The Departamento de Aviacao Civil (DAC), which is the airworthiness authority for Brazil, recently notified the FAA that an unsafe condition may exist on certain EMBRAER Model EMB-145 series airplanes. The CTA advises that it has received reports indicating that, during a routine inspection, cracks were found in the firewall of the auxiliary power unit (APU). In one incident, the crack was 24 inches in length. The cause of such cracking has been attributed to vibration of the firewall in the location where the recessed area of the shell is spot welded to the firewall. Cracking in the firewall of the APU, if not corrected, could result in reduced structural integrity of the fuselage and empennage in the event that a fire penetrates through the firewall of the APU.
Explanation of Relevant Service Information
EMBRAER has issued Service Bulletin 145-53-0004, dated July 28, 1997, which describes procedures for repetitive visual inspections to detect cracks in the firewall of the APU. The service bulletin also describes procedures for installation of a visco-elastic damper blanket on the firewall, which eliminates the need for the repetitive inspections. The DAC issued Brazilian airworthiness directive NPR/AD-97-145-02, dated July 30, 1997, in order to assure the continued airworthiness of these airplanes in Brazil.
FAA's Conclusions
This airplane model is manufactured in Brazil and is type certificated for operation in the United States under the provisions of section 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, the DAC has kept the FAA informed of the situation described above. The FAA has examined the findings of the DAC, 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 cracking in the firewall of the APU, which could result in reduced structural integrity of the fuselage and empenage in the event that a fire penetrates through the firewall of the APU. This AD requires repetitive visual inspections to detect cracks in the firewall of the APU, and repair, if necessary. This AD also requires installation of a visco-elastic damper blanket on the firewall, which constitutes terminating action for the repetitive inspection requirements. The inspections and installation are required to be accomplished in accordance with the service bulletin described previously.
Differences Between the AD and the Relevant Service Information
Operators should note that, although the referenced service bulletin specifies that the manufacturer must be contactedfor disposition of certain conditions, this AD requires the repair of those conditions to be accomplished in accordance with a method approved by the FAA.
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.
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 Number 97-NM-221-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 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.
39.13 - [Amended]
2. Section 39.13 is amended by adding the following new airworthiness directive: