Airworthiness Directives; MHI RJ Aviation ULC (Type Certificate Previously Held by Bombardier Inc.) Airplanes

<RULE> DEPARTMENT OF TRANSPORTATION <SUBAGY>Federal Aviation Administration</SUBAGY> <CFR>14 CFR Part 39</CFR> <DEPDOC>[Docket No. FAA-2024-1896; Project Identifier MCAI-2023-00978-T; Amendment 39-22966; AD 2025-04-08]</DEPDOC> <RIN>RIN 2120-AA64</RIN> <SUBJECT>Airworthiness Directives; MHI RJ Aviation ULC (Type Certificate Previously Held by Bombardier Inc.) Airplanes</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Federal Aviation Administration (FAA), DOT. <HD SOURCE="HED">ACTION:</HD> Final rule. <SUM> <HD SOURCE="HED">SUMMARY:</HD> The FAA is adopting a new airworthiness directive (AD) for certain MHI RJ Aviation ULC Model CL-600-2B19 (Regional Jet Series 100 and 440), CL-600-2C10 (Regional Jet Series 700, 701, and 702), CL-600-2C11 (Regional Jet Series 550), CL-600-2D15 (Regional Jet Series 705), CL-600-2D24 (Regional Jet Series 900), and CL-600-2E25 (Regional Jet Series 1000) airplanes. This AD was prompted by the determination that radio altimeters cannot be relied upon to perform their intended function if they experience interference from wireless broadband operations in the 3.7-3.98 GHz frequency band (5G C-Band). This AD requires installing a new radio frequency (RF) bandpass filter on the coaxial line between the radio altimeter and the receive antenna in the aft equipment compartment. The FAA is issuing this AD to address the unsafe condition on these products. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> This AD is effective April 25, 2025. The Director of the Federal Register approved the incorporation by reference of certain publications listed in this AD as of April 25, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> <E T="03">AD Docket:</E> You may examine the AD docket at <E T="03">regulations.gov</E> under Docket No. FAA-2024-1896; 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 final rule, the mandatory continuing airworthiness information (MCAI), any comments received, and other information. The address for Docket Operations is U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue SE, Washington, DC 20590. <E T="03">Material Incorporated by Reference:</E> • For MHI RJ material identified in this AD, contact MHI RJ Aviation Group, Customer Response Center, 3655 Ave. des Grandes-Tourelles, Suite 110, Boisbriand, Québec J7H 0E2 Canada; North America toll-free telephone 833-990-7272 or direct-dial telephone 450-990-7272; fax 514-855-8501; email <E T="03">thd.crj@mhirj.com;</E> website <E T="03">mhirj.com.</E> • 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. It is also available at <E T="03">regulations.gov</E> under Docket No. FAA-2024-1896. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Steven Dzierzynski, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7300; email <E T="03">9-avs-nyaco-cos@faa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">Background</HD> The FAA issued AD 2023-10-02, Amendment 39-22438 (88 FR 34065, May 26, 2023) (AD 2023-10-02) to address the effect of interference from wireless broadband operations in the 5G C-Band on all transport and commuter category airplanes equipped with a radio altimeter. AD 2023-10-02 was prompted by a determination that radio altimeters cannot be relied upon to perform their intended function if they experience interference from wireless broadband operations in the 5G C-Band. AD 2023-10-02 requires revising the limitations section of the existing airplane flight manual to incorporate limitations prohibiting transport and commuter category airplanes from performing certain low-visibility landing operations at any airport unless they have upgraded their radio altimeters. Transport Canada, which is the aviation authority for Canada, issued corresponding Transport Canada AD CF-2023-46, dated June 30, 2023, to require similar limitations on flight operations requiring radio altimeter data in U.S. airspace affected by 5G C-Band wireless signals. The FAA subsequently issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain MHI RJ Aviation ULC Model CL-600-2B19 (Regional Jet Series 100 and 440), CL-600-2C10 (Regional Jet Series 700, 701, and 702), CL-600-2C11 (Regional Jet Series 550), CL-600-2D15 (Regional Jet Series 705), CL-600-2D24 (Regional Jet Series 900), and CL-600-2E25 (Regional Jet Series 1000) airplanes. The NPRM published in the <E T="04">Federal Register</E> on September 9, 2024 (89 FR 73009). The NPRM was prompted by AD CF-2023-62R1, dated November 21, 2023, issued by Transport Canada, which is the aviation authority for Canada (referred to after this as the MCAI). The MCAI states that, in addition to the effects of 5G C-Band broadband interference identified in FAA AD 2023-10-02, MHI RJ has