Discussion
What Events Have Caused This AD?
Recently, the wing of an Air Tractor Model AT-400A separated from the airplane during flight. Investigation reveals that the right-hand lower spar cap failed due to fatigue at the 3/8-inch outboard bolt, which is located 6.5 inches outboard of the fuselage centerline.
The following airplanes have a similar type design to that of the accident airplane:
--All Models AT-300, AT-301, AT-302, and AT-400A airplanes that have aluminum spar caps;
--Air Tractor Models AT-400 airplanes, serial numbers 400-0244 through 400-0415, that have aluminum spar caps; and
--All Models AT-300 and AT-301 airplanes that have aluminum spar caps and are or have been converted to turbine power.
In addition, some airplanes have had Snow Engineering Co. Service Letter #55 incorporated. When incorporated, the affected area would be (1) the left and right side second outermost 7/16-inch boltholes, which are located 5.38 inches from centerline; and (2) the left and right side outermost 3/8-inch boltholes, which are located 6.5 inches outboard from centerline.
What Are the Consequences if the Condition is Not Corrected?
If not detected and corrected in a timely manner, cracks in the wing centerline splice joint could eventually result in the wing separating from the airplane during flight.
Is There Service Information That Applies to This Subject?
Air Tractor has issued the following:
--Snow Engineering Co. Process Specification 197, dated February 23, 2001; Revised May 1, 2002, and Revised May 3, 2002, which specify procedures for accomplishing an eddy current inspection of the wing centerline splice joint on the affected airplanes; and
--Snow Engineering Co. Service Letter #220, dated May 3, 2002, which specifies the procedures for gaining access to perform the eddy current inspection.
The FAA's Determination and an Explanation of the Provisions of this ADWhat Has FAA Decided?
The FAA has reviewed all available information and determined that:
--The unsafe condition referenced in this document exists or could develop on other Air Tractor Models AT-300, AT-301, AT-302, AT-400, and AT-400A airplanes of the same type design;
--A one-time eddy current inspection should be accomplished on these airplanes to detect and correct cracks in the wing centerline splice joint;
--The wing lower spar caps should be replaced at a certain time; and
--Final rule; request for comments (immediately adopted rule) AD action should be taken to address this condition.
What Does This AD Require?
This AD requires you to inspect (one-time) the wing centerline splice joint for cracks and, if any crack is found, replace the affected wing spar lower cap. This AD also requires you to report the results of the inspection to FAA and replace the wing spar lower caps after a certain amount of usage.
You must accomplish these actions in accordance with the previously-referenced service information.
We will evaluate the information received from the reporting requirement of this AD to determine whether additional rulemaking action should be taken. This could include repetitive inspections, parts replacement, modifications, or no further action.
In preparation of this rule, we contacted type clubs and aircraft operators to obtain technical information and information on operational and economic impacts. We have included, in the rulemaking docket, a discussion of information that may have influenced this action.
Will I have the Opportunity To Comment Prior to the Issuance of the Rule?
Because the unsafe condition described in this document could result in the wing separating from the airplane during flight, we find that notice and opportunity for public prior comment are impracticable. Therefore, good cause exists for making this amendment effective in less than 30 days.
Comments Invited
How Do I Comment on This AD?
Although this action is in the form of a final rule and was not preceded by notice and opportunity for public comment, FAA invites your comments on the 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 specified above. We may amend this rule in light of comments received. Factual information that supports your ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether we need to take additional rulemaking action.
Are There Any Specific Portions of the AD I Should Pay Attention to?
We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the 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 FAA contact with the public that concerns the substantive parts of this AD.
How Can I be Sure FAA Receives My Comment?
If you want us to acknowledge the receipt of your comments, you must include a self-addressed, stamped postcard. On the postcard, write "Comments to Docket No. 2002-CE-22-AD." We will date stamp and mail the postcard back to you.
Regulatory Impact
Does This AD Impact Various Entities?
These regulations 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. Therefore, FAA has determined that this final rule does not have federalism implications under Executive Order 13132.
Does This AD Involve a Significant Rule or Regulatory Action?
We have determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and is not a significant regulatory action under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket (otherwise, an evaluation is not required). A copy of it, if filed, may be obtained from the Rules Docket.
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 CFRpart 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.
Sec. 39.13 [Amended]
2. FAA amends 39.13 by adding a new airworthiness directive (AD) to read as follows: