What happened
On 29 March 2018, a Nippon Cargo Airlines (NCA) Boeing 747-8KZF, registration JA18KZ, was operating a cargo flight from Narita International Airport, Japan, to Hong Kong International Airport. As the aircraft was approximately 50 feet above the ground approaching Runway 07L, the crew received a "FIRE ENG 3" EICAS warning message.
The pilot-in-command landed the aircraft and utilized thrust reversers to bring it to a stop. The crew then moved the aircraft to the intersection of Taxiway A8 and Taxi to A, notifying Air Traffic Control of the fire. The first officer proceeded to shut down the No. 3 engine and discharged the engine fire suppression system. Upon arrival, the Airport Fire Contingent observed white smoke emitting from the No. 3 engine. Following inspections, the aircraft was cleared to taxi to the cargo apron under fire service escort.
The investigation
Investigators examined the engine components and found evidence of thermal damage, sooting, and discoloration on the exterior top section of the No. 3 engine core. The investigation established that a small fire was caused by a fuel leak originating from a cracked fuel manifold.
Technical analysis focused on why the crack had not been identified during a previous ultrasonic inspection conducted in January 2018. The investigation looked into the energy levels of echoes reflected from the crack, the possibility that the signal was below the rejection threshold, and the potential influence of a frayed cable on the ultrasonic probe used during maintenance.