DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0784; Project Identifier MCAI-2020-01455-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 CL-600-1A11 (600), CL-600-2A12
(601), and CL-600-2B16 (601-3A, 601-3R, and 604 Variants) airplanes.
This proposed AD was prompted by a determination that new or more
restrictive airworthiness limitations are necessary. This proposed AD
would require revising the existing maintenance or inspection program,
as applicable, to incorporate new or more restrictive airworthiness
limitations. 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 October 29,
2021.

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 https://www.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.

For service information identified in this NPRM, contact
Bombardier, Inc., 200 Cote Vertu Road West, Dorval, Quebec
H4S 2A3, Canada; North America toll-free telephone 1-866-538-1247 or
direct-dial telephone 1-514-855-2999; email ac.yul@aero.bombardier.com;
internet https://www.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.

Examining the AD Docket

You may examine the AD docket on the internet at https://www.regulations.
gov by searching for and locating Docket No. FAA-2021-0784;
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, any comments received, and other information. The street
address for Docket Operations is listed above.

FOR FURTHER INFORMATION CONTACT: Elizabeth Dowling, Aerospace Engineer,
Mechanical Systems and Administrative Services Section, FAA, New York
ACO Branch, 1600 Stewart Avenue, Suite 410, Westbury, NY 11590;
telephone 516-228-7300; fax 516-794-5531; 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-2021-0784; Project Identifier
MCAI-2020-01455-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
https://www.regulations.gov, including any personal information you
provide. The agency will also post a report summarizing each
substantive verbal contact received about this proposed AD.

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 Elizabeth Dowling, Aerospace Engineer, Mechanical Systems and
Administrative Services Section, FAA, New York ACO Branch, 1600 Stewart
Avenue, Suite 410, Westbury, NY 11590; telephone 516-228-7300; fax 516-
794-5531; email 9-avs-nyaco-cos@faa.go. 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 Civil Aviation (TCCA), which is the aviation
authority for Canada, has issued TCCA AD CF-2020-44, dated October 23,
2020 (referred to after this as the Mandatory Continuing Airworthiness
Information, or "the MCAI"), to correct an unsafe condition for
certain Bombardier, Inc., Model CL-600-1A11 (600), CL-600-2A12 (601),
and CL-600-2B16 (601-3A, 601-3R, and 604 Variants) airplanes. You may
examine the MCAI in the AD docket on the internet at https://www.
regulations.gov by searching for and locating Docket No. FAA-2021-0784.

This proposed AD was prompted by a determination that new or more
restrictive airworthiness limitations are necessary. The FAA is
proposing this AD to address fatigue cracking and loss of structural
integrity of the circumferential splice joint, which could result in
reduced structural integrity of the airplane. See the MCAI for
additional background information.

Related Service Information Under 1 CFR Part 51

The FAA reviewed the following Bombardier service information,
which describes new or more restrictive airworthiness limitations (a
special detailed inspection for cracking of the skin circumferential
splice at fuselage station (FS) 559.00, between stringer (STR) 10L and
STR10R. These documents are distinct since they apply to different
airplane configurations. (Note: The asterisk (or "one star") with the
last three digits of the task number indicates that the task is an
airworthiness limitation task.)

Task 53-30-00-165*, "Special Detailed Inspection of the
Skin Circumferential Splice at FS559.00 between STR10L and STR10R," of
Bombardier Challenger 605 CL-600-1A11 Time Limits/Maintenance Checks
(TLMC), Product Support Publication (PSP) 605, Temporary Revision (TR)
5-163, dated April 30, 2020.

Task 53-30-00-188*, "Special Detailed Inspection of the
Skin Circumferential Splice at FS559.00 between STR10L and STR10R," of
Bombardier Challenger CL-600-2A12 TLMC, PSP 601-5, TR 5-267, dated
April 30, 2020.

Task 53-30-00-191*, "Special Detailed Inspection of the
Skin Circumferential Splice at FS559.00 between STR10L and STR10R," of
Bombardier Challenger CL-600-2B16 TLMC, PSP 601A-5, TR 5-281, dated
April 30, 2020.

Task 53-20-00-192*, "Special Detailed Inspection of the
Skin Circumferential Splice at FS559.00 between STR10L and STR10R," of
Bombardier Challenger CL-600-2B16, CH 604, TLMC, Revision 32, dated
December 18, 2019.

Task 53-20-00-192*, "Special Detailed Inspection of the
Skin Circumferential Splice at FS559.00 between STR10L and STR10R," of
Bombardier Challenger CL-600-2B16, CH 605, TLMC, Revision 21, dated
December 18, 2019.

Task 53-20-00-192*, "Special Detailed Inspection of the
Skin Circumferential Splice at FS559.00 between STR10L and STR10R," of
Bombardier Challenger CL-600-2B16, CH 650, TLMC, Revision 8, dated
December 18, 2019.

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 the State of Design Authority,
the FAA has been notified of the unsafe condition described in the MCAI
and service information referenced above. The FAA is proposing this AD
because the FAA evaluated all the relevant information and determined
the unsafe condition described previously is likely to exist or develop
on other products of the same type design.

Proposed Requirements of This NPRM

This proposed AD would require revising the existing maintenance or
inspection program, as applicable, to incorporate new or more
restrictive airworthiness limitations.

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 proposed AD affects 463 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: