Airworthiness Directives; Bombardier, Inc., Airplanes

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]</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> Notice of proposed rulemaking (NPRM). <SUM> <HD SOURCE="HED">SUMMARY:</HD> The FAA proposes to adopt 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 proposed AD was prompted by a determination that new or more restrictive airworthiness limitations are necessary. This proposed AD would require revising the existing maintenance or inspection program, as applicable, to incorporate new or more restrictive airworthiness limitations. The FAA is proposing this AD to address the unsafe condition on these products. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> The FAA must receive comments on this proposed AD by September 19, 2025. </EFFDATE> <HD SOURCE="HED">ADDRESSES:</HD> You may send comments, using the procedures found in 14 CFR 11.43 and 11.45, by any of the following methods: • <E T="03">Federal eRulemaking Portal:</E> Go to <E T="03">regulations.gov.</E> Follow the instructions for submitting comments. • <E T="03">Fax:</E> 202-493-2251. • <E T="03">Mail:</E> 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">Hand Delivery:</E> Deliver to Mail address above between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. <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 NPRM, the mandatory continuing airworthiness information (MCAI), any comments received, and other information. The street address for Docket Operations is listed above. <E T="03">Material Incorporated by Reference:</E> • For Bombardier material identified in this proposed 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. <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Joseph Catanzaro, 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">Comments Invited</HD> The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments using a method listed under the <E T="02">ADDRESSES</E> section. Include “Docket No. FAA-2025-1728; Project Identifier MCAI-2025-00076-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 the 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 <E T="03">regulations.gov,</E> including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM. <HD SOURCE="HD1">Confidential Business Information</HD> 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 Joseph Catanzaro, 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> Any commentary that the FAA receives that is not specifically designated as CBI will be placed in the public docket for this rulemaking. <HD SOURCE="HD1">Background</HD> Transport Canada, which is the aviation authority for Canada, has issued Transport Canada AD CF-2025-06, dated January 20, 2025 (Transport Canada AD CF-2025-06) (also referred to as the MCAI), to correct an unsafe condition for all Bombardier, Inc., Model CL-600-2A12 (601), and CL-600-2B16 (601-3A, 601-3R, and 604 Variants) airplanes. 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. The FAA is proposing this AD to address an accumulation of fuel in the muffler caused by a drainage block in the APU 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">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 No. 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">FAA's Determination</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 and material referenced above. The FAA is proposing this AD because the FAA evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop on other products of the same type design. <HD SOURCE="HD1">Proposed Requirements of This NPRM</HD> This proposed AD would require revising the existing maintenance or inspection program, as applicable, to incorporate new or more restrictive airworthiness limitations. This proposed AD would require revisions to certain operator maintenance documents to include new actions ( <E T="03">e.g.,</E> inspections). Compliance with these actions is required by 14 CFR 91.403(c). For airplanes that have been previously modified, altered, or repaired in the areas addressed by this proposed AD, the operator may not be able to accomplish the actions described in the revisions. In this situation, to comply with 14 CFR 91.403(c), the operator must request approval for an alternative method of compliance according to paragraph (i)(1) of this proposed AD. <HD SOURCE="HD1">Costs of Compliance</HD> The FAA estimates that this AD, if adop ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 20k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━