Airworthiness Directives; Bombardier, Inc., Airplanes

<RULE> DEPARTMENT OF TRANSPORTATION <SUBAGY>Federal Aviation Administration</SUBAGY> <CFR>14 CFR Part 39</CFR> <DEPDOC>[Docket No. FAA-2025-1728; Project Identifier MCAI-2025-00076-T; Amendment 39-23208; AD 2025-24-11]</DEPDOC> <RIN>RIN 2120-AA64</RIN> <SUBJECT>Airworthiness Directives; 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 all Bombardier, Inc., Model CL-600-2A12 (601) and CL-600-2B16 (601-3A, 601-3R, and 604 Variants) airplanes. This AD was prompted by a determination that new or more restrictive airworthiness limitations are necessary. This AD requires revising the existing maintenance or inspection program, as applicable, to incorporate new or more restrictive airworthiness limitations. 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 January 16, 2026. The Director of the Federal Register approved the incorporation by reference of certain publications listed in this AD as of January 16, 2026. </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-2025-1728; 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 Bombardier material identified in this AD, contact Bombardier Business Aircraft Customer Response Center, 400 Côte-Vertu Road West, Dorval, Québec H4S 1Y9, Canada; telephone 514-855-2999; email <E T="03">ac.yul@aero.bombardier.com;</E> website <E T="03">bombardier.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-2025-1728. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Joseph Catanzaro, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; phone: 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 a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to all Bombardier, Inc., Model CL-600-2A12 (601) and CL-600-2B16 (601-3A, 601-3R, and 604 Variants) airplanes. The NPRM was published in the <E T="04">Federal Register</E> on August 5, 2025 (90 FR 37434). The NPRM was prompted by AD CF-2025-06, dated January 20, 2025 (Transport Canada AD CF-2025-06) (also referred to as the MCAI), issued by Transport Canada, which is the aviation authority for Canada. The MCAI states that new or more restrictive airworthiness limitations have been developed. The flightcrew of a Challenger airplane started the auxiliary power unit (APU) during the approach and allowed it to run for approximately 10 minutes after landing. When the flightcrew shut the APU down, an APU FIRE warning message was posted on the engine indicating and crew alerting system (EICAS). The APU fire suppression was discharged; however, the fire was not fully extinguished following the discharge of the fire bottles. Upon further investigation, it was discovered that a fuel solenoid valve was leaking, and the APU muffler drainage was blocked leading to an accumulation of fuel in the muffler. The fuel in the APU muffler was ignited by the high-temperature exhaust gases in the muffler. In the NPRM, the FAA proposed to require revising the existing maintenance or inspection program, as applicable, to incorporate new or more restrictive airworthiness limitations. The FAA is issuing this AD to address an accumulation of fuel in the APU muffler caused by a drainage block in the muffler. This condition, if not corrected, could lead to an accumulation of fuel in the muffler being ignited by the high-temperature exhaust gases in the muffler, and could subsequently lead to an uncontrolled fire in the APU bay. You may examine the MCAI in the AD docket at <E T="03">regulations.gov</E> under Docket No. FAA-2025-1728. <HD SOURCE="HD1">Discussion of Final Airworthiness Directive</HD> <HD SOURCE="HD1">Comments</HD> The FAA received a comment from Bombardier. The following presents the comment received on the NPRM and the FAA's response to the comment. <HD SOURCE="HD1">Request To Clarify Source of Fuel Leakage</HD> Bombardier noted the Background section of the proposed AD states that upon further investigation, it was discovered that a fuel solenoid valve was leaking. Bombardier stated it was suspected that there was an internal fuel leakage from the fuel solenoid valve, not that the valve was found leaking. The FAA acknowledges Bombardier's request. The FAA notes that the information in the Background section of the proposed AD restates the information provided in the MCAI, so no change to the AD is necessary in this regard. <HD SOURCE="HD1">Conclusion</HD> These products have been approved by the civil aviation authority of another country and are approved for operation in the United States. Pursuant to the FAA's bilateral agreement with this State of Design Authority, that authority has notified the FAA of the unsafe condition described in the MCAI referenced above. The FAA reviewed the relevant data, considered any comments received, and determined that air safety requires adopting this AD as proposed. Accordingly, the FAA is issuing this AD to address the unsafe condition on these products. Except for minor editorial changes, this AD is adopted as proposed in the NPRM. None of the changes will increase the economic burden on any operator. <HD SOURCE="HD1">Material Incorporated by Reference Under 1 CFR Part 51</HD> The FAA reviewed the following Bombardier material: • Temporary Revision No. 5-2-6, dated June 28, 2024, which includes new Task 49-15-01-101*, “Functional Test of the Auxiliary Power Unit (APU) Muffler Drain.” • Temporary Revision No. 5-2-30, dated June 28, 2024, which includes new Task 49-15-01-101*, “Functional Test of the Auxiliary Power Unit (APU) Muffler Drain.” • Temporary Revision No. 5-2-74, dated June 28, 2024, which includes new Task 49-15-01-101*, “Functional Test of the Auxiliary Power Unit (APU) Muffler Drain (A/C 5301 to 5630, Post SB 604-49-006, and A/C 5631 and Subs).” • Temporary Revision No. TR 5-271, dated September 30, 2024, which includes, among other tasks, new Task 49-15-01-101*, “Functional Test of the APU Muffler Drain.” • Temporary Revision No. TR 5-285, dated September 30, 2024, which includes, among other tasks, new Task 49-15-01-101*, “Functional Test of the APU Muffler Drain.” (The asterisk (or “one star”) with the last three digits of the task numbers listed above indicates that the task is an airworthiness limitation task.) Temporary Revision Nos. 5-2-6, 5-2-30, 5-2-74, TR 5-271, and TR 5-285 introduce, among other tasks, functional tests of the APU muffler drain. These documents are distinct since they apply to different airplane configurations. 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 <E T="02">ADDRESSES</E> section. <HD SOURCE="HD1">Costs of Compliance</HD> The FAA estimates that this AD affects 550 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD: The FAA has determined that revising the maintenance or inspection program takes an average of 90 work-hours per operator, although the agency 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. Therefore, the agency estimates the average total cost per operator to be $7,650 (90 work-hours × $85 per work-hour). <HD SOURCE="HD1">Authority for This Rulemaking</HD> 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. <HD SOURCE="HD1">Regulatory Findings</HD> This AD will not have federalism implications under Executive Order 13132. This AD will 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 that this ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 17k characters. 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