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###### Department of Transportation

###### Federal Aviation Administration

          - 14 CFR Part 39
          - [Docket No. FAA-2024-1479; Project Identifier MCAI-2023-00657-T; Amendment 39-22824; AD 2024-16-18]
          - 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-100-1A10 airplanes. This AD was prompted by a determination that a revised restrictive airworthiness limitation is necessary. This AD requires revising the existing maintenance or inspection program, as applicable, to incorporate a revised restrictive airworthiness limitation for the aft engine mount attachment bolts. The FAA is issuing this AD to address the unsafe condition on these products.

# DATES:

This AD is effective October 30, 2024.

The Director of the Federal Register approved the incorporation by reference of certain publications listed in this AD as of October 30, 2024.

# ADDRESSES:

*AD Docket:*                         You may examine the AD docket at                         *regulations.gov*                         under Docket No. FAA-2024-1479; 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-2024-1479.                    

      ( print page 78232)    

# FOR FURTHER INFORMATION CONTACT:

                        Yaser Osman, 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-100-1A10 airplanes. The NPRM published in the                     **Federal Register**                     on June 5, 2024 (89 FR 48139). The NPRM was prompted by AD CF-2023-29, dated May 5, 2023, issued by Transport Canada, which is the aviation authority for Canada (referred to after this as the MCAI). The MCAI states that the time limits/maintenance check (TLMC) airworthiness limitation (AWL) Task 54-51-00-111*, “Discard of the Aft Engine Mount Bolts, Part No. MS21250-07, Non-Serialized,” was not performed on some Challenger 300 in-service airplanes due to a misleading part number (P/N) referenced in the TLMC manual. The task requires the discard and replacement of the aft engine mount attachment bolt, P/N MS21250-07, while the P/N shown in the TLMC manual is P/N MS21250-7 in lieu of P/N MS21250-07. Bombardier revised the TLMC AWL task and the relevant sections in the aircraft maintenance manual and the aircraft illustrated parts catalog with P/N MS21250-07 to ensure timely discard and replacement of the aft engine mount attachment bolts.                

In the NPRM, the FAA proposed to require revising the existing maintenance or inspection program, as applicable, to incorporate a revised restrictive airworthiness limitation for the aft engine mount attachment bolts. The FAA is issuing this AD to address potential failures of the aft engine mount attachment bolt, P/N MS21250-07. The unsafe condition, if not addressed, could lead to the detachment of the engine from the airplane, which could contribute to a catastrophic failure.

                    You may examine the MCAI in the AD docket at                     *regulations.gov*                     under Docket No. FAA-2024-1479.                

## Discussion of Final Airworthiness Directive

## Comments

The FAA received no comments on the NPRM or on the determination of the cost to the public.

## 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 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.

## Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed the following documents. This material specifies a revised airworthiness limitation for the replacement of the aft engine mount attachment bolts, P/N MS21250-07. These documents are distinct since they apply to different airplane configurations. The asterisk (or “one star”) with the last three digits of the task numbers indicates that the task is an airworthiness limitation task.
    - Task 54-51-00-111* “Discard of the Aft Engine Mount Bolts, Part No. MS21250-07, Non-Serialized,” Section 5-10-10 “Life Limits (Structures),” Part 2 “Airworthiness Limitations,” of the Bombardier Challenger 300 Time Limits/Maintenance Check, Publication No. CH 300 TLMC, Revision 24, dated August 9, 2023.
    - Task 54-51-00-111* “Discard of the Aft Engine Mount Bolts, Part No. MS21250-07, Non-Serialized,” Section 5-10-10 “Life Limits (Structures),” Part 2 “Airworthiness Limitations,” of the Bombardier Challenger 350 Time Limits/Maintenance Check, Publication No. CH 350 TLMC, Revision 14, dated August 9, 2023.

                    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 731 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).

## 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:

      ( print page 78233)    

# 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: 

**2024-16-18 Bombardier, Inc.:**                             Amendment 39-22824; Docket No. FAA-2024-1479; Project Identifier MCAI-2023-00657-T.                        

## (a) Effective Date

This airworthiness directive (AD) is effective October 30, 2024.

## (b) Affected ADs

None.

## (c) Applicability

This AD applies to Bombardier, Inc., Model BD-100-1A10 airplanes, certificated in any category, having serial numbers (S/Ns) 20002 through 20912 inclusive.

## (d) Subject

Air Transport Association (ATA) of America Code America Code 54, Nacelles/Pylons.

## (e) Unsafe Condition

This AD was prompted by a determination that new or more restrictive airworthiness limitations are necessary. The FAA is issuing this AD to address potential failures of the aft engine mount attachment bolt, part number MS21250-07. The unsafe condition, if not addressed, could lead to the detachment of the engine from the airplane, which could contribute to a catastrophic failure.

## (f) Compliance

Comply with this AD within the compliance times specified, unless already done.

## (g) Maintenance or Inspection Program Revision

Within 60 days after the effective date of this AD, revise the existing maintenance or inspection program, as applicable, to incorporate the information specified in paragraphs (g)(1) and (2) of this AD, as applicable. The initial compliance time for doing the tasks is at the time specified in the applicable time limit/maintenance check (TLMC) document specified in paragraphs (g)(1) and (2) of this AD, or within 60 days after the effective date of this AD, whichever occurs later.

(1) For airplane S/Ns 20002 through 20500 inclusive: Task 54-51-00-111* “Discard of the Aft Engine Mount Bolts, Part No. MS21250-07, Non-Serialized,” Section 5-10-10 “Life Limits (Structures),” Part 2, “Airworthiness Limitations,” of the Bombardier Challenger 300 Time Limits/Maintenance Check, Publication No. CH 300 TLMC, Revision 24, dated August 9, 2023.

(2) For airplane S/Ns 20501 through 20912 inclusive: Task 54-51-00-111* “Discard of the Aft Engine Mount Bolts, Part No. MS21250-07, Non-Serialized,” Section 5-10-10 “Life Limits (Structures),” Part 2 “Airworthiness Limitations,” of the Bombardier Challenger 350 Time Limits/Maintenance Check, Publication No. CH 350 TLMC, Revision 14, dated August 9, 2023.

**Note 1 to paragraph (g):**                             The asterisk (or “one star”) with the last three digits of the task numbers listed in paragraphs (g)(1) and (2) of this AD indicates that the task is an airworthiness limitation task.                        

## (h) No Alternative Actions or Intervals

                            After the existing maintenance or inspection program has been revised as required by paragraph (g) of this AD, no alternative actions (                            *e.g.,*                             inspections) or intervals may be used unless the actions or intervals, are approved as an alternative method of compliance in accordance with the procedures specified in paragraph (i)(1) of this AD.                        

## (i) Other FAA 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; 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.                        

## (j) Additional Information

                            For more information about this AD, contact Yaser Osman, Aviation Safety Engineer, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7300; email                             *9-avs-nyaco-cos@faa.gov.*

## (k) 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) Task 54-51-00-111* “Discard of the Aft Engine Mount Bolts, Part No. MS21250-07, Non-Serialized,” Section 5-10-10 “Life Limits (Structures),” Part 2 “Airworthiness Limitations,” of the Bombardier Challenger 300 Time Limits/Maintenance Check, Publication No. CH 300 TLMC, Revision 24, dated August 9, 2023.

**Note 2 to paragraph (k)(2)(i):**                             The asterisk (or “one star”) with the last three digits of the task numbers listed in paragraphs (k)(2)(i) and (ii) of this AD indicates that the task is an airworthiness limitation task.                        

(ii) Task 54-51-00-111* “Discard of the Aft Engine Mount Bolts, Part No. MS21250-07, Non-Serialized,” Section 5-10-10 “Life Limits (Structures),” of Part 2 “Airworthiness Limitations,” of the Bombardier Challenger 350 Time Limits/Maintenance Check, Publication No. CH 350 TLMC, Revision 14, dated August 9, 2023.

                            (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 August 7, 2024.

Victor Wicklund,

Deputy Director, Compliance & Airworthiness Division, Aircraft Certification Service.

[FR Doc. 2024-21807 Filed 9-24-24; 8:45 am]

BILLING CODE 4910-13-P