DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-0007; Project Identifier 2018-CE-048-AD; Amendment
39-22002; AD 2022-07-14]
RIN 2120-AA64

Airworthiness Directives; Viking Air Limited (Type Certificate
Previously Held by Bombardier Inc. and de Havilland, 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
certain Viking Air Limited (type certificate previously held by
Bombardier Inc. and de Havilland, Inc.) Model DHC-6-400 airplanes. This
AD was prompted by mandatory continuing airworthiness information
(MCAI) originated by an aviation authority of another country to
identify and correct an unsafe condition on an aviation product. The
MCAI describes the unsafe condition as corrosion of the fuel system
components located in the fuel gallery due to inadequate corrosion
protection. This AD requires repetitively inspecting the fuel gallery
for corrosion, rectifying any deficiencies, and accomplishing
modifications to the fuel gallery system. The FAA is issuing this AD to
address the unsafe condition on these products.

DATES: This AD is effective May 13, 2022.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of May 13, 2022.

ADDRESSES: For service information identified in this final rule,
contact Viking Air Limited Technical Support, 1959 de Havilland Way,
Sidney, British Columbia, Canada, V8L 5V5; phone: (North America) (800)
663-8444; fax: (250) 656-0673; email: technical.support@vikingair.com;
website: https://www.vikingair.com/support/service-bulletins. You may
view this service information at the FAA, Airworthiness Products
Section, Operational Safety Branch, 901 Locust, Kansas City, MO 64106.
For information on the availability of this material at the FAA, call
(817) 222-5110. Service information that is incorporated by reference
is also available at https://www.regulations.gov by searching for and
locating Docket No. FAA-2022-0007.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2022-0007; 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
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.

FOR FURTHER INFORMATION CONTACT: Joseph Catanzaro, Aviation Safety
Engineer, New York ACO Branch, FAA, 1600 Stewart Avenue, Suite 410,
Westbury, NY 11590; phone: (516) 228-7366; email:
joseph.catanzaro@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 serial-numbered
Viking Air Limited (type certificate previously held by Bombardier Inc.
and de Havilland, Inc.) Model DHC-6-400 airplanes. The NPRM published
in the Federal Register on January 21, 2022 (87 FR 3238). The NPRM was
prompted by MCAI originated by Transport Canada, which is the aviation
authority for Canada. Transport Canada issued AD CF-2018-07, dated
February 23, 2018 (referred to after this as ``the MCAI''), to address
an unsafe condition on certain serial-numbered Viking Air Limited Model
DHC-6-400 airplanes. The MCAI states:

There have been reports of corrosion affecting components of the
fuel system that are located in the fuel gallery because of
inadequate corrosion protection. This condition affects only
aeroplanes operating on floats.
The effects of corrosion-related damage to fuel system
components have included fuel
leaks, electrical arcing, loss of fuel boost pump function and
erroneous fuel quantity readings. Inaccurate fuel quantity
indication and loss of fuel boost pump function can lead to fuel
starvation followed by loss of engine power. Electrical arcing in
the fuel gallery and loss of electrical bonding between fuel system
components increases the risk of fire.

The MCAI requires repetitively inspecting the fuel gallery for
corrosion, rectifying any deficiencies, and accomplishing modifications
to the fuel gallery system. You may examine the MCAI in the AD docket
at https://www.regulations.gov by searching for and locating Docket No.
FAA-2022-0007.

Discussion of Final Airworthiness Directive

Comments

The FAA received one comment on the NPRM from an individual. The
commenter supported the NPRM without change.

Conclusion

These products have been approved by the aviation authority of
another country and are 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 comment 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 these products. This AD is
adopted as proposed in the NPRM.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Viking DHC-6 Twin Otter Service Bulletin No. V6/
0044, Revision B, dated September 13, 2021. The service information
specifies incorporating multiple design improvement modifications in
the fuel gallery.
The FAA also reviewed Temporary Revision No. 241, dated July 27,
2021, to the Viking DHC-6 Inspection Requirements Manual, PSM 1-6-7.
Items 15.(1) and 15.(2) of this service information specify rinsing and
inspecting the entire fuel gallery for corrosion; removing corrosion;
reapplying any protective finishes; and removing and replacing any
damaged components. The temporary revision updates the fuel gallery
inspection to include airplanes with a new fuel probe (Modification
(MOD) 6/2395).
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.

Other Related Service Information

The FAA reviewed the following technical bulletins, which contain
instructions for the different modifications to components in the fuel
gallery:
Viking DHC-6 Twin Otter Technical Bulletin No. TBV6/00034,
Revision NC, dated October 16, 2013 (MOD 6/2267);
Viking DHC-6 Twin Otter Technical Bulletin No. TBV6/00084,
Revision A, dated May 26, 2017 (MOD 6/2299);
Viking DHC-6 Twin Otter Technical Bulletin No. V6/00099,
Revision NC, dated December 23, 2016 (MOD 6/2389);
Viking DHC-6 Twin Otter Technical Bulletin No. TBV6/00094,
Revision NC, dated November 1, 2016 (MOD 6/2390);
Viking DHC-6 Twin Otter Technical Bulletin No. V6/00100,
Revision NC, dated February 20, 2017 (MOD 6/2393); and
Viking DHC-6 Twin Otter Technical Bulletin No. V6/00152,
Revision NC, dated January 29, 2021 (MOD 6/2464).

Costs of Compliance

The FAA estimates that this AD affects 4 airplanes of U.S.
registry.
The FAA estimates the following costs to comply with this AD:

Estimated Costs

On-Condition Costs

The extent of corrosion damage found during the inspections may
vary significantly from airplane to airplane. The FAA has no way of
determining how much corrosion damage may be found on each airplane,
the cost for repairing corrosion damage on each airplane, or the number
of airplanes that may require repair.

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 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: