E7-1874. Airworthiness Directives; Air Tractor, Inc. Model AT-602 Airplanes

AGENCY:

Federal Aviation Administration (FAA), Department of Transportation (DOT).

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

We propose to adopt a new airworthiness directive (AD) for certain Air Tractor, Inc. (Air Tractor) Model AT-602 airplanes. This proposed AD would require you to install access holes to do repetitive detailed visual inspections for cracks in the horizontal stabilizer brace tube assembly, and if any cracks are found as a result of a visual inspection, to replace the horizontal stabilizer brace tube assembly with a new design horizontal stabilizer brace tube assembly. The installation of the new design horizontal stabilizer brace tube assembly is terminating action for the repetitive inspection requirement. This proposed AD results from two reports of Model AT-602 airplanes with cracked horizontal stabilizer brace tube assemblies. We are proposing this AD to detect and correct cracks in the horizontal stabilizer brace tube assembly, which could result in failure of the horizontal stabilizer. This failure could affect the ability to control pitch with consequent loss of control.

DATES:

We must receive comments on this proposed AD by April 9, 2007.

ADDRESSES:

Use one of the following addresses to comment on this proposed AD:

• DOT Docket Web site: Go to http://dms.dot.gov and follow the instructions for sending your comments electronically.
• Government-wide rulemaking Web site: Go to http://www.regulations.gov and follow the instructions for sending your comments electronically.
• Mail: Docket Management Facility; U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, Washington, DC 20590-0001.
• Fax: [phone].
• Hand Delivery: Room PL-401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.
• Federal eRulemaking Portal: http://www.regulations.gov. Follow the instructions for submitting comments.

For service information identified in this proposed AD, contact Air Tractor Inc., P.O. Box 485, Olney, Texas 76374; telephone: [phone]; fax: [phone].

FOR FURTHER INFORMATION CONTACT:

Andrew McAnaul, Aerospace Engineer, ASW-150 (c/o MIDO-43), 10100 Reunion Place, Suite 650, San Antonio, Texas 78216; telephone: [phone]; fax: [phone].

SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or arguments regarding this proposed AD. Send your comments to an address listed under the ADDRESSES section. Include the docket number, “FAA-2006-26775; Directorate Identifier 2007-CE-01-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the proposed AD. We will consider all comments received by the closing date and may amend the proposed AD in light of those comments.

We will post all comments we receive, without change, to http://dms.dot.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive concerning this proposed AD.

Discussion

We have received two reports of Model AT-602 airplanes with cracked horizontal stabilizer brace tube assemblies. One tube was cracked completely in two. The horizontal stabilizer brace tube assemblies failed as a result of fatigue. Air Tractor has also identified excessive corrosion as a potential contributing factor.

This condition, if not corrected, could result in failure of the horizontal stabilizer. This failure could affect the ability to control pitch with consequent loss of control.

Air Tractor has developed an improved design horizontal stabilizer brace tube assembly with a larger shank.

Relevant Service Information

We have reviewed Snow Engineering Co. Service Letter #129A, dated August 7, 2004, revised November 15, 2005; Service Letter #235, dated August 25, 2004, revised October 23, 2006; and Drill Template—602, Drawing Number SL129-602, dated August 2, 2004.

The service information describes procedures for:

• Installing access holes for visual inspection of the horizontal stabilizer brace tube assembly (part number (P/N) 30012-7);
• Conducting a detailed visual inspection for cracks in the horizontal stabilizer brace tube assembly (P/N 30012-7); and
• Replacing the horizontal stabilizer brace tube assembly (P/N 30012-7) with a new design horizontal stabilizer brace tube assembly (P/N 30766-1).

FAA's Determination and Requirements of the Proposed AD

We are proposing this AD because we evaluated all information and determined the unsafe condition described previously is likely to exist or develop on other products of the same type design. This proposed AD would require you to:

• Install access holes to do visual inspections;
• Do repetitive detailed visual inspections for cracks in the horizontal stabilizer brace tube assembly; and
• If any cracks are found as a result of a visual inspection, replace the horizontal stabilizer brace tube assembly with a new design horizontal stabilizer brace tube assembly.

The installation of the new design horizontal stabilizer brace tube assembly is terminating action for the repetitive inspection requirement.

Costs of Compliance

We estimate that this proposed AD would affect 128 airplanes in the U.S. registry.

We estimate the following costs to do the proposed installation of access holes to do visual inspections:

Labor cost	Parts cost	Total cost per airplane	Total cost on U.S. operators
1 work-hour × $80 per hour = $80	$5	$85	$10,880

We estimate the following costs to do each visual inspection for cracks of the horizontal stabilizer brace tube assembly:

Labor cost	Parts cost	Total cost per airplane	Total cost on U.S. operators for initial inspection
1 work-hour × $80 per hour = $80	Not Applicable	$80	$10,240

We estimate the following costs to do any necessary replacement of the horizontal stabilizer brace tube assembly with a new design horizontal stabilizer brace tube assembly that would be required based on the results of the proposed inspection or as the terminating action for the repetitive inspection requirement. We have no way of determining the number of airplanes that may need this replacement:

Labor cost	Parts cost	Total cost per airplane
35 work-hours × $80 per hour = $2,800	$896	$3,696

Authority for This Rulemaking

Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority.

We are issuing this rulemaking under the authority described in subtitle VII, part A, subpart III, section 44701, “General requirements.” Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.

Regulatory Findings

We have determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD 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.

For the reasons discussed above, I certify that the proposed regulation:

1. Is not a “significant regulatory action” under Executive Order 12866;

2. Is not a “significant rule” under the 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 entities under the criteria of the Regulatory Flexibility Act.

We prepared a regulatory evaluation of the estimated costs to comply with this proposed AD and placed it in the AD docket.

Examining the AD Docket

You may examine the AD docket that contains the proposed AD, the regulatory evaluation, any comments received, and other information on the Internet at http://dms.dot.gov; or in person at the Docket Management Facility between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Office (telephone [phone]) is located at the street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

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 FAA proposes to amend 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. The FAA amends § 39.13 by adding the following new AD:

Air Tractor Inc.: Docket No. FAA-2006-26775; Directorate Identifier 2007-CE-01-AD.

Comments Due Date

(a) We must receive comments on this airworthiness directive (AD) action by April 9, 2007.

Affected ADs

(b) None.

Applicability

(c) This AD applies to Model AT-602 airplanes, all serial numbers through 602-0695 that:

(1) have horizontal stabilizer brace tube assembly, part number (P/N) 30012-7, installed; and

(2) are certificated in any category.

Unsafe Condition

(d) This AD results from two reports of Model AT-602 airplanes with cracked horizontal stabilizer brace tube assemblies. We are issuing this AD to detect and correct cracks in the horizontal stabilizer brace tube assembly, which could result in failure of the horizontal stabilizer. This failure could affect the ability to control pitch with consequent loss of control.

Compliance

(e) To address this problem, you must do the following, unless already done:

Actions	Compliance	Procedures
(1) Do the following: (i) Install access holes for visual inspection of the part number (P/N) 30012-7 horizontal stabilizer brace tube assembly. (ii) Conduct a detailed visual inspection for cracks in the P/N 30012-7 horizontal stabilizer brace tube assembly.	Install the access holes and do the initial inspection upon accumulating 2,000 hours time-in-service (TIS) or within the next 60 days after the effective date of this AD, whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS. Replacement of the P/N 30012-7 horizontal stabilizer brace tube assembly with a new design P/N 30766-1 horizontal stabilizer brace tube assembly following paragraph (e)(2) of this AD is terminating action for the repetitive inspection requirement of this AD	Follow Snow Engineering Co. Service Letter #235, dated August 25, 2004, revised October 23, 2006.
(2) Replace the P/N 30012-7 horizontal stabilizer brace tube assembly with a new design P/N 30766-1 horizontal stabilizer brace tube assembly	Before further flight after any inspection required by paragraph (e)(1) of this AD where cracks are found. The installation of a new design P/N 30766-1 horizontal stabilizer brace tube assembly is terminating action for the repetitive inspection requirement of this AD	Follow Snow Engineering Co. Service Letter #129A, dated August 7, 2004, revised November 15, 2005; Snow Engineering Co. Service Letter #235, dated August 25, 2004, revised October 23, 2006; and Snow Engineering Co. Drill Template—602, Drawing Number SL129-602, dated August 2, 2004.
(3) Do not install any P/N 30012-7 horizontal stabilizer brace tube assembly	As of the effective date of this AD	Not Applicable.

Alternative Methods of Compliance (AMOCs)

(f) The Manager, Fort Worth Airplane Certification Office, FAA, ATTN: Andrew McAnaul, Aerospace Engineer, ASW-150 (c/o MIDO-43), 10100 Reunion Place, Suite 650, San Antonio, Texas 78216; telephone: [phone]; fax: [phone], has the authority to approve AMOCs for this AD, if requested using the procedures found in 14 CFR 39.19.

Related Information

(g) To get copies of the service information referenced in this AD, contact Air Tractor Inc., P.O. Box 485, Olney, Texas 76374; telephone: [phone]; fax: [phone]. To view the AD docket, go to the Docket Management Facility; U.S. Department of Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, Washington, DC, or on the Internet at http://dms.dot.gov. The docket number is Docket No. FAA-2006-26775; Directorate Identifier 2007-CE-01-AD.

Issued in Kansas City, Missouri, on January 31, 2007.

Margaret Kline,

Acting Manager, Small Airplane Directorate, Aircraft Certification Service.