DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0214; Project Identifier 2018-CE-064-AD; Amendment
39-21839; AD 2021-24-18]
RIN 2120-AA64

Airworthiness Directives; Viking Aircraft Limited 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
Viking Air Limited Model DHC-3 airplanes. This 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 fatigue damage of the wing strut lug fitting components
and the fuselage to wing strut attachment (tie-bar). This AD requires
determining service life limits
for the wing strut fitting on the main spar and for the tie-bar and
following instructions for removal and replacement of affected parts.
The FAA is issuing this AD to address the unsafe condition on these
products.

DATES: This AD is effective January 24, 2022.
The Director of the Federal Register approved the incorporation by
reference of certain publications listed in this AD as of January 24,
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
(816) 329-4148. It is also available at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0214.

Examining the AD Docket

You may examine the AD docket at https://www.regulations.gov by
searching for and locating Docket No. FAA-2021-0214; 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: Aziz Ahmed, Aviation Safety Engineer,
New York ACO Branch, FAA, 1600 Stewart Avenue, Suite 410, Westbury, NY
11590; phone: (516) 287-7329; fax: (516) 794-5531; email:
aziz.ahmed@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 Viking Air Limited
Model DHC-3 airplanes. The NPRM published in the Federal Register on
June 28, 2021 (86 FR 33916). The NPRM was prompted by MCAI originated
by Transport Canada, which is the aviation authority for Canada.
Transport Canada has issued AD CF-2017-29, dated August 24, 2017
(referred to after this as ``the MCAI''), to correct an unsafe
condition for Viking Air Limited Model DHC-3 airplanes. The MCAI
states:

It has been determined that the current maintenance program does
not adequately address potential fatigue damage of the wing strut
lug fitting components or the fuselage to wing strut attachment (Tie
Bar). Affected parts must be replaced before specified air time
limits are reached to avoid fatigue cracking of the affected parts.
Cracking which is not detected may compromise the structural
integrity of the wing or the Tie-Bar.
Fatigue damage occurs more rapidly on aeroplanes that are
operated at higher gross weights. For that reason, the corrective
actions of this [Transport Canada] AD must be accomplished sooner
for aeroplanes that have been certified for operation at higher
gross weights.
Fatigue damage also occurs more rapidly on aeroplanes that are
operated below 2000 feet above ground level (AGL) over land due to
higher and more frequent gust and maneuvering loads. Low level
flights over water are not known to produce increased fatigue damage
on the DHC-3. For that reason, the corrective actions of this
[Transport Canada] AD must be accomplished sooner for aeroplanes
that have been operated at low altitudes over land.

This condition, if not addressed, could result in cracking and
failure of the structural integrity of the wing or the tie-bar.
You may examine the MCAI in the AD docket at https://www.regulations.gov
by searching for and locating Docket No. FAA-2021-0214.
In the NPRM, the FAA proposed to require determining service life
limits for the wing strut fitting on the main spar and for the tie-bar
and following instructions for removal and replacement of affected
parts. The FAA is issuing this AD to address the unsafe condition on
these products.

Discussion of Final Airworthiness Directive

Comments

The FAA received comments from two commenters. The commenters were
Talkeetna Air Taxi Inc. (Talkeetna Air) and Rust's Flying Service/K2
Aviation (Rust's Flying Service). The following presents the comments
received on the NPRM and the FAA's response to each comment.

Request Regarding Equivalent Air Time

Both commenters requested the FAA change the proposed method of
calculating equivalent air time by doubling the total hours on each
component. Talkeetna Air requested the FAA allow increased visual and
non-destructive testing inspections instead. Talkeetna Air and Rust's
Flying Service suggested the FAA allow operators to calculate by using
the formula and estimating the altitudes at which an airplane has
operated, as provided in the service information, instead of by
assuming all operations occur below 2,000 feet. Rust's Flying Service
stated it has data to verify the operating altitudes of its aircraft.
As the FAA explained in the NPRM, there is no regulatory
requirement for owners or operators to record or maintain the operating
altitude history of an airplane. As a result, this AD requires
calculating the compliance time by assuming all operations occurred
below 2,000 feet AGL (and therefore doubling the total hours). However,
operators may request approval to determine equivalent air time
differently as an alternative method of compliance under the provisions
of paragraph (g)(1) of this AD. The FAA did not change this AD based on
this comment.

Request Regarding Costs of Compliance

Talkeetna Air requested that the FAA adjust its estimated costs of
compliance. The commenter stated that the hourly rate and number of
estimated labor hours is too low for what would be required.
The FAA obtained the 300-hour labor time estimated in the NPRM from
Viking Air Limited DHC-3 Otter Service Bulletin Number V3/0008,
Revision NC, dated February 9, 2017. The FAA verified this number with
Viking Air Limited and confirmed it is valid.
The FAA Office of Aviation Policy and Plans provides the labor rate
of $85 per work-hour for the FAA to use when estimating the labor costs
of complying with AD requirements.
The FAA did not change this AD based on this comment.

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 any
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 these products. This AD is adopted as proposed
in the NPRM.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Viking DHC-3 Otter Service Bulletin Number V3/
0008, Revision NC, dated February 9, 2017. The service information
specifies determining service life limits for the wing strut fitting on
the main spar and for the tie-bar and contains instructions for removal
and replacement. The FAA also reviewed De Havilland Aircraft of Canada,
Limited DHC-3 Otter Service Bulletin Number 3/37, Revision B, dated
October 8, 1982. The service information specifies instructions for
removing and replacing the fuselage to wing strut attachment tie-bar.
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 ADDRESSES.

Differences Between This AD and the MCAI

The MCAI requires calculating the compliance time by using a
formula and estimating the altitudes at which an airplane has operated.
The MCAI also instructs operators to assume operations below 2,000 feet
AGL when the operating altitude of the airplane is unknown. Because the
FAA has no regulatory requirement for owners or operators to record or
maintain the operating altitude history of an airplane, this AD
requires calculating the compliance time by assuming all operations
occurred below 2,000 feel AGL.

Costs of Compliance

The FAA estimates that this AD affects 41 airplanes of U.S.
registry.
The FAA also estimates that it would take about 300 work-hours per
airplane to replace both the wing strut fitting and the tie-bar. The
average labor rate is $85 per work-hour. Required parts would cost
about $5,599 per airplane.
Based on these figures, the FAA estimates the cost of this AD on
U.S. operators to be $1,275,059 or $31,099 per airplane.

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: