DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2022-0284; Project Identifier MCAI-2021-01369-A]
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: Notice of proposed rulemaking (NPRM).

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SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for certain Viking Air Limited (type certificate previously held by
Bombardier Inc. and de Havilland, Inc.) Model DHC-6-1, DHC-6-100, DHC-
6-200, DHC-6-300, and DHC-6-400 airplanes. This proposed AD results
from 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 identifies the unsafe
condition as binding of the rod end bearing connecting the lower fuel
control unit (FCU) push rod assembly to the FCU power lever. This
proposed AD would require performing tests, inspections, and
lubrication of the FCU push rod assemblies, and replacing them with
improved parts as necessary. 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 May 6,
2022.

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 Viking Air
Ltd., 1959 de Havilland Way, Sidney British Columbia, Canada V8L 5V5;
phone: (800) 663-8444; email: continuing.airworthiness@vikingair.com;
website: https://www.vikingair.com. 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.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2022-0284; 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 MCAI,
any comments received, and other information. The street address for
Docket Operations is listed above.

FOR FURTHER INFORMATION CONTACT: Elizabeth Dowling, Aviation Safety
Engineer, FAA, New York ACO Branch, 1600 Stewart Avenue, Suite 410,
Westbury, NY 11590; phone: (516) 228-7300; email:
elizabeth.m.dowling@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 the ADDRESSES section. Include ``Docket No. FAA-2022-0284;
Project Identifier MCAI-2021-01369-A'' 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
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 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
Elizabeth Dowling, Aviation Safety Engineer, New York ACO Branch, FAA,
1600 Stewart Avenue, Suite 410, Westbury, NY 11590. 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-2021-42, dated November 26, 2021
(referred to after this as ``the MCAI''), to address an unsafe
condition on certain serial-numbered Viking Air Limited Model DHC-6
series 1, DHC-6 series 100, DHC-6 series 110, DHC-6 series 200, DHC-6
series 210, DHC-6 series 300, DHC-6 series 310, DHC-6 series 320, and
DHC-6 series 400 airplanes with certain part-numbered FCU push rod
assemblies installed. The MCAI states:

There have been in-service reports of binding of [part number]
P/N VSC30-3A rod end bearings used in the linkage for the lower FCU
push rod assembly P/N C6CE1398-7. The lower FCU push rod assembly is
connected to the FCU power lever and contains a rod end bearing at
each end. P/N VSC30-3A rod end bearings, fabricated with a metal
inner race and a dry film lubricant, have been incorporated on FCU
push rod assemblies introduced through Viking Air Ltd (Viking) MOD
6/2347. P/N VSC30-3A rod end bearings may have also been installed
in-service as a replacement part in lower FCU push rod assembly P/N
C6CE1398-3. In one instance, binding of the lower FCU push rod
bearing resulted in one engine failing to return to a lower power
setting from a higher power setting when
commanded, which subsequently resulted in the need to perform an in-
flight engine shutdown during final approach. An investigation also
revealed that binding of P/N VSC30-3A rod end bearings can occur
after a period of non-utilization of the aeroplane.
This condition, if not detected and corrected, may lead to the
inability to reduce power on the affected engine, resulting in the
need to perform an in-flight engine shutdown, and consequently
leading to reduced control of the aeroplane and increased pilot
workload during this critical phase of flight.
To address this unsafe condition, this [Transport Canada] AD
mandates initial and repetitive functional checks, special detailed
inspection (SDI) and lubrication of the affected FCU push rod
assembly, and its replacement, as required, with a redesigned FCU
push rod assembly with improved reliability (MOD 6/2484), in
accordance with Viking Service Bulletin (SB) V6/0063. This
[Transport Canada] AD also prohibits the installation of an affected
FCU push rod assembly as a replacement part on applicable
aeroplanes.

You may examine the MCAI in the AD docket at https://www.regulations.gov
by searching for and locating Docket No. FAA-2022-0284.

Related Service Information Under 1 CFR Part 51

The FAA reviewed the following:
Viking DHC-6 Twin Otter Service Bulletin (SB) No. V6/0063,
Revision A, dated February 1, 2021 (Viking SB V6/0063, Revision A),
which specifies procedures for performing tests, inspections, and
lubrication of the FCU push rod assemblies; and
Viking DHC-6 Twin Otter Technical Bulletin No. V6/00155,
Revision NC, dated September 14, 2020, which specifies procedures for
replacing the FCU push rod assemblies with improved parts.
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 also reviewed Viking DHC-6 Twin Otter SB No. V6/0063,
Revision NC, dated June 7, 2019 (Viking SB V6/0063, Revision NC), which
specifies procedures for performing tests, inspections, and lubrication
of the FCU push rod assemblies. Viking revised this service information
and issued Viking SB V6/0063 Revision A to extend the lubrication
requirement of Mod 6/2347 rod ends to all operating environments, add
repeat inspections, and introduce a test and lubrication for airplanes
that have not been in operation after a period of time before re-entry
into service.

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
and service information referenced above. The FAA is issuing this NPRM
after determining 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 the service information described previously.

Differences Between This Proposed AD and the MCAI

The MCAI applies to Viking Air Limited Model DHC-6 series 110, DHC-
6 series 210, DHC-6 series 310, and DHC-6 series 320, and this proposed
AD would not because these models do not have an FAA type certificate.
Transport Canada Model DHC-6 series 1, DHC-6 series 100, DHC-6 series
200, DHC-6 series 300, and DHC-6 series 400 airplanes correspond to FAA
Model DHC-6-1, DHC-6-100, DHC-6-200, DHC-6-300, and DHC-6-400
airplanes, respectively.
The MCAI requires reporting information to the manufacturer, and
this proposed AD would not.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 34 airplanes of U.S. registry. The FAA estimates the following
costs to comply with this proposed AD:

Estimated Costs

The FAA estimates the following costs to replace the FCU push rod
assemblies. The agency has no way of determining the number of
airplanes that might need these replacements:

On-Condition Costs

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) 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 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: