Events Leading to the AD
The FAA has received 11 reports of the aft lower fuselage wing attach fittings cracking on Aviat Models S-1S, S-1T, S-2, S-2A, S-2S, and S-2B airplanes. Five of these incidents were reported on in-service airplanes and six were found defective during Aviat's in-house manufacturing process. Each of the cracked aft lower fuselage wing attach fittings incorporate either part number (P/N) 76090, P/N 2-2107-1, or P/N 1-210-102. If not detected and corrected, a cracked aft lower fuselage wing attach fitting could lead to in-flight separation of the wing from the airplane.
Further analysis of the design of the P/N 76090, 2-2107-1, and 1-210-102 aft lower fuselage wing attach fittings reveals a bend radius that could reduce the fatigue life and subsequently make the parts more susceptible to cracking. Aviat started manufacturing airplanes in 1990 with aft lower fuselage wing attach fittings with a larger bend radius. The FAA hasreceived no reports of cracking on airplanes incorporating attach fittings that incorporate this larger bend radius design.
Aviat has issued Service Bulletin (SB) No. 25, dated April 3, 1996, which specifies procedures for inspecting and modifying the aft lower fuselage wing attach fittings incorporating either P/N 76090, 2-2107-1, and 1-210-102.
After examining the circumstances and reviewing all available information related to the incidents described above, the FAA has determined that AD action should be taken to prevent possible in-flight separation of the wing from the airplane caused by a cracked fuselage wing fitting. Explanation of the Provisions of the AD
Since an unsafe condition has been identified that is likely to exist or develop in other Aviat Models S-1S, S-1T, S-2, S-2A, S-2S, and S-2B airplanes of the same type design that are equipped with aft lower fuselage wing attach fittings incorporating either P/N 76090, 2-2107-1, or 1-210-102, this AD requiresrepetitively inspecting the aft lower fuselage wing attach fitting on both wings for cracks, and modifying any cracked aft lower fuselage wing attach fitting. Modifying the aft lower fuselage wing fitting on both wings eliminates the repetitive inspection requirement of this AD. Accomplishment of the required actions is in accordance with Aviat SB No. 25, dated April 3, 1996.
Since a situation exists (possible in-flight separation of the wing from the airplane) that requires the immediate adoption of this regulation, it is found that notice and opportunity for public prior comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days.
Comments Invited
Although this action is in the form of a final rule that involves requirements affecting immediate flight safety and, thus, was not preceded by notice and opportunity to comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications should identify the Rules Docket number and be submitted in triplicate to the address specified above. All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.
Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the RulesDocket.
Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket No. 96-CE-23-AD." The postcard will be date stamped and returned to the commenter.
Regulatory Impact
The regulations adopted herein will not have substantial direct effects 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, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
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, pursuant to 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 USC 106(g), 40113, 44701.
Section 39.13 - [AMENDED]
2. Section 39.13 is amended by adding a new airworthiness directive (AD) to read as follows: