[Federal Register Volume 62, Number 33 (Wednesday, February 19, 1997)]
[Proposed Rules]
[Pages 7377-7378]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-3958]



[[Page 7377]]

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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 96-CE-47-AD]
RIN 2120-AA64


Airworthiness Directives; Air Tractor Incorporated Models AT-301, 
AT-302, AT-400, AT-400A, AT-401, AT-402, AT-501, and AT-502 Airplanes

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes to supersede AD 95-20-06, which 
currently requires inspecting the front spar attachment lugs and the 
rear spar for fatigue cracks and modifying the vertical fin if cracks 
are found. If no cracks are found, continue repetitively inspecting the 
area until cracks are found; and then incorporate the modification as a 
terminating action. The proposed action would retain the actions 
required in AD 95-20-06 for all Air Tractor models that have a \3/16\-
inch fin front spar fitting. Air Tractor models that are fitted with a 
\1/4\-inch fin front spar fitting would not be required to accomplish 
this action. This action is prompted by two incident reports involving 
the failure of the front and rear spar attachment of the vertical fin. 
The actions specified by this AD are intended to prevent in-flight 
vertical fin structural failure of the front spar attachments and 
eventually the rear spar attachment, which, if not detected and 
corrected, could result in loss of directional control and loss of 
control of the airplane.

DATES: Comments must be received on or before April 21, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Central Region, Office of the Assistant Chief 
Counsel, Attention: Rules Docket No. 96-CE-47-AD, Room 1558, 601 E. 
12th Street, Kansas City, Missouri 64106. Comments may be inspected at 
this location between 8 a.m. and 4 p.m., Monday through Friday, 
holidays excepted.
    Service information that applies to the proposed AD may be obtained 
from Air Tractor Incorporated, P. O. Box 485, Olney, Texas 76374. This 
information also may be examined at the Rules Docket at the address 
above.

FOR FURTHER INFORMATION CONTACT: Bob May, Aerospace Engineer, FAA, 
Airplane Certification Office, 2601 Meacham Boulevard, Fort Worth, 
Texas 76193-0150; telephone (817) 222-5156; facsimile (817) 222-5960.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications should identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report that summarizes each FAA-public contact concerned 
with the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket No. 96-CE-47-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, Central Region, Office of the Assistant Chief Counsel, 
Attention: Rules Docket No. 96-CE-47-AD, Room 1558, 601 E. 12th Street, 
Kansas City, Missouri 64106.

Discussion

    It has been brought to the attention of the FAA that AD 95-20-06, 
which is applicable to Air Tractor Models AT-301, AT-302, AT-400, AT-
400A, AT-401, AT-402, AT-501, and AT-502 airplanes, should not have 
included models that are fitted with \1/4\-inch thick fin front spar 
attach fittings. The current AD requires inspecting for cracks on all 
of the models referenced above, regardless of whether they have \1/4\-
inch or \3/16\-inch thick front spar attachment fitting, and if no 
cracks are found, repetitively inspecting at different time intervals. 
The time interval would depend on the thickness of the fin front spar 
attach fitting on the airplane. If cracks are found, the current AD 
requires modifying the front spar attachment. Since publication of AD 
95-20-06, further investigation has revealed that the only Air Tractor 
models developing cracks are the models fitted with a \3/16\-inch thick 
front spar attachment fitting. For this reason, the FAA is proposing to 
supersede the current AD to change the instructions of the AD.

Relevant Service Information

    Air Tractor has issued a revised Service Letter (SL) No. 138, 
Revised August 7, 1996, which specifies procedures for inspecting, 
repetitively inspecting, and modifying the Air Tractor Models that have 
the 3/16-inch thick front spar attach fitting.

FAA's Determination

    After examining the circumstances and reviewing all available 
information related to the incidents described above, the FAA has 
determined that AD action should be taken to prevent in-flight vertical 
fin structural failure of the front spar attachments and eventually the 
rear spar attachment, which, if not detected and corrected, could 
result in loss of directional control and loss of control of the 
airplane.

Explanation of the Provisions of the Proposed AD

    Since an unsafe condition has been identified that is likely to 
exist or develop in other Air Tractor Incorporated Models AT-301, AT-
302, AT-400, AT-400A, AT-401, AT-402, AT-501, and AT-502 airplanes of 
the same type design that are fitted with 3/16-inch thick front spar 
attachment fittings, the proposed AD would supersede AD 95-20-06 with a 
new AD that would require inspecting the fin front spar attach fitting 
lugs of models that have 3/16-inch thick fin front spar attach fittings 
for cracks and if cracks are found, prior to further flight, modifying 
the front spar attachment lugs. If no cracks are found, the proposed AD 
would require repetitively inspecting the front spar attachment lugs 
until cracks are found. Accomplishing the modification would terminate 
the repetitive inspections.

