[Federal Register Volume 64, Number 206 (Tuesday, October 26, 1999)]
[Proposed Rules]
[Pages 57606-57608]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-27938]



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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-ANE-32-AD]
RIN 2120-AA64


Airworthiness Directives; General Electric Company CF6-45/50 
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 initial and 
repetitive inspections for cracks in the stage 14 high pressure 
compressor (HPC) disk lock slots, and removal from service of certain 
disks, at the first piece-part level or HPC rotor module level 
exposure, after 6,000 cycles since new (CSN). This proposal is prompted 
by reports of stage 14 HPC disk lock slot cracks discovered during shop 
fluorescent penetrant inspections. The actions specified by the 
proposed AD are intended to prevent stage 14 HPC disk failure, which 
could result in an uncontained engine failure and damage to the 
aircraft.

DATES: Comments must be received by December 27, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Regional 
Counsel, Attention: Rules Docket No. 98-ANE-32-AD, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may also be sent 
via the Internet using the following address: ``9-ane-
[email protected]''. Comments sent via the Internet must contain the 
docket number in the subject line. Comments may be inspected at this 
location between 8:00 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 Company via Lockheed Martin Technology 
Services, 10525 Chester Road, Suite C, Cincinnati, Ohio 45215, 
telephone (513) 672-8400, fax (513) 672-8422. This information may be 
examined at the FAA, New England Region, Office of the Regional 
Counsel, 12 New England Executive Park, Burlington, MA.

FOR FURTHER INFORMATION CONTACT: William S. Ricci, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone (781) 
238-7742, fax (781) 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 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 Number 98-ANE-32-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. 98-ANE-32-AD, 12 New England Executive 
Park, Burlington, MA 01803-5299.

Events Leading to This Proposed Rule

    The Federal Aviation Administration (FAA) has received reports of 
stage 14 high pressure compressor (HPC) disk lock slot cracks 
discovered on General Electric Company (GE) CF6-45/50 series turbofan 
engines during routine shop fluorescent penetrant inspections. The 
investigation revealed higher stresses in the load and lock slots than 
prior analyses have predicted. Two populations or groups of disks have 
been identified. One group of disks was produced from forgings with 
coarser grain sizes than the other group of disks and therefore is less 
resistant to fatigue crack initiation. The referenced GE CF6-50 Alert 
Service Bulletins (ASB) 72-A1144, dated March 19, 1998, or ASB 72-
A1144, Revision 1, dated May 13, 1999, define these forging groups by 
serial numbers and describe the applicable inspection procedures for 
each disk forging group. This condition, if not corrected, could result 
in a stage 14 HPC disk failure, which could result in uncontained 
engine failure and damage to the aircraft. The stage 14 HPC rotor disks 
are no longer being manufactured, and have been replaced with a stage 
11-14 spool shaft.
    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 initial and repetitive inspections for cracks 
in the stage 14 HPC disk lock slots in accordance with procedures and 
intervals defined by forging group, and would require the removal from 
service of certain disks at the first piece-part level exposure or HPC 
rotor module level exposure above 6,000 CSN. The actions would be 
required to be accomplished in accordance with the ASB's described 
previously.

Cost Impact

    There are approximately 1,538 engines of the affected design in the 
worldwide fleet. The FAA estimates that 460 engines installed on 
aircraft of U.S. registry would be affected by this proposed AD, that 
it would take approximately 22 work hours per engine to accomplish the 
proposed actions, and that the average labor rate is $60 per work hour. 
Required parts would cost approximately $3,600 per engine. Based on 
these figures, the total cost impact of the proposed AD on U.S. 
operators is estimated to be $2,263,200.

Regulatory Impact

    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 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44

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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 
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. 98-ANE-32-AD.

    Applicability: General Electric Company (GE) Model CF6-45/50 
series turbofan engines, installed on but not limited to Airbus 
Industrie A300 series, Boeing Company 747 series, and McDonnell 
Douglas Corporation DC-10 series airplanes.

    Note 1: This airworthiness directive (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 (j) 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 a stage 14 high pressure compressor (HPC) disk 
failure, which could result in uncontained engine failure and damage 
to the aircraft, accomplish the following:

