Document ID: FAA-2006-23646-0035
Agency: faa
Document Type: Rule
Title: Airworthiness Directives; Air Tractor, Inc., Models AT-400, AT- 401, AT-401B, AT-402, AT-402A, and AT-402B Airplanes
Posted Date: 2008-12-10T05:00Z

[Federal Register: December 10, 2008 (Volume 73, Number 238)]
[Proposed Rules]               
[Page 74999-75007]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr10de08-16]                         

=======================================================================
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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2006-23646; Directorate Identifier 2006-CE-005-AD]
RIN 2120-AA64

 
Airworthiness Directives; Air Tractor, Inc., Models AT-400, AT-
401, AT-401B, AT-402, AT-402A, and AT-402B Airplanes

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

ACTION: Notice of proposed rulemaking (NPRM).

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

SUMMARY: We propose to revise Airworthiness Directive (AD) 2006-08-08, 
which applies to certain Air Tractor, Inc. (Air Tractor), Models AT-
400, AT-401, AT-401B, AT-402, AT-402A, and AT-402B airplanes. AD 2006-
08-08 currently requires you to repetitively eddy current inspect the 
wing lower spar cap in order to reach the safe life and, for certain 
Models AT-402A and AT-402B airplanes and those that incorporate or have 
incorporated Marburger Enterprises, Inc. (Marburger), winglets, lowers 
the safe life for the wing lower spar cap. Since we issued AD 2006-08-
08, we have received information to update inspection intervals for the 
Models AT-401B, AT-402A, and AT-402B airplanes based on a revised 
damage tolerance analysis. Consequently, this proposed AD would not 
only retain the actions of AD 2006-08-08, but would reduce the number 
of repetitive inspections for all affected Model AT-401B airplanes and 
certain Models AT-402A and AT-402B airplanes. We are proposing this AD 
to prevent fatigue cracks from occurring in the wing lower spar cap 
before the originally established safe life is reached. Fatigue cracks 
in the wing lower spar cap, if not detected and corrected, could result 
in wing separation and loss of control of the airplane.

DATES: We must receive comments on this proposed AD by February 9, 
2009.

ADDRESSES: Use one of the following addresses to comment on this 
proposed AD:
     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.
    For service information identified in this proposed AD, contact Air 
Tractor, Inc., P.O. Box 485, Olney, Texas 76374; telephone: (940) 564-
5616; facsimile: (940) 564-5612; Internet: http://www.airtractor.com; 
or Marburger Enterprises, Inc., 1227 Hillcourt, Williston, North Dakota 
58801; telephone: (800) 893-1420 or (701) 774-0230; facsimile: (701) 
572-2602.

FOR FURTHER INFORMATION CONTACT: Direct all questions to:
--For airplanes that do not incorporate and never have incorporated 
Marburger winglets: Rob Romero, Aerospace Engineer, FAA, Fort Worth 
Airplane Certification Office, 2601 Meacham Boulevard, Fort Worth, 
Texas 76193-0150; telephone: (817) 222-5102; facsimile: (817) 222-5960; 
and
--For airplanes that incorporate or have incorporated Marburger 
Enterprises, Inc., winglets: John Cecil, Aerospace Engineer, Los 
Angeles Aircraft Certification Office, FAA, 3960 Paramount Boulevard, 
Lakewood, California, 90712; telephone: (562) 627-5228; facsimile: 
(562) 627-5210.

SUPPLEMENTARY INFORMATION:

Comments Invited

    We invite you to send any written relevant data, views, or 
arguments regarding this proposed AD. Send your comments to an address 
listed under the ADDRESSES section. Include the docket number, ``FAA-
2006-23646; Directorate Identifier 2006-CE-005-AD'' at the beginning of 
your comments. We specifically invite comments on the overall 
regulatory, economic, environmental, and energy aspects of the proposed 
AD. We will consider all comments received by the closing date and may 
amend the proposed AD in light 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 concerning this proposed AD.

Discussion

    An Air Tractor Model AT-502A experienced an in-flight wing 
separation. As a result, the FAA issued AD 2000-14-51 as an emergency 
AD. That AD required the inspection of the wing lower spar cap for 
cracks on Air Tractor Models AT-501, AT-502, and AT-502A airplanes and 
modification or replacement of any cracked wing lower spar cap. Since 
the release of that AD, the manufacturer has evaluated the AT-400, AT-
500, AT-600, and AT-800 series lower spar cap fatigue life.
    AD 2006-08-08 currently requires you to repetitively eddy current 
inspect the wing lower spar cap for fatigue cracks in order to reach 
the safe life and, for certain Models AT-402A and AT-402B airplanes and 
those that incorporate or have incorporated Marburger winglets, lowers 
the safe life for the wing lower spar cap.
    Since we issued AD 2006-08-08, we have received updated inspection 
intervals for fatigue cracks for the Models AT-401B, AT-402A, and AT-
402B airplanes based on a revised damage tolerance analysis. Any 
occurrence of fatigue cracks in the wing lower spar cap, if not 
detected and corrected, could result in wing separation and loss of 
control of the airplane.
    The following table contains AD actions that address the wing spar 
safe life of the Air Tractor airplane fleet:

[[Page 75000]]

                                               Related AD Actions
----------------------------------------------------------------------------------------------------------------
                                          Affected Air Tractor Airplane
                 AD No.                               Model                             Issue date
----------------------------------------------------------------------------------------------------------------
2003-07-04.............................  AT-300, AT-400, AT-400A, AT-     March 25, 2003.
                                          401, AT-401B, AT-402, AT-402A,
                                          AT-402B, AT-501, AT-502, and
                                          AT-502B.
2006-08-08.............................  AT-400, AT-401, AT-401B, AT-     April 10, 2006.
                                          402, AT-402A, and AT-402B.
2006-08-09.............................  AT-802 and AT-802A.............  April 10, 2006.
2006-23-09.............................  AT-602.........................  October 26, 2006.
2006-24-10.............................  AT-501, AT-502, AT-502A, AT-     November 22, 2006.
                                          502B, and AT-503A.
2008-09-10.............................  AT-300, AT-301, AT-302, AT-400,  April 18, 2008.
                                          and AT-400A.
----------------------------------------------------------------------------------------------------------------

    You may view these Airworthiness Directives at the following 
Internet Web site addresses: http://rgl.faa.gov or http://
www.gpoaccess.gov/fr/index.html.

Relevant Service Information

    We have reviewed this Snow Engineering Co. service information:
     Process Specification 197, page 1, revised June 
4, 2002, pages 2 through 4, dated February 23, 2001, and page 5, dated 
May 3, 2002;
     Drawing Number 21088, dated November 3, 2004; and
     Service Letter 202, page 3, dated October 16, 
2000.
    Snow Engineering Co. has a licensing agreement with Air Tractor 
that allows them to produce technical data to use for Air Tractor 
products.
    The process specification and drawing include procedures for doing 
the eddy-current inspection and replacing the spar caps and associated 
hardware. The service letter provides information for installing access 
panels, if not already installed.

FAA's Determination and Requirements of the Proposed AD

    We are proposing this AD because we evaluated all information and 
determined the unsafe condition described previously is likely to exist 
or develop on other products of the same type design. This proposed AD 
would revise AD 2006-08-08 with a new AD that would not only retain the 
actions AD 2006-08-8, but would reduce the number of repetitive 
inspections for:
     All affected Model AT-401B airplanes;
     Model AT-402A airplanes, all serial numbers beginning with 
0952; and
     Model AT-402B airplanes, all serial numbers beginning with 
0966.
    This proposed AD would require you to use the service information 
described previously to perform these actions.

Costs of Compliance

    We estimate that this AD affects 343 airplanes in the U.S. 
registry.
    We estimate the following costs to do the inspection. We have no 
way of determining the number of airplanes that may need repair or 
modification as a result of any inspection:

----------------------------------------------------------------------------------------------------------------
                                                                                            Total cost on U.S.
              Labor cost                      Parts cost        Total cost per airplane         operators
----------------------------------------------------------------------------------------------------------------
* $500 to $800.......................  Not Applicable.........  $500 to $800...........  $171,500 to
                                                                                         $274,400.
----------------------------------------------------------------------------------------------------------------
* Eddy-current inspections are an estimated flat cost that includes labor and use of equipment.

    We estimate the following costs to do the modification. We have no 
way of determining the number of airplanes that may need this 
modification:

------------------------------------------------------------------------
                                                          Total cost per
               Labor cost                   Parts cost       airplane
------------------------------------------------------------------------
120 work-hours x $80 = $9,600...........         $11,500         $21,100
------------------------------------------------------------------------

    We estimate the following costs to do the replacement. We have no 
way of determining the number of airplanes that may need this 
replacement:

------------------------------------------------------------------------
                                                              Total cost
                  Labor cost                     Parts cost      per
                                                               airplane
------------------------------------------------------------------------
$16,500.......................................      $16,500     $33,000
------------------------------------------------------------------------
* The labor costs of the replacement are an estimated flat cost that
  includes labor and use of equipment.

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 have 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 that the 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

[[Page 75001]]

    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.

Examining the AD Docket

    You may examine the AD docket that contains the proposed AD, the 
regulatory evaluation, any comments received, and other information 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 Docket Office (telephone (800) 647-5527) 
is located at the street address stated in the ADDRESSES section. 
Comments will be available in the AD docket shortly after receipt.

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 Airworthiness Directive 
(AD) 2006-08-08, Amendment 39-14563 (71 FR 19986, April 19, 2006), and 
adding the following new AD:

Air Tractor, Inc.: Docket No. FAA-2006-23646; Directorate Identifier 
2006-CE-005-AD.

Comments Due Date

    (a) We must receive comments on this AD action by February 9, 
2009.

Affected ADs

    (b) This AD revises AD 2006-08-08, Amendment 39-14563.

Applicability

    (c) This AD applies to certain Models AT-400, AT-401, AT-401B, 
AT-402, AT-402A, and AT-402B airplanes that are certificated in any 
category. Use paragraph (c)(1) of this AD for affected airplanes 
that do not incorporate and never have incorporated Marburger 
winglets. Use paragraph (c)(3) of this AD for airplanes that have 
been modified to install lower spar caps, part number (P/N) 21058-1 
and P/N 21058-2. Use paragraph (c)(4) of this AD for certain Models 
AT-401, AT-401B, AT-402, AT-402A, and AT-402B airplanes that 
incorporate or have incorporated Marburger winglets.
    (1) The following table applies to airplanes that do not 
incorporate and never have incorporated Marburger winglets along 
with the safe life (presented in hours time-in-service (TIS)) of the 
wing lower spar cap for all affected airplane models and serial 
numbers:

 Table 1--Safe Life for Airplanes That Do Not Incorporate and Never Have
                     Incorporated Marburger Winglets
------------------------------------------------------------------------
                                                            Wing lower
                                                           spar cap safe
             Model                     Serial Nos.         life  (hours
                                                               TIS)
------------------------------------------------------------------------
AT-400.........................  All beginning with 0416          13,300
AT-401.........................  0662 through 0951......          10,757
AT-401B........................  0952 through 1020,                6,948
                                  except 1015.
AT-401B........................  1015 and all beginning            7,777
                                  with 1021.
AT-402.........................  0694 through 0951......           7,440
AT-402A........................  0738 through 0951......           7,440
AT-402A........................  0952 through 1020......           2,000
AT-402A........................  All beginning with 1021           2,300
AT-402B........................  0966 through 1020,                2,000
                                  except 1015.
AT-402B........................  1015 and all beginning            2,300
                                  with 1021.
------------------------------------------------------------------------

    (2) If piston-powered aircraft have been converted to turbine 
power, you must use the limits for the corresponding serial number 
turbine-powered aircraft.
    (3) If you have an aircraft that has been modified by installing 
lower spar caps, P/N 21058-1 and P/N 21058-2, you must use a wing 
lower spar cap safe life of 9,800 hours TIS. No inspections are 
required to reach this life.
    (i) Airplanes that have been modified with replacement spar 
caps, P/N 21058-1 and P/N 21058-2, are not eligible to have 
Supplemental Type Certificate (STC) No. SA00490LA, Marburger 
winglets, installed.
    (ii) If your airplane currently has spar caps, P/N 21058-1 and 
P/N 21058-2, and winglets installed, then you must remove the 
winglets before further flight and you must contact the FAA at the 
address in paragraph (m)(1) of this AD for a new safe life.
    (iii) Installation of Marburger winglets on airplanes that have 
been modified with replacement spar caps, P/N 21058-1 and P/N 21058-
2, will require additional fatigue data substantiating an 
appropriate safe-life. If you have replacement spar caps and wish to 
install winglets, you must contact the FAA at the address in 
paragraph (m)(2) of this AD for additional information.
    (4) The following table applies to airplanes that incorporate or 
have incorporated Marburger winglets. These winglets are installed 
following STC No. SA00490LA. Use the winglet usage factor in Table 2 
of paragraph (c)(4) of this AD, the wing lower spar cap safe life 
specified in Table 1 of paragraph (c)(1) of this AD, and the 
instructions included in Appendix 1 to this AD to determine the new 
safe life of airplanes that incorporate or have incorporated 
Marburger winglets:

[[Page 75002]]

 Table 2--Winglet Usage Factor To Determine the Safe Life for Airplanes
  That Incorporate or Have Incorporated Marburger Winglets per STC No.
                                SA00490LA
------------------------------------------------------------------------
                                                               Winglet
              Model                       Serial Nos.           usage
                                                                factor
------------------------------------------------------------------------
AT-401...........................  0662 through 0951.......          1.6
AT-401B..........................  0952 through 1020,                1.1
                                    except 1015.
AT-401B..........................  1015 and all beginning            1.1
                                    with 1021.
AT-402...........................  0694 through 0951.......          1.6
AT-402A..........................  0738 through 0951.......          1.6
AT-402A..........................  0952 through 1020.......          1.1
AT-402A..........................  All beginning with 1021.          1.1
AT-402B..........................  0966 through 1020,                1.1
                                    except 1015.
AT-402B..........................  1015 and all beginning            1.1
                                    with 1021.
------------------------------------------------------------------------

Unsafe Condition

    (d) This AD is the result of fatigue cracking of the wing main 
spar lower cap at the center splice joint outboard fastener hole. 
The actions specified in this AD are intended to detect and correct 
cracks in the wing main spar lower cap, which could result in 
failure of the spar cap and lead to wing separation and loss of 
control of the airplane.

Compliance

    (e) Safe Life Record: For all affected airplanes, modify the 
applicable aircraft records (logbook) as follows to show the safe 
life for the wing lower spar cap listed in this AD (use the 
information from paragraph (c) of this AD and Appendix 1 to this AD, 
as applicable).
    (1) Incorporate the following into the aircraft logbook: 
``Following this AD, the wing lower spar cap is life limited to ---- 
hours time-in-service (TIS).'' Insert the applicable safe life 
number from the applicable tables in paragraph (c) of this AD and 
Appendix 1 to this AD.
    (i) Do the logbook entry within the next 10 hours TIS after 
April 21, 2006 (the effective date of AD 2006-08-08).
    (ii) A person holding at least a private pilot certificate as 
authorized by section 43.7 of the Federal Aviation Regulations (14 
CFR 43.7) may modify the aircraft records. Make an entry into the 
aircraft logbook showing compliance with this portion of the AD in 
accordance with section 43.9 of the Federal Aviation Regulations (14 
CFR 43.9)..
    (2) Wing Spar Replacement: For all affected airplanes, replace 
the wing lower spar cap following Snow Engineering Drawing Number 
21088, dated November 3, 2004. Replace upon accumulating the safe 
life used in paragraph (e)(1) of this AD or within the next 50 hours 
TIS after April 21, 2006 (the effective date of AD 2006-08-08), 
whichever occurs later. The owner/operator may not do the spar cap 
replacement, unless he/she is a properly certified mechanic.
    (f) Inspection Requirements: For all affected airplanes, except 
Model AT-402A, all serial numbers beginning with 0952, and Model AT-
402B, all serial numbers beginning with 0966, do the initial 
inspection of the outboard two lower spar cap bolt holes using the 
wing spar lower cap TIS schedules listed in Table 3. Follow Snow 
Engineering Co. Process Specification 197, page 1, revised 
June 4, 2002, pages 2 through 4, dated February 23, 2001, and page 
5, dated May 3, 2002. After the initial inspection, perform 
repetitive inspections at the repetitive inspection intervals listed 
in Table 3. Use the same procedure for the repetitive inspections as 
for the initial inspection. If not already done, install access 
panels at the time of the first inspection following Snow 
Engineering Service Letter 202, page 3, dated October 16, 
2000.

