[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]


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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.

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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proposed rule is withdrawn.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]
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