Operators of Engine Alliance GP7200-powered Airbus A380s are set for a new round of inspections after a fracture was found in a fan hub of the engine that suffered a mid-air failure on an Air France aircraft over Greenland in September 2017.
The fan hub component, also known as the first-stage low-pressure compressor rotor assembly, was discovered in July by France’s BEA air accident investigation agency after an almost two-year search. The assembly section was buried deep in snow after disintegrating over Greenland during a flight from Paris to Los Angeles. The aircraft, which had 521 passengers and crew, diverted to Goose Bay, Canada.
The BEA said Aug. 21 that the fan hub had been examined by the Engine Alliance, under the BEA’s supervision, and that an engine inspection campaign would be launched soon. “Metallurgical examination of the recovered titanium fan hub fragment identified a subsurface fatigue crack origin,” says the safety agency. “The fracture was initiated in a microtextured area approximately in the middle of the slot bottom,” it adds. “Examination of the fracture is ongoing.”
The BEA statement comes after the FAA issued two new airworthiness directives (AD) on the GP7200 that called for checks of the rotor assembly, including a one-time eddy-current inspection of the fan hub blade slot bottom and blade slot front edge. Operators are asked to check for cracks and perform a visual inspection of the engine fan hub assembly for damage.
For all GP7270 and GP7277 engines the AD also requires an independent inspection of the engine fan hub assembly prior to reassembly of the engine fan hub blade lock assembly, while for certain serial-numbered GP7270 and GP7277 models replacement of the engine fan hub blade lock assembly is also required, the agency added.
In addition, the FAA has also mandated inspection of the engine’s stage 6 seal ring for correct installation and inspection of the high-pressure compressor (HPC) stages 2-5 spool for cracks. Depending on the results of the inspections, it also calls for replacement of the HPC stages 2-5 spool with an eligible part. The agency says the AD requires the same inspections but reduces the inspection interval and adds a repetitive inspection and a mandatory terminating action. “This AD was prompted by a shop finding of axial cracks in the interstage 5-6 seal teeth of the HPC stages 2-5 spool spacer arm due to an incorrectly installed stage 6 seal ring.”
Both ADs come into force Aug. 30 and are issued to address unsafe conditions on these products, the FAA said. Emirates, Etihad, Korean, Air France and Qatar operate Airbus A380s powered by Engine Alliance engines. An Air France spokesman said: "Air France strictly follows the inspection plan requested by the engine manufacturer Engine Alliance, whose engines power its A380s.”
He noted that Engine Alliance had issued a service bulletin requesting the inspection of the part concerned on GP7200 engines shortly after the incident. “These inspections were carried out on all A380s in service at Air France, including 10 aircraft and 40 engines."
The Engine Alliance says it “is already performing inspections and maintenance in accordance with the Aug. 15 FAA airworthiness directive. We are supporting our customers and coordinating with them to ensure the process is completed in a timely manner.”