Cost Impact

    The FAA estimates that 24 airplanes in the U.S. registry would be 
affected by the proposed AD, that it would take approximately 16 
workhours per airplane to accomplish the proposed action, and that the 
average labor rate is approximately $60 an hour. Parts cost 
approximately $10 per airplane. Based on these figures, the total cost 
impact of the proposed AD on U.S. operators is estimated to be $970 per 
airplane and

[[Page 7378]]

$23,280 for the U.S. fleet. The FAA has no way of determining how many 
owners/operators of these affected airplanes have accomplished this 
action.

Regulatory Impact

    The regulations proposed herein would not have substantial direct 
effects 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, in 
accordance with Executive Order 12612, it is determined that this 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this 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, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 14 
CFR part 39 of the Federal Aviation Regulations as follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 USC 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by removing Airworthiness Directive 
(AD) 95-20-06, Amendment 39-9384, and by adding a new AD to read as 
follows:

Air Tractor Incorporated: Docket No. 96-CE-47-'AD; Supersedes AD 95-
20-06, Amendment 39-9384.

    Applicability: The following airplane models and serial numbers 
that have not accomplished the modification in Snow Engineering Company 
Report No. 138, dated July 29, 1995, which is referenced in superseded 
AD 95-20-06, certificated in any category:

    Note 1: The modification in Snow Engineering Company Report No. 
138, dated July 29, 1995 and AD 95-20-06 required the airplanes to 
replace 3/16-inch thick fin front spar attach fittings with 1/4-inch 
thick fin front spar attach fittings.

------------------------------------------------------------------------
               Models                             Serial Nos.           
------------------------------------------------------------------------
AT-301 and AT-401...................  301-0261 through 301-0736, and 401-
                                       0662 through 401-0736 that have  
                                       been converted to turbine        
                                       powerplants and equipped with the
                                       all metal rudder, part number (P/
                                       N) 30456-1.                      
AT-302..............................  All aircraft equipped with the all
                                       metal rudder, P/N 30456-1.       
AT-400 and AT-400A..................  All aircraft equipped with the all
                                       metal rudder, P/N 30456-1.       
AT-402..............................  402-0694 and 402-0695 through 402-
                                       0736.                            
AT-501..............................  501-0002 through 501-0030 that    
                                       have been converted to turbine   
                                       powerplants and equipped with the
                                       all metal rudder, P/N 30456-1.   
AT-502..............................  502-0002 through 502-0030.        
------------------------------------------------------------------------

    Note 2: This AD applies to each airplane identified in the 
preceding applicability provision, 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 (f) 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 the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required initially within the next 25 hours time-in-
service (TIS) after the effective date of this AD, unless already 
accomplished, and thereafter as indicated in the body of this AD.
    To prevent in-flight vertical fin structural failure of the 
front spar attachments and eventually the rear spar attachment, 
which, if not detected and corrected, could result in loss of 
directional control and loss of control of the airplane, accomplish 
the following:
    (a) Inspect the fin front spar attachment fittings for fatigue 
cracks in accordance with the INSTRUCTIONS section of the Snow 
Engineering Report (SER) number (No.) 138, Revised August 7, 1996.
    (b) If no cracks are found during the initial inspection, repeat 
the inspection required by paragraph (a) of this AD at intervals not 
to exceed 25 hours TIS thereafter in accordance with the 
INSTRUCTIONS section of the SER No. 138, Revised August 7, 1996.
    (c) If cracks are found during any inspections required by this 
AD, prior to further flight, modify the fin front spar attachment 
fittings in accordance with the INSTRUCTIONS section of the SER No. 
138, Revised August 7, 1996.
    (d) Incorporating the modification specified in paragraph (c) of 
this AD is considered terminating action for the repetitive 
inspection requirements of this AD.
    (e) Special flight permits may be issued in accordance with 14 
CFR 21.197 and 21.199 to operate the airplane to a location where 
the requirements of this AD can be accomplished.
    (f) An alternative method of compliance or adjustment of the 
initial or repetitive compliance times that provides an equivalent 
level of safety may be approved by the Manager, Fort Worth Airplane 
Certification Office, 2601 Meacham Boulevard, Fort Worth, Texas 
76193-0150. The request shall be forwarded through an appropriate 
FAA Maintenance Inspector, who may add comments and then send it to 
the Manager, Fort Worth Airplane Certification Office. Alternative 
methods of compliance approved in accordance with AD 95-20-06 are 
considered approved as alternative methods of compliance for this 
AD.

    Note 3: Information concerning the existence of approved 
alternative methods of compliance with this AD, if any, may be 
obtained from the Fort Worth Aircraft Certification Office.

    (g) All persons affected by this directive may obtain copies of 
the document referred to herein upon request to Air Tractor 
Incorporated, P. O. Box 485, Olney, Texas 76374; or may examine this 
document at the FAA, Central Region, Office of the Assistant Chief 
Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri 64106.
    (h) This amendment supersedes AD 95-20-06, Amendment 39-9384. 
Issued in Kansas City, Missouri, on February 10, 1997.
Henry A. Armstrong,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 97-3958 Filed 2-18-97; 8:45 am]
BILLING CODE 4910-13-U