[Federal Register Volume 60, Number 195 (Tuesday, October 10, 1995)]
[Rules and Regulations]
[Pages 52620-52622]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-24604]



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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39

[Docket No. 95-CE-60-AD; Amendment 39-9384; AD 95-20-06]


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: Final rule; request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
applies to certain Air Tractor Incorporated (Air Tractor) Models AT-
301, AT-302, AT-400, AT-400A, AT-401, AT-402, AT-501, and AT-502 
airplanes. This action 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, then incorporate the 
modification as a terminating action. This action is prompted by two 
incident reports involving the failure of the front and rear spar 
attachment lugs 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: Effective October 25, 1995.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of October 25, 1995.
    Comments for inclusion in the Rules Docket must be received on or 
before November 27, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), Central Region, Office of the Assistant Chief 
Counsel, Attention: Rules Docket 95-CE-60-AD, Room 1558, 601 E. 12th 
Street, Kansas City, Missouri 64106.
    Service information that applies to this AD may be obtained from 
Air Tractor Incorporated, P.O. Box 485, Olney, Texas 76374. This 
information may also be examined at the Federal Aviation Administration 
(FAA), Central Region, Office of the Assistant Chief Counsel, 
Attention: Rules Docket 95-CE-60-AD, Room 1558, 601 E. 12th Street, 
Kansas City, Missouri 64106; or at the Office of the Federal Register, 
800 North Capitol Street NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Bob May, Aerospace Engineer, FAA, 
Aircraft Certification Office, 2601 Meacham Boulevard, Fort Worth, 
Texas 76193-0150; telephone (817) 222-5155; facsimile (817) 222-5960.

SUPPLEMENTARY INFORMATION: The FAA received reports of two incidents in 
which the front spar and rear spar failed on an Air Tractor AT-802A 
while in flight causing the vertical tail to lay over against the 
elevator creating difficulty in controlling the airplane. Both front 
spar failures occurred across the \3/16\-inch thick fin front spar 
fitting, which is made of aluminum and bolts to the fuselage frame. 
Investigations reveal that Air Tractor models designed with \3/16\-inch 
front spar attach plates are subject to fatigue failure. When front 
spar failure occurs the rear spar will only support the rudder loads 
for a short time before it also fails, which could result in loss of 
control of the airplane. 

[[Page 52621]]

    Air Tractor has issued Service Letter (SL) number (No.) 138, dated 
July 29, 1995, which specifies procedures for inspecting and modifying 
the fin front spar plate and the rear fin spar at the upper attachment 
to the fuselage frame.
    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 possible in-flight 
structural failure to the vertical fin 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.
    Since an unsafe condition has been identified that is likely to 
exist or develop in other Air Tractor Models AT-301, AT-302, AT-400, 
AT-400A, AT-401, AT-402, AT-501, and AT-502 airplanes of the same type 
design, this AD would require inspecting the front and rear spar 
attachments and, if fatigue cracks are found, modifying the airplane. 
The inspections and modifications are to be done in accordance with the 
INSTRUCTIONS section in Air Tractor SL No. 138, dated July 29, 1995. 
The accomplishment of the proposed modification will be considered a 
terminating action.
    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for public 
prior comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting immediate flight safety and, thus, was not 
preceded by notice and opportunity to comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 will be considered, 
and this rule may be amended in light of the comments received. Factual 
information that supports the commenter's ideas and suggestions is 
extremely helpful in evaluating the effectiveness of the AD action and 
determining whether additional rulemaking action would be needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 
AD 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. 95-CE-60-AD.'' The postcard will be date stamped and 
returned to the commenter.
    The regulations adopted herein will 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 final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and that it is not a significant regulatory 
action under Executive Order 12866. It has been determined further that 
this action involves an emergency regulation under DOT Regulatory 
Policies and Procedures (44 FR 11034, February 26, 1979). If it is 
determined that this emergency regulation otherwise would be 
significant under DOT Regulatory Policies and Procedures, a final 
regulatory evaluation will be prepared and placed in the Rules Docket 
(otherwise, an evaluation is not required). A copy of it, if filed, may 
be obtained from the Rules Docket.

List of Subjects in 14 CFR Part 39

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

Adoption of the Amendment

    Accordingly, pursuant to 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

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

    Authority: 49 USC 106(g), 40101, 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding a new airworthiness directive 
(AD) to read as follows:

95-20-06  Air Tractor Incorporated: Amendment 39-9384; Docket No. 
95-CE-60-AD.

    Applicability: The following airplane models and serial numbers, 
certificated in any category:

------------------------------------------------------------------------
              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 all metal rudder, 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 1: 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 (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 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 possible vertical fin structural failure of the front 
spar attachments and consequently 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 front spar attachment lugs on all models 
referenced in the APPLICABILITY section for fatigue cracks in 
accordance with the INSTRUCTIONS section of the Air Tractor Service 
Letter (SL) number (No.) 138, dated July 29, 1995. 

[[Page 52622]]

    (b) If no cracks are found during the initial inspection, repeat 
the inspection required by paragraph (a) of this AD at the 
applicable intervals as follows:
    (1) For airplanes that have \3/16\-inch thick fin front spar 
fittings, inspect at intervals not to exceed 25 hours TIS, in 
accordance with the INSTRUCTIONS section of the Air Tractor SL No. 
138, dated July 29, 1995.
    (2) For airplanes that have \1/4\-inch fin front spar fittings, 
inspect at intervals not to exceed 100 hours TIS, in accordance with 
the INSTRUCTIONS section of the Air Tractor SL No. 138, dated July 
29, 1995.
    (c) If cracks are found during any inspection required by this 
AD, prior to further flight, modify the front spar attachment 
fittings in accordance with the INSTRUCTIONS section of the Air 
Tractor SL No. 138, dated July 29, 1995.
    (d) Incorporating the modification specified in paragraph (c) of 
this AD is considered terminating action for the repetitive 
inspection requirements of this AD. This modification may be 
accomplished at any time provided the front and rear spar attachment 
fitting are crack free.
    (e) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (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 
compliance time that provides an equivalent level of safety may be 
approved by the Manager, Fort Worth Aircraft 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 
Aircraft Certification Office.

    Note 2: 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) The inspection and modification required by this AD shall be 
done in accordance with Air Tractor Service Letter number 138, dated 
July 29, 1995. This incorporation by reference was approved by the 
Director of the Federal Register in accordance with 5 U.S.C. 552(a) 
and 1 CFR part 51. Copies may be obtained from Air Tractor 
Incorporated, P.O. Box 485, Olney, Texas 76374. Copies may be 
inspected at the FAA, Central Region, Office of the Assistant Chief 
Counsel, Room 1558, 601 E. 12th Street, Kansas City, Missouri, or at 
the Office of the Federal Register, 800 North Capitol Street NW., 
7th Floor, suite 700, Washington, DC.
    (h) This amendment (39-9384) becomes effective on October 25, 
1995.

    Issued in Kansas City, Missouri, on September 26, 1995.
Henry A. Armstrong,
Acting Manager, Small Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. 95-24604 Filed 10-6-95; 8:45 am]
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