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CFR Citation: 14 CFR Part 39

Docket ID: [Docket No. 2004-CE-05-AD]

RIN ID: RIN 2120-AA64

NOTICE: PROPOSED RULES

ACTION: Airworthiness directives:

DOCUMENT ACTION: Notice of proposed rulemaking (NPRM).

SUBJECT CATEGORY: 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

DATES: We must receive any comments on this proposed AD by June 7, 2004.

DOCUMENT SUMMARY: The FAA proposes to supersede Airworthiness Directive (AD) 20021910, which applies to certain Air Tractor, Inc. (Air Tractor) Models AT402, AT402A, AT402B, AT602, AT802, and AT802A airplanes. AD 20021910 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 proposed AD is the result of reports of the same cracks recently found on AT500 series airplanes. The manufacturer has also issued new and revised service information that incorporates a modification to terminate the repetitive inspection requirements. Consequently, this proposed AD would retain the inspection actions required in AD 20021910, would add certain AT500 series airplanes to the applicability section, would change the compliance times, and would incorporate new and revised manufacturer service information that contains a terminating action for the repetitive inspection requirement. We are issuing this proposed 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.

SUMMARY: Air Tractor, Inc.,

SUPPLEMENTAL INFORMATION

How do I comment on this proposed AD? We invite you to submit any written relevant data, views, or arguments regarding this proposal. Send your comments to an address listed under ADDRESSES. Include ``AD Docket No. 2004CE05AD'' in the subject line of your comments. If you want us to acknowledge receipt of your mailed comments, send us a self addressed, stamped postcard with the docket number written on it. We will datestamp your postcard and mail it back to you.

Are there any specific portions of this proposed AD I should pay attention to? We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. If you contact us through a nonwritten communication and that contact relates to a substantive part of this proposed AD, we will summarize the contact and place the summary in the docket. We will consider all comments received by the closing date and may amend this proposed AD in light of those comments and contacts.

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 AT602 airplanes. Additional cracking was later reported on AT400, AT602, and AT802 series airplanes.

Air Tractor started installing extended reinforcement gussets on AT402 and AT802 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 AT802 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 20021910, Amendment 39 12890 (67 FR 61481, October 1, 2002). AD 20021910 currently requires you to do the following on certain Air Tractor Models AT402, AT402A, AT402B, AT602, AT802, and AT802A 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 20021910 to initiate this proposed action? We have received additional reports of the same cracks found on an Air Tractor Model AT502 and AT502A 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.

Is there service information that applies to this subject? Snow [[Page 18849]]
Engineering Co. has issued the following Service Letters:
Service Letter 195, reissued: November 10, 2003;
Service Letter 195A, revised: November 10, 2003;
Service Letter 195B, dated November 10, 2003;
Service Letter 213A, dated November 10, 2003;
Service Letter 213B, revised November 10, 2003;
Service Letter 217A, dated November 10, 2003;
Service Letter 217B, revised November 10, 2003;
Service Letter 218A, dated November 10, 2003; and
Service Letter 218B, revised November 10, 2003.

What are the provisions of this service information? These service letters include procedures for:
Service Letter 195 specifies inspecting the upper longeron in the aft fuselage structure on all the affected model airplanes; Service Letter 195B, Service Letter 213A, Service Letter 217A, and Service Letter 218A provides the inspection requirements for all affected model airplanes; and Service Letter 195A, Service Letter 213B, Service Letter 217B, and Service Letter 218B give the procedures for replacing and modifying the upper aft longeron if cracks are found for all affected model airplanes and is the terminating action for the repetitive inspection requirements.

FAA's Determination and Requirements of This Proposed AD

What has FAA decided? We have evaluated all pertinent information and identified an unsafe condition that is likely to exist or develop on other products of this same type design. Therefore, we are proposing AD action.

What would this proposed AD require? This proposed AD would supersede 20021910 with a new AD that would require you to repetitively inspect the upper longeron and upper diagonal tube on the left hand side of the aft fuselage structure for cracks. If cracks are found, this proposed AD would also require you to replace and modify the upper aft longeron. Replacing and modifying the upper aft longeron would terminate the repetitive inspection requirement.

How does the revision to 14 CFR part 39 affect this proposed AD? On July 10, 2002, we published a new version of 14 CFR part 39 (67 FR 47997, July 22, 2002), which governs 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 would this proposed AD impact? We estimate that this proposed AD affects 1,194 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 inspections:
Total cost per Labor cost Parts cost airplane Total cost on U.S. operators 1 workhour x $65 per hour = $65....... No parts required........ $65 $65 x 1,194 = $77,610.

We estimate the following costs to accomplish any necessary replacements that would be required based on the results of the proposed inspection(s). We have no way of determining the number of airplanes that may need this replacement:
Total cost per Labor cost Parts cost airplane 27 workhours x $65 per hour For AT400, AT500, For AT400, AT500, = $1,755. and AT600 series and AT600 series airplanes: $35. airplanes: $1,755 + $35 = $1,790. For AT800 series For AT800 series airplanes: $45. airplanes: $1,755 + $45 = $1,800.

What is the difference between the cost impact of this proposed AD and the cost impact of AD 20021910? The difference is the addition of certain Model AT501, AT502, AT502A, AT502B, and AT503A airplanes to the applicability section of this proposed AD and the cost of replacing any cracked upper aft longeron. There is no difference in cost to perform the proposed inspection.

Regulatory Findings

Would this proposed AD impact various entities? 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.

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

FOR FURTHER INFORMATION CONTACT Andrew D. McAnaul, Aerospace Engineer, FAA, Fort Worth Airplane Certification Office (ACO), 2601 Meacham Boulevard, Fort Worth, Texas 761930150. Current duty station: San Antonio Manufacturing Inspection District Office (MIDO), 10100 Reunion Place, Suite 650, San Antonio, Texas 78216; telephone: (210) 3083365; facsimile: (210) 3083370.