02-32685. Airworthiness Directives; Air Tractor, Inc. Models AT-300, AT-400, AT-400A, AT-401, AT-401B, AT-402, AT-402A, AT-402B, AT-501, AT-502, and AT-502B Airplanes

AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

This document proposes to adopt a new airworthiness directive (AD) that would apply to certain Air Tractor, Inc. (Air Tractor) Models AT-300, AT-400, AT-400A, AT-401, AT-401B, AT-402, AT-402A, AT-402B, AT-501, AT-502, and AT-502B airplanes. This proposed AD would require you to repetitively inspect the vertical fin front spar fitting for cracks and replace any cracked fitting found. This proposed AD would also require you to install a steel doubler as a terminating action for the repetitive inspections. This proposed AD is the result of a report of failure of a 1/4-inch thick vertical fin front spar fitting. The actions specified by this proposed AD are intended to prevent failure of the vertical fin front spar fitting, which could result in failure of the rear spar fitting. Such failures could lead to loss of directional control of the airplane.

DATES:

The Federal Aviation Administration (FAA) must receive any comments on this proposed rule on or before February 28, 2003.

ADDRESSES:

Submit comments to FAA, Central Region, Office of the Regional Counsel, Attention: Rules Docket No. 2000-CE-59-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 also send comments electronically to the following address: [e-mail]. Comments sent electronically must contain “Docket No. 2000-CE-59-AD” in the subject line. If you send comments electronically as attached electronic files, the files must be formatted in Microsoft Word 97 for Windows or ASCII text.

You may get service information that applies to this proposed AD from Air Tractor, Inc., P.O. Box 485, Olney, Texas 76374. You may also view this information at the Rules Docket at the address above.

FOR FURTHER INFORMATION CONTACT:

Andy McAnaul, Aerospace Engineer, FAA, Fort Worth Airplane Certification Office, 2601 Meacham Boulevard, Fort Worth, Texas 76193-0150; telephone: [phone]; facsimile: [phone].

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 mailed comments, you must include a self-addressed, stamped postcard. On the postcard, write “Comments to Docket No. 2000-CE-59-AD.” We will date stamp and mail the postcard back to you.

Discussion

What Events Have Caused This Proposed AD?

The FAA received reports of two incidents, one in 1994 and one in 1995, in which the vertical fin front spar fitting and rear spar fitting failed, while in flight, on an Air Tractor Model AT-402 and a Model AT-502 airplane. Failure of the vertical fin front spar fitting causes the rear spar fitting to fail. These failures result in the vertical tail lying over against the elevator creating difficulty in controlling the airplane.

These vertical fin front spar fittings were made of 3/16-inch thick aluminum. Investigation revealed that Air Tractor models with the 3/16-inch front spar attach plates installed were subject to fatigue failure.

This unsafe condition was addressed in AD 95-20-06, Amendment 39-9384. AD 95-20-06 applied to airplanes with 3/16-inch thick and 1/4-inch thick aluminum fin front spar fittings installed.

In 1997, we issued AD 97-14-05, Amendment 39-10063, that supersedes AD 95-20-06. Further investigation revealed that only Air Tractor models with a 3/16-inch thick fin front spar fitting installed were developing cracks. Therefore, we issued AD 97-14-05 to remove Air Tractor models with a 1/4-inch thick fin front spar fitting installed from the applicability.

Recently, a Model AT-502 airplane was found with a cracked 1/4-inch thick fin front spar fitting. The crack was found during a routine inspection. The rear spar had not yet failed. This recent finding demonstrates that Air Tractor models with a 1/4-inch thick fin front spar fitting are subject to fatigue failure.

What Are the Consequences if the Condition Is Not Corrected?

This condition, if not detected and corrected, could result in structural failure of the vertical fin front spar fitting and eventually the rear spar fitting. Such failure could result in loss of directional control of the airplane.

Is There Service Information That Applies to This Subject?

Snow Engineering Company has issued Service Letter # 155, Revised November 27, 2002.

What Are the Provisions of This Service Information?

The service letter includes procedures for:

—Repetitively inspecting the vertical fin front spar fitting cracks;

—Replacing any cracked fitting found; and

—Installing a steel doubler as a terminating action for the repetitive inspections.

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 Air Tractor Models AT-300, AT-400, AT-400A, AT-401, AT-401B, AT-402, AT-402A, AT-402B, AT-501, AT-502, and AT-502B airplanes of the same type design;

—The actions specified in the previously-referenced service information should be accomplished on the affected airplanes; and

—AD action should be taken in order to correct this unsafe condition.

What Would This Proposed AD Require?

This proposed AD would require you to incorporate the actions in the previously-referenced service bulletin.

Cost Impact

How Many Airplanes Would This Proposed AD Impact?

We estimate that this proposed AD affects 440 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:

Labor cost	Parts cost	Total cost per airplane	Total cost on U.S. operators
4 workhours × $60 = $240	No parts required	$240	$240 × 440 = $105,600.

We estimate the following costs to accomplish the proposed modification:

Labor cost	Parts cost	Total cost per airplane
7 workhours × $60 = $420	Parts will be provided by Air Tractor at no charge to the customer	$420

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.

§ 39.13

[Amended]

2. FAA amends § 39.13 by adding a new airworthiness directive (AD) to read as follows:

Air Tractor, Inc.: Docket No. 2000-CE-59-AD.

(a) What airplanes are affected by this AD? This AD affects the following airplane models and serial numbers that are certificated in any category:

Model	Serial numbers
AT-300, AT-400, and AT-400A	All serial numbers with a turbine powerplant and is retrofitted with a 1/4-inch thick aluminum vertical fin front spar fitting and an all-metal rudder.
AT-401 and AT-401B	401-0737 through 401-1015 and 401B-0737 through 401B-1015.
AT-402, AT-402A, and AT-402B	402-0737 through 402B-1015.
AT-501	501-0031 and subsequent that have been converted to turbine powerplants.
AT-502 and AT-502B	502-0031 through 502B-0398.

(b) Who must comply with this AD? Anyone who wishes to operate any of the airplanes identified in paragraph (a) of this AD must comply with this AD.

(c) What problem does this AD address? The actions specified by this AD are intended to prevent failure of the vertical fin front spar fittings, which could result in failure of the rear spar fitting. Such failures could lead to loss of directional control of the airplane.

(d) What actions must I accomplish to address this problem? To address this problem, you must accomplish the following:

Actions	Compliance	Procedures
(1) Inspect the vertical fin front spar fitting for cracks	Upon the accumulation of 2,000 hours time-in-service (TIS) on the vertical fin front spar fitting or within the next 100 hours TIS after the effective date of this AD, whichever occurs later. If no cracks are found, repetitively inspect thereafter at intervals not to exceed 100 hours TIS	In accordance with Snow Engineering Co. Service Letter #155, Revised November 27, 2002.
(2) If cracks are found during any inspection required in paragraph (d)(1) of this AD, replace the vertical fin front spar fitting	Prior to further flight after the crack is found. Continue with the repetitive inspection requirements in paragraph (d)(1) of this AD until the terminating action is accomplished	In accordance with Snow Engineering Co. Service Letter #155, Revised November 27, 2002.
(3) Modify the vertical fin front spar fitting by installing a steel doubler	Within the next 2,000 hours TIS after the effective date of this AD. Installing the steel doubler is considered terminating action for the repetitive inspection requirements of this AD. The installation may be accomplished at any time provided the vertical fin front spar fitting is crack free	In accordance with Snow Engineering Co. Service Letter #155, Revised November 27, 2002.

(e) Can I comply with this AD in any other way? You may use an alternative method of compliance or adjust the compliance time if:

(1) Your alternative method of compliance provides an equivalent level of safety; and

(2) The Manager, Ft. Worth Aircraft Certification Office (ACO), approves your alternative. Submit your request through an FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Ft. Worth ACO.

Note:

This AD applies to each airplane identified in paragraph (a) 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) Where can I get information about any already-approved alternative methods of compliance? Contact Andy McAnaul, Aerospace Engineer, FAA, Fort Worth Airplane Certification Office, 2601 Meacham Boulevard, Fort Worth, Texas 76193-0150; telephone: [phone]; facsimile: [phone].

(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.

(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, Inc., P.O. Box 485, Olney, Texas 76374. You may view these documents at FAA, Central Region, Office of the Regional Counsel, 901 Locust, Room 506, Kansas City, Missouri 64106.

Issued in Kansas City, Missouri, on December 20, 2002.

Michael Gallagher,

Manager, Small Airplane Directorate, Aircraft Certification Service.