The US Federal Aviation Administration (FAA) has issued an Airworthiness Directive (AD) regarding a possible defect in General Electric’s GE90 turbofan engines, which Boeing 777 jets are equipped with.
The recommendation was released on 1 September and identifies a problem called “iron inclusion”, which according to the FAA, is a manufacturing fault, where the materials used for making the defect components contain certain impurities. This affects the durability of, in this case, the engine and can cause cracks or failures, ultimately leading to risks of uncontained debris release, damage to the engine and damage to the airplane.
The FAA is proposing this AD to address the unsafe condition on these products.FAA
Among the affected components are high-pressure turbine discs, rotor spools and compressor seals. The directive is open for public feedback for 45 days before entering into force. Once details are finalised, airlines will need to replace all the faulty components before allowing aircraft equipped with certain GE90 high-pressure turbine stage-one and stage-two discs engines to fly again. Specifically, the affected models are GE90-90B, GE90-94B, GE90-100B1 and GE90-115B engines.
The part replacement will only be an interim solution, the FAA explained, with further measures to be taken upon the completion of the administration’s authority. “The FAA considers that this proposed AD would be an interim action. This unsafe condition is still under investigation by the manufacturer and, depending on the results of that investigation, the FAA may consider further rulemaking action”, reads the directive.
“This proposed AD was prompted by a manufacturer investigation that revealed certain high-pressure turbine (HPT) stage 1 disks, HPT stage 2 disks, forward HPT rotor seals, interstage HPT seals, and stages 7-9 compressor rotor spools were manufactured from powder metal material suspected to contain iron inclusion”, the FAA explained.
Indeed General Electric (GE) notified the FAA about the found faulty materials themselves. The company further mentioned that it contacted all concerned airlines to inform them about the possible risks and offer potential corrective action. “[The AD] is consistent with existing GE recommendations to operators and reflects our proactive approach to safety management”, GE Aerospace, a joint venture between GE and Safran Aircraft Engines, said in a statement.
The FAA estimates that, if adopted as proposed, the directive would affect 9 engines installed on airplanes of US registry, but none needing replacement of the interstage HPT seal. Moreover, the administration estimates a cost of almost $5 million, including labour and replacement parts, for airlines to change the faulty components.