Document ID: FAA-2008-1267-0001
Agency: faa
Document Type: Rule
Title: Airworthiness Directives; Viking Air Limited Models DHC-6-1, DHC- 6-100, DHC-6-200, and DHC-6-300 Airplanes
Posted Date: 2008-12-03T05:00Z

[Federal Register: December 3, 2008 (Volume 73, Number 233)]
[Proposed Rules]               
[Page 73618-73620]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr03de08-14]                         

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2008-1267; Directorate Identifier 2008-CE-069-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 that would supersede an existing AD. 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 January 2, 2009.

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.
     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

[[Page 73619]]

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, ANE-171, 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-2008-1267; 
Directorate Identifier 2008-CE-069-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

    On May 15, 2008, we issued AD 2008-11-10, Amendment 39-15532 (73 FR 
37353; July 1, 2008). That AD required actions intended to address an 
unsafe condition on the products listed above.
    Since we issued AD 2008-11-10, a complete list of affected part 
numbers has been issued.

Relevant Service Information

    Viking Air Limited has issued 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. 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

    We estimate that this AD will affect 157 products of U.S. registry. 
We also estimate that it will take about 18 work-hours per product to 
comply with the basic requirements of this AD. The average labor rate 
is $80 per work-hour.
    Based on these figures, we estimate the cost of this AD on U.S. 
operators to be $226,080 or $1,440 per product.
    In addition, we estimate that any necessary follow-on actions will 
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 this proposed AD and placed it in the AD docket.

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 removing Amendment 39-15532 (73 FR 
37353; July 1, 2008), and adding the following new AD:

Viking Air Limited: Docket No. FAA-2008-1267; Directorate Identifier 
2008-CE-069-AD.

Comments Due Date

    (a) We must receive comments by January 2, 2009.

Affected ADs

    (b) This AD supersedes AD 2008-11-10, Amendment 39-15532 (73 FR 
37353; July 1, 2008).

[[Page 73620]]

Applicability

    (c) This AD applies to the following Models DHC-6-1, DHC-6-100, 
DHC-6-200, and DHC-6-300 airplanes, all serial numbers, that are 
certificated in any category:
    (1) Group 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) Group 2: Equipped with wing boxes, P/Ns C6W1002-5, C6W1002-
7, C6W1002-9, C6W1002-11, C6W1002-13, C6W1002-15, C6W1002-17, 
C6W1002-19, C6W1002-21, C6W1002-23, C6W1002-51, C6W1002-53, C6W1002-
55, C6W1002-57 and C6W1002-61 that incorporate a P/N C6WM1027-1 
front spar adapter assembly with 10 or more years of service.

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) For Group 1 airplanes, within the next 180 days after August 
5, 2008 (the effective date of AD 2008-11-10), 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) For Group 2 airplanes, within the next 180 days after the 
effective date of this AD, install inspection holes in the LH and RH 
lower wing skins following Viking DHC-6 Twin Otter Service Bulletin 
Number V6/541, dated October 1, 2007.
    (3) For Group 1 and Group 2 airplanes, before further flight 
after installing the inspection holes required in paragraph (f)(1) 
or (f)(2) of this AD, initially inspect the LH and RH front spar 
adapter assemblies for cracks, and repetitively thereafter inspect 
all affected wing box P/Ns at intervals not to exceed 1,200 hours 
time-in-service or 12 months, whichever occurs first, until the 
replacement required in paragraph (f)(4) of this AD is done.
    (i) For wing box P/Ns C6W1002-1, C6W1002-3, C6W1002-5, C6W1002-
7, C6W1002-9, C6W1002-11, C6W1002-13, C6W1002-15, C6W1002-17, 
C6W1002-19, C6W1002-21, C6W1002-23, C6W1002-51, C6W1002-53, C6W1002-
55, C6W1002-57, C6W1002-59, and C6W1002-61, inspect following Viking 
DHC-6 Twin Otter Service Bulletin Number V6/540, dated October 1, 
2007.
    (ii) For wing box P/Ns WR6-1002-59 or WR6-1002-61, inspect 
following R.W. Martin, Inc. Service Bulletin No. 00160/2, Revision 
A, dated November 15, 2007.
    (4) For Group 1 and 2 airplanes, before further flight after 
doing any inspection required in paragraph (f)(3) 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)(3) of this AD 
for the replaced front spar adapter assembly.
    (5) As a terminating action for the repetitive inspections 
required in paragraph (f)(3) of this AD, at any time after the 
initial inspection required in paragraph (f)(3) of this AD, you may 
replace P/N C6WM1027-1 with P/N C6WM1027-3, except it must be 
replaced prior to further flight as required by paragraph (f)(4) of 
this AD.

FAA AD Differences

    Note: This AD differs from the MCAI and/or service information 
as follows: MCAI Transport Canada AD No. CF-2007-31, dated December 
17, 2007, is applicable to airplane models with front spar adapter 
assembly P/N C6WM1027-3 that incorporate task C57-10-18 of the DHC-6 
Corrosion Prevention and Control Manual (CPCM), PSM 1-6-5. The 
applicability of this proposed AD does not include airplane models 
with front spar adapter assembly P/N C6WM1027-3 that incorporate 
task C57-10-18 of the DHC-6 CPCM, PSM 1-6-5, which is required in 
the Transport Canada ADs No. CF-94-12R1, dated April 13, 1999, and 
AD No. CF-99-11, dated May 28, 1999. We have addressed the Corrosion 
Prevention and Control Program in AD 2008-13-11 (73 FR 37355, July 
1, 2008), which 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, ANE-171, 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 November 26, 2008.
Kim Smith,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. E8-28645 Filed 12-2-08; 8:45 am]

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