The Regulatory body Federal Aviation Administration (FAA) is adopting a new airworthiness directive (AD) for all the Boeing Company Model 777-200, -200LR, -300, -300ER, and 777F series aircraft.
As per the publication, this AD was required due to a report of a 5-inch crack on the upper wing skin at a certain wing station of the right wing.
The scope is repetitive inspections for cracking of the upper wing skin common to certain fasteners and applicable on-condition actions. The FAA is issuing this AD to address the unsafe condition on these products.
The AD requires an open hole high frequency eddy current (HFEC) inspection of fasteners on the left wing and the right wing, those were required by the Boeing Alert Requirements Bulletin 777-57A0125 RB, dated July 25, 2023, for carrying ou an ultrasonic (UT) inspection of the upper wing skin common to those fasteners.
The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of April 23, 2025.
The FAA issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all The Boeing Company Model 777-200, -200LR, -300, -300ER, and 777F series airplanes.
The NPRM published in the Federal Register on November 17, 2023 (88 FR 80216). The NPRM was prompted by a report of a 5-inch crack on the upper wing skin at wing station (WSTA) 460 of the right wing.
In the NPRM, the FAA proposed to require repetitive inspections for cracking of the upper wing skin common to certain fasteners and applicable on-condition actions, including repair.
The FAA issued a supplemental notice of proposed rulemaking (SNPRM) to amend 14 CFR part 39 by adding an AD that would apply to all The Boeing Company Model 777-200, -200LR, -300, -300ER, and 777F series airplanes.
The SNPRM published in the Federal Register on September 20, 2024 (89 FR 77049). The SNPRM was prompted by reports from Boeing of two events of cracking at the fastener 6 and 7 locations where the cracks initiated in the spanwise (inboard/outboard) direction.
These cracks were detected only because of a repair accomplished on an adjacent fastener. The areas around the repaired fasteners were subsequently inspected with an open hole high frequency eddy current (HFEC) inspection, rather than with the ultrasonic (UT) inspection that was proposed in the NPRM.
The SNPRM therefore proposed to require open hole HFEC inspections instead of UT inspections. The FAA is issuing this AD to address the possibility of an undetected upper wing skin crack.
Aircraft wings are required to be able to withstand 150 percent of the maximum expected load for 4 seconds.The 777 wings broke at 154%.
Boeing 777 wing was tested to destruction on January 14, 1995, finally breaking at 154 percent of the designed limit load.
Operators like American Airlines and United requested a compliance time extension for previously inspected airplanes under the Boeing Alert Requirements Bulletin 777-57A0125 RB, dated July 25, 2023.
American Airlines requested that aircraft MSNs on which Boeing Alert Requirements Bulletin is accomplished by completing the UT inspections without the fastener open hole HFEC inspections and had no crack findings be allowed to fly up to 4,700 flight cycles or 10,300 flight hours from the time of the inspection before they have to be brought back to accomplish the inspections with the newly proposed open hole HFEC inspections.
Federal Aviation Administration said that the commenters did not provide justification for the request.
Similarly, United also requested an additional grace period to conduct the fastener open hole HFEC inspection on airplanes where the Ultrasonic Inspection (UT) inspection was already conducted prior to the issuance of the final rule.
As per United airlines, the additional time is requested to allow for proper planning and execution of the open hole HFEC inspection; these inspections require a significant amount of time and effort to accomplish and will impact United's maintenance check scheduling.
Additionally, United noted the materials required for the on-condition corrective action are currently out of stock and are subject to extended lead times from Boeing.
On the requests from the operators for compliance time extension, the FAA disagrees on the airplanes on which UT inspections have been done as specified in the NPRM prior to the publication of the final rule.
FAA understands that the UT inspection would not adequately detect cracks common to the fasteners, a grace period extension or allowing credit for accomplish the UT inspection may not adequately maintain an acceptable level of safety due to factors such as airplane age, utilization, inspection history, etc.
The FAA notes that the on-condition corrective action is to contact Boeing for repair instructions and do the repair. The parts needed to do the repair will vary depending on the inspection findings.
If parts for a specific repair are not available, operators may request a compliance time extension through alternative methods of compliance (AMOC) in accordance with paragraph (i) of this AD provided sufficient supporting data is submitted to show an acceptable level of safety is maintained.
The FAA reviewed the relevant data, considered any comments received, and determined that air safety requires adopting this AD as proposed.
Accordingly, the FAA is issuing this AD to address the unsafe condition on these products. Except for minor editorial changes, this AD is adopted as proposed in the SNPRM. FAA says,None of the changes will increase the economic burden on any operator.
Except as specified by the additional requirements of the AD, FAA requires the operators to comply with the the “Compliance” paragraph and Accomplishment Instructions of Boeing Alert Requirements Bulletin 777-57A0125 RB, dated July 25, 2023.
This airworthiness directive AD 2025-06-02 is effective April 23, 2025.
Display Picture Courtesy: Boeing Airplanes
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