[Federal Register Volume 64, Number 64 (Monday, April 5, 1999)]
[Proposed Rules]
[Pages 16364-16366]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-8307]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-ANE-62-AD]
RIN 2120-AA64


Airworthiness Directives; General Electric Aircraft Engines CF34 
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 Aircraft Engines 
CF34 series turbofan engines. This proposal would establish new life 
limits for certain high pressure compressor (HPC) spools, Part Number 
(P/N) 6078T56P01, stage 9 HPC disks, P/N 6087T01P03 or 6087T01P04, and 
rear HPC spools, P/N 5087T46P01 or 5087T46P02. This proposal is 
prompted by a cyclic life analysis using increased stress levels 
resulting from manufacturing discrepancies. The actions specified by 
the proposed AD are intended to prevent HPC spool and disk cracking, 
which could result in an uncontained engine failure and damage to the 
aircraft.

DATES: Comments must be received by June 4, 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-62-AD, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may also be sent 
via the Internet using the following address: ``9-ad-
[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.,

[[Page 16365]]

Monday through Friday, except Federal holidays.

FOR FURTHER INFORMATION CONTACT: Eugene Triozzi, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone (781) 
238-7148, 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-62-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-62-AD, 12 New England Executive 
Park, Burlington, MA 01803-5299.

Discussion

    General Electric Aircraft Engines (GEAE) has advised the Federal 
Aviation Administration (FAA) of the results of a cyclic life analysis 
using increased stress levels resulting from manufacturing 
discrepancies in certain forward high pressure compressor (HPC) spools, 
Part Number (P/N) 6078T56P01, stage 9 HPC disks, P/N 6087T01P03 or 
6087T01P04, and rear HPC spools, P/N 5087T46P01 or 5087T46P02, 
installed on GEAE Models CF34-1A, -3A, -3A1, and -3A2 turbofan engines. 
No failures have occurred to date; the unsafe condition was identified 
by revised low cycle fatigue (LCF) analysis, after manufacturing 
discrepancies were discovered on parts. These discrepancies would 
result in component stress levels greater than those shown in original 
LCF life analyses, and consequently result in lower LCF lives. This 
condition, if not corrected, could result in HPC spool and disk 
cracking, which could result in an uncontained engine failure and 
damage to the aircraft.

    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 from service of affected forward HPC 
spools, rear HPC spools, and stage 9 HPC disks prior to accumulating 
cycles in service beyond new, reduced cyclic life limits. This proposal 
also would require for HPC spools, which have accumulated 6,000 or more 
CSN on the effective date of this AD, remove at the next shop visit 
after the effective date of this AD, but prior to accumulating 12,000 
CSN.

    There are approximately 600 engines of the affected design in the 
worldwide fleet. The FAA estimates that 28 engines installed on 
aircraft of U.S. registry would be affected by the requirement within 
this proposed AD to replace the forward spool. The FAA has calculated 
the prorated cost for forward spool replacements to be $36,500 per 
engine, based on the estimated new part cost divided by the original 
life limit, multiplied by the number of cycles that will be reduced by 
the proposed AD requirement. Therefore, the FAA estimates the total 
cost impact for replaced forward spools to be $1,022,000.

    The FAA estimates that 200 engines installed on aircraft of U.S. 
registry would be affected by the requirement to replace the stage 9 
disk. The FAA has calculated the prorated cost for stage 9 disk 
replacements to be $3,500 per engine, based on the estimated new part 
cost divided by the original life limit, multiplied by the number of 
cycles that will be reduced by the proposed AD requirement. The FAA 
estimates the total cost impact for replaced stage 9 disks to be 
$700,000.

    The FAA estimates that 300 engines installed on aircraft of U.S. 
registry would be affected by the requirement to replace the rear 
spool. The FAA has calculated the prorated cost for rear spool 
replacements to be $8,900 per engine, based on the new part cost 
divided by the original life limit, multiplied by the number of cycles 
that will be reduced by the proposed AD requirement. Therefore, the FAA 
estimates the total cost impact for replaced rear spools to be 
$2,670,000.

    The FAA has determined that it would take no additional work hours 
per engine to remove affected components, as removal would take place 
at available opportunities. Based on these figures, the total cost 
impact of the proposed AD on U.S. operators is estimated to be 
$4,392,000.

    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.

[[Page 16366]]

Sec. 39.13  [Amended]

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

    General Electric Aircraft Engines: Docket No. 98-ANE-62-AD.

    Applicability: General Electric Aircraft Engines (GEAE) Models 
CF34-1A, -3A, -3A1, and -3A2 turbofan engines, installed on but not 
limited to Canadair aircraft models CL-600-2A12, -2B16, and -2B19.

    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 high pressure compressor (HPC) spool and disk 
cracking, which could result in an uncontained engine failure and 
damage to the aircraft, accomplish the following:
    (a) Remove from service the following HPC spools and disks prior 
to accumulating cycles in service beyond new, reduced cyclic life 
limits, and replace with a serviceable part, as follows:
    (1) For forward HPC spools, Part Number (P/N) 6078T56P01, which 
have accumulated fewer than 6,000 cycles since new (CSN) on the 
effective date of this AD, remove prior to accumulating 6,000 CSN.
    (2) For forward HPC spools, P/N 6078T56P01, which have 
accumulated 6,000 or more CSN on the effective date of this AD, 
remove at the next shop visit after the effective date of this AD, 
but prior to accumulating 12,000 CSN.
    (3) For the purpose of this AD, engine shop visit is defined as 
engine disassembly that includes separation of the compressor 
section from the fan section front frame and from the combustion 
section combustion chamber frame.
    (4) For stage 9 HPC disks, P/N 6087T01P03 or 6087T01P04, remove 
prior to accumulating 20,000 CSN.
    (5) For rear HPC spools, P/N 5087T46P01 or 5087T46P02, remove 
prior to accumulating 17,000 CSN.
    (b) 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.

    (c) 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 aircraft to a location where 
the requirements of this AD can be accomplished.

    Issued in Burlington, Massachusetts, on March 30, 1999.
David A. Downey,
Assistant Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 99-8307 Filed 4-2-99; 8:45 am]
BILLING CODE 4910-13-P