Discussion
What Events Have Caused This AD?
Several reports of cracked wing lower spar caps on Air Tractor AT-400, AT-500, and AT-800 series airplanes have caused the manufacturer (Air Tractor) to recalculate the fatigue life of the wing lower spar cap on these airplanes. One report was an accident where the wing separated from the airplane during flight. The cracks are originating in the outboard \3/8\-inch bolthole of the wing lower spar cap.
Air Tractor fatigue tested 24 wings and all had cracks in the area of the \3/8\-inch bolthole. Follow-on field inspections revealed more cracks in this area.
What Are the Consequences if the Condition Is Not Corrected?
This condition could result in fatigue cracks in the wing lower spar cap before the originally established safe life is reached. Fatigue cracks in the wing lower spar cap, if not detected and corrected, could result in the wing separating from the airplane during flight.
IsThere Service Information That Applies to This Subject?
Air Tractor has issued the following:
-- Snow Engineering Company Service Letter #197, Revised March 26, 2001, which applies to certain Models AT-501, AT-502, and AT-502A airplanes;
-- Snow Engineering Company Service Letter #202, Revised March 26, 2001, which applies to certain Models AT-400, AT-401, AT-401B, AT-402, AT-402A, and AT-402B airplanes;
-- Snow Engineering Company Service Letter #203, Revised March 26, 2001, which applies to certain Models AT-802 and AT-802A airplanes; and
-- Snow Engineering Company Service Letter #205, Revised March 26, 2001, which applies to certain Models AT-501, AT-502, AT-502B, and AT-503A airplanes.
These service letters include procedures for inspecting and replacing/modifying the wing lower spar cap on the affected airplanes.
The FAA's Determination and an Explanation of the Provisions of This AD
What Has FAA Decided?
The FAA has reviewed all available information, including the service information referenced above; and determined that:
-- The unsafe condition referenced in this document exists or could develop on other Air Tractor AT-400, AT-500, and AT-800 series airplanes of the same type design;
-- The actions specified in the previously-referenced service information (as specified in this AD) should be accomplished on the affected airplanes; and
-- AD action should be taken in order to correct this unsafe condition.
What Does This AD Require?
This AD lowers the safe life for the wing lower spar cap on Air Tractor AT-400, AT-500, and AT-800 series airplanes. This AD also allows for inspection, using eddy current methods, of the wing lower spar cap for airplanes that are at or over the lower safe life and parts are not available. Operation of the airplane is not allowed if cracks are found and inspections must be terminated when parts become available or after performing three repetitive inspections.
ThisAD supersedes AD 2000-14-51, Amendment 39-11837 (65 FR 46567, July 31, 2000), which currently requires inspection of the wing lower spar cap for cracks on Air Tractor Models AT-501, AT-502, and AT-502A airplanes, and modification or replacement of any cracked wing lower spar cap.
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 possible separation of the wing from the airplane during flight, FAA finds 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, we invite your comments on the rule. You may submit whatever written data, views, or arguments you choose. You need to include the rule's docket numberand submit your comments in triplicate 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?
The FAA specifically invites comments on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. You may examine 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.
We are reviewing the writing style we currently use in regulatory documents, in response to the Presidential memorandum of June 1, 1998. That memorandum requires federal agencies to communicate more clearly with the public. We are interested in your comments on whether the style of this document is clear, and any other suggestions you might have to improve the clarity of FAA communications that affect you. You can get more information about the Presidential memorandum and the plain language initiative at http://www.plainlanguage.gov.
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. 2000-CE-72-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?
The FAA has 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 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.
Sec. 39.13 [Amended]
2. FAA amends Sec. 39.13 by removing AD 2000-14-51, Amendment 39-11837 (65 FR 46567, July 31, 2000), and by adding a new airworthiness directive (AD) to read as follows: