What happened
The aircraft was in the process of taxiing toward its designated gate when the pilot noticed a warning light illuminate for the number two engine. In response to the indication, the crew discharged the onboard fire bottle. This action successfully extinguished the fire that had developed.
The investigation
A subsequent examination of the aircraft revealed that a fuel line, identified by part number 3103385-1, had broken and was the source of the fire. Further inspection of this component uncovered distinct tool marks on its surface. A laboratory analysis confirmed that the line had failed due to fatigue, with the cracks originating specifically in the area where the tool marks were located.
Findings
The presence of these tool marks suggested that a crescent wrench or a similar hand tool had been used to bend the fuel line. This modification was likely performed in an attempt to align the line with its attachment fitting. Following the review of these findings, the operating company was advised of the cause, and a directive was issued to discontinue this practice.
Safety message
Modifying aircraft components using hand tools can introduce stress concentrations that lead to premature failure. Adhering to manufacturer specifications for part alignment is critical to maintaining structural integrity.