On June 27, 1997, the FAA issued emergency AD 97-14-11, which is applicable to certain Bombardier Model CL-600-2B19 (Regional Jet Series 100 and 200) series airplanes. That action was prompted by a report of a pressurization problem during flight on a Model CL-600-2B19 series airplane. Investigation revealed a crack approximately 14 inches long in the center pressure bulkhead. In addition, such cracking was found on seven other Model CL-600-2B19 series airplanes. The cause of this cracking has been attributed to structural fatigue. Fatigue cracking in the underfloor pressure bulkhead of the fuselage, if not detected and corrected in a timely manner, could result in uncontrolled depressurization of the airplane and/or reduced structural integrity of the fuselage.
Explanation of Relevant Service Information
The manufacturer has issued Canadair Regional Jet Alert Service Bulletin A601R-53-045, dated June 25, 1997, which describes procedures for repetitive detailed visual inspections to detect cracks at FS 409 + 128 of a certain bulkhead web of the fuselage at certain locations, and repair, if necessary. Transport Canada Aviation classified this alert service bulletin as mandatory and issued Canadian airworthiness directive CF-97-11, dated June 25, 1997, in order to assure the continued airworthiness of these airplanes in Canada.
FAA's Conclusions
This airplane model is manufactured in Canada 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, Transport Canada Aviation has kept the FAA informed of the situation described above. The FAA has examined the findings of Transport Canada Aviation, 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 the Requirements of the Rule
Since the unsafe condition described is likely to exist or develop on other airplanes of the same type design registered in the United States, the FAA issued emergency AD 97-14-11 to require repetitive detailed visual inspections to detect cracks at FS 409 + 128 of a certain bulkhead web of the fuselage at certain locations, and repair, if necessary. This AD also requires that operators report the results of the detailed visual inspection to the FAA. The inspections are required to be accomplished in accordance with the alert service bulletin previously described. The repair is required to be accomplished in accordance with a method approved by the FAA.
Operators should note that, while it is not the FAA s normal policy to allow flight with known cracks, this AD does permit further flight with cracking within certain limits. The results of a review, conducted by the manufacturer, revealed that cracking in the underfloor pressure bulkhead of the fuselage will not result in rapid decompression of the airplane. Therefore, according to the review, if the crack size limits are strictly observed and if repetitive inspections are performed at the required intervals, cracks that grow beyond the limits will be detected, and corrective action taken, before they can grow to a size that would create an unacceptable risk of structural failure. Transport Canada Aviation concurs with the findings of this review. In consideration of these findings and based on the FAA s criteria for flight with known cracking, the FAA has determined that further flight with cracking within certain limits in the center pressure bulkhead is permissible for an interim period.
This is considered to be interim action. The manufacturer has advised that it currently is developing a modification that will positively address the unsafe condition addressed by this AD. Once this modification is developed, approved, and available, the FAA may consider additional rulemaking.
Since it was found that immediate corrective action was required, notice and opportunity for prior public comment thereon were impracticable and contrary to the public interest, and good cause existed to make the AD effective immediately by individual notices issued on June 27, 1997, to all known U.S. owners and operators of certain Bombardier Model CL-600-2B19 (Regional Jet Series 100 and 200) series airplanes. These conditions still exist, and the AD is hereby published in the Federal Register as an amendment to section 39.13 of the Federal Aviation Regulations (14 CFR 39.13) to make it effective as to all persons.
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 inthe 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-136-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" underExecutive 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: