# [Amended]
**AGENCY:**
Federal Aviation Administration (FAA), DOT.
**ACTION:**
Notice of proposed rulemaking (NPRM).
**SUMMARY:**
The FAA proposes to adopt a new airworthiness directive (AD) for certain The Boeing Company Model 757-200 and -300 series airplanes. This proposed AD was prompted by cracking found during an inspection on an airplane equipped with Aviation Partners Boeing (APB) scimitar blended winglets (SBWs). This proposed AD would require performing a general visual inspection (GVI) or maintenance records check of certain stringers for an approved freeze plug repair, performing a high frequency eddy current (HFEC) inspection of the same area for any crack common to a certain stringer and a reinforcement strap, and applicable on-condition actions. The FAA is proposing this AD to address the unsafe condition on these products.
**DATES:**
The FAA must receive comments on this proposed AD by June 20, 2025.
**ADDRESSES:**
You may send comments, using the procedures found in 14 CFR 11.43 and 11.45, by any of the following methods:
• *Federal eRulemaking Portal:* Go to *regulations.gov* . Follow the instructions for submitting comments.
• *Fax:* 202-493-2251.
• *Mail:* U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590.
• *Hand Delivery:* Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.
*AD Docket:* You may examine the AD docket at *regulations.gov* under Docket No. FAA-2025-0744; or in person at Docket Operations between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this NPRM, any comments received, and other information. The street address for Docket Operations is listed above.
*Material Incorporated by Reference:*
• For Aviation Partners Boeing material identified in this proposed AD, contact Aviation Partners Boeing, 2811 South 102nd St., Suite 200, Seattle, WA 98168; telephone 206-830-7699; email *[email protected];* website *aviationpartnersboeing.com* .
• You may view this material at the FAA, Airworthiness Products Section, Operational Safety Branch, 2200 South 216th St., Des Moines, WA. For information on the availability of this material at the FAA, call 206-231-3195.
**FOR FURTHER INFORMATION CONTACT:**
Sarah Illg, Aviation Safety Engineer, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712; phone: 206-231-3517; email: *[email protected].*
**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-2025-0744; Project Identifier AD-2024-00586-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 amend 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 NPRM.
**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 NPRM 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 NPRM, 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 NPRM. Submissions containing CBI should be sent to Sarah Illg, Aviation Safety Engineer, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712; phone: 206-231-3517; email: *[email protected].* 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 has received a report indicating a crack on a Model 757-200 airplanes equipped with APB scimitar blended winglets found during an HFEC inspection during accomplishment of a 4C maintenance check. The airplane had 22,185 total flight cycles and 106,470 total flight hours. The 0.40-inch crack was found on the right wing lower stringer L-8 vertical web flange at approximately wing station (WS) 401, located at a fastener common to the stringer L-8 and a reinforcement strap. The blended winglet configuration on Model 757-200 and -300 airplanes is similar; therefore, the 757-300 airplanes are also subject to the unsafe condition identified in this NPRM. This condition, if not addressed, could result in the inability of a principal structural element to sustain limit loads, which could adversely affect the structural integrity of the airplane.
**FAA's Determination**
The FAA is issuing this NPRM after determining that the unsafe condition described previously is likely to exist or develop on other products of the same type design.
**Material Incorporated by Reference Under 1 CFR Part 51**
The FAA reviewed Aviation Partners Boeing Service Bulletin AP757-57-012 Revision 1, dated October 17, 2024. This material specifies procedures for performing a GVI or maintenance records check of the lower stringer L-6 and lower stringer L-8 vertical web flange, between WS 397.50 and WS 403 for an approved freeze plug repair; a surface HFEC inspection for cracking of the wing lower stringer L-6 and lower stringer L-8 vertical web flange, common to the reinforcement strap attach fasteners located between WS 397.50 and WS 403.00; and applicable on-condition actions. On-condition actions include repetitive surface HFEC inspections for cracking, crack length measurement, a surface HFEC inspection of the lower stringer L-6 or L-8 vertical web flange around each of the four fasteners for cracks, crack removal, freeze plug repair, and crack repair.
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 NPRM**
This proposed AD would require accomplishing the actions specified in the material already described, except for any differences identified as exceptions in the regulatory text of this proposed AD.
