DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-1653; Project Identifier MCAI-2022-01193-T;
Amendment 39-22370; AD 2023-05-01]
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: Final rule.

-----------------------------------------------------------------------

SUMMARY: The FAA is adopting a new airworthiness directive (AD) for
certain De Havilland Aircraft of Canada Limited Model DHC-8-400 series
airplanes. This AD was prompted by reports of flap power unit (FPU)
pressure switch failures resulting in flap inoperative events. This AD
requires replacing the FPU or replacing the FPU pressure switch and
reidentifying the FPU. This AD also prohibits the installation of
affected parts. The FAA is issuing this AD to address the unsafe
condition on these products.

DATES: This AD is effective April 18, 2023.
The Director of the Federal Register approved the incorporation by
reference of a certain publication listed in this AD as of April 18,
2023.

ADDRESSES:
AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2022-1653; 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 service information identified in this final rule,
contact De Havilland Aircraft of Canada Limited, Dash 8 Series Customer
Response Centre, 5800 Explorer Drive, Mississauga, Ontario, L4W 5K9,
Canada; telephone North America (toll-free): 855-310-1013, Direct: 647-
277-5820; email thd@dehavilland.com; website dehavilland.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 in the AD docket at
regulations.gov under Docket No. FAA-2022-1653.

FOR FURTHER INFORMATION CONTACT: Gabriel Kim, 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; 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 De Havilland
Aircraft of Canada Limited Model DHC-8-400 series airplanes. The NPRM
published in the Federal Register on December 23, 2022 (87 FR 78881).
The NPRM was prompted by AD CF-2022-52, dated September 1, 2022, issued
by Transport Canada, which is the aviation authority for Canada
(Transport Canada AD CF-2022-52) (also referred to as the MCAI). The
MCAI states there have been increasing reports of FPU pressure switch
failures, part number (P/N) 150135-1 or P/N 162660-1, over the past
year leading to a high number of flap inoperative events in flight and
on the ground. An investigation has determined the root cause to be a
deformation of the FPU pressure switch internal mechanism due to
hydraulic pressure spikes. If not corrected, a failed FPU pressure
switch could lead to a failure of the FPU resulting in abnormal flap
landings and increased landing distances, which could require the use
of emergency landing procedures and/or airfield diversions. The
improved pressure switch, P/N 162660-2, has a restrictor insert in the
pressure switch inlet.
In the NPRM, the FAA proposed to require replacing the FPU pressure
switch or the FPU. The NPRM also proposed to prohibit the installation
of affected parts. The FAA is issuing 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-2022-1653.

Discussion of Final Airworthiness Directive

Comments

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

Explanation of Additional Changes

In the NPRM, the FAA inadvertently omitted the operational test of
the wing flaps specified in Section 3.C. paragraph (2) of De Havilland
Aircraft of Canada Limited Service Bulletin 84-27-75, dated June 23,
2022, including Collins Aerospace Service Bulletin 27-0029, dated June
13, 2022. The MCAI requires this step, which is important to ensure the
aircraft is airworthy before it is returned to service. The FAA has
therefore revised paragraphs (g)(1) and (2) of this AD to clarify that
the operational test is required by this AD.
The FAA has revised paragraph (g)(2) of this AD to clarify that De
Havilland Aircraft of Canada Limited Service Bulletin 84-27-75, dated
June 23, 2022, including Collins Aerospace Service Bulletin 27-0029,
dated June 13, 2022, is the appropriate service information for
accomplishing the actions in this AD. The FAA had referred to these
bulletins separately, but since they are published as one document, the
FAA corrected the citation.

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, and any other changes described
previously, this AD is adopted as proposed in the NPRM. None of the
changes will increase the economic burden on any operator.

Related Service Information Under 1 CFR Part 51

The FAA reviewed De Havilland Aircraft of Canada Limited Service
Bulletin 84-27-75, dated June 23, 2022, including Collins Aerospace
Service Bulletin 27-0029, dated June 13, 2022. This service information
specifies procedures for replacing FPU P/N C148656-1 or C148656-2 with
a new FPU P/N C148656-3, or replacing FPU pressure switch P/N 150135-1
or 162660-1 within the FPU with a new pressure switch P/N 162660-2 and
re-identifying the FPU as P/N C148656-3, and accomplishing an
operational test of the wing flaps. 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.

Costs of Compliance

The FAA estimates that this AD affects 53 airplanes of U.S.
registry. The FAA estimates the following costs to comply with this AD:

Estimated Costs for Required 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 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

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: