DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2023-2137; Project Identifier MCAI-2022-01389-T;
Amendment 39-22737; AD 2024-08-04]
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.

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SUMMARY: The FAA is adopting a new airworthiness directive (AD) for all
De Havilland Aircraft of Canada Limited Model DHC-8-401 and -402
airplanes. This AD was prompted by a determination that new or more
restrictive airworthiness limitations are necessary. This AD requires
revising the existing maintenance or inspection program, as applicable,
to incorporate new or more restrictive airworthiness limitations. The
FAA is issuing this AD to address the unsafe condition on these
products.

DATES: This AD is effective June 20, 2024.

ADDRESSES:
AD Docket: You may examine the AD docket at regulations.gov under
Docket No. FAA-2023-2137; 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 De Havilland material, 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
dehavilland.com">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 at regulations.gov under
Docket No. FAA-2023-2137.

FOR FURTHER INFORMATION CONTACT: Fatin Saumik, 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 all De Havilland
Aircraft of Canada Limited Model DHC-8-401 and -402 airplanes. The NPRM
published in the Federal Register on October 27, 2023 (88 FR 73775).
The NPRM was prompted by AD CF-2022-59, dated October 27, 2022, issued
by Transport Canada, which is the aviation authority for Canada
(referred to after this as the MCAI). The MCAI states that new or more
restrictive airworthiness limitations have been developed.
In the NPRM, the FAA proposed to require revising the existing
maintenance or inspection program, as applicable, to incorporate new or
more restrictive airworthiness limitations. The FAA is issuing this AD
to address new or more restrictive maintenance interval limitations.
Failure to adhere to the specified interval limitations may result in
reduced structural integrity of the airplane.
You may examine the MCAI in the AD docket at regulations.gov under
Docket No. FAA-2023-2137.

Discussion of Final Airworthiness Directive

Comments

The FAA received a comment from an individual who supported the
NPRM without change.
The FAA received additional comments from De Havilland Aircraft of
Canada Limited and Horizon Air. The following presents the comments
received on the NPRM and the FAA's response to each comment.

Request To Update the Number of Affected Airplanes

De Havilland requested that the Costs of Compliance section of the
NPRM be updated to show the correct number of affected airplanes.
The FAA agrees. The Costs of Compliance section of this AD has been
updated to show 52 affected airplanes.

Request To Require Tasks as Mandated in the MCAI

Horizon Air requested that the proposed AD directly mandate
maintenance review board report (MRBR) tasks instead of Aircraft
Maintenance Manual (AMM) tasks. Horizon noted that Transport Canada AD
CF-2022-59 mandates MRBR tasks directly, and that using the AMM tasks
would put an additional burden on the operator to monitor multiple
sources for the same tasks. The commenter also asserted that AMM task
77-31-00-710-803, which would be required by the proposed AD, adds MRBR
tasks 731100-203, 733100-201, 740000-201, 750000-201, 772100-202, and
793000-201. These tasks are not identified in Section 7-00, PSM 1-84-
7--Maintenance Requirements Manual--Part 2 ALI.
The FAA does not agree because the FAA has decided to not mandate
MRBRs that are part of Candidate Certification Maintenance Requirements
(CCMRs), which are required by Transport Canada AD CF-2022-59. Instead
of mandating the CCMR as done in the Transport Canada AD, the FAA,
after coordination with Transport Canada, determined the corresponding
AMM task numbers will be used. With the AMM tasks, operators must check
for all engine fault codes at once, which involves reading codes from
the engine fault code indicator. Although this involves more tasks, it
does not add a significant number of steps. Requiring the AMM task does
not pose a significant burden on the operator. This AD has not been
changed with regard to this request.

Request To Limit Required Tasks to Procedure Section

Horizon Air requested that the proposed AD require only the
procedure section of the AMM, with provisions for equivalent tooling
and materials, rather than requiring the entire AMM maintenance task,
including the job set-up, specific tools, equipment, and close-out
sections. The commenter stated that mandating the entire AMM
maintenance task procedure may restrict the operator's ability to
perform other maintenance along with AMM tasks.
The FAA does not agree. The job set-up and close-out procedures are
essential for ensuring the safety of maintenance personnel, and for
ensuring the correct completion of the AMM task. This AD has not been
changed with regard to this request.

Request To Allow Further AMM Revisions

Horizon Air requested clarification of whether future revisions of
the AMM are allowed. Horizon noted that the proposed AD did not address
whether task changes such as additions, removals, and interval
adjustments could cause an operator to be out of compliance with the
rule as issued.
The FAA agrees to clarify. Using the current revision of the AMMs
or other revisions that incorporate the information specified in
paragraph (g) of this AD is acceptable for compliance with this AD.
This AD does not mandate using a specific revision of the AMM, provided
that the revision used complies with the requirements of paragraph (g)
of this AD.

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, considered the
comments received, 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.

Costs of Compliance

The FAA estimates that this AD affects 52 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: