[Federal Register Volume 64, Number 194 (Thursday, October 7, 1999)]
[Proposed Rules]
[Pages 54584-54587]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-26208]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NE-49-AD]
RIN 2120-AA64


Airworthiness Directives; General Electric Company CF34 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 (TLS) of the General Electric Company CF34 Series Turbofan 
Engine Manual to include required enhanced inspection of selected 
critical life-limited parts at each piece-part exposure. This action 
would add additional 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 a Federal Aviation Administration (FAA) 
study of in-service events involving uncontained failures of critical 
rotating engine parts that indicated the need for improved inspections. 
The improved inspections are needed to identify those critical rotating 
parts with conditions, which if allowed to continue in service, could 
result in uncontained failures. The actions specified by this proposed 
airworthiness directive (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 December 6, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Regional 
Counsel, Attention: Rules Docket No. 99-NE-49-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

[[Page 54585]]

between 8:00 a.m. and 4:30 p.m., Monday through Friday, except Federal 
holidays.

FOR FURTHER INFORMATION CONTACT: Kevin Donovan, Aerospace Engineer 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone (781) 
238-7743, fax (238) 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 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 99-NE-49-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. 99-NE-49-AD, 12 New England Executive Park, 
Burlington, MA 01803-5299.

Discussion

    A recent Federal Aviation Administration (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 penetrating of the cabin, damaging flight control surfaces, severing 
flammable fluid lines, or otherwise compromising the airworthiness of 
the airplane.

Intervention Strategy

    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 fan disks, certain 
high pressure turbine (HPT) rotor disks, and HPT rotor outer torque 
couplings, which could most likely result in a safety hazard to the 
airplane in the event of a fracture.

Future Rulemaking

    The FAA is also considering the need for additional rule making. 
Future airworthiness directives (ADs) may be issued introducing 
additional intervention strategies to further reduce or eliminate 
uncontained engine failures.

Safety Critical Parts and Inspection Methods

    Properly focused enhanced inspections require identification of the 
parts whose failure presents the highest 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 most 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 Turbofan Engine Manual.

Part 121 Operators

    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.

Proposed Actions

    This proposal would require, within the next 30 days after the 
effective date of this AD, revisions to the Time Limits Section (TLS) 
in the General Electric Company (GE) CF34 Series Turbofan Engine 
Manual, and, for air carriers, the approved continuous airworthiness 
maintenance program. GE, the manufacturer of CF34-3A1 and CF34-3B1 
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.

[[Page 54586]]

Economic Analysis

    The FAA estimates that 352 engines installed on airplanes of US 
registry would be affected by this proposed AD, that it would take 
approximately 2 work hours per engine to accomplish the proposed 
actions. The average labor rate is $60 per work hour. The total cost of 
the new inspections per engine would be approximately $120 per year. 
Using average shop visit rates, 275 engines are expected to be affected 
per year. The annual cost impact of the proposed AD on US operators is 
therefore estimated to be $33,000.

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 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 99-NE-49-AD.

    Applicability: General Electric Company (GE) CF34-3A1 and -3B1 
series turbofan engines, installed on but not limited to Bombardier 
Canadair CL601R (RJ) aircraft.

    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:

Inspections

    (a) Within the next 30 days after the effective date of this AD, 
revise the Time Limits Section (TLS), Chapter 5-21-00, of the GE 
CF34 Series Turbofan Engine Manual, SEI-756, and for air carrier 
operations revise the approved continuous airworthiness maintenance 
program, by adding the following:
    ``9. CF34-3A1 and CF34-3B1 Engine Maintenance Program--Shop 
Level Mandatory Inspection Requirements.
    A. This procedure is used to identify specific piece-parts that 
require mandatory inspections that must be accomplished at each 
piece-part exposure using the applicable Chapters referenced in 
Table 804 for the inspection requirements.
    B. Piece-part exposure is defined as follows:
    (1) For engines that utilize the ``On Condition'' maintenance 
requirements: The part is considered completely disassembled when 
done in accordance with the disassembly instructions in the GAE 
engine authorized overhaul Engine Manual. 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.
    (2) For engines that utilize the ``Hard Time'' maintenance 
requirements: The part is considered completely disassembled when 
done in accordance with the disassembly instructions used in the 
``Minor Maintenance'' and ``Overhaul'' instructions in the GEAE 
engine authorized Engine Manual. 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.
    C. Refer to Table 804 below for the mandatory inspection 
requirements.

                                  Table 804.--Mandatory Inspection Requirements
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                                              Manual chapter/section/
         Part Name/Part No. (P/N)                     subject                      Mandatory inspection
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Fan Disk (all)...........................  72-21-00, Inspection........  All areas (FPI).\1\
                                                                         Bores (ECI).\2\
Stage 1 high pressure turbine (HPT) Rotor  72-46-00, Inspection........  All areas (FPI).\1\
 Disk (P/N 6078T93 and all reworked P/N                                  Bores (ECI).\2\
 rotor disks).                                                           Boltholes (ECI).\2\
                                                                         Air Holes (ECI).\2\
Stage 1 HPT Rotor Disk, P/N 5079T52......  72-46-00, Inspection........  All areas (FPI).\1\
                                                                         Bores (ECI).\2\
                                                                         Boltholes (ECI).\2\
                                                                         Air Holes (ECI).\2\
Stage 2 HPT Rotor Disk (P/N 6078T94 and    72-46-00, Inspection........  All areas (FPI).\1\
 all reworked P/N rotor disks).                                          Bores (ECI).\2\
                                                                         Boltholes (ECI).\2\
                                                                         Air Holes (ECI).\2\
Stage 2 HPT Rotor Disk, P/N 5079T53......  72-46-00, Inspection........  All areas (FPI).\1\
                                                                         Bores (ECI).\2\

[[Page 54587]]

 
HPT Rotor Outer Torque Coupling (P/N       72-46-00, Inspection........  All areas (FPI).\1\
 5041T67, PN 5079T64, and all reworked P/                                Bore (ECI).\2\
 N couplings).
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\1\ FPI = Fluorescent Penetrant Inspection Method.
\2\ ECI = Eddy Current Inspection''.

    (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 TLS, Chapter 5-21-00, 
of the General Electric Company, CF34 Series Turbofan Engine Manual, 
SEI-756.
    (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) FAA-certificated air carriers that have an approved 
continuous airworthiness maintenance program in accordance with the 
record keeping requirement of Sec. 121.369(c) of the Federal 
Aviation Regulations (14 CFR 121.369(c)) of this chapter must 
maintain records of the mandatory inspections that result from 
revising the TLS and the air carrier's continuous airworthiness 
program. Alternately, certificated air carriers may establish an 
approved 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 Sec. 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. Records of the piece-part inspections are not 
required under Sec. 121.380(a)(2)(vi) of the Federal Aviation 
Regulations (14 CFR 121.380(a)(2)(vi)). All other operators must 
maintain the records of mandatory inspections required by the 
applicable regulations governing their operations.

    Note 3: The requirements of this AD have been met when the 
engine manual changes are made and air carriers have modified their 
continuous airworthiness maintenance plans to reflect the 
requirements in the GE CF34 Series Turbofan Engine Manual.

    Issued in Burlington, Massachusetts, on September 30, 1999.
David A. Downey,
Assistant Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 99-26208 Filed 10-6-99; 8:45 am]
BILLING CODE 4910-13-P