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Federal Register / Vol. 86, No. 241 / Monday, December 20, 2021 / Rules and Regulations
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 6638444; fax:
250 6560673; 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 3294148. It is also available at https www.regulations.gov by searching for and locating Docket No.
FAA20210214.

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Examining the AD Docket You may examine the AD docket at https www.regulations.gov by searching for and locating Docket No.
FAA20210214; 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, M30, West Building Ground Floor, Room W12140, 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 2877329; fax: 516
7945531; 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 DHC3 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 CF201729, dated
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August 24, 2017 referred to after this as the MCAI, to correct an unsafe condition for Viking Air Limited Model DHC3 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 DHC3. 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. FAA2021
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 Rusts Flying Service/K2 Aviation Rusts Flying Service. The following presents the comments received on the NPRM and the FAAs 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 nondestructive testing inspections instead.

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Talkeetna Air and Rusts 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. Rusts 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 g1 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 DHC3 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 FAAs 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.

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