    Note: Hours listed in the table are in hours TIS and the phrase 
``within the next ---- hours'' refers to ``within the next ---- 
hours after April 21, 2006 (the effective date of AD 2006-08-08).''

                                            Table 3--Inspection Times
----------------------------------------------------------------------------------------------------------------
                                                                                                      Repetitive
                                                           Current wing spar                          inspection
              Model                    Serial Nos.        lower cap TIS hours   Initial inspection     interval
                                                                                                       (hours)
----------------------------------------------------------------------------------------------------------------
AT-400..........................  All beginning with     Greater than 7,750..  Within the next 50            900
                                   0416.                                        hours TIS or upon
                                                                                the accumulation of
                                                                                8,000 hours TIS,
                                                                                whichever is later.
AT-401..........................  0662-0951............  Greater than 6,250..  Within the next 50            700
                                                                                hours TIS or upon
                                                                                the accumulation of
                                                                                6,500 hours TIS,
                                                                                whichever is later.
AT-401..........................  0662-0951............  Greater than 4,350    Within the next 250           700
                                                          but less than or      hours TIS or upon
                                                          equal to 6,250.       the accumulation of
                                                                                4,850 hours TIS,
                                                                                whichever is later.
AT-401..........................  0662-0951............  Greater than 2,750    Within the next 500           700
                                                          but less than or      hours TIS.
                                                          equal to 4,350.
AT-401..........................  0662-0951............  Less than or equal    Upon the                      700
                                                          to 2,750.             accumulation of
                                                                                3,250 hours TIS.
AT-401B.........................  0952-1020 except 1015  Greater than 3,950..  Within the next 50            600
                                                                                hours TIS or upon
                                                                                the accumulation of
                                                                                4,200 hours TIS,
                                                                                whichever is later.
AT-401B.........................  0952-1020 except 1015  Greater than 2,650    Within the next 250           600
                                                          but less than or      hours TIS or upon
                                                          equal to 3,950.       the accumulation of
                                                                                3,150 hours TIS,
                                                                                whichever is later.
AT-401B.........................  0952-1020 except 1015  Greater than 1,600    Within the next 500           600
                                                          but less than or      hours TIS.
                                                          equal to 2,650.
AT-401B.........................  0952-1020 except 1015  Less than or equal    Upon the                      600
                                                          to 1,600.             accumulation of
                                                                                2,100 hours TIS.

[[Page 75003]]

AT-401B.........................  1015 and 1021-1124...  Greater than 4,450..  Within the next 50            600
                                                                                hours TIS or upon
                                                                                the accumulation of
                                                                                4,700 hours TIS,
                                                                                whichever is later.
AT-401B.........................  1015 and 1021-1124...  Greater than 3,000    Within the next 250           600
                                                          but less than or      hours TIS or upon
                                                          equal to 4,450.       the accumulation of
                                                                                3,500 hours TIS,
                                                                                whichever is later.
AT-401B.........................  1015 and 1021-1124...  Greater than 1,850    Within the next 500           600
                                                          but less than or      hours TIS.
                                                          equal to 3,000.
AT-401B.........................  1015 and 1021-1124...  Less than or equal    Upon the                      600
                                                          to 1,850.             accumulation of
                                                                                2,350 hours TIS.
AT-401B.........................  All beginning with     Greater than 4,450..  Within the next 50          1,000
                                   1125.                                        hours TIS or upon
                                                                                the accumulation of
                                                                                4,700 hours TIS,
                                                                                whichever is later.
AT-401B.........................  All beginning with     Greater than 3,000    Within the next 250         1,000
                                   1125.                  but less than or      hours TIS or upon
                                                          equal to 4,450.       the accumulation of
                                                                                3,500 hours TIS,
                                                                                whichever is later.
AT-401B.........................  All beginning with     Greater than 1,850    Within the next 500         1,000
                                   1125.                  but less than or      hours TIS.
                                                          equal to 3,000.
AT-401B.........................  All beginning with     Less than or equal    Upon the                    1,000
                                   1125.                  to 1,850.             accumulation of
                                                                                2,350 hours TIS.
AT-402/AT-402A..................  0694-0951............  Greater than 4,250..  Within the next 50            700
                                                                                hours TIS or upon
                                                                                the accumulation of
                                                                                4,500, whichever is
                                                                                later.
AT-402/AT-402A..................  0694-0951............  Greater than 2,850    Within the next 250           700
                                                          but less than or      hours TIS or upon
                                                          equal to 4,250.       the accumulation of
                                                                                3,350 hours TIS,
                                                                                whichever is later.
AT-402/AT-402A..................  0694-0951............  Greater than 1,750    Within the next 500           700
                                                          but less than or      hours TIS.
                                                          equal to 2,850.
AT-402/AT-402A..................  0694-0951............  Less than or equal    Upon the                      700
                                                          to 1,750.             accumulation of
                                                                                2,250 hours TIS.
----------------------------------------------------------------------------------------------------------------

    (g) For all affected airplanes: Before further flight after the 
inspection in which cracks are found, replace any cracked wing lower 
spar cap following Snow Engineering Drawing Number 21088, dated 
November 3, 2004.
    (h) For all affected airplanes, except Model AT-402A, all serial 
numbers beginning with 0952, and except Model AT-402B, all serial 
numbers beginning with 0966: Report to the FAA any cracks detected 
as the result of each inspection required by paragraph (f) of this 
AD on the form in Figure 1 of this AD.
    (1) Only if cracks are found, send the report within 10 days 
after the inspection required in paragraph (f) of this AD.
    (2) The Office of Management and Budget (OMB) approved the 
information collection requirements contained in this regulation 
under the provisions of the Paperwork Reduction Act and assigned OMB 
Control Number 2120-0056.
    (i) For all affected airplanes: Upon the accumulation of the 
life used in paragraph (e)(1) of this AD or within the next 50 hours 
TIS after April 21, 2006 (the effective date of AD 2006-08-08), 
whichever occurs later, you must replace your wing lower spar cap 
before further flight following Snow Engineering Drawing Number 
21088, dated November 3, 2004.
    (j) For Model AT-402A airplanes, all serial numbers beginning 
with 0952; and Model AT-402B airplanes, all serial numbers beginning 
with 0966: In lieu of the safe life used in paragraph (e)(1) of this 
AD, you may eddy-current inspect and modify the wing lower spar cap. 
The inspection schedule and modification procedures are included in 
Appendix 2 to this AD.
    (k) For all affected airplanes (those complying with the actions 
in the AD or alternative method of compliance (AMOC)): One of the 
following must do the inspection:
    (1) A level 2 or 3 inspector certified in eddy current 
inspection using the guidelines established by the American Society 
for Nondestructive Testing or MIL-STD-410; or
    (2) A person authorized to perform AD work and who has completed 
and passed the Air Tractor, Inc. training course on Eddy Current 
Inspection on wing lower spar caps.
BILLING CODE 4910-13-P

[[Page 75004]]

[GRAPHIC] [TIFF OMITTED] TP10DE08.002

BILLING CODE 4910-13-C
    Mail report to: Manager, Fort Worth ACO, ASW-150, 2601 Meacham 
Blvd., Fort Worth, TX 76193-0150; or fax to (817) 222-5960.

Special Flight Permit

    (l) Under 14 CFR part 39.23, we are allowing special flight 
permits for the purpose of compliance with this AD under the 
following conditions:
    (1) Only operate in day visual flight rules (VFR).
    (2) Ensure that the hopper is empty.
    (3) Limit airspeed to 135 miles per hour (mph) indicated 
airspeed (IAS).
    (4) Avoid any unnecessary g-forces.
    (5) Avoid areas of turbulence.
    (6) Plan the flight to follow the most direct route.

Alternative Methods of Compliance (AMOCs)

    (m) The Manager, Fort Worth or Los Angeles Airplane 
Certification Office (ACO), FAA, has the authority to approve AMOCs 
for this AD, if requested using the procedures found in 14 CFR 
39.19. 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. For AMOC approval, send information to ATTN:
    (1) For the airplanes that do not incorporate and never have 
incorporated Marburger winglets: Rob Romero, Aerospace Engineer, 
FAA, Fort Worth Airplane Certification Office, 2601 Meacham 
Boulevard, Fort Worth, Texas 76193-0150; telephone: (817) 222-5102; 
facsimile: (817) 222-5960.

[[Page 75005]]

    (2) For airplanes that incorporate or have incorporated 
Marburger winglets: John Cecil, Aerospace Engineer, Los Angeles 
Aircraft Certification Office, FAA, 3960 Paramount Boulevard, 
Lakewood, California 90712; telephone: (562) 627-5228; facsimile: 
(562) 627-5210.
    (n) AMOCs approved for AD 2001-10-04, AD 2001-10-04 R1, or AD 
2002-11-05 for the AT-400 series airplanes are not considered 
approved for this AD.
    (o) AMOCs approved for the repetitive inspection requirements of 
AD 2006-08-08 are approved for this AD until the scheduled 
modification date required by this AD.

Related Information

    (p) To get copies of the service information referenced in this 
AD, contact Air Tractor, Incorporated, P.O. Box 485, Olney, Texas 
76374; telephone: (940) 564-5616; facsimile: (940) 564-5612; 
Internet: http://www.airtractor.com; or Marburger Enterprises, Inc., 
1227 Hillcourt, Williston, North Dakota 58801; telephone: (800) 893-
1420 or (701) 774-0230; facsimile: (701) 572-2602. To view the AD 
docket, go to U.S. Department of Transportation, Docket Operations, 
M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey 
Avenue, SE., Washington, DC 20590, or on the Internet at http://
www.regulations.gov.

Appendix 1 to Docket No. FAA-2006-23646

    The following provides procedures for determining the safe life 
for those Models AT-401, AT-401B, AT-402, AT-402A, and AT-402B 
airplanes that incorporate or have incorporated Marburger winglets. 
These winglets are installed following Supplemental Type Certificate 
(STC) No. SA00490LA.
    What if I removed the Marburger winglets prior to further flight 
after April 21, 2006 (the effective date of AD 2006-08-08) or prior 
to April 21, 2006 (the effective date of AD 2006-08-08)?
    1. Review your airplane's logbook to determine your airplane's 
time in service (TIS) with winglets installed per Marburger STC No. 
SA00490LA. This includes all time spent with the winglets currently 
installed and any previous installations where the winglet was 
installed and later removed.

