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 Department of Transportation Federal Aviation Administration 14 CFR Part 39
[Docket No. FAA-2024-0227; Project Identifier MCAI-2023-00886-T; Amendment 39-22838; AD 2024-18-04]
RIN 2120-AA64
 AGENCY: Federal Aviation Administration (FAA), DOT.
 ACTION: Final rule.
 SUMMARY: The FAA is adopting a new airworthiness directive (AD) for certain Bombardier, Inc., Model BD-700-2A12 airplanes. This AD was prompted by a report indicating that the fan in a transformer rectifier unit (TRU) can become inoperative in a manner that is not detectable by the fan monitoring circuit. This AD requires replacement of the existing TRU Number 2 with a new part number that incorporates a correction to the fan and the monitoring circuit. This AD also prohibits the installation of affected parts. The FAA is issuing this AD to address the unsafe condition on these products.
 DATES: This AD is effective November 12, 2024. The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of November 12, 2024.
 ADDRESSES:  *AD Docket:*
                         You may examine the AD docket at regulations.gov under Docket No. FAA-2024-0227; 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. *Material Incorporated by Reference:* 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*ac.yul@aero.bombardier.com;*
                         website 
                        *bombardier.com.*
                    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*regulations.gov*
                         under Docket No. FAA-2024-0227.
 FOR FURTHER INFORMATION CONTACT: William Reisenauer, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7300; email 
                        *9-avs-nyaco-cos@faa.gov.*


SUPPLEMENTARY INFORMATION: 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 Bombardier, Inc., Model BD-700-2A12 airplanes. The NPRM published in the 
                    **Federal Register**
                     on February 14, 2024 (89 FR 11228). The 
                    ( print page 81334)
                    NPRM was prompted by AD CF-2023-53, dated July 14, 2023, issued by Transport Canada, which is the aviation authority for Canada (referred to after this as the MCAI). The MCAI states that the fan in a TRU can become inoperative in a manner that is not detectable by the fan monitoring circuit. An inoperative fan leads to higher TRU operating temperatures, which can trigger the activation of the load shed function to reduce the electrical load and temperature in the TRU. If the TRU temperature continues to rise and exceeds the maximum temperature threshold, the TRU will automatically disconnect. The shed electrical load will be transferred to the remaining two TRUs, which could lead to overheating and cascading failures on the remaining TRUs. In the NPRM, the FAA proposed to require replacement of the existing TRU Number 2 with a new part number that incorporates a correction to the fan and the monitoring circuit. The NPRM also proposed to prohibit the installation of affected parts. The FAA is issuing this AD to address the inability of a TRU to detect the fan failure. The unsafe condition, if not addressed, could lead to overheating and failures on the remaining TRUs, which could contribute to additional pilot workload and adversely affect the safe operation of the airplane. You may examine the MCAI in the AD docket at 
                    *regulations.gov*
                     under Docket No. FAA-2024-0227. Discussion of Final Airworthiness Directive Comments The FAA received comments from NetJets Inc. The following presents the comments received on the NPRM and the FAA's response to the comments. Request To Update the Service Bulletin to the Latest Revision NetJets requested that paragraphs (g) and (i) of the proposed AD be revised to change Bombardier Service Bulletin 700-24-7507, Revision 1, dated May 19, 2023, to Bombardier Service Bulletin 700-24-7507, Revision 2, dated October 16, 2023. The FAA agrees with the request. For airplanes on which the actions of Revision 1 of the service bulletin have already been done, no more work is required by Revision 2. The FAA clarified with Bombardier that credit can be given for the accomplishment of actions specified in Bombardier Service Bulletin 700-24-7507, Revision 1, dated May 19, 2023. The FAA has therefore revised this AD to require Revision 2 and to add credit in paragraph (i) of this AD for accomplishment of the actions specified in Bombardier Service Bulletin 700-24-7507, Revision 1, dated May 19, 2023, if completed before the effective date of this AD. Request for Allowance To Install Part Number G02404521-001 for TRU Number 1 and Number 3 NetJets noted that the Bombardier Service Bulletin 700-24-7507, Revision 2, dated October 16, 2023, limits the installation of TRU part number (P/N) G02404521-001 to the Number 2 position. NetJets requested that an exception be added to paragraph (h) of the proposed AD to also allow the installation of TRU P/N G02404521-001 for TRU Number 1 and TRU Number 3. The FAA does not agree to allow installation of TRU P/N G02404521-001 for TRU Number 1 or Number 3. The TRU P/N G02404521-001 design fails to detect a fan failure. Bombardier Service Bulletin 700-24-7507, Revision 2, dated October 16, 2023, replaces only TRU Number 2 position because it has a higher electrical load and is more susceptible to the fan inoperative condition. TRU P/N G02404521-001 is no longer manufactured. The new production airplanes are all installed with TRU P/N G02404521-003. All TRUs that are removed from service (
                    *e.g.,*
                     for repair) are upgraded to TRU P/N G02404521-003. Therefore, this AD has not been changed regarding this request. 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, and any other changes described previously, this AD is adopted as proposed in the NPRM. None of the changes will increase the economic burden on any operator. Material Incorporated by Reference Under 1 CFR Part 51 The FAA reviewed Bombardier Service Bulletin 700-24-7507, Revision 2, dated October 16, 2023. This material specifies procedures for replacing the existing TRU Number 2 P/N G02404521-001 with new P/N G02404521-003, including removal of the secondary layer of insulation blanket ENM386519113C or P/N ENM386519113D in front of the TRU Number 2 fan air inlet, reidentifying the blanket installation by ink stamp, checking the electrical bond resistance for TRU Number 2, and performing the operational test. 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 56 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. operatorsUp to 5 work-hours × $85 per hour = Up to $425
Up to $34,754
Up to $35,179
Up to $1,970,024.
 The FAA has included all known costs in its cost estimate. According to the manufacturer, however, some or all the costs of this AD may be covered under warranty, thereby reducing the cost impact on affected operators. 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 
                    ( print page 81335)
                    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
 2.The FAA amends § 39.13 by adding the following new airworthiness directive: **2024-18-04 Bombardier, Inc.:**
                             Amendment 39-22838; Docket No. FAA-2024-0227; Project Identifier MCAI-2023-00886-T. (a) Effective Date This airworthiness directive (AD) is effective November 12, 2024. (b) Affected ADs None. (c) Applicability This AD applies to Bombardier, Inc., Model BD-700-2A12 airplanes, certificated in any category, serial numbers 70006 through 70166 inclusive. (d) Subject Air Transport Association (ATA) of America Code 24, Electrical power. (e) Unsafe Condition This AD was prompted by a report that the fan in a transformer rectifier unit (TRU) can become inoperative in a manner that is not detectable by the fan monitoring circuit. The FAA is issuing this AD to address the inability of a TRU to detect the fan failure. The unsafe condition, if not addressed, could lead to overheating and failures on the remaining TRUs, which could contribute to additional pilot workload and adversely affect the safe operation of the airplane. (f) Compliance Comply with this AD within the compliance times specified, unless already done. (g) Transformer Rectifier Unit (TRU) Number 2 Replacement Within 1,500 flight hours or 3 years, whichever occurs first after the effective date of this AD, replace TRU Number 2 part number (P/N) G02404521-001 with P/N G02404521-003, in accordance with the Accomplishment Instructions of Bombardier Service Bulletin 700-24-7507, Revision 2, dated October 16, 2023. (h) Parts Installation Prohibition As of the effective date of this AD, no person may install, on any airplane, a TRU part number G02404521-001. (i) Credit for Previous Actions This paragraph provides credit for actions required by paragraph (g) of this AD, if those actions were performed before the effective date of this AD using Bombardier Service Bulletin 700-24-7507, dated March 31, 2023, or Bombardier Service Bulletin 700-24-7507, Revision 1, dated May 19, 2023. (j) Special Flight Permits Special flight permits may be issued in accordance with 14 CFR 21.197 and 21.199 to operate the airplane to a location where the actions required by this AD can be accomplished, provided no passengers and only essential crew are on board, and day visual flight rules are used. (k) 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 (l)(2) 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; or Transport Canada or Bombardier, Inc.'s Transport Canada Design Approval Organization (DAO). If approved by the DAO, the approval must include the DAO-authorized signature. (l) Additional Information (1) For more information about this AD, contact William Reisenauer, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7300; email 
                            *9-avs-nyaco-cos@faa.gov.* (2) Material identified in this AD that is not incorporated by reference is available at the addresses specified in paragraph (m)(3) of this AD. (m) Material Incorporated by Reference (1) The Director of the Federal Register approved the incorporation by reference 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) Bombardier Service Bulletin 700-24-7507, Revision 2, dated October 16, 2023. (ii) [Reserved] (3) 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 
                            *ac.yul@aero.bombardier.com;*
                             website 
                            *bombardier.com.* (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 September 4, 2024. Victor Wicklund, Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service.


[FR Doc. 2024-23115 Filed 10-7-24; 8:45 am] BILLING CODE 4910-13-P