**Costs of Compliance**
The FAA estimates that this AD, if adopted as proposed, would affect 156 airplanes of U.S. registry. The FAA estimates the following costs to comply with this proposed AD:
| Action | Labor cost | Parts cost | Cost per | Cost on U.S. |
| --- | --- | --- | --- | --- |
| Left- and Right-wing GVI and HFEC Inspection | 7 work-hours × $85 per hour = $595 | $0 | Up to $595 | Up to $92,820. |
The FAA has received no definitive data on which to base the cost estimates for the on-condition actions specified in this proposed AD.
**Authority for This Rulemaking**
Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII: Aviation Programs, describes in more detail the scope of the Agency's authority.
The FAA is issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701: General requirements. Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.
**Regulatory Findings**
The FAA determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would not have a substantial direct effect on the States, on the relationship between the national government and the States, or on the distribution of power and responsibilities among the various levels of government.
For the reasons discussed above, I certify this proposed regulation:
(1) Is not a “significant regulatory action” under Executive Order 12866,
(2) Would not affect intrastate aviation in Alaska, and
(3) Would not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act.
**List of Subjects in 14 CFR Part 39**
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
**The Proposed Amendment**
Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:
**PART 39—AIRWORTHINESS DIRECTIVES**
1. The authority citation for part 39 continues to read as follows:
**Authority:**
49 U.S.C. 106(g), 40113, 44701.
§ 39.13
2. The FAA amends § 39.13 by adding the following new airworthiness directive:
*The Boeing Company:* Docket No. FAA-2025-0744; Project Identifier AD-2024-00586-T.
**(a) Comments Due Date**
The FAA must receive comments on this airworthiness directive (AD) by June 20, 2025.
**(b) Affected ADs**
None.
**(c) Applicability**
This AD applies to The Boeing Company Model 757-200 and -300 series airplanes, certificated in any category, as specified in paragraph 1.A.1 of Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024.
**(d) Subject**
Air Transport Association (ATA) of America Code 57, Wings.
**(e) Unsafe Condition**
This AD was prompted by an operator reporting a crack on a Model 757-200 airplane equipped with Aviation Partners Boeing (APB) scimitar blended winglets (SBWs). The FAA is issuing this AD to address the potential for cracking on the right- or left-wing lower stringer L-8 or L-6 vertical web flange at a fastener common to the reinforcement strap. The unsafe condition, if not addressed, could result in the inability of a principal structural element to sustain limit loads, which could adversely affect the structural integrity of the airplane.
**(f) Compliance**
Comply with this AD within the compliance times specified, unless already done.
**(g) Required Actions**
Except as specified in paragraphs (h) and (i) of this AD: At the applicable times specified in paragraph 1.E., “Compliance,” of Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024, do all applicable actions identified as “RC” (required for compliance) in, and in accordance with, the Accomplishment Instructions of Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024.
**(h) Exceptions to Service Bulletin Specifications**
(1) Where the Compliance Time columns of the tables in “Compliance” paragraph of Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024, refer to “the original issue date of this Service Bulletin,” this AD requires using the effective date of this AD.
(2) Where Table 2 and Table 3 of the “Compliance” paragraph of Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024, specify Action 1 without a compliance time, for this AD, the compliance time is before 9,500 flight cycles after the blended winglet installation, within 3,000 flight cycles after the effective date of this AD, or within 24 months after the effective date of this AD, whichever occurs latest.
(3) Where Table 5 and Table 6 of the “Compliance” paragraph of Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024, specify Action 1 without a compliance time, for this AD, the compliance time is before 8,000 flight cycles after the blended winglet installation, within 3,000 flight cycles after the effective date of this AD, or within 24 months after the effective date of this AD, whichever occurs latest.
(4) Where Table 9 and Table 10 of the “Compliance” paragraph of Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024, specify Action 1 without a compliance time, for this AD, the compliance time is before 9,500 flight cycles after the blended winglet installation, within 3,000 flight cycles after the effective date of this AD, or within 22 months after the effective date of this AD, whichever occurs latest.
(5) Where Table 12 and Table 13 of the “Compliance” paragraph of Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024, specify Action 1 without a compliance time, for this AD, the compliance time is before 8,000 flight cycles after the blended winglet installation, within 3,000 flight cycles after the effective date of this AD, or 22 within months after the effective date of this AD, whichever occurs latest.