    Example: A review of your airplane's logbook shows that you have 
accumulated 350 hours TIS since incorporating Marburger STC No. 
SA00490LA. Further review of the airplane's logbook shows that a 
previous owner had installed the STC and later removed the winglets 
after accumulating 150 hours TIS. Therefore, your airplane's TIS 
with the winglets installed is 500 hours.
    If you determine that the winglet STC has never been 
incorporated on your airplane, then your safe life is presented in 
paragraph (c)(1) of this AD. Any future winglet installation will be 
subject to a reduced safe life per these instructions.
    2. Determine your airplane's unmodified safe life from paragraph 
(c)(1) of this AD.

    Example: Your airplane is a Model AT-401B, serial number 1022. 
From paragraph (c)(1) of this AD, the unmodified safe life of your 
airplane is 7,777 hours TIS.
    All examples from hereon will be based on the Model AT-401B, 
serial number 1022 airplane.
    3. Determine the winglet usage factor from paragraph (c)(4) of 
this AD.

    Example: Again, your airplane is a Model AT-401B, serial number 
1022. From paragraph (c)(4) of this AD, your winglet usage factor is 
1.1.
    4. Adjust the winglet TIS to account for the winglet usage 
factor. Multiply the winglet TIS (result of Step 1 above) by the 
winglet usage factor (result of Step 3 above).

    Example: Winglet TIS is 500 hours x a winglet usage factor of 
1.1. The adjusted winglet TIS is 550 hours.
    5. Calculate the winglet usage penalty. Subtract the winglet TIS 
(result of Step 1 above) from the adjusted winglet TIS (result of 
Step 4 above).

    Example: Adjusted winglet TIS-the winglet TIS = winglet usage 
penalty.
    (550 hours)-(500 hours TIS) = (50 hours TIS).
    6. Adjust the safe life of your airplane to account for winglet 
usage. Subtract the winglet usage penalty (result of Step 5 above) 
result from the unmodified safe life from paragraph (c)(1) of this 
AD (result of Step 2 above.).

    Example: Unmodified safe life-winglet usage penalty = adjusted 
safe life.
    (7,777 hours TIS)-(50 hours TIS) = (7,727 hours TIS).
    7. If you remove the winglets from your airplane before further 
flight or no longer have the winglets installed on your airplane, 
the safe life of your airplane is the adjusted safe life (result of 
Step 6 above). Enter this number in paragraph (e)(1) of this AD and 
the airplane logbook.
    What if I have the Marburger winglet installed as of April 21, 
2006 (the effective date of AD 2006-08-08) and plan to operate my 
airplane without removing the winglet?
    1. Review your airplane's logbook to determine your airplane's 
TIS without the winglets installed.

    Example: A review of your airplane's logbook shows that you have 
accumulated 1,500 hours TIS, including 500 hours with the Marburger 
winglets installed. Therefore, your airplane's TIS without the 
winglets installed is 1,000 hours.
    2. Determine your airplane's unmodified safe life from paragraph 
(c)(1) of this AD.

    Example: Your airplane is a Model AT-401B, serial number 1022. 
From paragraph (c)(1) of this AD, the unmodified safe life of your 
airplane is 7,777 hours TIS.
    All examples from hereon will be based on the Model AT-401B, 
serial number 1022 airplane.
    3. Determine the winglet usage factor from paragraph (c)(4) of 
this AD.

    Example: Again, your airplane is a Model AT-401B, serial number 
1022. From paragraph (c)(4) of this AD, your winglet usage factor is 
1.1.
    4. Determine the potential winglet TIS. Subtract the TIS without 
the winglets installed (result of Step 1 above) from the unmodified 
safe life (result of Step 2 above).

    Example: Unmodified safe life-TIS without winglets = Potential 
winglet TIS.
    (7,777 hours TIS)-(1,000 hours TIS) = (6,777 hours TIS).
    5. Adjust the potential winglet TIS to account for the winglet 
usage factor. Divide the potential winglet TIS (result of Step 4 
above) by the winglet usage factor (result of Step 3 above).

    Example: Potential winglet TIS / Winglet usage factor = Adjusted 
potential winglet TIS.
    (6,777 hours TIS) / (1.1) = (6,155 hours TIS).
    6. Calculate the winglet usage penalty. Subtract the adjusted 
potential winglet TIS (result of Step 5 above) from the potential 
winglet TIS (result of Step 4 above).

    Example: Potential winglet TIS-Adjusted potential winglet TIS = 
Winglet usage penalty.
    (6,777 hours TIS)-(6,155 hours TIS) = (622 hours TIS).
    7. Adjust the safe life of your airplane to account for the 
winglet installation. Subtract the winglet usage penalty (result of 
Step 6 above) from the unmodified safe life from paragraph (c)(1) of 
this AD (the result of Step 2 above).

    Example: Unmodified safe life-Winglet usage penalty = Adjusted 
safe life.
    (7,777 hours TIS)-(622 hours TIS) = (7,155 hours TIS).
    8. Enter the adjusted safe life (result of Step 7 above) in 
paragraph (e)(1) of this AD and the airplane logbook.
    What if I install or remove the Marburger winglet from my 
airplane in the future?
    If, at any time in the future, you install or remove the 
Marburger winglet STC from your airplane, you must repeat the 
procedures in this Appendix to determine the airplane's safe life.

Appendix 2

Alternative Method of Compliance (AMOC) to Docket No. FAA-2006-23646

Optional Inspection Program

    For Model AT-402A airplanes, all serial numbers (S/Ns) beginning 
with 0952, and Model AT-402B airplanes, all S/Ns beginning with 
0966, that do not incorporate and never have incorporated Marburger 
winglets installed following STC No. SA00490LA; you may begin a 
repetitive inspection interval program as an alternative to the safe 
life requirement of this AD with the following provisions:
    1. Upon accumulating 1,600 hours time-in-service (TIS) or within 
the next 50 hours TIS after April 21, 2006 (the effective date of AD 
2006-08-08), whichever occurs later, eddy-current inspect the 
outboard two lower spar cap bolt holes following Snow Engineering 
Process Specification 197, page 1, revised June 4, 2002; 
pages 2 through 4, dated February 23, 2001; and page 5, dated May 3, 
2002. The inspection must be done by one of the following:
    a. A Level 2 or Level 3 inspector that is certified for eddy-
current inspection using the guidelines established by the American 
Society for Nondestructive Testing or MIL-STD-410; or
    b. A person authorized to do AD work and who has completed and 
passed the Air

[[Page 75006]]

Tractor, Inc. training course on Eddy Current Inspection on wing 
lower spar caps.
    2. Repeat these inspections at intervals of (as applicable):
    a. 600 hours TIS:
    i. Model AT-402A, S/Ns 1021 through 1124.
    ii. Model AT-402B, S/Ns 1015, and 1021 through 1124.
    b. 600 hours TIS:
    i. Model AT-402A, S/Ns 0952 through 1020.
    ii. Model AT-402B, S/Ns 0966 through 1020, except 1015.
    c. 1,000 hours TIS:
    i. Model AT-402A, all S/Ns beginning with 1112.
    ii. Model AT-402B, all S/Ns beginning with 1125.
    d. If the outboard two lower spar cap bolt holes have been cold 
worked following Snow Engineering Service Letter  238 or 
239, both dated September 30, 2004, then you may double the 
inspection intervals listed in a., b., and c. above (800 hours TIS, 
1,200 hours TIS, or 2,000 hours TIS, as applicable) (See Step 8.--
re: mid cycle cold work).
    e. Your logbook entry must include the work done and the 
inspection intervals that are upcoming, as follows:
    ``Following AD 2006-08-08, at XXXX {insert hours TIS of the 
initial pre-modification inspection{time}  hours TIS an eddy-current 
inspection has been performed. As of now, the safe life listed in 
the AD no longer applies to this airplane. This airplane must be 
eddy-current inspected at intervals not to exceed {400/600/800/
1,000/1,200/2,000, as applicable{time}  hours TIS. The first of 
these inspections is due at {insert the total number of hours TIS 
the first of these inspections is due{time}  hours TIS.''
    3. If at any time a crack is found, and:
    a. If the crack indication goes away by doing the initial steps 
of the modification following the applicable sheet of Snow 
Engineering Co. Drawing Number 20992, then you may continue to 
modify your wing. After modification, proceed to Step 5.
    b. If the crack indication does not go away by doing the initial 
steps of the modification following the applicable sheet of Snow 
Engineering Co. Drawing Number 20992, then you must replace all 
parts and hardware listed in Step 7.
    c. Report to the FAA any cracks found using the form in Figure 1 
of this AD.
    4. Upon accumulating 4,000 hours TIS, you must:
    a. Modify your center splice connection following the applicable 
sheet of Snow Engineering Co. Drawing Number 20992, unless already 
done. Before doing the modification, do an eddy-current inspection 
following Snow Engineering Process Specification 197, page 
1, revised June 4, 2002; pages 2 through 4, dated February 23, 2001; 
and page 5, dated May 3, 2002. (See Step 9.). If, as of April 21, 
2006 (the effective date of AD 2006-08-08), your airplane is over or 
within 50 hours of reaching the 4,000-hour TIS modification 
requirement, then you must perform the modification within 50 hours 
TIS.
    b. Your logbook entry must include the work done and the 
inspection intervals that are upcoming, as follows:
    ``Following AD 2006-08-08, at XXXX {insert hours TIS of the 
modification{time}  hours TIS an eddy-current inspection has been 
performed. As of now, the safe life listed in the AD no longer 
applies to this airplane. This airplane must be eddy-current 
inspected at {insert the number of hours TIS at modification plus 
1,600 hours TIS{time}  hours TIS.
    5. Upon accumulating 1,600 hours TIS after modification, inspect 
the left-hand and right-hand outboard two lower spar cap bolt holes 
following Snow Engineering Process Specification 197, page 
1, revised June 4, 2002; pages 2 through 4, dated February 23, 2001; 
and page 5, dated May 3, 2002.
    6. Repetitively thereafter inspect at intervals not to exceed:
    a. 1,000 hours TIS; or
    b. 2,000 hours TIS if the outboard two lower spar cap bolt holes 
have been cold worked following Snow Engineering Service Letter 
239, dated September 30, 2004 (See Step 8.).
    c. Your logbook entry must include the work done and the post-
modification inspection intervals that are upcoming, as follows:
    ``Following AD 2006-08-08, at XXXX {insert hours TIS of the 
initial post-modification inspection{time}  hours TIS an eddy-
current inspection has been performed. As of now, the safe life 
listed in the AD no longer applies to this airplane. This airplane 
must be eddy-current inspected at intervals not to exceed {1,000/
2,000, as applicable{time}  hours TIS. The first of these 
inspections is due at {insert the total number of hours TIS the 
first of these inspections is due{time}  hours TIS.''
    d. If at any time a crack is found, then before further flight 
you must replace the lower spar caps, splice blocks, and wing attach 
angles and hardware. You must also notify the FAA using the form in 
Figure 1 of this AD.
    7. Upon accumulating 8,000 hours TIS, before further flight you 
must replace the lower spar caps, splice blocks, and wing attach 
angles (P/N 20693-1) and associated hardware. No additional time 
will be authorized for airplanes that are at or over 8,000 hours TIS 
(See Step 9.).
    8. If you decide to cold work your bolt holes following Snow 
Engineering Service Letter 238 or 239, both dated 
September 30, 2004, at a TIS that does not coincide with a scheduled 
inspection following this AD, then eddy-current inspect at the time 
of cold working and then begin the 800/1,200/2000 hour TIS 
inspection intervals (2 times the intervals listed in Steps 2.a., 
2.b., 2.c., and 6.a. listed above).
    9. If you have modified your airplane before accumulating 4,000 
hours TIS, then you may continue to fly your airplane past 
(modification + 4,000 hours TIS) provided you cut your inspection 
intervals in half. Make a logbook entry following Step 6.c. to 
reflect these reduced inspection intervals. Upon accumulating 8,000 
hours TIS, you must comply with Step 7 above. See example:

    Example: An AT-402B had the two-part modification installed at 
3,000 hours TIS and the bolt holes have not been cold worked.
    The first inspection would occur at 4,600 hours TIS. From Step 
5, this is modification plus 1,600 hours.
    Inspections would follow at 5,600 and 6,600 hours TIS. From Step 
6a, this is 1,000-hour TIS inspection intervals.
    There is another inspection at 7,000 hours TIS (modification 
plus 4,000 hours TIS). This relates to the 8,000-hour TIS inspection 
from Step 7, which is modification plus 4,000 hours TIS, except in 
this example the modification took place at 3,000 hours TIS instead 
of 4,000 hours TIS listed in Step 4.
    This airplane may continue to fly if inspected again at 7,500 
hours TIS, which is 500 hours TIS. This 500-hour time corresponds to 
Step 9 where you cut your inspection interval from Step 6a in half.
    Upon accumulating 8,000 hours TIS (this is the same as Step 7), 
you must replace the parts listed in Step 7 above.
    For Model AT-402A airplanes, all S/Ns beginning with 0952, and 
Model AT-402B airplanes, all S/Ns beginning with 0966, that 
incorporate or have incorporated Marburger winglets installed 
following STC No. SA00490LA; you may begin a repetitive inspection 
interval program as an alternative to the safe life requirement of 
this AD following the steps above with the following provisions:
    If you have removed the winglets, then calculate new, reduced 
hours for Steps 1, 4, 5, and 7 above, as applicable, based on the 
winglet usage factor listed in paragraph (c)(4) and Appendix 2 of 
this AD.
    You may repetitively inspect at the same intervals listed in 
Step 2 above provided that you do not re-install the winglets.

    Example: An AT-402B airplane, S/N 1020, had winglets installed 
at 200 hours TIS and removed at 800 hours TIS.
    The winglet usage factor is: 1.1.
    Calculate equivalent hours: 600 hours TIS with winglets x 1.1 = 
660 hours TIS.
    Winglet usage penalty = 660 - 600 = 60.
    New Step 1 Pre-Modification Initial Inspection time = 1,600 - 60 
= 1,540 hours TIS.
    Retained Step 2 Pre-Modification Inspection interval: Since the 
winglets are removed, the Pre-Modification Inspection interval 
remains at 600 hours TIS.
    New Step 4 Modification time = 4,000 - 60 = 3,940 hours TIS.
    New Step 5 Post-Modification Initial Inspection time = 3,940 + 
1,600 = 5,540 hours TIS.
    Retained Step 6 Post-Modification Inspection interval: Since the 
winglets are removed the Post-Modification Inspection interval 
remains at 1,000/2,000 hours TIS.
    New Step 7 Replacement time = 8,000 - 60 = 7,940 hours TIS.
    Use the Retained Step 2 interval, the New Step 5 time, and the 
Retained Step 6 interval to make appropriate logbook entries for the 
pre- and post-modification intervals, using the format presented in 
Steps 2.e., 4.b., and 6.c.
    If you have not removed the winglets, then calculate new, 
reduced hours for Steps 1, 2, 4, 5, 6, and 7 above, as applicable, 
based on the winglet usage factor listed in paragraph (c)(4) and 
Appendix 2 of this AD.
    Repetitively thereafter inspect at intervals not to exceed the 
appropriate interval listed

[[Page 75007]]

in the step above divided by the winglet usage factor.

    Example: An AT-402B, S/N 1,000 has had winglets on since new.
    The winglet usage factor is: 1.1.
    New Step 1 Pre-Modification Initial Inspection time: 1,600 / 1.1 
= 1,455 hours TIS.
    New Step 2 Pre-Modification Inspection interval: 600 / 1.1 = 545 
hours TIS.
    New Step 4 Modification time: 4,000 / 1.1 = 3,636 hours TIS.
    New Step 5 Post-Modification Initial Inspection time: 3,636 + 
(1,600 / 1.1) = 5,090 hours TIS.
    New Step 6 Post-Modification Inspection interval: 1,000 / 1.1 = 
909 hours TIS.
    New Step 7 Replacement time: 8,000 / 1.1 = 7,273 hours TIS.
    Use the reduced hours you calculate in New Step 2, New Step 5, 
and New Step 6 to make appropriate logbook entries for the pre- and 
post-modification inspection intervals, using the format presented 
in Steps 2.e., 4.b., and 6.c.

    Issued in Kansas City, Missouri, on December 4, 2008.
Kim Smith,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. E8-29165 Filed 12-9-08; 8:45 am]

BILLING CODE 4910-13-P