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

Airworthiness Directives; Bombardier, Inc., Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final rule.

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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 Cote-
Vertu Road West, Dorval, Quebec H4S 1Y9, Canada; telephone 514-
855-2999; email bombardier.com">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.

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 x $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:

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.

Sec. 39.13 [Amended]

2. The FAA amends Sec. 39.13 by adding the following new airworthiness
directive: