific wear had not undergone the required re-nitriding process as mandated by Mandatory Service Bulletin (SB) 222D.