Airworthiness Directives; The Boeing Company Airplanes

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2024-1287; Project Identifier AD-2023-00992-T” at the beginning of your comments. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing date and may again revise this proposal because of those comments.

Except for Confidential Business Information (CBI) as described in the following paragraph, and other information as described in 14 CFR 11.35, the FAA will post all comments received, without change, to regulations.gov, including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this proposed AD.

Confidential Business Information

CBI is commercial or financial information that is both customarily and actually treated as private by its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public disclosure. If your comments responsive to this SNPRM contain commercial or financial information that is customarily treated as private, that you actually treat as private, and that is relevant or responsive to this SNPRM, it is important that you clearly designate the submitted comments as CBI. Please mark each page of your submission containing CBI as “PROPIN.” The FAA will treat such marked submissions as confidential under the FOIA, and they will not be placed in the public docket of this SNPRM. Submissions containing CBI should be sent to: Luis Cortez-Muniz, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; phone: 206-231-3958; email: Luis.A.Cortez-Muniz@faa.gov. Any commentary that the FAA receives that is not specifically designated as CBI will be placed in the public docket for this rulemaking.

Background

The FAA issued AD 2012-07-06, Amendment 39-17012 (77 FR 21429, April 10, 2012) (AD 2012-07-06), for The Boeing Company Model 777-200, 200LR, -300, -300ER, and 777F series airplanes with an original airworthiness certificate or original export certificate of airworthiness issued before September 1, 2010. AD 2012-07-06 requires revising the maintenance program to update inspection requirements to detect fatigue cracking of principal structural elements (PSEs). The FAA issued AD 2012-07-06 to ensure that fatigue cracking of various PSEs is detected and corrected; such fatigue cracking could adversely affect the structural integrity of these airplanes.

The FAA issued an NPRM to amend 14 CFR part 39 by adding an AD to supersede AD 2012-07-06 that would apply to certain The Boeing Company Model 777-200, -200LR, -300, -300ER, and 777F series airplanes. The NPRM was published in the Federal Register on May 14, 2024 (89 FR 41908). The NPRM was prompted by a new revision to the airworthiness limitations (AWLs) of the maintenance planning document (MPD) and the damage tolerance rating (DTR) Check Form Document. In the NPRM, the FAA proposed to retain the requirements of AD 2012-07-06 and revise the existing maintenance or inspection program by incorporating the information in Subsection B, Airworthiness Limitations-Structural Inspections and Subsection C, Airworthiness Limitations-Structural Safe-Life Limits, of Section 9, Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs), D622W001-9, Revision December 2022, of the Boeing 777-200/200LR/300/300ER/777F Maintenance Planning Data (MPD) Document; and Boeing 777-200/200LR/300/300ER/777F Damage Tolerance Rating (DTR) Check Form Document, D622W001-DTR, dated December 2022.

Actions Since the NPRM Was Issued

Since the FAA issued the NPRM, Boeing published Section 9, Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs), D622W001-9, Revision April 2023, of the Boeing 777-200/200LR/300/300ER/777F Maintenance Planning Data (MPD) Document; and Boeing 777-200/200LR/300/300ER/777F Damage Tolerance Rating (DTR) Check Form Document, D622W001-DTR, dated April 2023, which contain new and more restrictive airworthiness limitations (inspections and life limits have been updated). The FAA has determined it is necessary to mandate those airworthiness limitations.

Airplanes with an original airworthiness certificate or original export certificate of airworthiness issued on or after September 5, 2024, must comply with the airworthiness limitations specified as part of the approved type design and referenced on the type certificate data sheet; this proposed AD therefore does not include those airplanes in the applicability.

Comments

The FAA received a comment from FedEx Express who supported the NPRM without change.

The FAA received additional comments from four commenters, including American Airlines (AAL), Boeing, Japan Airlines (JAL), and United Airlines (UAL). The following presents the comments received on the NPRM and the FAA's response to each comment.

