
[Federal Register: March 31, 2008 (Volume 73, Number 62)]
[Proposed Rules]
[Page 16782-16784]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr31mr08-23]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-0368; Directorate Identifier 2008-CE-007-AD]
RIN 2120-AA64


Airworthiness Directives; Viking Air Limited Models DHC-6-1, DHC-
6-100, DHC-6-200, and DHC-6-300 Airplanes

AGENCY: Federal Aviation Administration (FAA), Department of
Transportation (DOT).

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: We propose to adopt a new airworthiness directive (AD) for the
products listed above. 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 describes the unsafe
condition as:

    There have been reports of inter-rivet cracking on several wing
front spar adapter assemblies (P/N C6WM1027-1) on the horizontal and
vertical flanges. It was determined that the cracking was caused by
stress corrosion in the short transverse grain initiated by local
riveting induced stresses.

The proposed AD would require actions that are intended to address the
unsafe condition described in the MCAI.

DATES: We must receive comments on this proposed AD by April 30, 2008.

ADDRESSES: You may send comments by any of the following methods:
     Federal eRulemaking Portal: Go to http://
www.regulations.gov. Follow the instructions for submitting comments.

[[Page 16783]]

     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: U.S. Department of Transportation, Docket
Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New
Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m.,
Monday through Friday, except Federal holidays.

Examining the AD Docket

    You may examine the AD docket on the Internet at http://
www.regulations.gov; or in person at the Docket Management Facility
between 9 a.m. and 5 p.m., Monday through Friday, except Federal
holidays. The AD docket contains this proposed AD, the regulatory
evaluation, any comments received, and other information. The street
address for the Docket Office (telephone (800) 647-5527) is in the
ADDRESSES section. Comments will be available in the AD docket shortly
after receipt.

FOR FURTHER INFORMATION CONTACT: Pong Lee, Aerospace Engineer, FAA, New
York Aircraft Certification Office, 1600 Stewart Avenue, Suite 410,
Westbury, New York 11590; telephone: (516) 228-7324; fax: (516) 794-
5531.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to send any written relevant data, views, or
arguments about this proposed AD. Send your comments to an address
listed under the ADDRESSES section. Include ``Docket No. FAA-2008-0368;
Directorate Identifier 2008-CE-007-AD'' at the beginning of your
comments. We specifically invite comments on the overall regulatory,
economic, environmental, and energy aspects of this proposed AD. We
will consider all comments received by the closing date and may amend
this proposed AD because of those comments.
    We will post all comments we receive, without change, to http://
www.regulations.gov, including any personal information you provide. We
will also post a report summarizing each substantive verbal contact we
receive about this proposed AD.

Discussion

    Transport Canada, which is the aviation authority for Canada, has
issued AD No. CF-2007-31, dated December 17, 2007 (referred to after
this as ``the MCAI''), to correct an unsafe condition for the specified
products. The MCAI states:

    There have been reports of inter-rivet cracking on several wing
front spar adapter assemblies (P/N C6WM1027-1) on the horizontal and
vertical flanges. It was determined that the cracking was caused by
stress corrosion in the short transverse grain initiated by local
riveting induced stresses. This directive mandates modification and
inspection of the wing front spar adapter fitting and replacement of
cracked fittings.

    You may obtain further information by examining the MCAI in the AD
docket.

Relevant Service Information

    Viking Air Limited has issued the following DHC-6 Twin Otter
Service Bulletins:
     No. V6/540, dated October 1, 2007;
     No. V6/541, dated October 1, 2007; and
     No. V6/542, dated October 1, 2007.
    R.W. Martin, Inc. has issued Service Bulletin No. 00160/2, Revision
A, dated November 15, 2007.
    The actions described in this service information are intended to
correct the unsafe condition identified in the MCAI.

FAA's Determination and Requirements of the Proposed AD

    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, they
have notified us of the unsafe condition described in the MCAI and
service information referenced above. We are proposing this AD because
we evaluated all information and determined the unsafe condition exists
and is likely to exist or develop on other products of the same type
design.

Differences Between This Proposed AD and the MCAI or Service
Information

    We have reviewed the MCAI and related service information and, in
general, agree with their substance. But we might have found it
necessary to use different words from those in the MCAI to ensure the
AD is clear for U.S. operators and is enforceable. In making these
changes, we do not intend to differ substantively from the information
provided in the MCAI and related service information.
    We might also have proposed different actions in this AD from those
in the MCAI in order to follow FAA policies. Any such differences are
highlighted in a NOTE within the proposed AD.

Costs of Compliance

    Based on the service information, we estimate that this proposed AD
would affect about 157 products of U.S. registry. We also estimate that
it would take about 18 work-hours per product to comply with the basic
requirements of this proposed AD. The average labor rate is $80 per
work-hour.
    Based on these figures, we estimate the cost of the proposed AD on
U.S. operators to be $226,080 or $1,440 per product.
    In addition, we estimate that any necessary follow-on actions would
take about 200 work-hours and require parts costing $3,696 for a cost
of $19,696 per product. We have no way of determining the number of
products that may need these actions.

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.
    We are 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

    We 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. Is not a ``significant rule'' under the DOT Regulatory Policies
and Procedures (44 FR 11034, February 26, 1979); 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.
    We prepared a regulatory evaluation of the estimated costs to
comply with

[[Page 16784]]

this proposed AD and placed it in the AD docket.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, 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 AD:

Viking Air Limited: Docket No. FAA-2008-0368; Directorate Identifier
2008-CE-007-AD.

Comments Due Date

    (a) We must receive comments by April 30, 2008.

Affected ADs

    (b) None.

Applicability

    (c) This AD applies to Models DHC-6-1, DHC-6-100, DHC-6-200, and
DHC-6-300 airplanes, all serial numbers, that are:
    (1) Equipped with wing boxes, part numbers (P/Ns) C6W1002-1,
C6W1002-3, WR6-1002-59, or WR6-1002-61, that incorporate a P/N
C6WM1027-1 front spar adapter assembly with 10 or more years of
service; and
    (2) Certificated in any category.

Subject

    (d) Air Transport Association of America (ATA) Code 57: Wings.

Reason

    (e) The mandatory continuing airworthiness information (MCAI)
states:

    There have been reports of inter-rivet cracking on several wing
front spar adapter assemblies (P/N C6WM1027-1) on the horizontal and
vertical flanges. It was determined that the cracking was caused by
stress corrosion in the short transverse grain initiated by local
riveting induced stresses. This directive mandates modification and
inspection of the wing front spar adapter fitting and replacement of
cracked fittings.

Actions and Compliance

    (f) Unless already done, do the following actions:
    (1) Within the next 180 days after the effective date of this
AD, install inspection holes in the left-hand (LH) and right-hand
(RH) lower wing skins following Viking DHC-6 Twin Otter Service
Bulletin Number V6/541, dated October 1, 2007.
    (2) Before further flight after installing the inspection holes
required in paragraph (f)(1) of this AD, inspect the LH and RH front
spar adapter assemblies for cracks. For wing box P/Ns C6W1002-1 and
C6W1002-3, inspect following Viking DHC-6 Twin Otter Service
Bulletin Number V6/540, dated October 1, 2007. For wing box P/Ns
WR6-1002-59 and WR6-1002-61, inspect following R.W. Martin, Inc.
Service Bulletin No. 00160/2, Revision A, dated November 15, 2007.
Repetitively inspect all affected wing box P/Ns thereafter at
intervals not to exceed 1,200 hours time-in-service or 12 months,
whichever occurs first, until the replacement required in paragraph
(f)(3) of this AD is done.
    (3) Before further flight after doing any inspection required in
paragraph (f)(2) of this AD where cracks are found, replace the
cracked front spar adapter assembly with a front spar adapter
assembly, P/N C6WM1027-3. Do the replacement following Viking DHC-6
Twin Otter Service Bulletin Number V6/542, dated October 1, 2007.
This replacement terminates the repetitive inspections required in
paragraph (f)(2) of this AD for the replaced front spar adapter
assembly.
    (4) As a terminating action for the repetitive inspections
required in paragraph (f)(2) of this AD, at any time after the
initial inspection required in paragraph (f)(2) of this AD, you may
replace P/N C6WM1027-1 with P/N C6WM1027-3.

FAA AD Differences

    Note: This AD differs from the MCAI and/or service information
as follows: (1) MCAI Transport Canada AD No. CF-2007-31, dated
December 17, 2007, requires incorporating task C57-10-18 of the DHC-
6 Corrosion Prevention and Control Manual (CPCM), PSM 1-6-5, within
90 days after the effective date of this AD.
    (2) We are not incorporating task C57-10-18 of the DHC-6 CPCM,
PSM 1-6-5, into this AD because we are currently examining Transport
Canada AD No. CF-94-12R1, dated April 13, 1999; and AD No. CF-99-11,
dated May 28, 1999. Transport Canada issued these ADs to incorporate
a Corrosion Prevention and Control Program that identifies specific
areas that must be inspected to ensure the structural integrity of
the DHC-6 fleet.

Other FAA AD Provisions

    (g) The following provisions also apply to this AD:
    (1) Alternative Methods of Compliance (AMOCs): The Manager, New
York Aircraft Certification Office, FAA, has the authority to
approve AMOCs for this AD, if requested using the procedures found
in 14 CFR 39.19. Send information to ATTN: Pong Lee, Aerospace
Engineer, FAA, New York Aircraft Certification Office,1600 Stewart
Avenue, Suite 410, Westbury, New York 11590; telephone: (516) 228-
7324; fax: (516) 794-5531. Before using any approved AMOC on any
airplane to which the AMOC applies, notify your appropriate
principal inspector (PI) in the FAA Flight Standards District Office
(FSDO), or lacking a PI, your local FSDO.
    (2) Airworthy Product: For any requirement in this AD to obtain
corrective actions from a manufacturer or other source, use these
actions if they are FAA-approved. Corrective actions are considered
FAA-approved if they are approved by the State of Design Authority
(or their delegated agent). You are required to assure the product
is airworthy before it is returned to service.
    (3) Reporting Requirements: For any reporting requirement in
this AD, under the provisions of the Paperwork Reduction Act (44
U.S.C. 3501 et seq.), the Office of Management and Budget (OMB) has
approved the information collection requirements and has assigned
OMB Control Number 2120-0056.

Related Information

    (h) Refer to MCAI Transport Canada AD No. CF-2007-31, dated
December 17, 2007; Viking DHC-6 Twin Otter Service Bulletins No. V6/
540, dated October 1, 2007; No. V6/541, dated October 1, 2007; and
No. V6/542, dated October 1, 2007; and R.W. Martin, Inc. Service
Bulletin No. 00160/2, Revision A, dated November 15, 2007, for
related information.

    Issued in Kansas City, Missouri, on March 8, 2008.
David R. Showers,
Acting Manager, Small Airplane Directorate, Aircraft Certification
Service.
 [FR Doc. E8-6469 Filed 3-28-08; 8:45 am]

BILLING CODE 4910-13-P
