What happened
During a cruise flight segment, the aircraft's engine failed without any prior warning or indication of impending trouble. The pilot evaluated the surrounding terrain and determined that the adjacent beach did not offer a suitable area for a safe landing. Consequently, the decision was made to ditch the aircraft in the ocean. Following the impact with the water, the pilot exited the aircraft and swam approximately one-half mile to reach shore.
The investigation
A technical examination of the failed engine revealed that the crankshaft had fractured at the forward cheek of the number three main bearing. Further inspection identified a reddish sealant residue located around the main bearing through the stud holes in the crankcase. This finding indicated improper assembly or maintenance procedures regarding the sealing of the crankcase.
Findings
The investigation determined that the application of sealant in this specific area violated established maintenance guidelines. According to Lycoming Service Instruction #1125A, sealant should not have been applied around the main bearing through stud holes of the crankcase. This improper sealing likely contributed to the mechanical failure that resulted in the engine seizure.
Safety message
Maintenance personnel must strictly adhere to manufacturer service instructions when applying sealants. Improper application of sealant in critical engine areas can lead to catastrophic mechanical failures.