04-17119. Airworthiness Directives; Air Tractor, Inc. Models AT-401, AT-401B, AT-402, AT-402A, AT-402B, AT-501, AT-502, AT-502A, AT-502B, AT-503A, AT-602, AT-802, and AT-802A Airplanes

AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Final rule.

SUMMARY:

The FAA supersedes Airworthiness Directive (AD) 2002-19-10, which applies to certain Air Tractor, Inc. (Air Tractor) Models AT-402, AT-402A, AT-402B, AT-602, AT-802, and AT-802A airplanes. AD 2002-19-10 currently requires you to repetitively inspect the upper longeron and upper diagonal tube on the left hand side of the aft fuselage structure for cracks and contact the manufacturer for a repair scheme if cracks are found. This AD is the result of reports of the same cracks recently found on AT-500 series airplanes. The manufacturer has also issued new and revised service information that incorporates a modification to terminate the repetitive inspection requirements. Consequently, this AD retains the inspection actions required in AD 2002-19-10, adds certain AT-500 series airplanes to the applicability section, changes the compliance times, and incorporates new and revised manufacturer service information that contains a terminating action for the repetitive inspection requirement. We are issuing this AD to detect and correct cracks in the upper aft longeron, which could cause the fuselage to fail. Such failure could result in loss of control of the airplane.

DATES:

This AD becomes effective on September 7, 2004.

As of September 7, 2004, the Director of the Federal Register approved the incorporation by reference of certain publications listed in the regulation.

ADDRESSES:

You may get the service information identified in this AD from Air Tractor, Incorporated, P.O. Box 485, Olney, Texas 76374.

You may view the AD docket at FAA, Central Region, Office of the Regional Counsel, Attention: Rules Docket No. 2004-CE-05-AD, 901 Locust, Room 506, Kansas City, Missouri 64106. Office hours are 8 a.m. to 4 p.m., Monday through Friday, except Federal holidays.

FOR FURTHER INFORMATION CONTACT:

Andrew D. McAnaul, Aerospace Engineer, FAA, Fort Worth Airplane Certification Office (ACO), 2601 Meacham Boulevard, Fort Worth, Texas 76193-0150. Current duty station: San Antonio Manufacturing Inspection District Office (MIDO), 10100 Reunion Place, Suite 650, San Antonio, Texas 78216; telephone: [phone]; facsimile: [phone].

SUPPLEMENTARY INFORMATION:

Discussion

Has FAA taken any action to this point? We received reports of cracks found on the left hand upper longeron and upper diagonal support tubes where they intersect on the left hand side of the fuselage frame just forward of the vertical fin front spar attachment point on Air Tractor Model AT-602 airplanes. Additional cracking was later reported on AT-400, AT-602, and AT-802 series airplanes.

Air Tractor started installing extended reinforcement gussets on AT-402 and AT-802 series airplanes at the factory to alleviate the crack condition from occurring. The extended reinforcement gussets were intended to transfer the loads away from the joint. However, an AT-802 airplane with the extended reinforcement gusset installed during factory production was discovered cracked in service at the forward end of the gusset.

These conditions caused us to issue AD 2002-19-10, Amendment 39-12890 (67 FR 61481, October 1, 2002). AD 2002-19-10 currently requires you to do the following on certain Air Tractor Models AT-402, AT-402A, AT-402B, AT-602, AT-802, and AT-802A airplanes:

—Repetitively inspect the upper longeron and upper diagonal tube on the left hand side of the aft fuselage structure for cracks; and

—Contact the manufacturer for a repair scheme if cracks are found.

What has happened since AD 2002-19-10 to initiate this AD? We have received additional reports of the same cracks found on an Air Tractor Model AT-401, AT-502 and AT-502A airplane.

The manufacturer has also issued new and revised service information. The new service information contains procedures for replacing and modifying the upper aft longeron as a terminating action for the repetitive inspection requirement.

What is the potential impact if FAA took no action? This condition, if not detected and corrected, could cause the fuselage to fail. Such failure could result in loss of control of the airplane.

Has FAA taken any action to this point? We issued a proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that would apply to certain Air Tractor Models AT-401, AT-401B, AT-402, AT-402A, AT-402B, AT-501, AT-502, AT-502A, AT-502B, AT-503A, AT-602, AT-802, and AT-802A airplanes of the same type. This proposal was published in the Federal Register as a notice of proposed rulemaking (NPRM) on April 9, 2004 (69 FR 18848), as corrected on June 4, 2004 (69 FR 31658). The NPRM proposed to supersede 2002-19-10 with a new AD that would require you to repetitively inspect the upper longeron and the upper diagonal tube (as applicable) on the left hand side of the aft fuselage structure for cracks. If cracks are found, the NPRM also proposed to require you to replace and modify the upper and diagonal aft longeron (as applicable). Replacing and modifying the upper aft longeron and the diagonal longeron (as applicable) would terminate the repetitive inspection requirement.

Comments

Was the public invited to comment? The FAA encouraged interested persons to participate in the making of this amendment. The following presents the comments received on the proposal and FAA's responses to the comments:

Comment Issue No. 1: Remove the Requirement To Inspect, Replace, and Modify the Diagonal Longeron for Models AT-501, AT-502, AT-502A, AT-502B, AT-503A, AT-602, AT-802, and AT-802A Airplanes

What is the commenter's concern? The manufacturer states that we incorrectly proposed a requirement to inspect, replace, and modify the diagonal longeron on Models AT-501, AT-502, AT-502A, AT-502B, AT-503A, AT-602, AT-802, and AT-802A airplanes. The related service information referenced in the proposed AD does not require this action.

We infer that the manufacturer wants us to remove this requirement for the above referenced model airplanes from the final rule AD.

What is FAA's response to the concern? We concur with the commenter. We will change the final rule AD action based on this comment.

Comment Issue No. 2: Correct the Name of Snow Engineering Company in the Table in Paragraph (e) Under the Heading “Procedures”

What is the commenter's concern? The manufacturer states that the reference to Snow Engineer Co. Service Letter #195, reissued November 10, 2003, should be changed to Snow Engineering Co. Service Letter #195, reissued November 10, 2003.

What is FAA's response to the concern? We concur with the commenter. We will change the final rule AD action accordingly.

Comment Issue No. 3: Correct the Federal Register Version of the Notice of Proposed Rulemaking (NPRM) Published on April 9, 2004 (69 FR 18848)

What is the commenter's concern? The manufacturer wants the following corrections made in the final rule AD:

—In the table in paragraph (e)(2) under the heading “Procedures”, reference to Service Letter #218A should be changed to Service Letter #195B;

—In the table in paragraph (e)(4) under the heading “Procedures”, reference to Service Letter #218B, dated November 10, 2003, should be changed to Service Letter #213B, revised November 10, 2003; and

—In the table in paragraph (e)(7) under the heading “Procedures”, reference to Service Letter #217B, dated November 10, 2003, should be changed to Service Letter #217B, revised November 10, 2003.

What is FAA's response to the concern? We concur with the commenter. On June 4, 2004 (69 FR 31658), the Office of the Federal Register published a correction to the NPRM that incorporated all of the above comments. We are not changing the final rule AD based on this comment.

Conclusion

What is FAA's final determination on this issue? We have carefully reviewed the available data and determined that air safety and the public interest require adopting the AD as proposed except for the changes discussed above and minor editorial corrections. We have determined that these changes and minor corrections:

—Are consistent with the intent that was proposed in the NPRM for correcting the unsafe condition; and

—Do not add any additional burden upon the public than was already proposed in the NPRM.

Changes to 14 CFR Part 39—Effect on the AD

How does the revision to 14 CFR part 39 affect this AD? On July 10, 2002, the FAA published a new version of 14 CFR part 39 (67 FR 47997, July 22, 2002), which governs the FAA's AD system. This regulation now includes material that relates to altered products, special flight permits, and alternative methods of compliance. This material previously was included in each individual AD. Since this material is included in 14 CFR part 39, we will not include it in future AD actions.

Costs of Compliance

How many airplanes does this AD impact? We estimate that this AD affects 1,194 airplanes in the U.S. registry.

What is the cost impact of this AD on owners/operators of the affected airplanes? We estimate the following costs to accomplish the inspection(s):

Labor cost	Parts cost	Total cost per airplane	Total cost on U.S. operators
1 workhour × $65 per hour = $65	No parts required	$65	$65 × 1,194 = $77,610

We estimate the following costs to accomplish any necessary replacements that will be required based on the results of the inspection(s). We have no way of determining the number of airplanes that may need this replacement:

Labor cost	Parts cost	Total cost per airplane
27 workhours × $65 per hour = $1,755	For AT-400, AT-500, and AT-600 series airplanes: $35	For AT-400, AT-500, and AT-600 series airplanes: $1,755 + $35 = $1,790
	For AT-800 series airplanes: $45	For AT-800 series airplanes: $1,755 + $45 = $1,800.

What is the difference between the cost impact of this AD and the cost impact of AD 2002-19-10? The difference is the addition of certain Model AT-401, AT-401B, AT-501, AT-502, AT-502A, AT-502B, and AT-503A airplanes to the applicability section of this AD and the cost of replacing any cracked upper aft longeron. We are also removing certain Model AT-402 airplanes from the applicability section of this AD. There is no difference in cost to perform the inspection(s).

Regulatory Findings

Will this AD impact various entities? We have determined that this AD will not have federalism implications under Executive Order 13132. This AD will 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.

Will this AD involve a significant rule or regulatory action? For the reasons discussed above, I certify that this AD:

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 summary of the costs to comply with this AD and placed it in the AD Docket. You may get a copy of this summary by sending a request to us at the address listed under ADDRESSES. Include “AD Docket No. 2004-CE-05-AD” in your request.

List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Incorporation by reference
• Safety

Adoption of the Amendment

Accordingly, under 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 U.S.C. 106(g), 40113, 44701.

§ 39.13

[Amended]

2. FAA amends § 39.13 by removing Airworthiness Directive (AD) 2002-19-10, Amendment 39-12890 ( 67 FR 61481, October 1, 2002), and by adding a new AD to read as follows:

2004-15-15 Air Tractor, Inc.: Amendment 39-13749; Docket No. 2004-CE-05-AD; Supersedes AD 2002-19-10; Amendment 39-12890.

When Does This AD Become Effective?

(a) This AD becomes effective on September 7, 2004.

What Other ADs Are Affected by This Action?

(b) This AD supersedes AD 2002-19-10.

What Airplanes Are Affected by This AD?

(c) This AD affects the following airplane models and serial numbers that are certificated in any category:

Model	Serial Nos.
AT-401, AT-401B, AT-402, AT-402A, and AT-402B	0716 through 1144
AT-501, AT-502, AT-502A, AT-502B, and AT-503A	0037 through 0658
AT-602	0337 through 0664
AT-802 and AT-802A	0001 through 0139

What Is the Unsafe Condition Presented in This AD?

(d) This AD is the result of reports of cracks in the aft fuselage upper longeron, originally detected as excessive movement in the empennage due to the loss of fuselage torsional rigidity. The actions specified in this AD are intended to detect and correct cracks in the upper aft longeron, which could cause the fuselage to fail. Such failure could result in loss of control of the airplane.

What Must I Do To Address This Problem?

(e) To address this problem, you must inspect the upper longeron and upper diagonal tube (as applicable) on the left hand side of the fuselage frame just forward of the vertical fin front spar attachment for cracks at the times specified below. You must also replace and modify any cracked upper and diagonal longerons (as applicable) found during any inspection required by this AD before further flight after the inspection in which cracks are found.

Affected models and serial nos.	Inspection compliance times	Procedures
(1) AT-401, AT-401B, serial numbers (S/Ns) 0716 through 1144	Initially inspect upon the accumulation of 1,250 total hours time-in-service (TIS) or within the next 100 hours TIS after September 7, 2004 (the effective date of this AD), whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper and diagonal longerons are replaced and modified. Replacing and modifying the upper and diagonal longerons is the terminating action for the repetitive inspection requirement in this AD	Inspect following Snow Engineering Co. Service Letter #218A, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #218B, dated November 10, 2003.
(2) AT-402, AT-402A, and AT-402B, S/Ns 0716 through 1144	Initially inspect upon the accumulation of 1,250 total hours TIS or within the next 100 hours TIS after the last inspection required by AD 2002-19-10, whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper and diagonal longerons are replaced and modified. Replacing and modifying the upper and diagonal longerons is the terminating action for the repetitive inspection requirement in this AD	Inspect following Snow Engineering Co. Service Letter #218A, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #218B, dated November 10, 2003.
(3) AT-501, AT-502, AT-502B, and AT-503A, S/Ns 0037 through 0658	Initially inspect upon the accumulation of 4,800 total hours TIS or within the next 100 hours TIS after September 7, 2004 (the effective date of this AD), whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper longeron is replaced and modified. Replacing and modifying the upper longeron is the terminating action for the repetitive inspection requirement in this AD	Inspect following Snow Engineering Co. Service Letter #195B, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #195A, revised November 10, 2003.
(4)AT-502A, S/Ns 0037 through 0658	Initially inspect upon the accumulation of 2,800 total hours TIS or within the next 100 hours TIS after September 7, 2004 (the effective date of this AD), whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper longeron is replaced and modified. Replacing and modifying the upper longeron is the terminating action for the repetitive inspection requirement in this AD	Inspect following Snow Engineering Co. Service Letter #195B, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #195A, revised November 10, 2003.
(5) AT-602, S/Ns 0337 through 0661	Initially inspect upon the accumulation of 700 total hours TIS or within the next 100 hours TIS after the last inspection required by AD 2002-19-10, whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper longeron is replaced and modified. Replacing and modifying the upper longeron is the terminating action for the repetitive inspection requirement in this AD	Inspect following Snow Engineering Co. Service Letter #213A, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #213B, revised November 10, 2003.
(6) AT-602, S/Ns 0662 through 0664	Initially inspect upon the accumulation of 1,750 total hours TIS or within the next 100 hours TIS after the last inspection required by AD 2002-19-10, whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper longeron is replaced and modified. Replacing and modifying the upper longeron is the terminating action for the repetitive inspection requirement in this AD	Inspect following Snow Engineering Co. Service Letter #213A, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #213B, revised November 10, 2003.
(7) AT-802 and AT-802A, S/Ns 0001 through 0004 and 0012 through 0118	Initially inspect upon the accumulation of 250 total hours TIS or within the next 100 hours TIS after the last inspection required by AD 2002-19-10, whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper longeron is replaced and modified. Replacing and modifying the upper longeron is the terminating action for the repetitive inspection requirement in this AD	Inspect following Snow Engineering Co. Service Letter #217A, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #217B, revised November 10, 2003.
(8) AT-802 and AT-802A, S/Ns 0005 through 0011	Initially inspect upon the accumulation of 900 total hours TIS or within the next 100 hours TIS after the last inspection required by AD 2002-19-10, whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper longeron is replaced and modified. Replacing and modifying the upper longeron is the terminating action for the repetitive inspection requirement in this AD	Inspect following Snow Engineering Co. Service Letter #217A, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #217B, revised November 10, 2003.
(9) AT-802 and AT-802A, S/Ns 0119 through 0139	Initially inspect upon the accumulation of 1,750 total hours TIS or within the next 100 hours TIS after the last inspection required by AD 2002-19-10, whichever occurs later. Repetitively inspect thereafter at intervals not to exceed 100 hours TIS until the upper longeron is replaced and modified. Replacing and modifying the upper longeron is the terminating action for the repetitive inspection requirement in this AD	Inspect following Snow Engineering Co. Service Letter #217A, dated November 10, 2003, as specified in Snow Engineering Co. Service Letter #195, reissued November 10, 2003. Replace and modify following Snow Engineering Co. Service Letter #217B, revised November 10, 2003.

(f) You may replace and modify the upper and diagonal longeron (as applicable) at any time as a terminating action for the repetitive inspection requirement in this AD. However, you must replace and modify the upper and diagonal longeron (as applicable) before further flight after any inspection in which cracks are found.

May I Request an Alternative Method of Compliance?

(g) You may request a different method of compliance or a different compliance time for this AD by following the procedures in 14 CFR 39.19. Unless FAA authorizes otherwise, send your request to your principal inspector. The principal inspector may add comments and will send your request to the Manager, Fort Worth Aircraft Certification Office (ACO), FAA. For information on any already approved alternative methods of compliance, contact Andrew D. McAnaul, Aerospace Engineer, FAA, Fort Worth ACO, 2601 Meacham Boulevard, Fort Worth, Texas 76193-0150. Current duty station: San Antonio Manufacturing Inspection District Office (MIDO), 10100 Reunion Place, Suite 650, San Antonio, Texas 78216; telephone: [phone]; facsimile: [phone].

Does This AD Incorporate Any Material by Reference?

(h) You must do the actions required by this AD following the instructions in Snow Engineering Co. Service Letter #195, reissued November 10, 2003; Snow Engineering Co. Service Letter #195A, revised November 10, 2003; Snow Engineering Co. Service Letter #195B, dated November 10, 2003; Snow Engineering Co. Service Letter #213A, dated November 10, 2003; Snow Engineering Co. Service Letter #213B, revised November 10, 2003; Snow Engineering Co. Service Letter #217A, dated November 10, 2003; Snow Engineering Co. Service Letter #217B, revised November 10, 2003; Snow Engineering Co. Service Letter #218A, dated November 10, 2003; and Snow Engineering Co. Service Letter #218B, dated November 10, 2003. The Director of the Federal Register approved the incorporation by reference of this service bulletin in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. You may get a copy from Air Tractor, Incorporated, P.O. Box 485, Olney, Texas 76374. You may review copies at FAA, Central Region, Office of the Regional Counsel, 901 Locust, Room 506, Kansas City, Missouri 64106; or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call [phone], or go to: http://www.archives.gov/​federal_​register/​code_​of_​federal_​regulations/​ibr_​locations.html.

Issued in Kansas City, Missouri, on July 20, 2004.

Dorenda D. Baker,

Manager, Small Airplane Directorate, Aircraft Certification Service.