Request To Update the Document to the Latest Revision

JAL and UAL requested that the proposed AD be revised to change the reference to the December 2022 versions of the airworthiness limitation documents cited in the proposed AD. JAL and UAL noted that Section 9, Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs), D622W001-9, Revision April 2023, of the Boeing 777-200/200LR/300/300ER/777F Maintenance Planning Data (MPD) Document; and Boeing 777-200/200LR/300/300ER/777F Damage Tolerance Rating (DTR) Check Form Document, D622W001-DTR, dated April 2023, are already published. UAL stated that this change will simplify the implementation process for operators by removing the need for a new alternative method of compliance (AMOC) to implement the latest MPD revision. UAL stated it has already been working toward implementing the April 2023 revision, even before release of the NPRM.

The FAA agrees with the request. As previously stated, the FAA has determined it is necessary to mandate the new airworthiness limitations specified in the Revision April 2023 AWLs documents because the inspections and life limits have been updated. The FAA has revised this proposed AD accordingly.

Request To Add a Compliance Time for New Parts

JAL requested that a compliance time for new parts, similar to the statement in paragraph (g)(2) of AD 2012-07-06, be added to this proposed AD, i.e., “within the applicable time specified in Subsection B, Airworthiness Limitations-Structural Inspections, of Section 9, `Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs),' D622W001-9, Revision July 2011, of the Boeing 777 Maintenance Planning Data (MPD) Document, from the time of installation for new parts.”

The FAA agrees with the request. The compliance time for new parts is still applicable as stated previously in AD 2012-07-06. This compliance time was inadvertently excluded from the proposed AD (in the NPRM). The FAA has revised paragraph (i)(2) of this proposed AD (in the SNPRM) accordingly.

Request To Remove a Duplicate Reporting Requirement

The Boeing company requested that the FAA removes paragraph (i)(3) of the proposed AD. Boeing stated that the same reporting requirement is included in Section 9, Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs), D622W001-9, Revision December 2022, of the Boeing 777-200/200LR/300/300ER/777F Maintenance Planning Data (MPD) Document.

The FAA agrees with the request. Both the Revision December 2022 and Revision April 2023 versions of the MPD already include a reporting requirement of 10 days after the airplane is returned to service. Therefore, the exception is not necessary for the Revision April 2023 MPD. However, the exception is still necessary for the Boeing 777-200/200LR/300/300ER/777F Damage Tolerance Rating (DTR) Check Form Document, D622W001-DTR, dated April 2023. The FAA has revised paragraph (i)(3) of the proposed AD (in the NPRM) accordingly.

Request for Clarification of Reporting Requirements

AAL requested that the language in the “Proposed AD Requirements in This NPRM” paragraph of the NPRM be revised from “This proposed AD would also require sending inspection results to Boeing” to “This proposed AD would also require sending inspection results of crack findings to Boeing.” AAL also requested that paragraph (i)(3) of the proposed AD be revised to change “Reports specified in Section 9 . . .” to “Reports of crack findings as specified in Section 9 . . . .” AAL stated that additional clarification is necessary to avoid any possible ambiguity in the intent of the proposed AD and makes the requirement eminently clear that only crack findings need to be reported, as specified in Section 9, Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs), D622W001-9, Revision April 2023, of the Boeing 777-200/200LR/300/300ER/777F Maintenance Planning Data (MPD) Document.

The FAA partially agrees with the requests. The FAA concurs that Section 9, Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs), D622W001-9, Revision April 2023, of the Boeing 777-200/200LR/300/300ER/777F Maintenance Planning Data (MPD) Document specifies to report crack findings of structural inspections. However, as stated previously, paragraph (i)(3) of the proposed AD (in the NPRM) has been removed. In addition, the “Proposed AD Requirements” paragraph in the NPRM is not restated in this SNPRM. Therefore, the FAA has not revised this SNPRM in this regard.

Request To Extend Compliance Time

AAL requested that paragraph (i)(2) of the proposed AD be revised to “. . . or within 18 months from the AD effective date, whichever occurs later,” as was permitted in paragraph (g)(2) of AD 2012-07-06. AAL stated that extending the compliance time from 12 months to 18 months will allow operators greater flexibility to bridge these requirements into their maintenance program without the possibility of forcing aircraft out of service, especially considering some maintenance check intervals may have been escalated during the time between when AD 2012-07-06 was released, and when the proposed AD becomes an AD.

The FAA does not agree with the request. The 12-month compliance time (grace period) is being proposed to ensure a timely implementation of Subsection B, Airworthiness Limitations-Structural Inspections and Subsection C, Airworthiness Limitations-Structural Safe-Life Limits, of Section 9, Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs), D622W001-9, Revision April 2023, of the Boeing 777-200/200LR/300/300ER/777F Maintenance Planning Data (MPD) Document; and Boeing 777-200/200LR/300/300ER/777F Damage Tolerance Rating (DTR) Check Form Document, D622W001-DTR, dated April 2023, and to maintain an adequate level of safety in the fleet. Therefore, the FAA has not changed this proposed AD regarding this request. However, under the provisions of paragraph (k) of this proposed AD, the FAA will consider requests for approval of alternative compliance times if sufficient data are submitted to substantiate that the change would provide an acceptable level of safety.

FAA's Determination

The FAA is proposing this SNPRM after determining the unsafe condition described previously is likely to exist or develop in other products of the same type design. Certain changes described above expand the scope of the NPRM. As a result, it is necessary to reopen the comment period to provide additional opportunity for the public to comment on this SNPRM.

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed Section 9, Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs), D622W001-9, Revision April 2023, of the Boeing 777-200/200LR/300/300ER/777F Maintenance Planning Data (MPD) Document. Subsection B, Airworthiness Limitations—Structural Inspections and Subsection C, Airworthiness Limitations—Structural Safe-Life Limits, of this material contains airworthiness limitations for structural inspections and structural life limits, among other limitations.

The FAA also reviewed Boeing 777-200/200LR/300/300ER/777F Damage Tolerance Rating (DTR) Check Form Document, D622W001-DTR, dated April 2023. This material provides the DTR check forms and the procedure for their use.

This proposed AD would also require Section 9, “Airworthiness Limitations (AWLs) and Certification Maintenance Requirements (CMRs),” D622W001-9, Revision July 2011, of the Boeing 777 Maintenance Planning Data (MPD) Document, which the Director of the Federal Register approved for incorporation by reference as of May 15, 2012 (77 FR 21429, April 10, 2012).

This material is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section.

Proposed AD Requirements in This SNPRM

For airplanes with an original airworthiness certificate or original export certificate of airworthiness issued before September 1, 2010, this proposed AD would retain all the requirements of AD 2012-07-06. For airplanes with an original airworthiness certificate or original export certificate of airworthiness issued before September 5, 2024, this proposed AD would require revising the existing maintenance or inspection program to incorporate new and more restrictive airworthiness limitations, which would then terminate the retained requirements of AD 2012-07-06. This proposed AD would also require sending inspection results to Boeing.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would affect 326 airplanes of U.S. registry. The FAA estimates the following costs to comply with this proposed AD:

The FAA estimates the total cost per operator for the retained actions from AD 2012-07-06 to be $7,650 (90 work-hours × $85 per work-hour).

The FAA has determined that revising the existing maintenance or inspection program takes an average of 90 work-hours per operator, although the FAA recognizes that this number may vary from operator to operator. Since operators incorporate maintenance or inspection program changes for their affected fleet(s), the FAA has determined that a per-operator estimate is more accurate than a per-airplane estimate.

The FAA estimates the total cost per operator for the new proposed actions to be $7,650 (90 work × hours × $85 per work-hour).