DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2024-1479; Project Identifier MCAI-2023-00657-T]
RIN 2120-AA64

Airworthiness Directives; Bombardier, Inc., Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for certain Bombardier Inc. Model BD-100-1A10 airplanes. This proposed
AD was prompted by a determination that a revised restrictive
airworthiness limitation is necessary. This proposed AD would 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 proposing this AD to
address the unsafe condition on these products.

DATES: The FAA must receive comments on this proposed AD by July 22,
2024.

ADDRESSES: You may send comments, using the procedures found in 14 CFR
11.43 and 11.45, by any of the following methods:
Federal eRulemaking Portal: Go to regulations.gov. Follow
the instructions for submitting comments.
Fax: 202-493-2251.
Mail: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue SE, Washington, DC 20590.
Hand Delivery: Deliver to Mail address above between 9
a.m. and 5 p.m., Monday through Friday, except Federal holidays.
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 NPRM, the mandatory continuing airworthiness
information (MCAI), any comments received, and other information. The
street address for Docket Operations is listed above.
Material Incorporated by Reference:
For service information identified in this NPRM, contact
Bombardier Business Aircraft Customer Response Center, 400 Cote-
Vertu Road West, Dorval, Quebec H4S 1Y9, Canada; telephone 514-
855-2999; emailac.yul@aero.bombardier.com; website bombardier.com.
You may view this service information 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.

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:

Comments Invited

The FAA invites you to send any written relevant data, views, or
arguments about this proposal. Send your comments to an address listed
under ADDRESSES. Include ``Docket No. FAA-2024-1479; Project Identifier
MCAI-2023-00657-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
regulations.gov, including any personal information you provide. The
agency will also post a report summarizing each substantive verbal
contact received about this NPRM.

Confidential Business Information

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 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. Any commentary that the FAA receives which is not
specifically designated as CBI will be placed in the public docket for
this rulemaking.

Background

Transport Canada, which is the aviation authority for Canada, has
issued Transport Canada AD CF-2023-29, dated May 5, 2023 (Transport
Canada AD CF-2023-29) (also referred to after this as the MCAI), to
correct an unsafe condition on all Bombardier, Inc., Model BD-100-1A10
airplanes. The MCAI states 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.

Airplanes having serial numbers 20913 and subsequent must comply
with the airworthiness limitations specified as part of the approved
type design and referenced on the type certificate data sheet; this
proposed AD therefore does not include those airplanes in the
applicability.
The FAA is proposing 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.

Related Service Information Under 1 CFR Part 51

The FAA reviewed the following documents. This service information
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.
Section 5-10-10, ``Life Limits (Structures),'' of part 2,
``Airworthiness Limitations,'' of the Bombardier Challenger 300 Time
Limits/Maintenance Check, CH 300, Revision 24, dated August 9, 2023,
which include 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, CH 350, Revision 14, dated August 9, 2023,
which include Task 54-51-00-111*, ``Discard of the Aft Engine Mount
Bolts, Part No. MS21250-07, Non-Serialized.''
This service information 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.

FAA's Determination

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
and service information referenced above. The FAA is issuing this NPRM
after determining that the unsafe condition described previously is
likely to exist or develop on other products of the same type design.

Proposed AD Requirements in This NPRM

This proposed AD would require accomplishing revising the existing
maintenance or inspection program, as applicable, to incorporate a
revised airworthiness limitation.
This proposed AD would require revisions to certain operator
maintenance documents to include new actions (e.g., 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.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 731 airplanes of U.S. registry. The FAA estimates the following
costs to comply with this proposed 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

The FAA determined that this proposed AD would not have federalism
implications under Executive Order 13132. This proposed AD would 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 this proposed
regulation:
(1) Is not a ``significant regulatory action'' under Executive
Order 12866,
(2) Would not affect intrastate aviation in Alaska, and
(3) Would 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 Proposed Amendment

Accordingly, under the authority delegated to me by the
Administrator, the FAA proposes to amend 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: