[Federal Register Volume 71, Number 232 (Monday, December 4, 2006)]
[Rules and Regulations]
[Pages 70286-70294]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-20324]


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

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. FAA-2004-19961; Directorate Identifier 2004-CE-48-AD; 
Amendment 39-14839; AD 2006-24-10]
RIN 2120-AA64


Airworthiness Directives; Air Tractor, Inc. Models AT-501, AT-
502, AT-502A, AT-502B, and AT-503A Airplanes

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

ACTION: Final rule.

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

SUMMARY: We are adopting a new airworthiness directive (AD) for certain 
Air Tractor, Inc. Models AT-501, AT-502, AT-502A, AT-502B, and AT-503A 
airplanes, which supersedes AD 2002-

[[Page 70287]]

26-05 and AD 2002-11-05 R1. Since we issued AD 2002-26-05 and AD 2002-
11-05 R1, we determined that additional airplanes should be added to 
the applicability section and determined the safe life for new 
production airplanes and replacement spar caps should be extended. We 
also developed an alternative method of compliance (AMOC) to the 
requirements of this AD. This AD retains the actions required in AD 
2002-26-05 and AD 2002-11-05 R1, adds additional airplanes to the 
Applicability section, extends the safe life for new production 
airplanes and replacement spar caps, and incorporates an AMOC. We are 
issuing this AD to prevent fatigue cracks from occurring in the wing 
lower spar cap before the established safe life is reached. Fatigue 
cracks in the wing lower spar cap could result in failure of the spar 
cap and lead to wing separation.

DATES: This AD becomes effective on January 8, 2007.
    As of January 8, 2007, the Director of the Federal Register 
approved the incorporation by reference of certain publications listed 
in the regulation.

ADDRESSES: For service information identified in this AD, contact Air 
Tractor, Incorporated, P.O. Box 485, Olney, Texas 76374; 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 the Docket Management Facility; U.S. 
Department of Transportation, 400 Seventh Street, SW., Nassif Building, 
Room PL-401, Washington, DC 20590-001 or on the Internet at http://dms.dot.gov. The docket number is FAA-2004-19961; Directorate 
Identifier 2004-CE-48AD.

FOR FURTHER INFORMATION CONTACT: Direct all questions to:
     For the airplanes that do not incorporate and never have 
incorporated Marburger Enterprises, Inc. 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; e-mail: [email protected]; 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:

Discussion

    On August 3, 2006, we issued a proposal to amend part 39 of the 
Federal Aviation Regulations (14 CFR part 39) to include an AD that 
would apply to certain Air Tractor, Inc. Models AT-501, AT-502, AT-
502A, AT-502B, and AT-503A airplanes. This proposal was published in 
the Federal Register as a notice of proposed rulemaking (NPRM) on 
August 9, 2006 (71 FR 45457). The NPRM proposed to supersede AD 2002-
26-05 and AD 2002-11-05 R1 with a new AD that would:
     retain the actions required in AD 2002-26-05 and AD 2002-
11-05 R1;
     add additional airplanes to the Applicability section;
     incorporate an alternative method of compliance (AMOC) to 
the requirements of this AD; and
     extend the safe life for new production airplanes and 
replacement spar caps.
    The table below summarizes the effects this AD will have on the 
airplane models affected by this AD:

------------------------------------------------------------------------
          Model                           Proposed Action
------------------------------------------------------------------------
AT-501...................   Supersede AD 2002-11-05 R1.
                            Retain the safe lives from AD 2002-
                            11-05 R1.
                            Provide an AMOC that allows
                            extension of the safe life through an
                            inspection and modification program.
AT-502...................   Supersede AD 2002-26-05.
                            Retain the safe lives from AD 2002-
                            26-05 and add S/Ns to applicability. AD 2002-
                            26-05 provided safe lives for S/Ns 0003
                            through 0236. Proposed action applies the
                            same safe life to all S/Ns beginning with
                            0003.
                            Provide an AMOC that allows
                            extension of the safe life through an
                            inspection and modification program.
AT-502A..................   Supersede AD 2002-26-05.
                            Retain the safe lives from AD 2002-
                            26-05.
                            Provide an AMOC that allows
                            extension of the safe life through an
                            inspection and modification program.
AT-502B..................   Supersede AD 2002-26-05.
                            Retain the safe lives from AD 2002-
                            26-05 for S/Ns 0187 through 0654, except
                            0643.
                            Increase the safe lives beyond those
                            listed in AD 2002-26-05 for S/Ns 0655 and
                            greater, as well as S/N 0643.
                            Add requirement to cold work
                            outboard wing center splice block bolt holes
                            in the lower spar cap on S/Ns 0643 and 0655
                            through 0692.
                            Provide an AMOC that allows
                            extension of the safe life through an
                            inspection and modification program for S/Ns
                            187 through 654, except 643.
AT-503A..................   Supersede AD 2002-26-05.
                            Retain the safe lives from AD 2002-
                            26-05.
                            Provide an AMOC that allows
                            extension of the safe life through an
                            inspection and modification program.
------------------------------------------------------------------------

Comments

    We provided the public the opportunity to participate in developing 
this AD. We received no comments on the proposal or on the 
determination of the cost to the public.

Conclusion

    We have carefully reviewed the available data and determined that 
air safety and the public interest require adopting the AD as proposed 
except for minor editorial corrections. We have determined that these 
minor corrections:
     are consistent with the intent that was proposed in the 
NPRM for correcting the unsafe condition; and
     do not add any additional burden upon the public than was 
already proposed in the NPRM.

Costs of Compliance

    We estimate that this AD affects 500 airplanes in the U.S. 
registry.
    We estimate the following costs to do each inspection:

[[Page 70288]]



----------------------------------------------------------------------------------------------------------------
                                                             Total cost per
             Labor cost                    Parts cost           airplane        Total cost on U.S.  operators
----------------------------------------------------------------------------------------------------------------
8 work-hours x $80 per hour = $640.  No parts required for             $640  $640 x 500 = $320,000
                                      inspection.
----------------------------------------------------------------------------------------------------------------

    We estimate the following costs to do the modification:

--------------------------------------------------------------------------------------------------------------------------------------------------------
             Labor cost                      Parts cost                   Total cost per airplane                    Total cost on U.S. operators
--------------------------------------------------------------------------------------------------------------------------------------------------------
120 work-hours x $80 per hour =       Approximately $3,700...  $9,600 + $3,700 = $13,300...................  $13,300 x 500 = $6,650,000
 $9,600.
--------------------------------------------------------------------------------------------------------------------------------------------------------

    We estimate the following costs to do the replacement:

--------------------------------------------------------------------------------------------------------------------------------------------------------
             Labor cost                      Parts cost                   Total cost per airplane                   Total cost on U.S.  operators
--------------------------------------------------------------------------------------------------------------------------------------------------------
254 work-hours x $80 per hour =       Approximately $16,500..  $20,320 + $16,500 = $36,820.................  $36,820 x 500 = $18,410,000
 $20,320.
--------------------------------------------------------------------------------------------------------------------------------------------------------

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 AD.

Regulatory Findings

    We have determined that this AD will not have federalism 
implications under Executive Order 13132. This AD will 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 this AD:
    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 summary of the costs to comply with this AD (and 
other information as included in the Regulatory Evaluation) and placed 
it in the AD Docket. You may get a copy of this summary by sending a 
request to us at the address listed under ADDRESSES. Include ``Docket 
No. FAA-2004-19961; Directorate Identifier 2004-CE-48-AD'' in your 
request.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

0
Accordingly, under the authority delegated to me by the Administrator, 
the Federal Aviation Administration amends part 39 of the Federal 
Aviation Regulations (14 CFR part 39) as follows:

PART 39--AIRWORTHINESS DIRECTIVES

0
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]

0
2. FAA amends Sec.  39.13 by removing Airworthiness Directive (AD) 
2002-26-05, Amendment 39-12991 (68 FR 18, January 2, 2003) and AD 2002-
11-05 R1, Amendment 39-14564 (71 FR 19628, April 17, 2006), and by 
adding a new AD to read as follows:
2006-24-10 Air Tractor, Inc.: Amendment 39-14839; Docket No. FAA-
2004-19961; Directorate Identifier 2004-CE-48-AD.

