BOEING 767AMERICAN AIRLINES INC

Fuel leaking from the fuel flow transmitter that ignited on contact with the engine’s hot cases which resulted in an engine undercowl fire. The fuel leak resulted from the fuel flow transmitter end housing backing off from the main housing, creating a gap that allowed high pressure fuel to escape. Under certain assembly variances and operational load and temperature variations, the end housing joint may not be able to maintain the preload without eventually yielding, which results in the loosening of the joint and…

The probable cause of the engine failure and subsequent undercowl engine fire was due to the fatigue fracture of a high pressure turbine stage 2 disk blade retaining lug that released two blades which impacted the low pressure turbine case causing a fuel line to fracture spraying fuel on the hot engine cases where it ignited. During a machining operation of the disk lug, a tool mark was introduced that set up the area for fatigue cracks to initiate.

The failure and separation of a section of the No. 2 engine's combustion chamber's small exit duct (SED), which created an airflow disruption that led to an engine surge and subsequent fire. Contributing to the accident was the insufficient weld penetration that remained totally contained within the SED outer dome and did not penetrate through to the inner duct as required by the manufacturing specifications.

The flight crewmembers’ misidentification of the damaged engine (after leveling off the airplane and reducing thrust) and their use of only the damaged engine for thrust during the remainder of the flight, resulting in an unintentional descent and forced ditching in the Pacific Ocean. Contributing to the accident were the flight crew’s ineffective crew resource management, high workload, and stress.

The penetration of turbine blade fragments through the rear turbine case, which punctured the No. 4 bearing oil pressure supply tube, allowing misted oil to contact the hot engine case and ignite the undercowl fire. Contributing to the incident was the installation of approved (but not preferred) stage 3 low pressure turbine outer transition duct segments with the riveted rear seal configuration and the failure of the engine design to comply with the engine debris containment requirements of 14 Code of Federal R…