[Federal Register Volume 59, Number 7 (Tuesday, January 11, 1994)] [Unknown Section] [Page 0] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 94-589] [[Page Unknown]] [Federal Register: January 11, 1994] ----------------------------------------------------------------------- DEPARTMENT OF TRANSPORTATION 14 CFR Part 39 [Docket No. 93-ANE-04] Airworthiness Directives; General Electric Company CF6 Series Turbofan Engines AGENCY: Federal Aviation Administration, DOT. ACTION: Notice of proposed rulemaking (NPRM). ----------------------------------------------------------------------- SUMMARY: This document proposes the adoption of a new airworthiness directive (AD) that is applicable to General Electric Company (GE) CF6- 45/-50 series turbofan engines. This proposal would require installation of a fan stator case stiffening ring assembly, and a new stage one fan shroud. This proposal is prompted by a report of an uncontained stage one fan blade failure, which resulted in an inflight engine shutdown, and damage to the aircraft. The actions specified by the proposed AD are intended to prevent an uncontained stage one fan blade failure, which can result in an inflight engine shutdown, and damage to the aircraft. DATES: Comments must be received by February 10, 1994. ADDRESSES: Submit comments in triplicate to the Federal Aviation Administration (FAA), New England Region, Office of the Assistant Chief Counsel, Attn: Rules Docket No. 93-ANE-04, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may be inspected at this location between 8 a.m. and 4:30 p.m., Monday through Friday, except Federal holidays. The service information referenced in the proposed rule may be obtained from General Electric Aircraft Engines, CF6 Distribution Clerk, room 132, 111 Merchant Street, Cincinnati, OH 45246. This information may be examined at the FAA, New England Region, Office of the Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA. FOR FURTHER INFORMATION CONTACT: Robert J. Ganley, Aerospace Engineer, Engine Certification Office, ANE-142, Engine and Propeller Directorate, Aircraft Certification Service, FAA, New England Region, 12 New England Executive Park, Burlington, MA 01803-5299, telephone (617) 238-7138; fax (617) 238-7199. SUPPLEMENTARY INFORMATION: Comments Invited Interested persons are invited to participate in the making of the proposed 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 above. All communications received on or before the closing date for comments, specified above, will be considered by the Administrator before taking action on the proposed rule. The proposals contained in this notice may be changed in light of the comments received. Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with the substance of this proposal 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 No. 93-ANE-04.'' The postcard will be date stamped and returned to the commenter. Availability of NPRMs Any person may obtain a copy of this NPRM by submitting a request to the FAA, New England Region, Office of the Assistant Chief Counsel, Attn: Rules Docket No. 93-ANE-04, 12 New England Executive Park, Burlington, MA 01803-5299. Discussion The Federal Aviation Administration (FAA) has received a report of an uncontained stage one fan blade failure, attributed to excessive fan blade tip clearance. Engines without a fan stator case stiffening ring assembly, and a new stage one fan shroud, operate with relatively open stage one fan blade tip clearances. Increased fan rotor vibration occurs when the average tip clearance exceeds the maximum allowable clearance tolerances. This increased vibration increases stresses in the fan blade shank, which leads to cracking and subsequent blade failure. This condition, if not corrected, could result in an uncontained stage one fan blade failure, which can result in an inflight engine shutdown, and damage to the aircraft. The FAA has reviewed and approved the technical contents of GE CF6- 50 Service Bulletin (SB) No. 72-573, Revision 5, dated September 15, 1981, that describes procedures for the installation of the stiffening ring assembly and new stage one fan shroud. Since an unsafe condition has been identified that is likely to exist, or develop, on other engines of this same type design, the proposed AD would require installation of a fan stator case stiffening ring assembly and a new stage one fan shroud, which will result in reduced running clearances, and lower fan blade stresses. The compliance end date of August 31, 1995, ensures timely compliance without forced engine removals based on hardware availability. The actions would be required to be accomplished, in accordance with the service bulletin described previously. There are approximately 67 GE CF6-45/-50 series turbofan engines of the affected design in the worldwide fleet. The FAA has been advised by the manufacturer that there are no engines on U.S. registered aircraft that would be affected by this AD. However, should an affected engine be imported on an aircraft and placed on the U.S. registry in the future, it would take approximately 48 work hours to accomplish the proposed actions, and that the average labor rate is $55 per work hour. Required parts would cost approximately $9,360 per engine. Based on these figures, the total cost impact of the proposed AD is estimated to be $12,000 per engine. The regulations proposed herein would 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 proposal would not have sufficient federalism implications to warrant the preparation of a Federalism Assessment. For the reasons discussed above, I certify that this proposed regulation (1) is not a ``significant regulatory action'' under Executive Order 12886; (2) is not a ``significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) if promulgated, will not have a significant economic impact, positive or negative, on a substantial number of small entities under the criteria of the Regulatory Flexibility Act. A copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption ADDRESSES. List of Subjects in 14 CFR Part 39 Air transportation, Aircraft, Aviation safety, Safety. The Proposed Amendment Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration proposes to amend 14 CFR part 39 of the Federal Aviation Regulations as follows: PART 39--AIRWORTHINESS DIRECTIVES 1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. Sec. 39.13 [Amended] 2. Section 39.13 is amended by adding the following new airworthiness directive: General Electric Company: Docket No. 93-ANE-04. Applicability: General Electric Company (GE) CF6-45/-50 series turbofan engines installed on, but not limited to, Airbus A300 series, Boeing 747 series, and McDonnell Douglas DC-10 series aircraft. Compliance: Required as indicated, unless accomplished previously. To prevent an uncontained stage one fan blade failure, which can result in inflight engine shutdown, and damage to the aircraft, accomplish the following: (a) For engines that have not been modified in accordance with any revision level of GE CF6-50 Service Bulletin (SB) No. 72-573, prior to the effective date of this AD, install a fan stator case stiffening ring assembly and stage one fan shroud, in accordance with GE CF6-50 SB No. 72-573, Revision 5, dated September 15, 1981, by August 31, 1995. (b) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Engine Certification Office. The request should be forwarded through an appropriate FAA Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office. Note: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office. (c) Special flight permits may be issued, in accordance with FAR 21.197 and 21.199, to operate the aircraft to a location where the requirements of this AD can be accomplished. Issued in Burlington, Massachusetts, on December 21, 1993. Jay J. Pardee, Acting Manager, Engine and Propeller Directorate, Aircraft Certification Service. [FR Doc. 94-589 Filed 1-10-94; 8:45 am] BILLING CODE 4910-13-P