[Federal Register Volume 66, Number 248 (Thursday, December 27, 2001)]
[Proposed Rules]
[Pages 66823-66828]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-31555]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2001-CE-36-AD]
RIN 2120-AA64


Airworthiness Directives; Air Tractor, Inc. AT-400, AT-500, and 
AT-800 Series Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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

SUMMARY: This document proposes to supersede Airworthiness Directive 
(AD) 2001-10-04 R1, which lowered the safe life for the wing lower spar 
cap on

[[Page 66824]]

certain Air Tractor, Inc. (Air Tractor) AT-400, AT-500, and AT-800 
series airplanes. AD 2001-10-04 R1 resulted from numerous reports of 
cracks in the \3/8\-inch bolthole of the wing lower spar cap on the 
affected airplanes. This proposed AD would maintain the safe life and 
add a requirement for you to eddy--current inspect the wing lower spar 
cap immediately prior to the replacement/modification in order to 
detect and correct any crack in a bolthole before it extends to the 
modified center section of the wing and repair that crack or replace 
the wing section. This proposed AD would also further reduce the safe 
life for certain AT-400 and AT-500 series airplanes that incorporate or 
have incorporated Marburger Enterprises, Inc. winglets. These winglets 
are installed in accordance with Supplemental Type Certificate (STC) 
SA00490LA. The actions specified by this proposed AD are intended 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 the 
wing separating from the airplane during flight.

DATES: The Federal Aviation Administration (FAA) must receive any 
comments on this proposed rule on or before February 15, 2002 .

ADDRESSES: Submit comments to FAA, Central Region, Office of the 
Regional Counsel, Attention: Rules Docket No. 2001-CE-36-AD, 901 
Locust, Room 506, Kansas City, Missouri 64106. You may view any 
comments at this location between 8 a.m. and 4 p.m., Monday through 
Friday, except Federal holidays.
    You may get service information that applies to this proposed AD 
from 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. You may also view this information at the Rules Docket at the 
address above.

FOR FURTHER INFORMATON 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; and
--For certain AT-400 and AT-500 series 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

    How do I comment on this proposed AD? The FAA invites comments on 
this proposed rule. You may submit whatever written data, views, or 
arguments you choose. You need to include the rule's docket number and 
submit your comments to the address specified under the caption 
ADDRESSES. We will consider all comments received on or before the 
closing date. We may amend this proposed rule in light of comments 
received. Factual information that supports your ideas and suggestions 
is extremely helpful in evaluating the effectiveness of this proposed 
AD action and determining whether we need to take additional rulemaking 
action.
    Are there any specific portions of this proposed AD I should pay 
attention to? The FAA specifically invites comments on the overall 
regulatory, economic, environmental, and energy aspects of this 
proposed rule that might suggest a need to modify the rule. You may 
view all comments we receive before and after the closing date of the 
rule in the Rules Docket. We will file a report in the Rules Docket 
that summarizes each contact we have with the public that concerns the 
substantive parts of this proposed AD.
    How can I be sure FAA receives my comment? If you want FAA to 
acknowledge the receipt of your comments, you must include a self-
addressed, stamped postcard. On the postcard, write ``Comments to 
Docket No. 2001-CE-36-AD.'' We will date stamp and mail the postcard 
back to you.

Discussion

    Has FAA taken any action to this point? Several reports of cracked 
wing lower spar caps on Air Tractor AT-400, AT-500, and AT-800 series 
airplanes have caused the manufacturer (Air Tractor) to recalculate the 
fatigue life of the wing lower spar cap on these airplanes. One report 
was of an accident where the wing separated from the airplane during 
flight. The cracks are originating in the outboard \3/8\-inch bolthole 
of the wing lower spar cap.
    To address this condition, FAA issued AD 2001-10-04, Amendment 39-
12230 (66 FR 27014, May 16, 2001). This AD lowers the safe life for the 
wing lower spar cap on Air Tractor AT-400, AT-500, and AT-800 series 
airplanes. This AD also allows for inspection, using eddy current 
methods, of the wing lower spar cap for airplanes that are at or over 
the lower safe life and parts are not available. Operation of the 
airplane is not allowed if cracks are found and inspections must be 
terminated when parts become available or after performing three 
repetitive inspections.
    AD 2001-10-04 superseded AD 2000-14-51, Amendment 39-11837 (65 FR 
46567, July 31, 2000). AD 2000-14-51 required 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.
    We inadvertently included certain AT-800 series airplanes in the 
Applicability of AD 2001-10-04. Those AT-800 series airplanes that are 
equipped with the factory-supplied part number 80540 computerized fire 
gate should not be affected by AD 2001-10-04. Therefore, we revised 
this AD to incorporate this change. AD 2001-10-04 R1, Amendment 39-
12247, was published in the Federal Register on June 4, 2001 (66 FR 
29900).
    What has happened since AD 2001-10-04 R1 to initiate this action? 
In response to AD 2001-10-04 R1, FAA received a comment from the 
National Transportation Safety Board that recommended an eddy-current 
inspection requirement immediately prior to the accomplishment of the 
two-part modification described in Snow Engineering Service Letters 
#197, #202, #203, or #205, all Revised March 26, 2001, as applicable. 
This is to eliminate the possibility that a crack that exists in a bolt 
hole prior to the modification is still present after accomplishing the 
modification. Prior to the modification, any crack present will be 
larger than it would appear after the outermost bolt holes are 
enlarged. This makes the crack easier to detect and gives the mechanic 
an area to concentrate on any post-modification inspections.
    Additional analysis also indicates a higher wing root bending 
moment that could lead to reduction of the safe life for certain AT-400 
and AT-500 series airplanes with a certain configuration. Airplanes 
with this configuration either incorporate or have incorporated 
Marburger Enterprises, Inc. winglets on the wing lower spar cap. These 
winglets are installed in accordance with Supplemental Type Certificate 
(STC) SA00490LA. We have developed criteria for determining what the 
new safe life should be for airplanes that either incorporate or have 
incorporated these winglets.

[[Page 66825]]

The FAA's Determination and an Explanation of the Provisions of 
this Proposed AD

What has FAA decided?

    After examining the circumstances and reviewing all available 
information related to the incidents described above, we have 
determined that:

--The unsafe condition referenced in this document exists or could 
develop on other AT-400, AT-500, and AT-800 series airplanes (specific 
models as referenced in the AD) of the same type design;
--All airplanes should have the eddy-current inspection accomplished on 
the wing lower spar cap immediately prior to the replacement/
modification in order to detect and correct any crack in a bolthole 
before it extends to the modified center section of the wing;
--Certain AT-400 and AT-500 series airplanes that incorporate or have 
incorporated Marburger Enterprises, Inc. winglets should have the safe 
life further reduced; and
--AD action should be taken in order to correct this unsafe condition.
    What would this proposed AD require? This proposed AD would 
supersede AD 2001-10-04 R1 with a new AD that would maintain the safe 
life and would add a requirement for you to eddy-current inspect the 
wing lower spar cap immediately prior to the replacement/modification 
in order to detect and correct any crack in a bolthole before it 
extends to the modified center section of the wing and repair that 
crack or replace the wing section. The proposed AD would also further 
reduce the safe life for those AT-400 and AT-500 series airplanes that 
incorporate or have incorporated Marburger Enterprises, Inc. winglets.

Cost Impact

    How many airplanes would this proposed AD impact? We estimate that 
this proposed AD affects 1,179 airplanes in the U.S. registry.
    What would be the cost impact of this proposed AD on owners/
operators of the affected airplanes? We estimate the following costs to 
accomplish the proposed inspection:

----------------------------------------------------------------------------------------------------------------
                                                                                    Total cost    Total cost on
                       Labor cost                               Parts cost         per airplane   U.S. operators
----------------------------------------------------------------------------------------------------------------
2 workhours at $60 per hour = $120.....................    No parts required for          $120         $141,480
                                                                     inspection.
----------------------------------------------------------------------------------------------------------------

    We estimate the following costs to accomplish the proposed 
replacement/modification:

----------------------------------------------------------------------------------------------------------------
                                                                                    Total cost    Total cost on
                             Labor cost                               Parts cost   Per Airplane   U.S. operators
----------------------------------------------------------------------------------------------------------------
210 workhours at $60 per hour = $7,200.............................      $11,500       $18,700      $22,047,300
----------------------------------------------------------------------------------------------------------------

    What is the difference between the cost impact of this proposed AD 
and the cost impact of AD 2001-10-04 R1? AD 2001-10-04 R1 already 
established the safe life for the lower wing spar cap on the affected 
airplanes. Therefore, the replacement/modification is already required 
through that AD. The only difference in the cost impact upon the public 
of this proposed AD and AD 2001-10-04 R1 is the cost for the eddy-
current inspection upon replacement and the further safe life reduction 
for those AT-400 and AT-500 series airplanes that incorporate or have 
incorporated Marburger Enterprises, Inc. winglets.

