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.