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PROPOSED AD VIKING AIR LIMITED: Docket No. FAA-2021-0214; Project Identifier 2018-CE-064-AD.
(a) COMMENTS DUE DATE

    The FAA must receive comments on this airworthiness directive (AD)  by
    August 12, 2021.

(b) AFFECTED ADS

    None.

(c) APPLICABILITY

    This  AD  applies  to  Viking Air Limited Model DHC-3  airplanes,  all
    serial numbers, certificated in any category.

(d) SUBJECT

    Joint Aircraft System Component (JASC) Code 5700, Wings.

(e) UNSAFE CONDITION

    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  fatigue damage  of the  wing
    strut lug fitting components or the fuselage to wing strut  attachment
    (tie-bar).  The  FAA  is  issuing  this  AD  to  identify  and correct
    potential fatigue damage of the  wing strut lug fitting components  of
    the fuselage to  wing strut attachment.  The unsafe condition,  if not
    addressed,  could result  in cracking  and failure  of the  structural
    integrity of the wing or the tie-bar.

(f) ACTIONS AND COMPLIANCE

    Unless already  done, do  the following  actions in  paragraphs (f)(1)
    through (3):

(1) For  all  airplanes:  Within 3 months after the effective date of this
    AD, determine and  record the number  of equivalent air  time hours on
    each  wing and  tie-bar by  doubling the  total hours  time-in-service
    (TIS) accumulated on each part. If the total hours TIS of a tie-bar is
    unknown or cannot be determined, use  the total hours TIS of the  wing
    strut lug fitting on the main spar.

(2) For airplanes  with a maximum certificated gross weight that has never
    exceeded 8,000 pounds:  Remove from service  each left and  right hand
    wing  strut  fitting  and  tie-bar  by  following  the  Accomplishment
    Instructions  in Viking  Air Limited  SB V3/0008,  Revision NC,  dated
    February 9, 2017,  and the Replacement  section of the  Accomplishment
    instructions in De  Havilland Aircraft of  Canada DHC-3 Otter  Service
    Bulletin Number 3/37, Revision B, dated October 8, 1982, at  whichever
    of the following compliance time that occurs later:

(i) Before the part accumulates 40,000 equivalent air time hours, or

(ii) Within 12 months after the effective date of this AD.

(3) For airplanes  with a maximum certificated gross weight  that has ever
    exceeded 8,000 pounds:  Remove from service  each left and  right hand
    wing  strut  fitting  and  tie-bar  by  following  the  Accomplishment
    Instructions  in Viking  Air Limited  SB V3/0008,  Revision NC,  dated
    February 9, 2017,  and the Replacement  section of the  Accomplishment
    instructions in De  Havilland Aircraft of  Canada DHC-3 Otter  Service
    Bulletin Number 3/37, Revision B, dated October 8, 1982, at  whichever
    of the following compliance time that occurs later:

(i) Before the part accumulates 32,200 equivalent air time hours, or

(ii) Within 12 months after the effective date of this AD.

(g) ALTERNATIVE METHODS OF COMPLIANCE (AMOCS)

(1) The Manager,  New York ACO Branch,  FAA,  has the authority to approve
    AMOCs for this AD, if requested  using the procedures found in 14  CFR
    39.19. In  accordance with  14 CFR  39.19, send  your request  to your
    principal  inspector  or  local Flight  Standards District  Office, as
    appropriate. If sending information directly to the manager of the ACO
    Branch, send it to the attention of the person identified in paragraph
    (h)(1) of this AD.

(2) Before using any approved AMOC,  notify your appropriate principal in-
    spector, or lacking  a principal inspector,  the manager of  the local
    flight standards district office/certificate holding district office.

(h) RELATED INFORMATION

(1) For more information about this AD, contact Aziz Ahmed, Aviation Safe-
    ty 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.

(2) Refer to Transport Canada AD Number CF-2017-29, dated August 24, 2017,
    for more information.  You may examine  the Transport Canada AD in the
    AD docket at https://www.regulations.gov by searching for and locating
    it in Docket No. FAA-2021-0214.

(3) For service information  identified  in  this  AD,  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 serv-
    ice 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.

Issued on June 21, 2021.  Lance T. Gant, Director, Compliance & Airworthi-
ness Division, Aircraft Certification Service.

DATES: The FAA must receive comments  on  this  proposed AD  by August 12,
2021.
PREAMBLE 

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2021-0214; Project Identifier 2018-CE-064-AD]
RIN 2120-AA64

Airworthiness Directives; Viking Aircraft Limited Airplanes

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Notice of proposed rulemaking (NPRM).

-----------------------------------------------------------------------

SUMMARY: The FAA proposes to adopt a new airworthiness directive (AD)
for all Viking Air Limited Model DHC-3 airplanes. This proposed 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 identifies
the unsafe condition as fatigue damage of the wing strut lug fitting
components and the fuselage to wing strut attachment (tie-bar). This
proposed AD would 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
proposing this AD to address the unsafe condition on these products.

DATES: The FAA must receive comments on this proposed AD by August 12,
2021.

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
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.

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 NPRM, any comments
received, and other information. The street address for Docket
Operations is listed above.

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:

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-2021-0214; Project Identifier
2018-CE-064-AD" 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 Aziz
Ahmed, 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 AD Number 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-2020-0214.

Related Service Information Under 1 CFR Part 51


The FAA reviewed Viking Air Limited 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. De Havilland Aircraft of
Canada has issued DHC-3 Otter Service Bulletin Number 3/37, Revision B,
dated October 8, 1982. The service information specifies instructions
for removal and replacement of 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.

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
our 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 AD requires accomplishing the actions specified in the service
information already described.

Differences Between This Proposed 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 aircraft, this proposed
AD would require calculating the compliance time by assuming all
operations occurred below 2,000 feel AGL.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would
affect 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 the proposed
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

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: