Discussion
The FAA recently received a report of loss of control on a REVO Incorporated Lake LA-4 series airplane during flight. The report indicated that during climb-out following take-off, the pilot heard a loud bang, and the airplane pitched over into a vertical dive, with loss of elevator control. During the pilot's efforts to regain control, another loud bang was heard and sufficient control was regained to manage a safe landing. Further investigation of the incident and inspection of the subject airplane revealed interference between the horizontal stabilizer skin and the attachment fitting. This interference caused fretting, which led to fatigue cracking and associated corrosion of the attachment fitting. The fracture of the attachment fitting resulted in loss of directional control of the airplane.
Relevant Service Information
REVO has issued Service Bulletin B-78, dated April 3, 1998, applicable to Models Colonial C-2, Lake LA-4,Lake LA-4A, Lake LA-4P, and Lake LA-4-200 airplanes, which specifies procedures for:
- measuring the gap between the horizontal stabilizer rear beam and the attachment fitting for a clearance of 5/32 of an inch,
- if the gap between the stabilizer rear beam and the attachment fitting is less than 5/32-inch, removing the fitting and visually inspect for cracks, fretting, or corrosion,
- if cracks, fretting, or corrosion is present, replacing the attachment fitting with a new fitting,
- measuring the gap between the attachment fitting and the horizontal stabilizer skin for a clearance of 1/16 of an inch, and
- if the clearance between the horizontal stabilizer skin and the attachment fitting is less than 1/16 of an inch, but the other measurement is at or greater than 5/32 of an inch, trimming the stabilizer skin to provide at least 1/16 of an inch clearance.
The FAA's Determination
After examining the circumstances and reviewing all available information related to the incidents described above, including the relevant service information, the FAA has determined that AD action should be taken to prevent fatigue cracks in the horizontal stabilizer attachment fitting, which if not detected and corrected, could result in loss of control of the airplane.
Explanation of the Provisions of the AD
Since an unsafe condition has been identified that is likely to exist or develop in other REVO Colonial C-2, Lake LA-4, Lake LA-4A, Lake LA-4P, Lake LA-4-200 airplanes of the same type design, this AD requires measuring the gap between the horizontal stabilizer rear beam and the attachment fitting for correct clearance, and measuring the gap between the attachment fitting and the horizontal stabilizer skin for correct clearance. If the gap between the stabilizer rear beam and the attachment fitting is not the correct clearance, the action requires removing the horizontal tail half to gain access to the fitting, and visually inspecting forcracks, fretting, or corrosion. If cracks, fretting, or corrosion are present, the action requires replacing the attachment fitting with a new fitting. If the clearance between the horizontal stabilizer skin and the attachment fitting is not the correct clearance, but the other measurement is correct, the action requires trimming the stabilizer skin to provide acceptable clearance. The actions are to be done in accordance with the instructions in REVO Service Bulletin B-78, dated April 3, 1998.
Determination of the Effective Date of the AD
Since a situation exists (loss of directional control of 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 Rules Docket.
Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket No. 98-CE-48-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 U.S.C. 106(g), 40113, 44701.
39.13 [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive (AD) to read as follows: