DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2020-1005; Project Identifier MCAI-2020-00709-A]
RIN 2120-AA64

Airworthiness Directives; Viking Air Limited (Type Certificate
Previously Held by Bombardier 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 Viking Air Limited (type certificate previously held by Bombardier
Inc.) Model DHC-3 airplanes with a certain wing strut assembly
installed. 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 fatigue
damage of the wing struts. This proposed AD would require a bolt hole
eddy current inspection of the lug plate holes, a visual and
fluorescent dye penetrant inspection of the lug fittings, and a visual
and eddy current surface scan inspection of the wing strut assemblies.
This unsafe condition could lead to failure of the wing strut, which
could result in an in-flight breakup of the wing. 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 February 4,
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-2020-1005; 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: Deep Gaurav, Aviation Safety Engineer,
New York ACO Branch, FAA, 1515 Stewart Avenue, Westbury, NY 11590;
phone: (516) 228-7300; fax: (516) 794-5331; email: deep.gaurav@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 ADDRESSES. Include ``Docket No. FAA-2020-1005; Project Identifier
MCAI-2020-00709-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 Deep
Gaurav, Aviation Safety Engineer, New York ACO Branch, FAA, 1515
Stewart Avenue, 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-2020-20, dated May 27, 2020 (referred to
after this as ``the MCAI''), to address an unsafe condition on Viking
Air Limited (formerly Bombardier Inc.) Model DHC-3 airplanes. The MCAI
states:

A DHC-3 experienced an in-flight failure of a wing strut in
October 2019. Inspection of the failed part determined that it had fractured and
that the fracture was consistent with fatigue damage. The investigation of
the occurrence is ongoing.
In 1969, it was determined from fatigue testing and analysis
that part number (P/N) C3W100 wing strut assemblies on DHC-3 that
were used for normal operations at a maximum weight of 8000 pounds
should be removed from service before they have accumulated more
than 20 000 hours air time. This information, including definitions
of normal operations, was published in Service Bulletin 3/10 dated
26 August 1969. It was also published at the same time in Appendix 4
Part 6, Structural Component Recommended Service Life Limits, of the
DHC-3 Maintenance Manual PSM 1-3-2.
It is Transport Canada Civil Aviation (TCCA) policy to mandate
compliance with new or more restrictive airworthiness limitations
(AWLs) by the issuance of an AD if the AWL is established after
products that are affected by the AWL are already in service. To
date, TCCA has not mandated compliance with the 20 000 hours air
time life limit AWL that is applicable to P/N C3W100 wing strut
assemblies. This AD includes a requirement to comply with the life
limit.
Some DHC-3 aeroplanes have been modified to permit operations at
maximum weights above 8000 pounds. For example, TCCA Supplemental
Type Certificate (STC) SA95-32 increases the maximum operating
weight to 8367 pounds. This STC includes a requirement to reduce the
life limit that is applicable to P/N C3W100 wing strut assembly from
20 000 hours air time to 17 500 hours air time, adjusted for the
amount of time that the wing strut assembly is used at the higher
maximum operating weight. Because this reduced life limit has been
in place since the initial issue of STC SA95-32 in 1995, TCCA
considers compliance to be mandatory for all aeroplanes that have
been modified in accordance with the STC.
In November 2019, Viking Air Ltd. (Viking) issued Alert Service
Bulletin (ASB) V3/0011. The ASB provides instructions for a one-time
inspection and follow-on corrective actions for all dash numbers of
wing strut assembly P/N C3W100. Since that time, several operators
have reported the results of the inspection to Viking. The
information in the operators' reports suggests that other DHC-3 wing
struts may be at risk of failure. The inspection of the wing struts
on five aeroplanes revealed crack indications during non-destructive
inspection of bolt holes, seized bolts, pitting corrosion and
fretting on the face of lug plates, scratches and gouges in the bolt
hole of a lug plate. Failure of a wing strut could result in a
catastrophic in-flight breakup of the wing.
This [Transport Canada] AD mandates the accomplishment of ASB
V3/0011 or alternative inspection instructions provided by Viking on
wing struts that have accumulated more than 2500 hours air time as
of the effective date of this AD. New or serviceable struts
installed on aeroplanes after the effective date of this AD that
accumulate more than 2500 hours air time after the effective date of
this AD are not subject to this AD or to the ASB V3/0011
inspections.

You may examine the MCAI in the AD docket at https://www.regulations.gov
by searching for and locating Docket No. FAA-2020-1005.

Related Service Information Under 1 CFR Part 51

The FAA reviewed Viking DHC-3 Otter Alert Service Bulletin No. V3/
0011, Revision NC, dated November 26, 2019. The service information
contains procedures for a bolt hole eddy current inspection of the lug
hole on the lug plate part number (P/N) C3W104, a visual and
fluorescent dye penetrant inspection of the lug fitting P/Ns C3W102 and
C3W103, and a visual and eddy current surface scan inspection of the
wing strut assembly P/N C3W101. 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.

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 on 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 already described.

Differences Between This Proposed AD and the MCAI

The MCAI allows an alternative inspection, obtained from the design
approval holder, if completed within 5 months. This proposed AD does
not include this alternative; however, operators who choose this option
may propose an alternative method of compliance in accordance with
paragraph (h) of the proposed AD.

Interim Action

The FAA considers this proposed AD interim action. The inspection
reports that would be required by this AD will be used by Viking and
Transport Canada to determine if there is a need for further action. If
additional action is later identified, the FAA might consider further
rulemaking.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 39 airplanes of U.S. registry. The FAA also estimates that it
would take about 32 work-hours per airplane to comply with the
inspection and repair or replacement requirements of this proposed AD.
The proposed reporting requirement would take about 1 work-hour. The
average labor rate is $85 per work-hour. Required parts would cost
about $31,415 per airplane.
Based on these figures, the FAA estimates the cost of the proposed
AD on U.S. operators would be $1,334,580 or $34,220 per airplane.
The FAA has included all known costs in its cost estimate.
According to the manufacturer, however, some of the costs of this
proposed AD may be covered under warranty, thereby reducing the cost
impact on affected operators.

Paperwork Reduction Act

A federal agency may not conduct or sponsor, and a person is not
required to respond to, nor shall a person be subject to a penalty for
failure to comply with a collection of information subject to the
requirements of the Paperwork Reduction Act unless that collection of
information displays a current valid OMB Control Number. The OMB
Control Number for this information collection is 2120-0056. Public
reporting for this collection of information is estimated to take
approximately 1 hour per response, including the time for reviewing
instructions, searching existing data sources, gathering and
maintaining the data needed, and completing and reviewing the
collection of information. All responses to this collection of
information are mandatory. Send comments regarding this burden estimate
or any other aspect of this collection of information, including
suggestions for reducing this burden, to: Information Collection
Clearance Officer, Federal Aviation Administration, 10101 Hillwood
Parkway, Fort Worth, TX 76177-1524.

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) Would not affect intrastate aviation in Alaska, and
(3) Would 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: