The Luftfartsverket (LFV), which is the airworthiness authority for Sweden, recently notified the FAA that an unsafe condition may exist on certain Saab Model SAAB SF340A and SAAB 340B series airplanes. The LFV advises that it has received several reports indicating that the brake assembly failed on several of these airplanes. Investigation revealed that the cause of the failures of the brake assemblies was due to separation of the stator clips from the stator disk. (The stator clip is a steel component that attaches to the stator lug to offer better resistance to damage of the drive face of the lug.) Brake assemblies having part numbers 5012589, 5007219-1, 5008541, 5008541-1, and 5008541-2 have been identified as those susceptible to such failure.
In certain reported instances, these separated clips migrated through the torque tube lightening hole and became trapped between the torque tube and the wheel hub. In at least one case, this resulted in acut through the hub, leakage of hydraulic fluid on the hot brakes, and subsequent brake fire fueled by hydraulic fluid. In other reported incidents, the separated clips migrated through the carbon stack and resulted in brake damage or disintegration.
These conditions, if not detected, could result in brake and wheel failure, which could lead to a brake fire.
Saab has issued Service Bulletin 340-32-105, dated September 5, 1995, which describes procedures for repetitive visual inspections to detect damage of the brake assembly and wheel assembly, repair of damaged assemblies, and installation of a heat shield in the torque tube. The LFV classified this service bulletin as mandatory and issued Swedish airworthiness directive SAD 1-075, dated September 7, 1995, in order to assure the continued airworthiness of these airplanes in Sweden.
This airplane model is manufactured in Sweden and is type certificated for operation in the United States under the provisions of section 21.29of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, the LFV has kept the FAA informed of the situation described above. The FAA has examined the findings of the LFV, 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.
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 failure of the brake assembly, which could result in a brake fire. This AD requires repetitive visual inspections to detect damage of the brake assembly and wheel assembly, repair of any damaged brake assembly or wheel assembly found, and installation of a heat shield. The actions are required to be accomplished in accordance with the service bulletin described previously.
This AD also provides for termination of the repetitive visual inspections by installing a redesigned stator clip. This installation is to be accomplished in accordance with a method approved by the FAA.
This is considered to be interim action. The manufacturer has advised that it is currently developing a modified stator clip that will positively address the unsafe condition addressed by this AD. Once this redesigned clip is developed, approved, and available, the FAA may consider additional rulemaking.
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.
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 reportthat 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 95-NM-187-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 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 forpart 39 continues to read as follows: Authority: 49 USC 106(g), 40101, 40113, 44701. 39.13 - [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: