[Federal Register Volume 59, Number 144 (Thursday, July 28, 1994)] [Unknown Section] [Page ] From the Federal Register Online via the Government Publishing Office [www.gpo.gov] [FR Doc No: 94-18360] [Federal Register: July 28, 1994] ----------------------------------------------------------------------- DEPARTMENT OF TRANSPORTATION 14 CFR Part 39 [Docket No. 89-ANE-26] Airworthiness Directives; Pratt & Whitney JT8D Series Turbofan Engines AGENCY: Federal Aviation Administration, DOT. ACTION: Proposed rule; withdrawal. ----------------------------------------------------------------------- SUMMARY: This action withdraws a notice of proposed rulemaking (NPRM) that proposed a new airworthiness directive (AD), applicable to Pratt & Whitney JT8D series turbofan engines. That action would have required removal of certain second stage turbine vanes repaired by Turbine Components Corporation (TCC), Federal Aviation Administration (FAA) Repair Station No. 119-20, of Branford, Connecticut. Since the issuance of the NPRM, the FAA has determined through test, analysis, and review of data from operator experience over the past four years that the unsafe condition described in the NPRM is not likely to exist or develop in other engines of the same type design. Accordingly, the proposed rule is withdrawn. FOR FURTHER INFORMATION CONTACT: Mark A. Rumizen, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone (617) 238-7137, fax (617) 238-7199. SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to add a new airworthiness directive (AD), applicable to Pratt & Whitney (PW) JT8D-1, -1A, -1B, - 7, -7A, -7B, -9, -9A, -11, -15, -15A, -17, -17A, -17R, and -17AR turbofan engines, incorporating second stage turbine vanes repaired by Turbine Components Corporatration (TCC), Federal Aviation Administration (FAA) Repair Station No. 119-20, of Branford, Connecticut, was published in the Federal Register on October 26, 1989 (54 FR 43586). The proposed rule would have required removal of certain second stage turbine vanes that contain repairs using trailing edge and airfoil midsection (``H'' dimension) dimension puddle welds that may not possess adequate structural integrity and may fail during engine operation of the vane airfoil. Puddle welding can produce a number of welding abnormalities including a significant amount of heat affected zone (HAZ) cracking. The FAA believed that the HAZ cracking coupled with the aerodynamic loading and thermal cycling of the airfoil can lead to further crack propagation and eventual airfoil fracture. The subsequent damage created by a second stage turbine vane airfoil fracture can cause downstream turbine blade and vane fractures, resulting in a possible fire, inflight engine shutdown, uncontained engine failure, and damage to the aircraft. Since the issuance of that NPRM approximately four years ago, the FAA and PW have conducted laboratory analyses, analytical studies, in- service engine inspections, and monitoring of the operating experience of the stage 2 turbine vanes. Based on data collected, the FAA has concluded that the unsafe condition described in the NPRM is not likely to exist or develop in other engines of the same type design. Therefore, requiring removal from service of the turbine vanes repaired by TCC is not warranted. Upon further consideration, several operators commented that since the vanes are not serialized and records were not kept on the parts, a shop visit and engine disassembly would, therefore, be the only means to locate the TCC-repaired second stage turbine vanes. The resulting forced engine removals, based on the proposed NPRM compliance schedule, would cost the operators an estimated $124,000,000. In addition, operators reported no technical concerns with the TCC- repaired second stage turbine vanes, that they were experiencing excellent durability with these parts, and that they have determined that the TCC-repaired stage 2 turbine vanes should be permitted to continue in service without additional inspection requirements beyond normal maintenance practices. Accordingly. the proposed rule is hereby withdrawn. Withdrawal of this notice of proposed rulemaking constitutes only such action, and does not preclude the agency from issuing another notice in the future, nor does it commit the agency to any course of action in the future. Since this action only withdraws a notice of proposed rulemaking, it is neither a proposed nor a final rule and therefore, is not covered under Executive Order 12866, the Regulatory Flexibility Act, or DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). List of Subjects in 14 CFR Part 39 Air transportation, Aircraft, Aviation safety, Safety. The Withdrawal Accordingly, the notice of proposed rulemaking, Docket 89-ANE-26, published in the Federal Register on October 26, 1989, (54 FR 43586), is withdrawn. Issued in Burlington, Massachusetts, on July 21, 1994. Jay J. Pardee, Manager, Engine and Propeller Directorate, Aircraft Certification Service. [FR Doc. 94-18360 Filed 7-27-94; 8:45 am] BILLING CODE 4910-13-P
