Incident
During the landing roll of a twin-engine aircraft, a fire erupted in the right engine. The pilot brought the airplane to a stop on the runway, shut down both engines, and all occupants evacuated safely.
Investigation
Post-incident examination revealed that one of three studs securing the fuel filter to the fuel/oil heat exchanger had pulled out of its lug hole in the housing. This allowed fuel to leak into the engine bay, where it contacted hot engine surfaces and ignited. The fuel filter unit had accumulated approximately 1,000 hours since its last overhaul.
Further inspection showed that the failed stud had been installed in an oversized lug hole. The lug hole was larger than the stud diameter, preventing proper retention.
Overhaul Manual Review
Investigators reviewed the overhaul manual published by the component manufacturer. The manual was found to contain insufficient information regarding procedures for working with the lug holes. Specifically, it lacked clear guidance on how to ensure that lug holes are properly drilled and that studs are correctly inserted and secured in the lug holes.
The combination of the oversized lug hole and inadequate manual instructions created the conditions for the stud to pull out under operational loads, leading to the fuel leak and fire.
Outcome
The aircraft was stopped on the runway, and the fire was extinguished after engine shutdown. The occupants evacuated without reported injury.