On August 8, 1998, a Piper PA-31-350 (registration N27196) operated by Air Bridge, Inc. was involved in an aviation accident near Alamosa, CO. Investigators recorded the probable cause as: Improper major overhaul of the engine by the overhaul facility. Factors were failure of the V-band clamp, the melting of the baffle and manifold clamp, and the pilot not being able to extend the landing gear. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
While ferrying after major overhauls, an airplane experienced left engine power loss. Examination revealed a broken turbocharger coupling bolt and improper maintenance, leading to forced landing.
Flight Details
The airplane was being ferried to its home base following major overhauls to both engines. As the aircraft approached Alamosa, the left engine lost power. The pilot attempted to restart the engine but was unsuccessful and subsequently feathered the propeller. The landing gear could only extend partially, and the airplane was unable to maintain flying speed or altitude. The pilot opted to perform a forced landing in a cow pasture.
Engine Examination
Inspection of the engine revealed a broken coupling bolt on the right side of the turbocharger. This prevented the V-band clamp from securely fastening the exhaust pipe to the turbocharger, allowing hot exhaust gases to escape into the engine compartment. The turbocharger transition baffle was found partially melted, and the manifold pressure line was burnt through and separated. This separation allowed the mixture to enrichen and flood the engine.
Maintenance Findings
Textron Lycoming Service Bulletin 240P specifies that all V-band couplings and gaskets must be replaced when an engine is overhauled. The failed V-band coupling was found to be rusted and discolored, indicating it had not been replaced during the overhaul. Additionally, the failed manifold pressure line was made of rubber instead of the required flex stainless steel line.