Effective Date

    (a) This AD becomes effective on January 8, 2007.

Affected ADs

    (b) This AD supersedes AD 2002-26-05, Amendment 39-12991, and AD 
2002-11-05 R1, Amendment 39-14564.

Applicability

    (c) This AD applies to certain Models AT-501, AT-502, AT-502A, 
AT-502B, and AT-503A airplanes. Use Table 1 in paragraph (c)(1) of 
this AD for airplanes that do not incorporate and never have 
incorporated Marburger Enterprises, Inc. (Marburger) winglets. Use 
Table 2 in paragraph (c)(4) of this AD for certain AT-500 series 
airplanes that incorporate or have incorporated Marburger winglets.
    (1) The following table applies to airplanes (certificated in 
any category) 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:

[[Page 70289]]



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
------------------------------------------------------------------------
AT-501..................  0002 through 0061...  4,531 hours TIS.
AT-501..................  All serial numbers    7,693 hours TIS.
                           beginning with 0062.
AT-502..................  All serial numbers    1,650 hours TIS.
                           beginning with 0003.
AT-502A.................  All serial numbers    1,650 hours TIS.
                           beginning with 0158.
AT-502B.................  0187 through 0654,    1,650 hours TIS.
                           except 0643.
AT-502B.................  0643, and 0655        9,000 hours TIS.
                           through 0692.
AT-502B.................  0693 through 0701...  9,500 hours TIS.
AT-502B.................  All serial numbers    9,800 hours TIS.
                           beginning with 0702.
AT-503A.................  All serial numbers    1,650 hours TIS.
                           beginning with 0067.
------------------------------------------------------------------------

    (2) If piston-powered airplanes have been converted to turbine 
power, you must use the limits for the corresponding serial number 
(S/N) turbine-powered airplanes.
    (3) Airplanes that have been modified to install lower spar 
caps, part numbers (P/N) 21058-1 and 21058-2, should use a safe life 
of 9,800 hours TIS.
    (4) The following table applies to airplanes (certificated in 
any category) that incorporate or have incorporated Marburger 
winglets. These winglets are installed following Supplemental Type 
Certificate (STC) SA00490LA. Use the winglet usage factor in Table 2 
of this paragraph, the safe life specified in Table 1 in 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:

 Table 2.--Winglet Usage Factor To Determine the Safe Life for Airplanes
   That Incorporate or Have Incorporated Marburger Winglets Installed
                         Following STC SA00490LA
------------------------------------------------------------------------
                                                          Winglet usage
            Model                   Serial numbers            factor
------------------------------------------------------------------------
AT-501.......................  0002 through 0061.......              1.6
AT-501.......................  All serial numbers                    1.6
                                beginning with 0062.
AT-502.......................  0003 through 0236.......              1.6
AT-502A......................  0158 through 0238.......              1.6
AT-502A......................  All serial numbers                    1.2
                                beginning with 0239.
AT-502B......................  All serial numbers                    1.2
                                beginning with 0187.
------------------------------------------------------------------------

    (5) Model AT-502B airplanes, S/N 0643, all S/Ns beginning with 
0655, and all other airplanes that have been modified with 
replacement spar caps, P/N 21058-1 and P/N 21058-2, are not eligible 
to have STC SA00490LA installed without additional fatigue data 
being provided to the FAA at the address in paragraph (f) of this 
AD.

Unsafe Condition

    (d) This AD is the result of service reports and analysis done 
on wing lower spar caps of Air Tractor, Inc. airplanes. The actions 
specified by this AD are intended to prevent fatigue cracks from 
occurring in the wing lower spar cap before the established safe 
life is reached. Fatigue cracks in the wing lower spar cap, if not 
detected and corrected, could result in failure of the spar cap and 
lead to wing separation and loss of control of the airplane.

Compliance

    (e) To address this problem, you must do the following:

------------------------------------------------------------------------
           Actions                 Compliance            Procedures
------------------------------------------------------------------------
(1) For all affected          For airplanes         Airplane Records
 airplanes: Modify the         previously affected   Modification: The
 applicable airplane records   by AD 2002-26-05:     owner/operator
 (logbook) as follows to       Do the logbook        holding at least a
 show the reduced safe life    entry within the      private pilot
 for the wing lower spar cap   next 10 hours TIS     certificate as
 (use the information from     after January 15,     authorized by
 Table 1 in paragraph          2003 (the effective   section 43.7 of the
 (c)(1), Table 2 in            date of AD 2002-26-   Federal Aviation
 paragraph (c)(4), and         05). For airplanes    Regulations (14 CFR
 Appendix 1 of this AD, as     not previously        43.7) may modify
 applicable):                  affected by AD 2002-  the airplane
(i) Incorporate the            26-05: Do the         records as
 following into the airplane   logbook entry         specified in
 logbook ``In accordance       within the next 10    paragraph (e)(1) of
 with AD 2006-24-10 (AD 2002-  hours TIS after       this AD. Make an
 26-05 or AD 2002-11-05, as    January 8, 2007       entry into the
 applicable) the wing lower    (the effective date   airplane records
 spar cap is life limited to   of this AD), unless   showing compliance
 --.'' Insert the applicable   already done. The     with this portion
 safe life number from the     logbook language      of the AD in
 applicable tables in          for AT-501            accordance with
 paragraphs (c)(1) and         airplanes is          section 43.9 of the
 (c)(4) of this AD and         referenced as AD      Federal Aviation
 Appendix 1 of this AD.        2002-11-05 instead    Regulations (14 CFR
(ii) If, as of the time of     of AD 2002-11-05 R1   43.9). Spar Cap
 the logbook entry             to maintain           Replacement: Do the
 requirement of paragraph      continuity and        replacement when
 (e)(1)(i) of this AD, your    assures no further    the safe life is
 airplane is over or within    action is necessary.  reached following
 50 hours of the safe life,                          Snow Engineering
 an additional 50 hours TIS                          Drawing Number
 after the effective date of                         21050, Snow
 this AD is allowed to do                            Engineering Service
 the replacement..                                   Letters 197 or 205, both revised
                                                     March 26, 2001, as
                                                     applicable. The
                                                     owner/operator may
                                                     not do the spar cap
                                                     modification/
                                                     replacement, unless
                                                     he/she holds the
                                                     proper mechanic
                                                     authorization.

[[Page 70290]]

 
(2) To extend the safe life   Inspection schedule   Procedures included
 of the wing lower spar cap    included as part of   as part of the AMOC
 for certain airplanes, you    the alternative       in Appendix 2 to
 may eddy-current inspect      method of             this AD.
 and modify the wing lower     compliance (AMOC)
 spar cap. The inspection      in Appendix 2 to
 schedule, modification        this AD.
 procedures, and list of
 eligible airplanes are
 included in Appendix 2 to
 this AD.
(3) For all affected          Only if cracks are    Send the form
 airplanes: Report to the      found, send the       (Figure 1 of this
 FAA any cracks detected as    report within 10      AD) to FAA, Fort
 the result of each            days after the        Worth Airplane
 inspection required by        inspection required   Certification
 paragraph (e)(2) of this AD   in paragraph (e)(2)   Office, Attn: Rob
 on the form in Figure 1 of    of this AD.           Romero, 2601
 this AD. The Office of                              Meacham Boulevard,
 Management and Budget (OMB)                         Fort Worth, Texas
 approved the information                            76193-0150;
 collection requirements                             telephone: (817)
 contained in this                                   222-5102;
 regulation under the                                facsimile: (817)
 provisions of the Paperwork                         222-5960.
 Reduction Act and assigned
 OMB Control Number 2120-
 0056.
(4) For Model AT-502B         Before accumulating   Following Snow
 airplanes, S/Ns 502B-0643     2,000 hours TIS or    Engineering Service
 and 502B-0655 through 502B-   within the next 100   Letter 244, dated April
 hand and right-hand two       January 8, 2007       25, 2005.
 outboard wing center splice   (the effective date
 block bolt holes (4 total)    of this AD),
 in the lower spar cap.        whichever occurs
                               later.
(5) For all affected          Not applicable......  Not applicable.
 airplanes: Airplanes that
 have the two-part
 modification done following
 the applicable service
 bulletins (Snow Engineering
 Service Letters 197 or 205, both
 revised March 26, 2001; or
 Snow Engineering Service
 Letter 244, dated
 April 25, 2005), but have
 over-sized outboard bolt
 holes at the splice block,
 must obtain an AMOC from
 FAA as specified in
 paragraph (f) of this AD to
 determine applicable
 inspection intervals.
------------------------------------------------------------------------

BILLING CODE 4910-13-P

[[Page 70291]]

[GRAPHIC] [TIFF OMITTED] TR04DE06.000

BILLING CODE 4910-13-C

[[Page 70292]]

Alternative Methods of Compliance (AMOCs)

    (f) The Manager, Fort Worth or Los Angeles Airplane 
Certification Office (ACO), as applicable (see paragraphs (f)(1)(i) 
and (f)(2)(ii) of this AD below for specific contacts), has the 
authority to approve AMOCs for this AD, if requested using the 
procedures found in 14 CFR 39.19.
    (1) For information on any already approved AMOCs, contact:
    (i) For the airplanes that do not incorporate and never have 
incorporated Marburger Enterprises, Inc. winglets: Rob Romero, 
Aerospace Engineer, FAA, Fort Worth ACO, 2601 Meacham Boulevard, 
Fort Worth, Texas 76193-0150; telephone: (817) 222-5102; facsimile: 
(817) 222-5960; e-mail: [email protected].
    (ii) For airplanes that incorporate or have incorporated 
Marburger Enterprises, Inc. winglets: John Cecil, Aerospace 
Engineer, Los Angeles ACO, FAA, 3960 Paramount Boulevard, Lakewood, 
California 90712; telephone: (562) 627-5228; facsimile: (562) 627-
5210.
    (2) AMOCs approved for AD 2001-10-04 and/or AD 2000-14-51 are 
not considered approved for this AD.
    (3) AMOCs approved for AD 2001-10-04 R1, AD 2002-11-03, AD 2002-
11-05, AD 2002-11-05 R1, or AD 2002-26-05 are considered approved 
for this AD.

Special Flight Permit

    (g) Under 14 CFR part 39.23, we are limiting the special flight 
permits for this AD by the following conditions:
    (1) Operate only 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.

Material Incorporated by Reference

    (h) You must use the service information specified in Table 3 of 
this AD to do the actions required by this AD, unless the AD 
specifies otherwise.
    (1) The Director of the Federal Register approved the 
incorporation by reference of this service information under 5 
U.S.C. 552(a) and 1 CFR part 51.
    (2) For service information identified in this AD, contact Air 
Tractor, Incorporated, P.O. Box 485, Olney, Texas 76374.
    (3) You may review copies at the FAA, Central Region, Office of 
the Regional Counsel, 901 Locust, Kansas City, Missouri 64106; or at 
the National Archives and Records Administration (NARA). For 
information on the availability of this material at NARA, call 202-
741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.

                                  Table 3.--Material Incorporated by Reference
----------------------------------------------------------------------------------------------------------------
       Service Bulletin No.                  Page                 Revision                     Date
----------------------------------------------------------------------------------------------------------------
Snow Engineering Drawing Number     Sheet 1 and Sheet 3..  Not applicable.......  January 30, 2003.
 21050.
                                    Sheet 2..............  Not applicable.......  February 1, 2003.
Snow Engineering Service Letter     1 and 2..............  Not applicable.......  March 26, 2001.
 197.
                                    3....................  Not applicable.......  June 13, 2000.
Snow Engineering Service Letters    1, 2, and 4..........  Not applicable.......  March 26, 2001.
 205.
                                    3....................  Not applicable.......  October 25, 2000.
Snow Engineering Service Letter     1 through 12.........  Not applicable.......  April 25, 2005.
 244.
----------------------------------------------------------------------------------------------------------------

Appendix 1 to AD 2006-24-10

    The following provides procedures for determining the safe life 
for those Models AT-501, AT-502, AT-502A, and AT-502B airplanes that 
incorporate or have incorporated Marburger Enterprises, Inc. 
(Marburger) winglets. These winglets are installed in accordance 
with Supplemental Type Certificate (STC) No. SA00490LA.
    If you have removed the Marburger winglets before further flight 
after the effective date of this AD or before the effective date of 
this AD, do the following:
    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 the Marburger STC. 
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 
Table 1 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 Table 1 
in paragraph (c)(1) of this AD.

Example: Your airplane is a Model AT-502B, serial number (S/N) 0292. 
From Table 1 in paragraph (c)(1) of this AD, the unmodified safe-
life of your airplane is 1,650 hours TIS.

    All examples from hereon will be based on the Model AT-502B, S/N 
0292 airplane.
    3. Determine the winglet usage factor from Table 2 in paragraph 
(c)(4) of this AD.

Example: Again, your airplane is a Model AT-502B, S/N 0292. From 
Table 2 in paragraph (c)(4) of this AD, your winglet usage factor is 
1.2.

    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 1.2. 
The adjusted winglet TIS is 600 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.
    (600 hours TIS)--(500 hours TIS) = (100 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 Table 1 in paragraph 
(c)(1) of this AD (the result of Step 2 above).

Example:
    Unmodified safe life--winglet usage penalty = Adjusted safe 
life.
    (1,650 hours TIS)--(100 hours TIS) = (1,550 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)(i) of this AD 
and the airplane logbook.
    If you have the Marburger winglets installed as of the effective 
date of this AD and plan to operate your airplane without removing 
the winglets, do the following:
    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 Table 1 
in paragraph (c)(1) of this AD.

Example: Your airplane is a Model AT-502B, S/N 0292. From Table 1 in 
paragraph (c)(1) of this AD, the unmodified safe life of your 
airplane is 1,650 hours TIS.

    All examples from hereon will be based on the Model AT-502B, S/N 
0292 airplane.

[[Page 70293]]

    3. Determine the winglet usage factor from Table 2 in paragraph 
(c)(4) of this AD.

Example: Again, your airplane is a Model AT-502B, S/N 0292. From 
Table 2 in paragraph (c)(4) of this AD, your winglet usage factor is 
1.2.

    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.
    (1,650 hours TIS)--(1,000 hours TIS) = (650 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.
    (650 hours TIS) (1.2) = (541 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.
    (650 hours TIS)--(541 hours TIS) = (109 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 Table 1 in 
paragraph (c)(1) of this AD (the result of Step 2 above).

Example:
    Unmodified safe life--winglet usage penalty = Adjusted safe 
life.
    (1,650 hours TIS)--(109 hours TIS) = (1,541 hours TIS).

    8. Enter the adjusted safe life (result of Step 7 above) in 
paragraph (e)(1)(i) of this AD and the airplane logbook.
    If you install or remove the Marburger winglets from your 
airplane in the future, do the following:
    If, at anytime in the future, you install or remove the 
Marburger winglets 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 AD 2006-24-10; 
Optional Inspection Program

    For all airplanes listed in this AD; except for Model AT-502B 
airplanes, serial number (S/N) 0643 and all S/Ns beginning with 
0655, and those airplanes that have been modified with the 
replacement spar caps, part number (P/N) 21058-1 and P/N 21058-2; 
you may begin a repetitive inspection interval program as an 
alternative to the safe life requirement of this AD with the 
following provisions:
    For the Model AT-501 airplanes affected by this AD, you may 
elect to follow this AMOC program and continue to operate your 
airplane up to 8,000 hours TIS, provided you comply with this AMOC 
in its entirety. If at the time of the effective date of this AD, 
you are over 1,600 hours TIS (the time required for the first 
inspection), you must inspect within 50 hours TIS. If at the time of 
the effective date of this AD, you are over 4,000 hours TIS (the 
time required for 2-part modification), you must have the 
modification done within 50 hours TIS. If you choose not to follow 
this inspection program, then you must replace your lower spar caps 
and associated hardware at the applicable safe life listed in this 
AD following the procedures in paragraph (e).
    For airplanes that do not and never have had Marburger 
Enterprise, Inc. winglets installed following Supplemental Type 
Certificate (STC) SA00490LA:
    1. Upon accumulating 1,600 hours time-in-service (TIS) or within 
the next 50 hours TIS after January 8, 2007 (the effective date of 
AD 2006-24-10), 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 5, revised 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 has completed and 
passed the Air Tractor, Inc. training course on Eddy Current 
Inspection on wing lower spar caps.
    2. Repeat these inspections at intervals of (as applicable):
    a. 800 hours TIS (all S/Ns except as noted in b); or
    b. 600 hours TIS (S/Ns 502B-0187 through 502B-0618 that do not 
have P/N 20998-1/-2 web plate installed).
    c. If the outboard two lower spar cap bolt holes have been cold 
worked following Snow Engineering Service Letter  233, 
dated May 18, 2004, then you may double (1,600 hours TIS or 1,200 
hours TIS, as applicable) the inspection interval (See Step 8--re: 
mid cycle cold work).
    d. Your logbook entry must include the work done and the 
inspection intervals that are upcoming, as follows:
    ``Following AD 2006-24-10, 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 {800/600/1,600/
1,200, 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. The crack indication goes away by doing the modification 
following the applicable sheet of Snow Engineering Modification--
Wing Centersplice--502, Drawing Number 20989, then you may modify 
your center splice following Snow Engineering Drawing 20989. After 
modification, proceed to Step 5.
    b. The crack indication does not go away by doing the 
modification following the applicable sheet of Snow Engineering 
Modification--Wing Centersplice--502, Drawing Number 20989, 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. For all S/Ns, upon accumulating 4,000 hours TIS, you must:
    a. Modify your center splice connection following the applicable 
sheet of Snow Engineering Modification--Wing Centersplice--502, 
Drawing Number 20989, unless already done following Snow Engineering 
Service Letter 197 or 205, both revised March 26, 
2001, as applicable. The owners/operator may not do the spar cap 
modification unless that person holds the proper mechanic 
authorization. If, as of January 8, 2007 (the effective date of AD 
2006-24-10), your airplane is over or within 50 hours of reaching 
the 4,000 hour TIS modification requirement, do the modification 
within the next 50 hours TIS.
    b. Before doing the modification, do an eddy-current inspection 
following Snow Engineering Process Specification 197, page 
1, revised June 4, 2002; pages 2 through 5, revised May 3, 2002, 
unless already done following the applicable Snow Engineering 
Service Letter 197 or 205, both revised March 26, 
2001.
    c. Your logbook entry must include the work done and the 
inspection intervals that are upcoming, as follows:
    ``Following AD 2006-24-10, at XXXX {insert hours TIS of the 
modification{time}  hours TIS an eddy-current inspection has been 
done. 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. For all S/Ns, 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 5, revised May 3, 2002.
    6. Repeat the inspection at intervals of:
    a. 800 hours TIS; or
    b. 1,600 hours TIS if the outboard two lower spar cap bolt holes 
have been cold worked following Snow Engineering Service Letter 
234, dated May 18, 2004 (See Step 8).
    c. Your logbook entry must include the work done and the post-
modification inspection intervals that are upcoming, as follows:
    ``This airplane must be eddy-current inspected at intervals not 
to exceed {800/1,600, 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 a crack is found at any time, 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).

[[Page 70294]]

    8. (Optional): If you decide to cold work your bolt holes 
following Snow Engineering Service Letter 233 or 
234, both dated May 18, 2002, 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 
1,600/1,200 hour TIS inspection intervals (2 times the intervals 
listed in Steps 2.a., 2.b., and 6.a. listed above).
    9. (Optional): If you have modified your airplane in accordance 
with Step 4 above 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. above to reflect these reduced inspection 
intervals. Upon accumulating 8,000 hours TIS, you must comply with 
Step 7 above.
    Example: An AT-502B airplane 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 TIS.
    Example (continued): Inspections would follow at 5,400 hours 
TIS, 6,200 hours TIS, and 7,000 hours TIS. From Step 6.a. above, 
this is 800-hour TIS inspection intervals.
    Regarding the inspection at 7,000 hours TIS (modification plus 
4,000 hours TIS), this relates to the 8,000-hour TIS inspection from 
Step 7 above, 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 as specified in Step 4 above.
    This airplane may continue to fly if inspected again at 7,400 
hours TIS and 7,800 hours TIS, which is 400-hour TIS inspection 
intervals. This 400-hour TIS inspection interval corresponds to Step 
9 where you cut your inspection interval from Step 6.a. in half.
    Upon accumulating 8,000 hours TIS (this is the same as Step 7 
above), you must replace the parts listed in Step 7.
    For airplanes that have or have had Marburger Enterprise, Inc. 
winglets installed following Supplemental Type Certificate (STC) 
SA00490LA:
    If you have removed the winglets, calculate new, reduced hours 
for Steps 1, 4, 5, and 7, as applicable, based on the winglet usage 
factor listed in Table 2 of 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-502 airplane, S/N 502-0200, had winglets 
installed at 200 hours TIS and removed at 800 hours TIS.

The winglet usage factor is: 1.6
Calculate equivalent hours: 600 hours TIS with winglets x 1.6 = 960 
hours TIS
Winglet usage penalty = 960 - 600 = 360
New Step 1 Pre-Modification Initial Inspection Time = 1,600 - 360 = 
1,240 hours TIS
Retained Step 2 Pre-Modification Inspection Interval: Since the 
winglets are removed, the Pre-Modification Inspection Interval 
remains 800 hours TIS
New Step 4 Modification time = 4,000 - 360 = 3,640 hours TIS
New Step 5 Post-Modification Initial Inspection time = 3,640 + 1,600 
= 5,240 hours TIS
Retained Step 6 Post-Modification Inspection interval: Since the 
winglets are removed the Post-Modification Inspection interval 
remains at 800/1,600 hours TIS.
New Step 7 replacement time = 8,000 - 360 = 7,640 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.d., 4.c., 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 Table 2 of paragraph 
(c)(4) of this AD and Appendix 2 of this AD.
    Repetitively inspect at the appropriate interval listed in the 
step above divided by the winglet usage factor.
    Example: An AT-502B, S/N 502B-0550, that has not had P/N 20998-
1/-2 web plate installed and has had winglets on since new.

The winglet usage factor is: 1.2
New Step 1 Pre-modification initial inspection time: 1,600 / 1.2 = 
1,333 hours TIS
New Step 2 Pre-modification inspection interval: 600 / 1.2 = 500 
hours TIS
New Step 4 Modification time: 4,000 / 1.2 = 3,333 hours TIS
New Step 5 Post-modification initial inspection time: 3,333 + 1,333 
(1,600 / 1.2) = 4,666 hours TIS
New Step 6 Post-modification inspection interval: 800 / 1.2 = 667 
hours TIS
New Step 7 Replacement time: 8,000 / 1.2 = 6,667 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.d., 4.c., and 6.c. above.

    Issued in Kansas City, Missouri, on November 22, 2006.
Kim Smith,
Manager, Small Airplane Directorate, Aircraft Certification Service.

[FR Doc. E6-20324 Filed 12-1-06; 8:45 am]
BILLING CODE 4910-13-P