2025-04-03: Exhaust

1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. 2. The FAA amends § 39.13 by adding the following new airworthiness directive: 2025-04-03 The Boeing Company: Amendment 39-22961; Docket No. FAA-2023-2235; Project Identifier AD-2023-01009-T. (a) Effective Date This airworthiness directive (AD) is effective April 8, 2025. (b) Affected ADs None. (c) Applicability This AD applies to The Boeing Company Model 737-600, -700, -700C, -800, -900, and -900ER series airplanes identified in Boeing Special Attention Requirements Bulletin 737-78-1106 RB, Revision 1, dated May 23, 2024. (d) Subject Air Transport Association (ATA) of America Code 78, Exhaust. (e) Unsafe Condition This AD was prompted by two engine fan blade-out (FBO) events that resulted in the separation of engine inlet cowl and fan cowl parts from the airplane damaging the fuselage, which caused loss of pressurization and subsequent emergency descent. The FBO events also resulted in cracks in the primary exhaust nozzle, which could result in the departure of the primary exhaust nozzle. The FAA is issuing this AD to address primary exhaust nozzles that are not strengthened, which during an FBO event, could depart the engine, potentially damaging a stabilizer or striking the fuselage and window. The unsafe condition, if not addressed, could result in loss of control of the airplane, or in a rapid decompression and hazard to window-seated passengers aft of the wing. (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 Special Attention Requirements Bulletin 737-78-1106 RB, Revision 1, dated May 23, 2024, do all applicable actions identified in, and in accordance with, the Accomplishment Instructions of Boeing Special Attention Requirements Bulletin 737-78-1106 RB, Revision 1, dated May 23, 2024. Note 1 to paragraph (g): Guidance for accomplishing the actions required by this AD can be found in Boeing Special Attention Service Bulletin 737-78-1106, Revision 1, dated May 23, 2024, which is referred to in Boeing Special Attention Requirements Bulletin 737-78-1106 RB, Revision 1, dated May 23, 2024. (h) Exceptions to Requirements Bulletin Specifications (1) Where the Compliance Time columns of the tables in the "Compliance" paragraph of Boeing Special Attention Requirements Bulletin 737-78-1106 RB, Revision 1, dated May 23, 2024, refer to the original issue date of Requirements Bulletin 737-78-1106 RB, this AD requires using the effective date of this AD. (2) Where System Airworthiness Limitation No. 4, as identified in Boeing Special Attention Requirements Bulletin 737-78-1106 RB, Revision 1, dated May 23, 2024, requires incorporation of solutions to address potential engine nacelle maintenance errors, solutions consist of a re-designed fan cowl latch and keeper and application of high visibility paint on the interior of the integrated drive generator (IDG) door. (i) No Alternative Actions After the existing maintenance or inspection program has been revised as required by paragraph (g) of this AD, no alternative actions may be used unless the actions are approved as an alternative method of compliance (AMOC) in accordance with the procedures specified in paragraph (k) of this AD. (j) Credit for Previous Actions This paragraph provides credit for the actions specified in paragraph (g) of this AD, if those actions were performed before the effective date of this AD using Boeing Special Attention Requirements Bulletin 737-78-1106 RB, dated September 1, 2023, provided where Tables 1 and 2 of Boeing Special Attention Requirements Bulletin 737-78-1106 RB specify incorporating 737-600/700/700C/800/900/900ER Airworthiness Limitations (AWLs) Document D626A001-9-01 "System Airworthiness Limitation NO. 2-Fan Blade Out Conditions," and "System Airworthiness Limitation NO. 3-Fan Blade Out Conditions" into the operators' maintenance program, the information specified in figure 1 to paragraph (j) of this AD has been incorporated into the airworthiness limitations. Figure 1 to Paragraph (j)-System Airworthiness Limitations SYSTEM AIRWORTHINESS LIMITATION No. 2 FAN BLADE OUT CONDITIONS All aircraft must install the following modifications: (1) engines inlets with new spacer design and increased fastener capability (2) fan cowls with new radial restraint fitting hooks, new radial restraint clips, and an external doubler at the starter vent (3) fan cowl support beam fastener changes (except for 737-900ER aircraft, because the fan cowl support beam fastener changes are already incorporated). All aircraft that have not incorporated these modifications cannot operate past July 31, 2028 unless upgraded to new hardware that is fully compliant to §§ 25.901(c) and Appendix K25.1.1 to Part 25. Boeing will release all service data to allow retrofit of hardware updates to the CFM56-7B nacelle prior to that date. SYSTEM AIRWORTHINESS LIMITATION No. 3 FAN BLADE OUT CONDITIONS All aircraft delivered without the Performance Improvement Package (PIP) must install engine exhaust nozzle structural stiffening elements. All aircraft that have not incorporated these modifications cannot operate past July 31, 2028 unless upgraded to new hardware that is fully compliant to §§ 25.901(c) and Appendix K25.1.1 to Part 25. Boeing will release all service data to allow retrofit of hardware updates to CFM56-7B nacelle prior to that date. SYSTEM AIRWORTHINESS LIMITATION No. 4 ENGINE NACELLE MAINTENANCE ERRORS All aircraft must incorporate solutions to address potential maintenance errors, e.g., the failure to completely latch the fan cowl or the can cowl integrated drive generator (IDG) door. All aircraft that have not incorporated changes to become fully compliance with §§ 25.901(c) and Appendix K25.1.1 to Part 25 cannot be operated past December 31, 2029. (k) 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 (l)(1) 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) 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. (l) Related Information (1) For more information about this AD, contact Luis Cortez-Muniz, Aviation Safety Engineer, FAA, 2200 South 216th St., Des Moines, WA 98198; telephone: 206-231-3958; email: [email protected] . (2) Boeing material identified in this AD that is not incorporated by reference is available at the address specified in paragraph (m)(3) this AD. (m) 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 the AD specifies otherwise. (i) Boeing Special Attention Requirements Bulletin 737-78-1106 RB, Revision 1, dated May 23, 2024. (ii) [Reserved] (3) For Boeing material 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 [email protected] . Issued on February 25, 2025. Suzanne Masterson, Deputy Director, Integrated Certificate Management Division, Aircraft Certification Service. [FR Doc. 2025-03396 Filed 3-3-25; 8:45 am]BILLING CODE 4910-13-P