[Federal Register Volume 63, Number 144 (Tuesday, July 28, 1998)]
[Proposed Rules]
[Pages 40213-40215]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-19628]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-ANE-41-AD]
RIN 2120-AA64


Airworthiness Directives; General Electric Company CF6-6, CF6-45, 
and CF6-50 Series Turbofan Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This proposal would require revisions to the Time Limits 
Section of the manufacturer's Instructions for Continued Airworthiness 
(ICA) for General Electric Company (GE) CF6-6, CF6-45, and CF6-50 
series turbofan engines to include required enhanced inspection of 
selected critical life-limited parts at each piece-part exposure. This 
proposal would also require an air carrier's approved continuous 
airworthiness maintenance program to incorporate these inspection 
procedures. Air carriers with an approved continuous airworthiness 
maintenance program would be allowed to either maintain the records 
showing the current status of the inspections using the record keeping 
system specified in the air carrier's maintenance manual, or establish 
an acceptable alternate method of record keeping. This proposal is 
prompted by an FAA study of in-service events involving uncontained 
failures of critical rotating engine parts which indicated the need for 
improved inspections. The improved inspections are needed to identify 
those critical rotating parts with conditions, that if allowed to 
continue in service, could result in uncontained failures. The actions 
specified by this proposed AD are intended to prevent critical life-
limited rotating engine part failure, which could result in an 
uncontained engine failure and damage to the airplane.

DATES: Comments must be received by October 26, 1998.

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-41-AD, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may also be sent 
via the Internet using the following address: ``<a href="/cdn-cgi/l/email-protection#ecd5c18d88c1e689828b8582899c9e839cac8a8d8dc2888398c28b839a">9-ad-
<span class="__cf_email__" data-cfemail="4b2e252c22252e3b39243b0b2d2a2a652f243f652c243d">[email protected]</span></a>''. 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.

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

    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-41-AD.'' 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 Regional Counsel, 
Attention: Rules Docket No. 98-ANE-41-AD, 12 New England Executive 
Park, Burlington, MA 01803-5299.

[[Page 40214]]

