The FAA has received a report where several cracks were found in the fuselage forward horizontal stabilizer attach spar fitting on an Aerostar Model PA-60-601P airplane. Further investigation revealed that stress corrosion caused the cracks. This airplane had been inspected for cracks in the fuselage horizontal stabilizer attach spar fittings consistently at intervals of 200 hours time-in-service (TIS).
The affected airplane had a total usage time of 4,279 hours (TIS), which is considered about average for the fleet of approximately 600 Aerostar PA-60-600 series airplanes registered in the United States. Undetected cracked fuselage horizontal stabilizer attach fittings could result in the fuselage horizontal stabilizer separating from the airplane while in flight with subsequent loss of control of the airplane.
Aerostar has issued Service Bulletin SB600-130, dated September 26, 1995, which specifies procedures for inspecting fuselage horizontalstabilizer attach fittings on Aerostar PA-60-600 series airplanes.
After examining the circumstances and reviewing all available information related to the incidents described above including the referenced service bulletin, the FAA has determined that AD action should be taken to prevent undetected cracked fuselage horizontal attach fittings, which could result in the fuselage horizontal stabilizer separating from the airplane while in flight with subsequent loss of control of the airplane.
Since an unsafe condition has been identified that is likely to exist or develop in other Aerostar PA-60-600 series airplanes of the same type design, this AD requires repetitively inspecting the fuselage horizontal stabilizer attach fittings for cracks, and replacing any cracked fuselage horizontal stabilizer attach fitting with a serviceable approved part of like design. Accomplishment of these inspections are in accordance with Aerostar Service Bulletin SB600-130, dated September 26,1995. Any fuselage horizontal stabilizer attach fitting replacement that is required shall be accomplished in accordance with the applicable maintenance manual.
The compliance time of this AD is presented in calendar time and hours TIS. Cracking of the fuselage horizontal stabilizer attach fittings on the affected airplane is caused by stress corrosion, which starts as a result of stress loads incurred through operation. Corrosion can then develop regardless of whether the airplane is in flight. The cracks may not be noticed initially as a result of the stress loads, but could then develop through corrosion. In order to ensure that these stress corrosion cracks do not go undetected, a compliance time of specific hours TIS and calendar time (whichever occurs first) is utilized.
Since a situation exists (possible separation of the fuselage horizontal stabilizer separating from the airplane during flight) that requires the immediate adoption of this regulation, it is foundthat 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 Rules Docket.
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. 95-CE-81-AD." The postcard will be date stamped and returned to the commenter.
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 and 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), 40101, 40113, 44701.
Section 39.13 - [AMENDED]
2. Section 39.13 is amended by adding a new airworthiness directive (AD) to read as follows: