The Direction Generale de l'Aviation Civile (DGAC), which is the airworthiness authority for France, recently notified the FAA that an unsafe condition may exist on certain Airbus Model A330 and A340 series airplanes. The DGAC advises that four cases of transfer tube disconnection from the ball nut of the trimmable horizontal stabilizer actuator (THSA) have been detected during greasing of in-service Model A330 and A340 series airplanes. The cause was found to be water entering the ball nut of the THSA, resulting in jamming of the ball transfer path when the water froze. There are three independent circuits of balls. The loss of one or two circuits does not impact the THSA operation, as it continues to operate on the remaining circuits. If three circuits are lost, then the THSA operates on the fail-safe nut. Due to the high friction between the fail-safe nut and the screw, THSA operation will be inefficient and it will lock after a few movements. This degraded operation is not detectable by the flight crew as long as the THSA is not locked and could damage the screw and the fail-safe nut. Jamming of the ball transfer paths, if not corrected, could result in degraded operation of the THSA and consequent reduced controllability of the airplane.
Explanation of Relevant Service Information
Airbus has issued All Operator Telexes (AOT) A330-27A3088 and A340-27A4093, both dated April 5, 2001, which describe procedures for repetitive detailed visual inspections of the ball nut in the area of the transfer tubes for, among other things, evidence of ball migration from the ball nut; distortion of the collar or transfer tubes; or disconnection of the transfer tubes from the ball nut; and replacement of the THSA, if necessary. The DGAC classified these AOTs as mandatory and issued French airworthiness directives 2001-141(B) and 2001-140(B), both dated April 18, 2001, in order to assure the continued airworthiness of these airplanes in finance.FAA's Conclusions
These airplane models are manufactured in and are type certificated for operation in the United States under the provisions of Sec. 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, the DGAC has kept the FAA informed of the situation described above. The FAA has examined the findings of the DGAC, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States.
Explanation of Requirements of Rule
Since an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design registered in the United States, this AD is being issued to prevent degraded operation of the THSA due to the entrance of water into the ball nut, and consequent reduced controllability of the airplane. This AD requires accomplishment of the actions specified in the applicable AOT described previously. This AD also requires that operators report results of inspection findings to Airbus.
Interim Action
This is considered to be interim action until final action is identified, at which time the FAA may consider further rulemaking.
Determination of Rule's Effective Date
Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public 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 flight safety and, thus, was not preceded by notice and an opportunity for public 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 shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption ADDRESSES. 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.
Submit comments using the following format:
Organize comments issue-by-issue. For example, discuss a request to change the compliance time and a request to change the service bulletin reference as two separate issues.
For each issue, state what specific change to the AD is being requested.
Include justification (e.g., reasons or data) for each request.
Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule thatmight 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 Number 2001-NM-135-AD." The postcard will be date stamped and returned to the commenter.
Regulatory Impact
The regulations adopted herein 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, it is determined that this final rule does not have federalism implications under Executive Order 13132.
The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it 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. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption ADDRESSES.
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.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: