[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: ``adcomment@faa.gov''. 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]
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