[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]


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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).

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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]
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