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 Department of Transportation Federal Aviation Administration 14 CFR Part 39
[Docket No. FAA-2024-0028; Project Identifier AD-2023-00919-T]
RIN 2120-AA64
 AGENCY: Federal Aviation Administration (FAA), DOT.
 ACTION: Notice of proposed rulemaking (NPRM).
 SUMMARY: The FAA proposes to supersede Airworthiness Directive (AD) 2021-09-06, which applies to all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. AD 2021-09-06 requires repetitive inspections for cracking of the left- and right-hand side outboard chords of certain frame fittings and failsafe straps at a certain station around eight fasteners, and repair if any cracking is found. Since the FAA issued AD 2021-09-06, additional reports of cracking in the area were received and it was determined that additional inspections are needed to address the unsafe condition. This proposed AD would require repetitive detailed and ultrasonic inspections for cracking of the left-and right-hand sides of certain frame fittings and failsafe straps, and repair if any cracking is found. 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 March 1, 2024.
 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-2024-0028; 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 service information identified in this NPRM, contact Boeing Commercial Airplanes, Attention: Contractual & Data Services (C&DS), 2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600; telephone 562-797-1717; website*myboeingfleet.com*.
                    You may view this service information 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. It is also available at*regulations.gov*
                         by searching for and locating Docket No. FAA-2024-0028.
 FOR FURTHER INFORMATION CONTACT: Owen Bley-Male, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; telephone 206-231-3992; email 
                        *owen.f.bley-male@faa.gov.*


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 
                    **ADDRESSES**
                    . Include “Docket No. FAA-2024-0028; Project Identifier AD-2023-00919-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 Owen Bley-Male, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; telephone 206-231-3992; email 
                    *owen.f.bley-male@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 2021-09-06, Amendment 39-21519 (86 FR 23595, May 4, 2021) (AD 2021-09-06), for all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes. AD 2021-09-06 was prompted by reports of cracking discovered in the station (STA) 663.75 frame fitting outboard chords and failsafe straps adjacent to the stringer S-18A straps and a determination that the initial inspection threshold and repetitive inspection interval required by AD 2019-22-10, Amendment 39-19789 (84 FR 61533, November 13, 2019), were inadequate to address cracking in a timely manner. AD 2021-09-06 requires repetitive inspections for cracking of the left- and right-hand side outboard chords of frame fittings and failsafe straps at a certain station around eight fasteners, repair if any cracking is 
                    ( print page 2516)
                    found, and an inspection report. The agency issued AD 2021-09-06 to address cracking in the STA 663.75 frame fitting outboard chords and failsafe straps adjacent to the stringer S-18A straps, which could result in failure of a principal structural element (PSE) to sustain limit load. This condition could adversely affect the structural integrity of the airplane and result in loss of control of the airplane. Actions Since AD 2021-09-06 Was Issued Since the FAA issued AD 2021-09-06, additional reports have been made of several cracks in the STA 663.75 frame fittings and failsafe straps. Cracks have also been found at the aft fastener common to the failsafe strap upper row. Several cracks in the frame fitting were found extending beyond the aft fastener hole to the forward fastener hole. An additional report was made of a visible crack in the failsafe strap without any visibly detectable crack in the frame fitting. These additional reports led to a determination that the detailed visual inspection required by AD 2021-09-06 might not be adequate to detect STA 663.75 failsafe strap cracking. Additionally, the preamble to AD 2021-09-06 explained that the FAA considered the requirements “interim action” and was considering further rulemaking. The FAA has now determined that further rulemaking is indeed necessary and this proposed AD follows from that determination. 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. Related Service Information Under 1 CFR Part 51 The FAA reviewed Boeing Alert Requirements Bulletin 737-53A1414 RB, Revision 1, dated November 20, 2023. This service information specifies procedures for repetitive internal detailed inspection for cracking of the frame fitting and visible areas of the failsafe strap at STA 663.73 (left- and right-hand sides), repetitive external detailed and ultrasonic inspections for cracking of the failsafe strap at STA 663.75 (left- and right-hand sides), and repair if any cracking is found. This service information is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in 
                    **ADDRESSES**
                    . Proposed AD Requirements in This NPRM Although this proposed AD does not explicitly restate the requirements of AD 2021-09-06, this proposed AD would retain the inspection requirements of AD 2021-09-06. Those requirements are referenced in the service information identified previously, which, in turn, is referenced in paragraph (g) of this proposed AD. This proposed AD would require accomplishing the actions specified in the service information already described except for any differences identified as exceptions in the regulatory text of this proposed AD. For information on the procedures and compliance times, see this service information at regulations.gov under Docket No. FAA-2024-0028. Costs of Compliance The FAA estimates that this AD, if adopted as proposed, would affect 1,911 airplanes of U.S. registry. The FAA estimates the following costs to comply with this proposed AD: Estimated Costs
Action
Labor cost
Parts cost
Cost per product
Cost on U.S. operatorsInspection
4 work-hours × $85 per hour = $340 per inspection cycle
$0
$340 per inspection cycle
$649,740 per inspection cycle.
 The FAA has received no definitive data on which to base the cost estimates for the on-condition repairs specified in this proposed AD. The FAA has included all known costs in its cost estimate. According to the manufacturer, however, some or all of the costs of this proposed AD may be covered under warranty, thereby reducing the cost impact on affected operators. 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: ( print page 2517) a.Removing Airworthiness Directive (AD) 2021-09-06, Amendment 39-21519 ( 86 FR 23595, May 4, 2021), and b.Adding the following new AD: **The Boeing Company:**
                         Docket No. FAA-2024-0028; Project Identifier AD-2023-00919-T. (a) Comments Due Date The FAA must receive comments on this airworthiness directive (AD) by March 1, 2024. (b) Affected ADs This AD replaces AD 2021-09-06, Amendment 39-21519 (86 FR 23595, May 4, 2021) (AD 2021-09-06). (c) Applicability This AD applies to all The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes, certificated in any category. (d) Subject Air Transport Association (ATA) of America Code 53, Fuselage. (e) Unsafe Condition This AD was prompted by reports of cracking in the station (STA) 663.75 frame fitting outboard chords and failsafe straps adjacent to the stringer S-18A area and a determination that additional inspections are needed to address the unsafe condition. The FAA is issuing this AD to address cracking in the STA 663.75 frame fitting outboard chords and failsafe straps adjacent to the stringer S-18A straps, which could result in failure of a Principal Structural Element (PSE) to sustain limit load. The unsafe condition, if not addressed, could adversely affect the structural integrity of the airplane and result in loss of control of the airplane. (f) Compliance Comply with this AD within the compliance times specified, unless already done. (g) Required Actions Except as specified by paragraph (h) of this AD: At the applicable times specified in the “Compliance” paragraph of Boeing Alert Requirements Bulletin 737-53A1414 RB, Revision 1, dated November 20, 2023, do all applicable actions identified in, and in accordance with, the Accomplishment Instructions of Boeing Alert Requirements Bulletin 737-53A1414 RB, Revision 1, dated November 20, 2023. **Note 1 to paragraph (g):**
                         Guidance for accomplishing the actions required by this AD can be found in Boeing Alert Service Bulletin 737-53A1414, Revision 1, dated November 20, 2023, which is referred to in Boeing Alert Requirements Bulletin 737-53A1414 RB, Revision 1, dated November 20, 2023. (h) Exceptions to Service Information Specifications (1) Where the Condition and Compliance Time columns of the tables in the “Compliance” paragraph of Boeing Alert Requirements Bulletin 737-53A1414 RB, Revision 1, dated November 20, 2023, use the phrase “the original issue date of Requirements Bulletin 737-53A1414 RB,” or “the Revision 1 date of Requirements Bulletin 737-53A1414 RB,” this AD requires using “the effective date of this AD.” (2) Where Boeing Alert Requirements Bulletin 737-53A1414 RB, Revision 1, dated November 20, 2023, specifies contacting Boeing for repair instructions: This AD requires doing the repair using a method approved in accordance with the procedures specified in paragraph (i) of this AD. (i) 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 (j)(1) of this AD. Information may be emailed to: 
                        *9-ANM-Seattle-ACO-AMOC-Requests@faa.gov.* (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) An AMOC that provides an acceptable level of safety may be used for any repair, modification, or alteration required by this AD if it is approved by The Boeing Company Organization Designation Authorization (ODA) that has been authorized by the Manager, AIR-520, Continued Operational Safety Branch, FAA, to make those findings. To be approved, the repair method, modification deviation, or alteration deviation must meet the certification basis of the airplane, and the approval must specifically refer to this AD. (j) Related Information (1) For more information about this AD, contact Owen Bley-Male, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; telephone 206-231-3992; email 
                        *owen.f.bley-male@faa.gov.* (2) Service information identified in this AD that is not incorporated by reference is available at the addresses specified in paragraphs (k)(3) and (4) of this AD. (k) Material Incorporated by Reference (1) The Director of the Federal Register approved the incorporation by reference (IBR) of the service information listed in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51. (2) You must use this service information as applicable to do the actions required by this AD, unless this AD specifies otherwise. (i) Boeing Alert Requirements Bulletin 737-53A1414 RB, Revision 1, dated November 20, 2023. (ii) [Reserved] (3) For service information identified in this AD, contact Boeing Commercial Airplanes, Attention: Contractual & Data Services (C&DS), 2600 Westminster Blvd., MC 110-SK57, Seal Beach, CA 90740-5600; telephone 562-797-1717; website 
                        *myboeingfleet.com.* (4) You may view this service information 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 
                        *fr.inspection@nara.gov*. Issued on January 5, 2024. Victor Wicklund, Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service.


[FR Doc. 2024-00345 Filed 1-12-24; 8:45 am] BILLING CODE 4910-13-P