Regulatory Impact

    Would this proposed AD impact various entities? The regulations 
proposed herein 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. Therefore, it is determined that this 
proposed rule would not have federalism implications under Executive 
Order 13132.
    Would this proposed AD involve a significant rule or regulatory 
action? For the reasons discussed above, I certify that this proposed 
action (1) is not a ``significant regulatory action'' under Executive 
Order 12866; (2) is not a ``significant rule'' under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979); and (3) if 
promulgated, 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. A copy of the draft regulatory 
evaluation prepared for this action has been placed in the Rules 
Docket. A copy of it may be obtained by contacting the Rules Docket at 
the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, under the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
part 39 of the Federal Aviation Regulations(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. FAA amends Sec. 39.13 by removing Airworthiness Directive (AD) 
2001-10-04 R1, Amendment 39-12247 (66 FR 29900, June 4, 2001), and by 
adding a new AD to read as follows:

Air Tractor, Inc.: Docket No. 2001-CE-36-AD; Supersedes AD 2001-10-
04 R1, Amendment 39-12247.

    (a) What airplanes are affected by this AD? Use paragraph (a)(1) 
of this AD for airplanes that do not incorporate and never have 
incorporated winglets and use paragraph (a)(2) of this AD for 
certain AT-400 and AT-500 series airplanes that incorporate or have 
incorporated Marburger Enterprises, Inc. winglets.
    (1) The following presents airplanes (certificated in any 
category) that are affected by this AD, along with the new safe life 
(presented in hours time-in-service (TIS)) of the wing lower spar 
cap for all airplane models and serial numbers:

[[Page 66826]]



----------------------------------------------------------------------------------------------------------------
              Model                                 Serial Nos.                              Safe life
----------------------------------------------------------------------------------------------------------------
AT-400...........................  all serial numbers beginning with 0416.......  13,300 hours TIS.
AT-401...........................  0662 through 0951............................  10,757 hours TIS.
AT-401B..........................  0952 through 1014 and 1016 though 1020.......  6,948 hours TIS.
AT-401B..........................  1015 and 1021 through 1124...................  7,777 hours TIS
AT-402...........................  0694 through 0951............................  7,440 hours TIS.
AT-402A..........................  0738 through 0951............................  7,440 hours TIS.
AT-402A..........................  0952 through 1020............................  4,589 hours TIS.
AT-402A..........................  1021 through 1124............................  5,268 hours TIS.
AT-402B..........................  0966 through 1020............................  4,589 hours TIS.
AT-402B..........................  1021 through 1124............................  5,268 hours TIS.
AT-501...........................  0002 through 0061............................  4,531 hours TIS.
AT-501...........................  all serial numbers beginning with 0062.......  7,693 hours TIS.
AT-502...........................  0003 through 0236............................  4,000 hours TIS.
AT-502A..........................  0158 through 0618............................  3,000 hours TIS.
AT-502B..........................  0187 through 0618............................  4,000 hours TIS.
AT-503A..........................  all serial numbers beginning with 0067.......  4,000 hours TIS.
AT-802...........................  0001 through 0059 except those equipped with   4,132 hours TIS.
                                    the factory-supplied part number 80540
                                    computerized fire gate.
AT-802...........................  0060 through 0091 except those equipped with   4,188 hours TIS.
                                    the factory-supplied part number 80540
                                    computerized fire gate.
AT-802...........................  0092 through 0101 except those equipped with   8,163 hours TIS.
                                    the factory-supplied part number 80540
                                    computerized fire gate.
AT-802A..........................  0003 through 0059 except those equipped with   4,969 hours TIS.
                                    the factory-supplied part number 80540
                                    computerized fire gate.
AT-802A..........................  0060 through 0091 except those equipped with   4,531 hours TIS.
                                    the factory-supplied part number 80540
                                    computerized fire gate.
AT-802A..........................  0092 through 0101 except those equipped with   8,648 hours TIS.
                                    the factory-supplied part number 80540
                                    computerized fire gate.
----------------------------------------------------------------------------------------------------------------


    Note 1: Piston powered aircraft that have been converted to 
turbine power should use the limits for corresponding serial number 
turbine-powered aircraft.

