DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2024-1692; Project Identifier MCAI-2024-00050-T]
RIN 2120-AA64

Airworthiness Directives; De Havilland Aircraft of Canada Limited
(Type Certificate Previously Held by 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 De Havilland Aircraft of Canada Limited Model DHC-8-401 and
-402 airplanes. This proposed AD was prompted by a report of an in-
flight event where isolation valve caution messages were received. This
proposed AD would require inspecting the fuse/shuttle valve serial
numbers, and replacing certain fuse/shuttle valves, as specified in a
Transport Canada AD, which is proposed for incorporation by reference
(IBR). 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 August 5,
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-2024-1692; 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 material, contact Transport Canada, Transport Canada
National Aircraft Certification, 159 Cleopatra Drive, Nepean, Ontario
K1A 0N5, Canada; telephone 888-663-3639; email
TC.AirworthinessDirectives-Consignesdenavigabilite.TC@tc.gc.ca. You may
find this material on the Transport Canada website at tc.canada.ca/en/
aviation. It is also available at regulations.gov under Docket No. FAA-
2024-1692.
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.

FOR FURTHER INFORMATION CONTACT: Gabriel Kim, 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-2024-1692; Project Identifier
MCAI-2024-00050-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
this 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
Gabriel Kim, 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-2024-01, dated January 11, 2024
(Transport Canada AD CF-2024-01) (also referred to as the MCAI), to
correct an unsafe condition for certain De Havilland Aircraft of Canada
Limited Model DHC-8-401 and DHC-8-402 airplanes. The MCAI states that
an in-service event was reported where the crew received a number two
isolation valve (ISO #2) caution message followed by a number one
isolation valve (ISO #1) caution message. The landing gear was extended
via an alternate extension system as the crew prepared for landing.
Upon landing, the crew used the emergency brake to stop the airplane.
The airplane stopped safely within the runway limits.
Subsequent maintenance activity discovered an external leak from
the main landing gear (MLG) brake assembly, and it was found that the
fuse/shuttle valve assembly did not function properly. Further
investigation revealed that the fuse/shuttle valve
assembly failure resulted from a factory assembly error, which occurred
on a limited number of fuse/shuttle valves.
The assembly error can cause valve deformation leading to premature
wear, and eventually fuse/shuttle valve failure. This condition, if not
corrected, could result in the loss of powered landing gear extension/
retraction, outboard and inboard spoilers, nose wheel steering, and
normal braking, and possibly a runway excursion.
The FAA is proposing this AD to address the unsafe condition on
these products. You may examine the MCAI in the AD docket at
regulations.gov under Docket No. FAA-2024-1692.

Related Service Information Under 1 CFR Part 51

Transport Canada AD CF-2024-01 specifies procedures for inspecting
the fuse/shuttle valve serial numbers, and if any fuse/shuttle valve
assemblies with the listed serial numbers are found, replacing the
affected fuse/shuttle valves.
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 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
referenced above. The FAA is issuing this NPRM after determining that
the unsafe condition described previously is likely to exist or develop
in other products of the same type design.

Proposed AD Requirements in This NPRM

This proposed AD would require accomplishing the actions specified
in Transport Canada AD CF-2024-01 described previously, except for any
differences identified as exceptions in the regulatory text of this
proposed AD.

Explanation of Required Compliance Information

In the FAA's ongoing efforts to improve the efficiency of the AD
process, the FAA developed a process to use some civil aviation
authority (CAA) ADs as the primary source of information for compliance
with requirements for corresponding FAA ADs. The FAA has been
coordinating this process with manufacturers and CAAs. As a result, the
FAA proposes to incorporate Transport Canada AD CF-2024-01 by reference
in the FAA final rule. This proposed AD would, therefore, require
compliance with Transport Canada AD CF-2024-01 in its entirety through
that incorporation, except for any differences identified as exceptions
in the regulatory text of this proposed AD. Service information
required by Transport Canada AD CF-2024-01 AD for compliance will be
available at regulations.gov under Docket No. FAA-2024-1692 after the
FAA final rule is published.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 54 airplanes of U.S. registry. The FAA estimates the following
costs to comply with this proposed AD:

Estimated Costs for Required Actions

The FAA estimates the following costs to do any necessary on-
condition action that would be required based on the results of any
required actions. The FAA has no way of determining the number of
aircraft that might need this on-condition action:

Estimated Costs of On-Condition Actions

The FAA has included all known costs in its cost estimate.
According to the manufacturer, however, some or all of the costs of
this proposed 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 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: