AD 97-14-05

This amendment supersedes Airworthiness Directive AD 95-20-06, which 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 and currently requires repetitively inspecting the front spar attachment lugs and the rear spar for fatigue cracks, and modifying the vertical fin if cracks are found. The modification terminates the repetitive inspection requirement of AD 95-20-06 and may be incorporated at any time, if cracks are not found. The FAA has determined that the Air Tractor Models mentioned above with a 1/4-inch fin front spar fitting installed should be exempt from the AD. The AD will retain the requirements of AD 95-20-06 for all Air Tractor airplanes that have a 3/16-inch fin front spar fitting. The actions specified by this AD are intended to prevent in-flight vertical fin cracking, which, if not detected and corrected, could result in structural failure of the front spar attachments and eventually the rear spar attachment and cause loss of directional control of the airplane.

Final rule.

97-14-05 AIR TRACTOR INCORPORATED: Amendment No. 39-10063; Docket No. 96-CE-47-AD; Supersedes AD 95-20-06, Amendment 39-9384.

Applicability: The following airplane Models and serial numbers fitted with a 3/16-inch fin front spar fitting that do not have the modification in Snow Engineering Company Report No. 138, dated July 29, 1995, Revised August 7, 1996, incorporated, certificated in any category:

NOTE 1: The modification in Snow Engineering Company Report No. 138, dated July 29, 1995, Revised August 7, 1996, 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 Numbers

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 andAT-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 cracking, which, if not detected and corrected, could result in structural failure of the front spar attachments and eventually the rear spar attachment and cause loss of directional 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, dated July 29, 1995, 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, dated July 29, 1995, 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, dated July 29, 1995, 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 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 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 MaintenanceInspector, who may add comments and then send it to the Manager, Fort Worth Airplane Certification Office.

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

(g) The inspection and modification required by this AD shall be done in accordance with Snow Engineering Report No. 138, dated July 29, 1995, Revised August 7, 1996. 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., suite 700, Washington, DC.

(h) This amendment (39-10063) supersedes AD 95-20-06, Amendment 39-9384.

(i) This amendment becomes effective on August 25, 1997.

Events Leading to the Issuance of This AD
A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to Air Tractor airplanes fitted with 3/16-inch thick front spar attachment fittings that do not have the modification in Snow Engineering Company Report No. 138, dated July 29, 1995, Revised August 7, 1996, included the following Models and serial numbers:

Models
Serial Numbers

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

The notice of proposed rulemaking (NPRM) for this action was published in the Federal Register on February 19, 1997 (62 FR 7377). The proposed AD would supersede AD 95-20-06 with a new AD that would require inspecting the fin front spar attachment fittings of Models that have 3/16-inch thick fin front spar attachment fittings for cracks, and if cracks are found, prior to further flight, modifying the front spar attachment fittings. If no cracks are found, the proposed AD would require repetitively inspecting the front spar attachment fittings until cracks are found. Accomplishing the modification upon finding cracks or at any time prior to finding cracks would terminate the repetitive inspections.

Accomplishment of the proposed action would be in accordance with Snow Engineering Report (SER) number (No.) 138, dated July 29, 1995, Revised August 7, 1996.

Interested persons havebeen afforded an opportunity to participate in the making of this amendment. No comments were received on the proposed rule or the FAA's determination of the cost to the public.

The FAA's Determination
After careful review of all available information related to the subject presented above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed except for minor editorial corrections. The FAA has determined that these minor corrections will not change the meaning of the AD and will not add any additional burden upon the public than was already proposed.

Cost Impact
The FAA estimates that 24 airplanes in the U.S. registry will be affected by this AD, that it will take approximately 16 workhours per airplane to accomplish this 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 this AD on U.S. operators is estimated to be $23,280 or $970 per airplane. This figure is based on the presumption that no owner/operator of the affected airplanes has accomplished the required actions.

Regulatory Impact
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.

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) will not have a significant economic impact, positive or negative, on a substantial number of small entitiesunder the criteria of the Regulatory Flexibility Act. A copy of the final evaluation prepared for this action is contained 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, 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), 40113, 44701.

39.13 [Amended]
2. Section 39.13 is amended by removing airworthiness directive (AD) 95-20-06, Amendment 39-9384 (60 FR 52620) and by adding a new AD to read as follows: