Analysis of failed engine fitted on an aircraft

A failed engine fitted on an aircraft which met with an incident was forwarded to National Aerospace Laboratories, Bangalore, for analyzing the cause of failure. Investigation revealed that seizure at crankpin No.6 led to the fracturing of the piston No.6 at the connecting rod small-end pin retaining holes resulting in the subsequent damages and failure of the engine. From the evidences, misalignment in the system or failure of the shell bearing materials or total starvation of lubricant leading to seizure can be ruled out as the primary cause for the failure. The most probable reason for seizure appears to be the lubricant film breakdown either due to low oil pressure or overload