AD 97-22-14

The Federal Aviation Administration (FAA) has received a report of an uncontained failure of a high pressure compressor rotor (HPCR) stage 3-9 spool installed on a GE model CF6-80C2 turbofan engine. The investigation revealed that a crack initiated in the HPCR stage 3-9 spool and propagated in low cycle fatigue to rapid fracture and disk rupture. The crack initiated from an oxygen stabilized alpha region located in the area of the stage 3 dovetail blade slot and propagated radially inward to the disk bore. The FAA has determined that HPCR stage 3-9 spools produced from the same melt of material may also be affected. The investigation is continuing and pending the results of the investigation the requirements of this AD may be changed. This condition, if not corrected, could result in failure of the HPCR stage 3-9 spool, which can result in an uncontained engine failure and damage to the aircraft. The FAA has reviewed and approved the technical contents of GE CF6-50 Service Bulletin (SB) 72-A1139, dated October 17, 1997, and GE CF6-80C2 SB 72-A906, dated October 17, 1997, that describe procedures for removal from service of defective HPCR 3-9 spools, and replacement with serviceable parts. Since an unsafe condition has been identified that is likely to exist or develop on other engines of the same type design, this AD is being issued to prevent failure of the HPCR 3-9 spool. This AD requires, within 30 days after the effective date of this AD, removal from service of defective HPCR 3-9 spools, and replacement with serviceable parts. This calendar end-date was determined based upon risk analysis. The actions are required to be accomplished in accordance with the SBs described previously. 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 should 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 aspectsof 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 notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 97-ANE-52-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 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: