Background The FAA 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-600-2D15 (Regional Jet Series 705) and CL-600-2D24 (Regional Jet Series 900) airplanes. The NPRM published in the Federal Register on April 23, 2024 (89 FR 30286). The NPRM was prompted by AD CF-2023-76, dated November 28, 2023, issued by Transport Canada, which is the aviation authority for Canada (Transport Canada AD CF-2023-76) (also referred to as the MCAI). The MCAI states MHI RJ Aviation received a supplier quality escape notice, reporting that torque wrenches used to install the ADG downlock cam nut were out of calibration, which resulted in a higher torque level setting than required during the initial production installation of the affected cam nut. This over-torque condition could cause the screw and cam to fail, which, if not corrected, could result in the loss of the ADG downlock mechanism functionality upon airplane touchdown which eliminates a critical power source for the aircraft, leaving the flightcrew with minimum flightdeck displays and difficulty controlling the aircraft. In the NPRM, the FAA proposed to require replacement of the affected ADG locking cam screw and cam nut, as specified in Transport Canada AD CF-2023-76. The FAA is issuing this AD to address this over-torque condition that could cause the screw and cam to fail. The unsafe condition, if not addressed, could result in the loss of the ADG downlock mechanism functionality upon airplane touchdown which eliminates a critical power source for the aircraft, leaving the flightcrew with minimum flightdeck displays and difficulty controlling the aircraft. You may examine the MCAI in the AD docket at regulations.gov under Docket No. FAA-2024-1006. Discussion of Final Airworthiness Directive Comments The FAA received comments from Air Line Pilots Association, International (ALPA) who supported the NPRM without change. Conclusion This product has been approved by the aviation authority of another country and is approved for operation in the United States. Pursuant to the FAA's bilateral agreement with this State of Design Authority, it has notified the FAA of the unsafe condition described in the MCAI referenced above. The FAA reviewed the relevant data, considered the comment 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 this product. 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. Related Material Under 1 CFR Part 51 Transport Canada AD CF-2023-76 specifies procedures for replacing the affected ADG locking cam screw and cam nut. 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 ADDRESSES section. Costs of Compliance The FAA estimates that this AD affects 24 airplanes of U.S. registry. The FAA estimates the following costs to comply with this AD: Estimated Costs for Required Actions Labor cost Parts cost Cost per product Cost on U.S. operators Up to 2 work-hours × $85 per hour = $170 $285 Up to $455 Up to $10,920. 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 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 AD: (1) Is not a "significant regulatory action" under Executive Order 12866, (2) Will not affect intrastate aviation in Alaska, and (3) Will 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 Amendment Accordingly, under the authority delegated to me by the Administrator, the FAA amends 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 [Amended] 2. The FAA amends § 39.13 by adding the following new airworthiness directive: 2024-13-07 MHI RJ Aviation ULC (Type Certificate Previously Held by Bombardier, Inc.): Amendment 39-22781; Docket No. FAA-2024-1006; Project Identifier MCAI-2023-01222-T. (a) Effective Date This airworthiness directive (AD) is effective September 25, 2024. (b) Affected ADs None. (c) Applicability This AD applies to MHI RJ Aviation ULC (Type Certificate previously held by Bombardier, Inc.) Model CL-600-2D15 (Regional Jet Series 705) and Model CL-600-2D24 (Regional Jet Series 900) airplanes, certificated in any category, as identified in Transport Canada AD CF-2023-76, dated November 28, 2023 (Transport Canada AD CF-2023-76). (d) Subject Air Transport Association (ATA) of America Code 24, Electrical power. (e) Unsafe Condition This AD was prompted by a notice from a supplier reporting that torque wrenches used to install the air driven generator (ADG) downlock cam nut were out of calibration, which resulted in a higher torque level setting than required during the initial production installation of the affected cam nut. The FAA is issuing this AD to address this over-torque condition that could cause the screw and cam to fail. The unsafe condition, if not addressed, could result in the loss of the ADG downlock mechanism functionality on aircraft touchdown which eliminates a critical power source for the aircraft, leaving the flightcrew with the minimum flightdeck displays and difficulty controlling the aircraft. (f) Compliance Comply with this AD within the compliance times specified, unless already done. (g) Requirements Except as specified in paragraph (h) of this AD: Comply with all required actions and compliance times specified in, and in accordance with, Transport Canada AD CF-2023-76. (h) Exceptions to Transport Canada AD CF-2023-76 (1) Where Transport Canada AD CF-2023-76 refers to its effective date, this AD requires using the effective date of this AD. (2) Where Transport Canada AD CF-2023-76 refers to hours air time, this AD requires using flight hours. (i) Additional AD Provisions The following provisions also apply to this AD: (1) Alternative Methods of Compliance (AMOCs): The Manager, International Validation 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 International Validation Branch, mail it to the address identified in paragraph (j) of this AD. Information may be emailed to: 9-AVS-NYACO-COS@faa.gov. Before using any approved AMOC, notify your appropriate principal inspector, or lacking a principal inspector, the manager of the responsible Flight Standards Office. (2) Contacting the Manufacturer: For any requirement in this AD to obtain instructions from a manufacturer, the instructions must be accomplished using a method approved by the Manager, International Validation Branch, FAA; Transport Canada; or MHI RJ Aviation ULC's Transport Canada Design Approval Organization (DAO). If approved by the DAO, the approval must include the DAO-authorized signature. (j) Additional Information For more information about this AD, contact Fatin Saumik, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7300; email Fatin.R.Saumik@faa.gov. (k) Material Incorporated by Reference (1) The Director of the Federal Register approved the incorporation by reference (IBR) of the material listed in this paragraph under 5 U.S.C. 552(a) and 1 CFR part 51. (2) You must use this material as applicable to do the actions required by this AD, unless this AD specifies otherwise. (i) Transport Canada AD CF-2023-76, dated November 28, 2023. (ii) [Reserved] (3) For Transport Canada AD CF-2023-76, contact Transport Canada, Transport Canada National Aircraft Certification, 159 Cleopatra Drive, Nepean, Ontario K1A 0N5, Canada; telephone 888-663-3639; email TC.AirworthinessDirectives-Consignesdenavigabilite.TC@tc.gc.ca. You may find this Transport Canada AD on the Transport Canada website at tc.canada.ca/en/aviation. (4) 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. (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 July 1, 2024. Caitlin Locke, Director, Compliance & Airworthiness Division, Aircraft Certification Service.