determined that 5G C-Band broadband interference can result in certain failure messages and aural alerts being inhibited longer than intended. Specifically, this can result in the inhibition of hydraulic system #3 and wing anti-ice overheat failure messages such that flightcrew are unable to perform appropriate airplane flight manual (AFM) procedures in the time needed to prevent loss of elevator control due to hydraulic system overheat and wing structural damage due to wing anti-ice system overheat. This condition, if not corrected, could result in delayed flightcrew response leading to loss of continued safe flight and landing. In the NPRM, the FAA proposed to require installing a new RF bandpass filter on the coaxial line between the radio altimeter and the receive antenna in the aft equipment compartment. When the airplane is modified as specified in this AD, the configuration with the RF bandpass filter installed has been determined to be “radio altimeter tolerant.” The FAA is issuing this AD because radio altimeter anomalies can result in the inhibition of certain failure messages such that the flightcrew are unable to perform appropriate airplane flight manual procedures in the time needed to prevent potential ignition hazard due to overheated hydraulic fluid circulating in the fuel tanks area, which may lead to loss of continued safe flight and landing, and/or structural deformation of the wing leading edge which may reduce the safety margin (to stall). You may examine the MCAI in the AD docket at <E T="03">regulations.gov</E> under Docket No. FAA-2024-1896. <HD SOURCE="HD1">Discussion of Final Airworthiness Directive</HD> <HD SOURCE="HD1">Comments</HD> The FAA received comments from Mesa Airlines, MHI RJ Aviation (MHI RJ), and an individual commenter. The following presents the comments received on the NPRM and the FAA's response to each comment. <HD SOURCE="HD1">Request To Refer To Revised Service Information</HD> MHI RJ and an individual commenter requested that the proposed AD be revised to refer to revised service bulletins. The individual commenter noted that MHI RJ Service Bulletin 670BA-34-054 is currently at Revision E. MHI RJ stated that the original issue and Revisions A, B, C, D, and E of MHI RJ Service Bulletin 670BA-34-054; and Revisions D and E of MHI RJ Service Bulletin 601R-34-152 should be listed as methods of compliance for the actions required by the proposed AD. MHI RJ also requested that all acceptable revisions of the referenced service information be added to paragraph (n) of the proposed AD. The FAA agrees to refer to the latest revisions of the service information. MHI RJ Service Bulletin 601R-34-152, Revision E, dated June 29, 2023, includes minor editorial changes (adding reference to an FAA AD and additional reference documents; and revising recommended compliance times, though the FAA notes that the compliance times in this AD take precedence over those in the service information). Those changes do not have an effect on the technical content and no additional work is necessary for operators that incorporated MHI RJ Service Bulletin 601R-34-152, Revision D, dated May 11, 2023. MHI RJ Service Bulletin 670BA-34-054, dated February 20, 2023; Revision A, dated February 28, 2023; Revision B, dated March 28, 2023; Revision C, dated June 29, 2023; Revision D, dated August 31, 2023; and Revision E, dated January 11, 2024; contain minor editorial revisions that do not have an effect on the technical content or require additional work for operators that incorporated earlier revisions. Therefore, the FAA has revised this AD to refer to MHI RJ Service Bulletin 670BA-34-054, Revision E, dated January 11, 2024; and MHI RJ Service Bulletin 601R-34-152, Revision E, dated June 29, 2023. Regarding the request to cite all acceptable revisions of the service information in paragraph (n) of this AD, the FAA notes that paragraph (n) of this AD identifies only material that is to be incorporated by reference in the AD, and this AD requires and incorporates by reference only Revision E of the service bulletins, as specified in paragraphs (h), (i), and (j) of this AD. <HD SOURCE="HD1">Requests To Revise Credit for Previous Actions</HD> An individual commenter requested that the FAA revise paragraph (k) of the proposed AD to include credit for actions performed using the original issue or Revisions A, B, C, or D of MHI RJ Service Bulletin 670BA-34-054. MHI RJ requested revising the conditional credit specified in the introductory text of paragraph (k) of the proposed AD to specify an additional document. MHI RJ noted that credit is conditional on operators installing the electrical idents for coax cables using Part G ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 32k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━