    (2) The following presents airplanes (certificated in any 
category) that could incorporate or could have incorporated 
Marburger Enterprises, Inc. winglets. These winglets are installed 
in accordance with Supplemental Type Certificate (STC) SA00490LA. 
Use the winglet usage factor in the table below, the safe life 
specified in paragraph (a)(1) of this AD, and the instructions 
included in the Appendix to this AD to determine the new safe life 
of these airplanes:

----------------------------------------------------------------------------------------------------------------
                                                                                                       Winglet
                   Model                                           Serial Nos.                          usage
                                                                                                        factor
----------------------------------------------------------------------------------------------------------------
AT-401.....................................  0662 through 0951.....................................          1.6
AT-401B....................................  0952 through 1014 and 1016 though 1020................          1.1
AT-401B....................................  1015 and 1021 through 1124............................          1.1
AT-402.....................................  0694 through 0951.....................................          1.6
AT-402A....................................  0738 through 0951.....................................          1.6
AT-402A....................................  0952 through 1020.....................................          1.1
AT-402A....................................  1021 through 1124.....................................          1.1
AT-402B....................................  0966 through 1020.....................................          1.1
AT-402B....................................  1021 through 1124.....................................          1.1
AT-501.....................................  0002 through 0061.....................................          1.6
AT-501.....................................  All serial numbers beginning with 0062................          1.6
AT-502.....................................  0003 through 0236.....................................          1.6
AT-502A....................................  0158 through 0618.....................................          1.6
AT-502B....................................  0187 through 0618.....................................          1.2
----------------------------------------------------------------------------------------------------------------

    (b) Who must comply with this AD? Anyone who wishes to operate 
any of the above airplanes must comply with this AD.
    (c) What problem does this AD address? The actions specified by 
this AD are intended 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 the wing separating from the airplane 
during flight.
    (d) What must I do to address this problem? To address this 
problem, you must accomplish the following actions:

    Note 2: The 10-hour time-in-service (TIS) compliance time is 
maintained from AD 2001-10-04 R1.


[[Page 66827]]



------------------------------------------------------------------------
           Action                Compliance time         Procedures
------------------------------------------------------------------------
(1) Modify the applicable     Accomplish the        The owner/operator
 aircraft records as follows   logbook entry         holding at least a
 to show the reduced safe      within the next 10    private pilot
 life for the wing lower       hours TIS after the   certificate as
 spar cap (use the             effective date of     authorized by
 information from the table    this AD.              section 43.7 of the
 in paragraph (a)(1) of this                         Federal Aviation
 AD and utilize the                                  Regulations (14 CFR
 information in paragraph                            43.7) may modify
 (a)(2) of and the Appendix                          the aircraft
 to this AD, as applicable):                         records as
(i) For the affected Models                          specified in
 AT-802 and AT-802A                                  paragraphs
 airplanes: update the                               (d)(1)(i) and
 Owners Manual, Section 6--                          (d)(1(ii) of this
 Airworthiness Limitations,                          AD. Make an entry
 Life Limited Parts.                                 into the aircraft
(ii) For all affected                                records showing
 airplanes other than the                            compliance with
 Models AT-802 and AT-802A                           this portion of the
 airplanes: incorporate the                          AD in accordance
 following into the Aircraft                         with section 43.9
 Logbook ``In accordance                             of Federal the
 with this AD, the wing                              Aviation
 lower spar cap is life                              Regulations (14 CFR
 limited to ____ (insert the                         43.9). Accomplish
 applicable safe life number                         the actual
 from the applicable tables                          replacement/
 in paragraphs (a)(1) and                            modification in
 (a)(2) of this AD).                                 accordance with
(iii) If, as of the time of                          Snow Engineering
 the logbook all entry                               Service Letter
 requirement of paragraph                            #197, #202, #203,
 (d)(1) of this AD, your                             or #205, Revised
 airplane is over or within                          March 26, 2001, as
 10 hours of the safe life,                          applicable. The
 an additional 10 hours TIS                          owner/operator may
 is allowed to accomplish                            not accomplish the
 the replacement/                                    replacement/
 modification                                        modification.
------------------------------------------------------------------------
(2) If you have ordered       Prior to further      In accordance with
 parts from the factory when   flight after          the procedures in
 it is time to replace the     ordering the parts    Snow Engineering
 wing lower spar cap (as       and thereafter at     Service Letter
 required per the logbook      intervals not to      #197, #202, #203,
 safe life reduction in        exceed 400 hours      or #205, all
 paragraph (d)(1) of this      TIS until one of      Revised March 26,
 AD), but the parts are not    the criteria          2001, as
 available, you may eddy-      paragraphs            applicable.
 current inspect the wing      (d)(2)(i),
 lower spar cap. These         (d)(2)(ii), and
 inspections are allowed       (d)(2)(iii) of this
 until one of the following    AD is met.
 occurs, at which time the
 replacement/modification
 (required when the lower
 spar cap has reached its
 safe life) must be
 accomplished:
(i) Crack(s) is/are found;..
(ii) Parts become available
 from the manufacturer; or.
(iii) Not more than three
 inspections or 1,200 hours
 TIS go by: the first
 inspection would have to be
 accomplished upon
 accumulating the safe life;
 the second inspection would
 have to be accomplished
 within 400 hours TIS after
 accumulating the safe life;
 the third inspection would
 have to be accomplished 400
 hours TIS after the second
 inspection; and the
 replacement/modification
 would have to be
 accomplished within 400
 hours TIS after the third
 inspection (maximum elapsed
 time would be 1,200 hours
 TIS).
------------------------------------------------------------------------
(3) Eddy-current inspect the  Immediately prior to  In accordance with
 wing lower spar cap in        the replacement/      the procedures in
 order to detect and correct   modification          Snow Engineering
 any crack before it extends   required when you     Service Letter
 to the modified center        reach the new safe    #197, #202, #203,
 section of the wing and       life. For airplanes   or #205, all
 repair that crack or          that had this         Revised March 26,
 replace the wing section      replacement/          2001, as
                               modification          applicable.
                               accomplished in
                               accordance with
                               either AD 2001-10-
                               04 or AD 2001-10-04
                               R1, accomplish this
                               inspection and any
                               necessary
                               corrective action
                               within the next 400
                               hours TIS after the
                               effective date of
                               this AD, unless
                               already
                               accomplished (have
                               the mechanic who
                               accomplished the
                               work mark the
                               logbooks
                               accordingly).
------------------------------------------------------------------------

    (e) Can I comply with this AD in any other way? (1) You may use 
an alternative method of compliance or adjust the compliance time 
if:
    (i) Your alternative method of compliance provides an equivalent 
level of safety; and
    (ii) The Manager, Fort Worth or Los Angeles Airplane 
Certification Office (ACO), as applicable, approves your 
alternative. Submit your request through an FAA Principal 
Maintenance Inspector. The inspector may add comments before sending 
it to the Manager, Fort Worth or Los Angeles ACO.
    (2) Alternative methods of compliance approved for AD 2001-10-04 
and/or AD 2000-14-51 are not considered approved for this AD.

[[Page 66828]]

    (3) Alternative methods of compliance approved for AD 2001-10-04 
R1 are considered approved for this AD.

    Note 3: This AD applies to each airplane identified in 
paragraphs (a)(1) and (a)(2) of this AD, regardless of whether it 
has been modified, altered, or repaired in the area subject to the 
requirements of this AD. For airplanes that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (e) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if you have not eliminated the unsafe 
condition, specific actions you propose to address it.

    (f) Are there any alternative methods of compliance already 
approved or being considered for this AD? The FAA may approve, as an 
alternative method of compliance, inspection of the wing lower spar 
cap. You must submit the request in accordance with the procedures 
in paragraph (e) of this AD and adhere to the following:
    (1) If you are over or within 10 hours TIS of the safe life for 
the wing lower spar cap and you have ordered parts and scheduled a 
date for the replacement/modification, but having the replacement/
modification done on this date grounds the airplane, accomplish the 
following:
    (i) Inspect the wing lower spar cap within 10 hours TIS after 
approval of the alternative method of compliance;
    (ii) Reinspect thereafter at intervals not to exceed 400 hours 
TIS until either cracks are found, the date of the scheduled 
replacement/modification occurs, or 1,200 hours TIS after the 
initial inspection are accumulated, whichever occurs first; and
    (iii) Accomplish the inspections in accordance with the 
procedures in Snow Engineering Service Letter #197, #202, #203, or 
#205, all Revised March 26, 2001, as applicable.
    (2) Submit the following to the Fort Worth or Los Angeles ACO, 
as applicable, using the procedures described in paragraph (e) of 
this AD:
    (i) The airplane model serial number designation, and airplane 
registration number (N-number);
    (ii) The number of hours TIS on the airplane;
    (iii) The scheduled date for the replacement/modification; and
    (iv) The name and location of the authorized repair shop.
    (3) For more information about this issue, contact:
    (i) 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; and
    (ii) For the airplanes that incorporate or have incorporated 
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.
    (g) What if I need to fly the airplane to another location to 
comply with this AD? The FAA can issue a special flight permit under 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate your airplane to a location where 
you can accomplish the requirements of this AD provided that the 
following is adhered to:
    (1) Only operate in day visual flight rules (VFR) only.
    (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.
    (h) How do I get copies of the documents referenced in this AD? 
You may get copies of the documents referenced in this AD from 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. You may view these documents at FAA, Central Region, 
Office of the Regional Counsel, 901 Locust, Room 506, Kansas City, 
Missouri 64106.

Appendix to Docket No. 2001-CE-36-AD

    The following provides procedures for determining the safe life 
for those AT-400 and AT-500 series airplanes that incorporate or 
have incorporated Marburger Enterprises, Inc. winglets. These 
winglets are installed in accordance with Supplemental Type 
Certificate (STC) SA00490LA.
    1. Review your airplane's logbook to determine your airplane's 
time in service (TIS) with winglets installed per Marburger 
Enterprises STC 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 
paragraph (a)(1) of this AD. Any future winglet installation would 
be subject to a reduced safe life per these instructions.
    2. Determine your airplane's unmodified safe life from paragraph 
(a)(1) of this AD.
    Example: Your airplane is a Model AT-502B, serial number 0292. 
From paragraph (a)(1) of this AD, the safe-life of your airplane is 
4,000 hours TIS. All examples from hereon will be based on the Model 
AT-502B, serial number 0292 airplane.
    3. Determine the winglet usage factor from paragraph (a)(2) of 
this AD.
    Example: Again, your airplane is a Model AT-502B, serial number 
0292. From paragraph (a)(2) 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 1.) by the winglet usage 
factor (result of 3.).
    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 1.) from the adjusted winglet TIS (result of 4.).
    Example: Adjusted winglet TIS is 600 hours--the winglet TIS of 
500 hours. The winglet usage penalty is 100 hours TIS.
    6. Adjust the safe life of your airplane to account for winglet 
usage. Subtract the winglet usage penalty (result of 5.) result from 
the unmodified safe life from paragraph (a)(1) of this AD (the 
result of 2.).
    Example: The unmodified safe life is 4,000 hours TIS - the 100 
hours TIS usage penalty = 3,900 hours TIS adjusted safe life.
    7. If you remove the winglets from your airplane prior to 
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 6.). Enter this number in paragraph (d)(1) of this AD and 
the airplane logbook.
    8. If you keep the current winglet installation on your 
airplane, you must further reduce the safe life by dividing the 
adjusted safe life (result of 6.) by the winglet usage factor 
(result of 3.). Record this result in your airplane's logbook.
    Example: Adjusted safe life is 3,900 hours <divide> winglet 
usage factor of 1.2 = 3,250 hours TIS.
    9. If, at anytime in the future, you install or remove the 
Marburger winglet STC from your airplane, you must repeat the 
procedures in this Appendix.


    Issued in Kansas City, Missouri, on December 17, 2001.
Michael Gallagher,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 01-31555 Filed 12-26-01; 8:45 am]
BILLING CODE 4910-13-P