(6) Where flagnote (b) of Figure 5 and Figure 10 of the Accomplishment Instructions of Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024, specifies “If the crack is less than or equal to 0.268 inch, remove the crack. Refer to 757-200 SRM 51-10-02 as an accepted procedure. Maximum hole diameter 0.80 inch,” for this AD, replace that text with “If the crack is less than or equal to 0.268 inch, remove the crack. Refer to 757-200 SRM 51-10-02 as an accepted procedure. Maximum hole diameter 0.80 inch. Do an open-hole HFEC inspection of the hole in the stringer in accordance with 757 NDT Manual Part 6, 51-00-04, 51-00-11, or 51-00-16.”
(7) Where Condition 2 of Table 6 in the Accomplishment Instructions of Aviation partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024, includes “remove crack” as part of the actions, the action “remove crack” is not required by this AD for Condition 2 of Table 6.
(8) Where Action 2 of Condition 4.2 in Table 3 of the Accomplishment Instructions of Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024, does not include a method of compliance for the inspection, for this AD, the method of compliance is Figure 3 of the Accomplishment Instructions of Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024.
(9) Where Action 2 of Condition 4.2 in Table 6 of the Accomplishment Instructions of Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024, does not include a method of compliance for the inspection, for this AD, the method of compliance is Figure 8 of the Accomplishment Instructions of Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024.
(10) Where Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024, specifies contacting Aviation Partners Boeing for repair instructions: This AD requires repair using a method approved in accordance with the procedures specified in paragraph (j) of this AD.
**(i) No Report**
Although Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024, specifies to report existing repairs, this AD does not require any report.
**(j) Alternative Methods of Compliance (AMOCs)**
(1) The Manager, AIR-520, Continued Operational Safety Branch, FAA, has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19. In accordance with 14 CFR 39.19, send your request to your principal inspector or responsible Flight Standards Office, as appropriate. If sending information directly to the manager of the certification office, send it to the attention of the person identified in paragraph (k) of this AD. Information may be emailed to: *[email protected].*
(2) Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the responsible Flight Standards Office.
(3) Except as specified by paragraph (g) of this AD: For material that contains steps that are labeled as Required for Compliance (RC), the provisions of paragraphs (j)(3)(i) and (ii) of this AD apply.
(i) The steps labeled as RC, including substeps under an RC step and any figures identified in an RC step, must be done to comply with the AD. If a step or substep is labeled “RC Exempt,” then the RC requirement is removed from that step or substep. An AMOC is required for any deviations to RC steps, including substeps and identified figures.
(ii) Steps not labeled as RC may be deviated from using accepted methods in accordance with the operator's maintenance or inspection program without obtaining approval of an AMOC, provided the RC steps, including substeps and identified figures, can still be done as specified, and the airplane can be put back in an airworthy condition.
**(k) Related Information**
For more information about this AD, contact Sarah Illg, Aviation Safety Engineer, FAA, 3960 Paramount Boulevard, Lakewood, CA 90712; phone: 206-231-3517; email: *[email protected].*
**(l) Material Incorporated by Reference**
(1) The Director of the Federal Register approved the incorporation by reference of the material listed in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51.
(2) You must use this material as applicable to do the actions required by this AD, unless the AD specifies otherwise.
(i) Aviation Partners Boeing Service Bulletin AP757-57-012, Revision 1, dated October 17, 2024.
(ii) [Reserved]
(3) For Aviation Partners Boeing material identified in this AD, contact Aviation Partners Boeing, 2811 South 102nd St., Suite 200, Seattle, WA 98168; telephone 206-830-7699; email *[email protected];* website *aviationpartnersboeing.com* .
(4) You may view this material at the FAA, Airworthiness Products Section, Operational Safety Branch, 2200 South 216th St., Des Moines, WA. For information on the availability of this material at the FAA, call 206-231-3195.
(5) You may view this material at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, visit *www.archives.gov/federal-register/cfr/ibr-locations,* or email *[email protected].*
Issued on April 24, 2025.
Victor Wicklund,
Deputy Director, Integrated Certificate Management Division, Aircraft Certification Service.