Inspections

    (a) Perform initial inspections of HPC stage 14 disks, part 
numbers (P/N's) 9080M34P03, 9080M34P04, 9080M34P05 and 9349M91P04, 
with serial number (SN) prefixes GWN, MPO, RRY, and SNL, and disk 
SN's SNE00001 through SNE00017, and disk SN's SNE01101 through 
SNE01110, in accordance with paragraphs 2.A. through 2.B. of GE CF6-
50 ASB No. 72-A1144, dated March 19, 1998, or ASB No. 72-A1144, 
Revision 1, dated May 13, 1999, and the following schedule:
    (1) Inspect disks with 6,500 cycles since new (CSN) or less on 
the effective date of this AD before accumulating 9,800 CSN.
    (2) Inspect disks with more than 6,500 CSN on the effective date 
of this AD no later than the next engine shop visit (ESV) after the 
effective date of this AD or before accumulating an additional 3,300 
cycles-in-service (CIS) after the effective date of this AD, 
whichever occurs first.
    (b) Perform repetitive inspections of HPC stage 14 disks, P/N's 
9080M34P03, 9080M34P04, 9080M34P05 and 9349M91P04, with SN prefixes 
GWN, MPO, RRY, and SNL, and disk SN's SNE00001 through SNE00017, and 
disk SN's SNE01101 through SNE01110, in accordance with paragraphs 
2.A. through 2.B. of GE CF6-50 ASB No. 72-A1144, dated March 19, 
1998, or ASB No. 72-A1144, Revision 1, dated May 13, 1999, and the 
following schedule:
    (1) For disks with less than 9,800 CSN at the time of the last 
inspection, perform repetitive inspections no later than 9,800 CSN 
or before accumulating 3,300 cycles since last inspection (CSLI), 
whichever occurs later.
    (2) For disks with 9,800 CSN or greater at the time of the last 
inspection, perform repetitive inspections no later than 3,300 CSLI.
    (c) Perform initial inspections of HPC stage 14 disks, P/N's 
9080M34P03, 9080M34P04, 9080M34P05 and 9349M91P04 with SN prefixes 
SNG and SNE, except disk SN's SNE00001 through SNE00017 and SNE01101 
through SNE01110, in accordance with paragraphs 2.A. through 2.B. of 
GE CF6-50 ASB No. 72-A1144, dated March 19, 1998, or ASB No. 72-
A1144, Revision 1, dated May 13, 1999, and the following schedule:
    (1) Inspect disks with 4,200 CSN or less on the effective date 
of this AD before accumulating 7,500 CSN.
    (2) Inspect disks with more than 4,200 CSN but less than 9,000 
CSN on the effective date of this AD at the next ESV after the 
effective date of this AD, before accumulating an additional 3,300 
CIS after the effective date of this AD, or before accumulating 
11,000 CSN, whichever occurs first.
    (3) Inspect disks with 9,000 CSN or greater on the effective 
date of this AD, at the next ESV after the effective date of this 
AD, or before accumulating an additional 2,000 CIS after the 
effective date of this AD, whichever occurs first.
    (d) Perform repetitive inspections of HPC stage 14 disks, P/N's 
9080M34P03, 9080M34P04, 9080M34P05 and 9349M91P04 with SN prefixes 
SNG and SNE, except disk SN's SNE00001 through SNE00017 and SNE01101 
through SNE01110, in accordance with paragraphs 2.A. through 2.B. of 
GE CF6-50 ASB No. 72-A1144, dated March 19, 1998, or ASB No. 72-
A1144, Revision 1, dated May 13, 1999, and the following schedule:
    (1) For disks with less than 7,500 CSN at the time of the last 
inspection, perform repetitive inspections no later than 7,500 CSN 
or before accumulating 3,300 CSLI, whichever occurs later.
    (2) For disks with 7,500 CSN or greater at the time of the last 
inspection, perform repetitive inspections no later than 3300 CSLI.

Removal from Service

    (e) Remove from service prior to further flight stage 14 HPC 
disks that equal or exceed the reject criteria established by GE 
CF6-50 ASB 72-A1144, dated March 19, 1998, or ASB No. 72-A1144, 
Revision 1, dated May 13, 1999.
    (f) Remove from service, HPC stage 14 disks, P/N's 9080M34P03, 
9080M34P04, 9080M34P05 and 9349M91P04 with SN prefixes SNG and SNE, 
except disk SN's SNE00001 through SNE00017 and SNE01101 through 
SNE01110, with greater than 6,000 CSN after the effective date of 
this AD, at the next piece-part level exposure or at the next HPC 
rotor module level exposure after the effective date of this AD.

Terminating Action

    (g) Replacement of the stage 14 HPC disk, P/N's 9080M34P03, 
9080M34P04, 9080M34P05, 9349M91P04, with a stage 11-14 spool shaft 
is terminating action for the inspection requirements of this AD.

Reporting Requirements

    (h) Report the results of inspections that equal or exceed the 
reject criteria within five days of the inspection to: Manager, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 
12 New England Executive Park, Burlington, MA 01803-5299. The 
following information must be included in the report:
    (1) HPC Stage 14 rotor disk P/N,
    (2) HPC Stage 14 rotor disk SN,
    (3) HPC Stage 14 rotor disk CSN,
    (4) HPC Stage 14 rotor disk CSLI, and
    (5) Date and location of inspection.
    Reporting requirements have been approved by the Office of 
Management and Budget (OMB) and assigned OMB control number 2120-
0056.

Definitions

    (i) For the purpose of this AD, the following definitions apply:
    (1) HPC Rotor disassembly occurs if any of the HPC
    Rotor bolted flange joints are separated, such as the Stage 2 
joint to accomplish the Stage 3-9 Spool inspection.
    (2) Piece-part exposure is defined as disassembly and removal of 
the stage 14 disk from the HPC rotor structure, regardless of any 
blades, locking lugs, bolts or balance weights assembled to the 
disk.
    (3) An engine shop visit is defined as the introduction of an 
engine into a shop where a major engine flange is separated. The 
following maintenance actions are not considered engine shop visits 
for the purpose of this AD:

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    (i) Introduction of an engine into a shop solely for removal or 
replacement of the Stage 1 Fan Disk;
    (ii) Introduction of an engine into a shop solely for 
replacement of the Turbine Rear Frame;
    (iii) Introduction of an engine into a shop solely for 
replacement of the Accessory Gearbox or Transfer Gearboxes;
    (iv) Introduction of an engine into a shop for any combination 
of exceptions specified in paragraphs (i)(3)(i) through (i)(3)(iii).

Alternate Methods of Compliance

    (j) 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. 
Operators shall submit their request through an appropriate FAA 
Principal Maintenance Inspector, who may add comments and then send 
it to the Manager, Engine Certification Office.

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

Special Flight Permit

    (k) Special flight permits may be issued in accordance with 
Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 
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 October 20, 1999.
David A. Downey,
Assistant Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 99-27938 Filed 10-25-99; 8:45 am]
BILLING CODE 4910-13-U