Created Thursday, Nov 30th 2023 11:51Z, last updated Thursday, May 1st 2025 17:52Z
A Fedex Federal Express Boeing 767-300, registration N287FE performing flight FX-541 from Memphis,TN to Las Vegas,NV (USA), was climbing out of Memphis' runway 18R when the crew heard a loud bang from the left hand side and observed a fire warning for the left hand engine (CF6). The crew pulled the fire handle for the left hand engine and discharged both fire bottles and initiated a return to Memphis stopping the climb at about 3700 feet MSL. On approach back to Memphis the fire warning ceased. The aircraft landed safely on Memphis' runway 18C about 15 minutes after departure. Attending emergency services observed no active fire but damage to the left hand engine.
The NTSB reported ground inspection revealed the engine had experienced an undercowl fire and the main fuel pump housing had fractured from the main fuel supply line. The fuel pump exhibited thermal distress and melting of the fracture surface. The NTSB opened an investigation.
The aircraft returned to service 14 days after the occurrence.
On May 1st 2025 the NTSB released their final report and investigation docket concluding the probable causes of the incident were:
A high-pressure fuel leak from a gap in the bolted flange interface between the main fuel pump’s fuel crossover supply tube and the hydromechanical unit idler adapter pad, which resulted in the crossover tube flange bolts partially pulling out and allowing fuel to escape and ignite on contact with the engine’s heatshield.
Contributing to the fuel leak was Avio Aero's incorrect manufacture of the idler adapter pad bolt holes, which deviated from GE's manufacturing print requirement; Avio Aero's improper installation of threaded inserts into the idler adapter bolt holes; Avio Aero's failure to inform GE about the manufacturing deviation and request approval; and GE's failure to identify the manufacturing deviation during adapter quality and compliance design reviews.
The NTSB analysed:
The incident engine, a General Electric (GE) CF6-80C2 turbofan, suffered an undercowl fire due to a high-pressure fuel leak originating from a bolted flange interface between a high-pressure fuel crossover tube and the hydromechanical unit (HMU) accessory gearbox adapter pad. The engine’s accessory heat shield surface temperatures and stagnant airflow near the fuel leak location were sufficient to cause ignition.
Two threaded inserts in the adapter pad were found protruding and likely prevented the fuel tube from correctly seating on the adapter pad surface. Threaded inserts were not securely installed into the adapter pad, which allowed the crossover tube bolts to partially pull out. Multiple insert holes had stripped threads, linear scoring, counterclockwise material smearing, missing surface anodization, cross-threading, and concave hole profiles.
Avio Aero, the adapter manufacturer, implemented an automated pre-tap operation that premachined threads into the adapter pad to ease installation of self-tapping steel inserts. In early 2023, this pre-tap operation was determined to be a deviation from the part’s drawing requirements.
Neither GE Aerospace nor Avio Aero could find documentation supporting the decision to pretap the adapter holes or Avio Aero communicating to GE of their decision to deviate from the print requirement. Avio Aero may have decided to pre-tap the adapter holes because other parts were using this process.
