[Federal Register Volume 65, Number 227 (Friday, November 24, 2000)]
[Proposed Rules]
[Pages 70533-70535]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-29940]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NE-30-AD]
RIN 2120-AA64


Airworthiness Directives; General Electric Company (GE) CF6-50 
Turbofan Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This amendment proposes the adoption of a new airworthiness 
directive (AD) that applies to GE CF6-50 turbofan engines. This 
proposal would require removal of old high

[[Page 70534]]

pressure compressor (HPC) air ducts and mating hardware and replacement 
with newly designed air ducts and reworked mating hardware. This 
proposal is prompted by reports of an uncontained low pressure turbine 
(LPT) disk failure that resulted from an air duct failure that caused a 
fan mid shaft (FMS) separation. The actions specified by the proposed 
AD are intended to prevent HPC air duct failures that could result in 
FMS failures, that in turn could result in rejected takeoffs or 
uncontained LPT events.

DATES: The FAA must receive comments on this proposal by January 23, 
2001.

ADDRESSES: Submit comments to Docket No. 2000-NE-30-AD in one of the 
following ways:
    Mail comments to the Federal Aviation Administration (FAA), Office 
of the Regional Counsel, New England Region, Attention: Rules Docket 
No. 2000-NE-30-AD, 12 New England Executive Park, Burlington, MA 01803-
5299. You may also send a request for a copy of the proposal or 
regulatory evaluation from that address. If you want us to acknowledge 
receipt of your comments, you must include a self-addressed, stamped 
postcard on which the Docket No. is written. We will date-stamp your 
postcard and mail it back to you. OR
    E-mail comments to [email protected]. You must include Docket 
No. 2000-NE-30-AD in the subject line.
    You can get the service information referenced in this proposal 
from General Electric Company via Lockheed Martin Technology Services, 
10525 Chester Road, Suite C, Cincinnati, Ohio 45215, telephone: (513) 
672-8400; fax: (513) 672-8422. You may examine the AD docket (including 
any comments and service information) at the FAA, New England Region, 
Office of the Regional Counsel, 12 New England Executive Park, 
Burlington, MA between 8:00 a.m. and 4:30 p.m., Monday through Friday, 
except Federal holidays. You may also examine the service information 
at the Office of the Federal Register, 800 North Capitol Street, NW., 
suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Karen Curtis, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone: (781) 
238-7192, fax: (781) 238-7199.

SUPPLEMENTARY INFORMATION:

Comments Invited

    You are invited to participate in the proposed rule making by 
submitting written data, views, or arguments as you may desire. Your 
communications should identify the Rules Docket number and be sent to 
the address specified above. All communications received on or before 
the closing date for comments, specified above, will be considered 
before we take action on the proposed rule. The proposals contained in 
this action 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 sent 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 action must send a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2000-NE-30-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRM's

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, New England Region, Office of the Regional Counsel, 
Attention: Rules Docket No. 2000-NE-30-AD, 12 New England Executive 
Park, Burlington, MA 01803-5299.

Discussion

    The FAA was recently made aware of a CF6-50 engine installed on a 
Boeing 747 airplane that experienced an uncontained LPT disk failure 
caused by an HPC air duct failure, which resulted in a FMS separation. 
This was the first documented air duct failure that has resulted in a 
disk separation. There have been 51 occurrences of air duct cracking, 
six of which have resulted in fan mid shaft (FMS) separation, and two 
of which have resulted in partial rupture of the HPC stage 14-bolted 
joint. All six FMS separations have also resulted in uncontained LPT 
blade failures. Although air duct failures were first documented in 
1976, two subsequent redesigns have failed to correct the cracking 
problem.
    The FAA has reviewed General Electric Aircraft Engines Service 
Bulletin (SB) CF6-50 72-1200, dated May 8, 2000; General Electric 
Aircraft Engines Alert Service Bulletin (ASB) CF6-50 72-A1200, Revision 
1, dated July 20, 2000; and Revision 2, dated November 2, 2000 which 
describe procedures for removal of the HPC air duct assembly part 
number 99128M36G03/G04/G05/G06/G08/G20/G21 or 1644M16G03 and mating 
hardware (rear shaft or 11-14 spool shaft) and replace with the new 
design air duct and reworked mating hardware.

Proposed Actions

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require removal of old HPC air ducts and mating 
hardware and replacement with newly designed air ducts and reworked 
mating hardware. This proposal is prompted by reports of an uncontained 
LPT disk failure that resulted from an air duct failure that caused a 
FMS separation. The FAA is proposing this AD to prevent HPC air duct 
failures that could result in FMS failures that in turn could result in 
rejected takeoffs or uncontained LPT events.

Economic Impact

    There are about 1730 engines of the affected design in the 
worldwide fleet. The FAA estimates that 469 engines installed on 
aircraft of U.S. registry would be affected by this proposed AD, that 
it would take about 70 work hours per engine to disassemble and 
reassemble the HPC module, that it would take 19 hours to rework the 
mating hardware and that the average labor rate is $60 per work hour. 
Each new air duct assembly will cost $32,985. Based on these figures, 
the total proposed AD cost impact on U.S. operators is estimated to be 
$17,974,425.

Regulatory Impact

    This proposal does not have federalism implications, as defined in 
Executive Order 13132, because it would not have a substantial direct 
effect 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. Accordingly, 
the FAA has not consulted with state authorities prior to publication 
of this proposal.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (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

[[Page 70535]]

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 
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.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

General Electric Company:  Docket No. 2000-NE-30-AD.

    Applicability: This airworthiness directive (AD) is applicable 
to CF6-50 turbofan engines with high pressure compressor (HPC) rotor 
air duct assemblies P/N's 9128M36G03/G04/G05/G06/G08/G20/G21, or 
1644M16G03 installed. These engines are installed on but not limited 
to Boeing 747, Airbus A300, and McDonnell Douglas DC10 airplanes.

    Note 1: This AD applies to each engine identified in the 
preceding applicability provision, regardless of whether it has been 
modified, altered, or repaired in the area subject to the 
requirements of this AD. For engines that have been modified, 
altered, or repaired so that the performance of the requirements of 
this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (c) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent HPC air duct failures that could result in fan mid 
shaft (FMS) failures and uncontained LPT events, accomplish the 
following:
    (a) At next HPC rotor exposure, remove the HPC air duct assembly 
part number 99128M36G03/G04/G05/G06/G08/G20/G21 or 1644M16G03 and 
mating hardware (rear shaft or 11-14 spool shaft) and replace with 
the new design air duct and reworked mating hardware in accordance 
with the accomplishment instructions of General Electric Aircraft 
Engines Service Bulletin (SB) CF6-50 72-1200, dated May 8, 2000; 
General Electric Aircraft Engines Alert Service Bulletin (ASB) CF6-
50 72-A1200, Revision 1, dated July 20, 2000; or General Electric 
Aircraft Engines Alert Service Bulletin (ASB) CF6-50 72-A1200, 
Revision 2, dated November 2, 2000.
    (b) For the purposes of this proposal, HPC rotor exposure is 
defined as disassembly of the HPC stage 2 disk flange or removal of 
the HPC stage 1 disk.

Alternative Methods of Compliance

    (c) 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 (ECO). 
Operators shall submit their request through an appropriate Federal 
Aviation Administration (FAA) Principal Maintenance Inspector, who 
may add comments and then send it to the Manager, ECO.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this airworthiness directive, 
if any, may be obtained from the ECO.



    Issued in Burlington, Massachusetts, November 15, 2000.
Robert Mann,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 00-29940 Filed 11-22-00; 8:45 am]
BILLING CODE 4910-13-U