The Federal Aviation Administration (FAA) has finalized a new airworthiness directive (AD 2025-25-07) effective February 6, 2026, targeting certain General Electric Company (GE) Model GE90-90B, GE90-94B, GE90-110B1, and GE90-115B engines. This directive stems from a manufacturer investigation uncovering iron inclusions in the powder metal used for high-pressure turbine (HPT) stage 1 and stage 2 disks, which could compromise material properties and lead to premature fracture or uncontained failure. Published in the Federal Register on January 2, 2026, the rule requires replacing affected disks to mitigate risks of engine damage and aircraft harm. This development underscores ongoing aviation safety efforts to address manufacturing defects in critical engine components, potentially affecting a limited number of U.S.-registered engines but highlighting broader implications for engine reliability in wide-body aircraft operations.
Background on the Issue
A GE investigation revealed iron inclusions in the powder metal material for certain HPT disks, attributed to manufacturing process deficiencies. These inclusions may reduce fatigue life, increasing the risk of fractures. The FAA's notice of proposed rulemaking (NPRM), published July 29, 2025, in the Federal Register (90 FR 35642), proposed mandatory replacements based on this finding. No prior incidents of failure linked to these inclusions occurred, but GE's risk assessments determined replacements necessary to prevent future events. This AD builds on similar FAA actions addressing powder metal anomalies in engines, such as previous directives for other GE models involving melt-related defects. For context, powder metallurgy involves compacting and sintering metal powders to form high-strength parts like turbine disks, prized for uniformity but vulnerable to contaminants like iron inclusions that can create weak points under high-stress conditions.
Affected Engines and Components
The AD applies to GE90-90B and GE90-94B engines with specific HPT stage 1 disks, and GE90-110B1 and GE90-115B engines with designated HPT stage 1 or stage 2 disks. Affected parts are listed in Table 1 of the AD and Tables 1 and 2 of GE GE90-100 Service Bulletin 72-0926, Revision 01, dated December 22, 2023, incorporated by reference. For instance, HPT stage 1 disks with part numbers like 1847M95G01 and serial numbers such as GWN05K5J are targeted. These engines power Boeing 777 aircraft, common in long-haul fleets. The FAA estimates only two U.S.-registered engines are impacted, one requiring stage 1 disk replacement and another stage 2. This narrow scope reflects targeted identification of suspect batches from GE's manufacturing records.
Required Actions and Compliance
Operators must remove and replace affected disks at specified times. For disks in Table 1 of the AD, replacement is required before further flight. For other HPT stage 1 disks in the service bulletin, action is needed at next piece-part exposure or before 4,650 cycles since new (CSN), whichever comes first. HPT stage 2 disks require replacement at next exposure or before 11,300 CSN. A grace period allows up to 50 additional flight cycles for stage 1 disks exceeding 4,650 CSN on the effective date. Piece-part exposure means the disk is removed and fully disassembled from the engine. Eligible replacement parts exclude those listed as affected. The AD defines unsafe conditions under Joint Aircraft System Component Code 7250, emphasizing prevention of uncontained debris that could damage the engine or aircraft.
Public Comments and FAA Response
The FAA received input from four entities during the NPRM comment period: the Air Line Pilots Association, International (ALPA), The Boeing Company, FedEx Express, and GE Aerospace. ALPA, Boeing, and FedEx supported the proposal without changes, indicating industry consensus on the safety need. GE requested a part number correction for three serial numbers in Table 1, from 1865M13G08 to 1865M13G07, which the FAA adopted after verification with the service bulletin. This adjustment ensures accuracy without altering the rule's scope or burden. No other substantive changes were made, reflecting the proposal's soundness.
Economic and Regulatory Analysis
Compliance costs are estimated at $932,816 for one HPT stage 1 disk replacement and $187,086 for one stage 2 disk, including prorated parts and eight work-hours at $85 per hour. Total U.S. operator costs reach about $1.12 million, deemed minimal given the limited affected engines. The FAA certified this as not a significant regulatory action under Executive Order 12866, with no substantial impact on small entities or intrastate aviation. Authority stems from 49 U.S.C. 44701, promoting safe civil aviation. This aligns with FAA priorities on proactive defect mitigation, echoing precedents like ADs for similar inclusions in CFM International engines.
Perspectives and Implications
Stakeholders view this AD as a prudent safety measure. From an operator perspective, as voiced by FedEx, it minimizes disruption while enhancing reliability. Pilots, via ALPA, prioritize preventing uncontained failures, which could endanger crews and passengers. Manufacturers like GE emphasize data-driven risk assessments, noting no prior failures but advocating prevention. Short-term implications include potential scheduling adjustments for maintenance, especially for fleets with high-cycle engines. Long-term, this could influence powder metal quality controls industry-wide, possibly leading to enhanced supplier audits or FAA oversight. Debates may arise on balancing costs with safety in low-incidence risks, but the AD's targeted approach avoids broader fleet groundings.
In summary, this AD addresses a manufacturing flaw in GE90 engine disks through mandatory replacements, supported by industry and grounded in risk analysis. Potential next steps include monitoring compliance via FAA dockets and possible alternative methods of compliance requests. Ongoing challenges involve ensuring global operators adhere to timelines, while debates may focus on advancing materials science to eliminate such inclusions in future engine designs.