Discussion

    A recent FAA study analyzing 15 years of accident data for 
transport category airplanes identified several failure mode root 
causes that can result in serious safety hazards to transport category 
airplanes. This study identified uncontained failure of critical life-
limited rotating engine parts as the leading engine-related safety 
hazard to airplanes. Uncontained engine failures have resulted from 
undetected cracks in rotating parts that initiated and propagated to 
failure. Cracks can originate from causes such as unintended excessive 
stress from the original design, or they may initiate from stresses 
induced from material flaws, handling damage, or damage from machining 
operations. The failure of rotating parts can present a significant 
safety hazard to the airplanes by release of high energy fragments that 
could injure passengers or crew by penetration of the cabin, damage 
flight control surfaces, sever flammable fluid lines, or otherwise 
compromise the airworthiness of the airplane.
    Accordingly, the FAA has developed an intervention strategy to 
significantly reduce uncontained engine failures. This intervention 
strategy was developed after consultation with industry and will be 
used as a model for future initiatives. This intervention strategy is 
to conduct enhanced, nondestructive inspections of critical life 
limited rotating components which could most likely result in a safety 
hazard to the airplane in the event of a disk fracture. The need for 
additional rule making is also being considered by the FAA. Future ADs 
may be issued introducing additional intervention strategies to further 
reduce or eliminate uncontained engine failures.
    Properly focused enhanced inspections require identification of the 
parts whose failures present a safety hazard to the airplane, 
identifying the most critical features to inspect on these parts, and 
utilizing inspection procedures and techniques that improve crack 
detection. The FAA, with close cooperation of the engine manufacturers, 
has completed a detailed analysis that identifies the safety 
significant parts and features, and the most appropriate inspection 
methods.
    Critical life-limited high energy rotating parts are currently 
subject to some form of recommended crack inspection when exposed 
during engine maintenance or disassembly. As a result of this AD, the 
inspections currently recommended by the manufacturer will become 
mandatory for those parts listed in the compliance section. 
Furthermore, the FAA intends that additional mandatory enhanced 
inspections resulting from this AD serve as an adjunct to the existing 
inspections. The FAA has determined that the enhanced inspections will 
significantly improve the probability of crack detection while the 
parts are disassembled during maintenance. All mandatory inspections 
must be conducted in accordance with detailed inspection procedures 
prescribed in the manufacturer's maintenance manual.
    Additionally, this AD allows for air carriers operating under the 
provisions of 14 CFR part 121 with an FAA-approved continuous 
airworthiness maintenance program, and entities with whom those air 
carriers make arrangements to perform this maintenance, to verify 
performance of the enhanced inspections by retaining the maintenance 
records that include the inspections resulting from this AD, provided 
that the records include the date and signature of the person 
performing the maintenance action. These records must be retained with 
the maintenance records of the part, engine module, or engine until the 
task is repeated. This will establish a method of record preservation 
and retrieval typical to those in existing continuous airworthiness 
maintenance programs. Instructions must be included in an air carrier's 
maintenance manual providing procedures on how this record preservation 
and retrieval system will be implemented and integrated into the air 
carrier's record keeping system.
    For engines or engine modules that are approved for return to 
service by an authorized FAA-certificated entity and that are acquired 
by an operator after the effective date of this AD, the mandatory 
enhanced inspections need not be accomplished until the next piece-part 
opportunity. For example, there is no need for an operator to 
disassemble to piece-part level an engine or module returned to service 
by an FAA-certificated facility simply because that engine or module 
was previously operated by an entity not required to comply with this 
AD. Furthermore, the FAA intends for operators to perform the enhanced 
inspections of these parts at the next piece-part opportunity following 
the initial acquisition, installation, and removal of the part 
following the effective date of this AD. For piece parts that have not 
been approved for return to service prior to the effective date of this 
AD, the FAA does intend that the mandatory enhanced inspections 
required by this AD be performed before such parts are approved for 
return to service. Piece parts that have been approved for return to 
service prior to the effective date of this AD may be installed; 
however, enhanced inspection will be required at the next piece-part 
opportunity.
    This proposal would require, within the next 30 days after the 
effective date of this AD, revisions to the Time Limits Section of the 
manufacturer's Instructions for Continued Airworthiness (ICA) for 
General Electric Company CF6-6, CF6-45, and CF6-50 series turbofan 
engines, and, for air carriers, the approved continuous airworthiness 
maintenance program. General Electric Company, the manufacturer of CF6-
6, CF6-45, and CF6-50 series turbofan engines, used on 14 CFR part 25 
airplanes has provided the FAA with a detailed proposal that identifies 
and prioritizes the critical life-limited rotating engine parts with 
the highest potential to hazard the airplane in the event of failure, 
along with instructions for enhanced, focused inspection methods. The 
enhanced inspections resulting from this AD will be conducted at piece-
part opportunity, as defined below in the compliance section, rather 
than specific time inspection intervals.
    There are approximately 2,500 engines of the affected design in the 
worldwide fleet. The FAA estimates that 1,139 engines installed on 
airplanes of U.S. registry would be affected by this proposed AD, that 
it would take approximately 5 work hours per engine for the fan disk 
inspections and 8 work hours for the high pressure turbine rotor (HPTR) 
(stage 1 and 2) disk inspections. The average labor rate is $60 per 
work hour. Using average shop visit rates, 219 fan disks and 911 HPTR 
(stage 1 and 2) disks are expected to be affected per year. The cost 
impact of the proposed AD on U.S. operators is estimated to be $500,000 
per year.
    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 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

[[Page 40215]]

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 98-ANE-41-AD.

    Applicability: General Electric Company (GE) CF6-6, CF6-45, and 
CF6-50 series turbofan engines, installed on but not limited to 
Airbus A300 series, Boeing 747 series, and McDonnell Douglas 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 (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 critical life-limited rotating engine part failure, 
which could result in an uncontained engine failure and damage to 
the airplane, accomplish the following:
    (a) Within the next 30 days after the effective date of this AD, 
revise the manufacturer's Time Limits Section of the Instructions 
for Continued Airworthiness (ICA), and for air carrier operations 
revise the approved continuous airworthiness maintenance program, by 
adding the following:
    ``MANDATORY INSPECTIONS
    (1) Perform inspections of the following parts at each piece-
part opportunity in accordance with the instructions provided in the 
applicable manual provisions:

----------------------------------------------------------------------------------------------------------------
         Part nomenclature              Part number (P/N)              Inspect per engine manual chapter        
----------------------------------------------------------------------------------------------------------------
For CF6-6, CF6-45, CF6-50 Engines:                                                                              
    Fan Rotor, Stage 1 Disk........  All....................  72-21-03 (CF6-6: Inspection CF6-45/50: Task 72-21-
                                                               03-200-000).                                     
    High Pressure Turbine (HPT),     All....................  72-53-03 (CF6-6: Inspection, CF6-45/50: Task 72-53-
     Stage 1 Disk.                                             03-200-000).                                     
    HPT, Stage 2 Disk..............  All....................  72-53-04 (CF6-6: Inspection, CF6-45/50: Task 72-53-
                                                               04-200-000).                                     
----------------------------------------------------------------------------------------------------------------

    (2) For the purposes of these mandatory inspections, piece-part 
opportunity means:
    (i) The part is considered completely disassembled when done in 
accordance with the disassembly instructions in the engine 
manufacturer's Engine Manual; and
    (ii) The part has accumulated more than 100 cycles in service 
since the last piece-part opportunity inspection, provided that the 
part was not damaged or related to the cause for its removal from 
the engine.''
    (b) Except as provided in paragraph (c) of this AD, and 
notwithstanding contrary provisions in section 43.16 of the Federal 
Aviation Regulations (14 CFR 43.16), these mandatory inspections 
shall be performed only in accordance with the Time Limits Section 
of the manufacturer's ICA.
    (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 Engine Certification Office. Operators shall 
submit their requests through an appropriate FAA Principal 
Maintenance Inspector (PMI), who may add comments and then send it 
to the 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.

    (d) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the airplane to a location where 
the requirements of this AD can be accomplished.
    (e) The records of the mandatory inspections required as a 
result of revising the Time Limits Section of the ICA and the air 
carrier's continuous airworthiness maintenance program as provided 
by paragraph (a) of this AD shall be maintained by FAA-certificated 
air carriers which have an approved continuous airworthiness 
maintenance program in accordance with the record keeping system 
currently specified in their manual required by sections 121.369 of 
the Federal Aviation Regulations (14 CFR 121.369); or, in lieu of 
the record showing the current status of each mandatory inspection 
required by sections 121.380(a)(2)(vi) of the Federal Aviation 
Regulations (14 CFR 121.380(a)(2)(vi)), certificated air carriers 
may establish an approved alternate system of record retention that 
provides a method for preservation and retrieval of the maintenance 
records that include the inspections resulting from this AD, and 
include the policy and procedures for implementing this alternate 
method in the air carrier's maintenance manual required by sections 
121.369 (c) of the Federal Aviation Regulations (14 CFR 121.369 
(c)); however, the alternate system must be accepted by the 
appropriate PMI and require the maintenance records be maintained 
either indefinitely or until the work is repeated.

    Note 3: These record keeping requirements apply only to the 
records used to document the mandatory inspections required as a 
result of revising the Time Limits Section of the ICA as provided in 
paragraph (a) of this AD, and do not alter or amend the record 
keeping requirements for any other AD or regulatory requirement.

    Issued in Burlington, Massachusetts, on July 16, 1998.
Jay J. Pardee,
Manager, Engine and Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 98-19628 Filed 7-27-98; 8:45 am]
BILLING CODE 4910-13-P


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