US investigators found a loose component in the engine cowling of an Atlas Air Boeing 747-8 that suffered an in-flight engine fire during a 18 January fight from Miami International airport.
A preliminary incident report from the US National Transportation Safety Board (NTSB), released on 9 February, says that inspection of the GE Aerospace GEnx-2B67 turbofan revealed a borescope port plug that was unsecured from the combustion diffuser nozzle.
The borescope plug “was not secured in the case and was found loose in the engine cowling”, the NTSB says, adding that ”the burn-through observed on the thrust-reverser wall was directly above the open” plug port.
The 747’s maintenance records show that the borescope plug in question was removed and replaced by a third-party vendor during a 14 January inspection of the combustion diffuser nozzle. The technician was provided instructions on how to properly reinstall borescope plugs “to ensure the locking feature was properly engaged”, the NTSB says.
The agency says the work had been signed by the performing technician to indicate it had been completed according to the maintenance manual.
No evidence of an uncontained engine failure – which involves internal rotating parts or fragments escaping the engine casing – was visible to inspectors, while engine data showed no evidence of a surge or stall.
Bound for San Juan’s Luis Munoz Marin International airport, the Atlas Air 747 took off from Miami around 22:30 local time. While passing an altitude of 3,000ft, the aircraft’s number two engine caught fire, prompting the pilots to declare mayday with air traffic control.
The flightcrew shut down the number two engine. ”One fire bottle was discharged, and the fire warning light subsequently extinguished,” the NTSB says.
The aircraft was cleared to land back in Miami less than 15min after take-off. ”Following an uneventful landing, the airplane was met by fire-fighting personnel and the airplane was cleared to taxi under its own power to parking,” the agency says.
Video posted to social media in the early hours of 19 January shows the jet flying at low altitude with flames erupting from its left side.
No flightcrew members or responding personnel were injured during the incident.