[Federal Register Volume 62, Number 64 (Thursday, April 3, 1997)]
[Proposed Rules]
[Pages 15861-15863]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-8475]


 ========================================================================
 Proposed Rules
                                                 Federal Register
 ________________________________________________________________________
 
 This section of the FEDERAL REGISTER contains notices to the public of 
 the proposed issuance of rules and regulations. The purpose of these 
 notices is to give interested persons an opportunity to participate in 
 the rule making prior to the adoption of the final rules.
 
 ========================================================================
 

  Federal Register / Vol. 62, No. 64 / Thursday, April 3, 1997 / 
Proposed Rules  

[[Page 15861]]



DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-ANE-15]
RIN 2120-AA64


Airworthiness Directives; General Electric Company CT58 Series 
Turboshaft 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) CT58 
series turboshaft engines. This proposal would require removal from 
service of compressor rear shafts, initial and repetitive inspections 
of ten rotating parts, and replacement if found cracked, until those 
parts are removed from service and replaced with improved design parts. 
This proposal is prompted by a stage 2 turbine wheel incident in 1993 
which resulted in an increased awareness of small features on critical 
rotating parts which could affect part life. The actions specified by 
the proposed AD are intended to prevent fatigue cracking on specific 
critical rotating parts, which could result in failure of the part, 
causing an uncontained engine failure and damage to the aircraft.

DATES: Comments must be received by June 2, 1997.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Assistant Chief 
Counsel, Attention: Rules Docket No. 97-ANE-15, 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., Monday through Friday, 
except Federal holidays.
    The service information referenced in the proposed rule may be 
obtained from General Electric Aircraft Engines, Technical 
Publications, 1000 Western Avenue, Lynn, MA 01910; telephone (617) 594-
5102, fax (617) 594-2717. This information may be examined at the FAA, 
New England Region, Office of the Assistant Chief Counsel, 12 New 
England Executive Park, Burlington, MA.

FOR FURTHER INFORMATION CONTACT: Diane Cook, Aerospace Engineer, Engine 
Certification Office, FAA, Engine and Propeller Directorate, 12 New 
England Executive Park, Burlington, MA 01803-5299; telephone (617) 238-
7134, fax (617) 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 97-ANE-15.'' 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 Assistant Chief Counsel, 
Attention: Rules Docket No. 97-ANE-15, 12 New England Executive Park, 
Burlington, MA 01803-5299.

Discussion

    The Federal Aviation Administration (FAA) received a report of a 
stage 2 uncontained turbine wheel failure on a General Electric Company 
(GE) Model CT58-140-1 turboshaft engine. The investigation resulted in 
the issuance of airworthiness directive (AD) 94-07-05 and an increased 
awareness of all small features on CT58 critical rotating parts. The 
manufacturer began a review of all small features on critical rotating 
parts on the CT58 engine that could affect the life capability of that 
part. A small feature is identified as a fillet radius, breakage, or 
edge radius that is 0.20 inches or less. Subsequent to the issuance of 
AD 94-07-05 the FAA has determined that a small feature may be the life 
limiting area of a critical rotating part and may result in a lower 
crack initiation part life than what is currently published. Because of 
the small feature's size, any local departures from the true contour 
(but still within the tolerance requirements) could affect the part 
fatigue life, and depending on the nature and location of the local 
departure(s), this small feature could become the life limiting area 
and subject to fatigue cracking prior to the published life limit. This 
condition, if not corrected, could result in fatigue cracking on 
specific critical rotating parts, which could result in failure of the 
part, causing an uncontained engine failure and damage to the aircraft.
    The FAA has reviewed and approved the technical contents of the 
following GE Aircraft Engines Service Bulletins (SB's): No. (CT58) 72-
181, CEB-284, Revision 1, dated November 29, 1995, that describes 
procedures for initial and repetitive inspections of life limited 
rotating parts; and No. (CT58) A72-163 (CEB-258), Revision 5, dated May 
12, 1994, that describes procedures for an improved methodology for 
determining hours and cycles in service for aircraft performing 
repetitive heavy lift (RHL) operations.
    Since an unsafe condition has been identified that is likely to 
exist or

[[Page 15862]]

develop on other products of this same type design, the proposed AD 
would require removal from service of compressor rear shafts, initial 
and repetitive inspections of ten rotating parts, and replacement if 
found cracked, until those parts are removed from service and replaced 
with improved design parts. The actions would be required to be 
accomplished in accordance with the SB's described previously.
    There are approximately 5,550 engines of the affected design in the 
worldwide fleet. The FAA estimates that 380 civil engines installed on 
aircraft of U.S. registry and 2,600 U.S. military engines would be 
affected by this proposed AD. The FAA estimates that for 95 engines the 
compressor will need to be debladed to accomplish the inspection, that 
it would take approximately 40 work hours per engine to accomplish the 
proposed actions, that the average labor rate is $60 per work hour, and 
that required parts would cost approximately $100 per engine. For 285 
engines, the inspection can be accomplished during scheduled 
maintenance, and the inspection would take an estimated 8.33 work 
hours, with no required parts cost. For 114 engines, the compressor 
would be required to be removed early, with a pro rated parts cost of 
$1,300 per engine. Based on these figures, the total cost impact of the 
proposed AD on U.S. operators is estimated to be $528,143.
    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 USC 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. 97-ANE-15.

    Applicability: General Electric Company (GE) Models CT58-100-2, 
-110-1/-2, -140-1/-2, and T58-GE-3/-5/-10/-100 turboshaft engines, 
installed on but not limited to Boeing Vertol 107 series, and 
Sikorsky S61 and S62 series 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 (f) 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 fatigue cracking on specific critical rotating parts, 
which could result in failure of the part, causing an uncontained 
engine failure and damage to the aircraft, accomplish the following:
    (a) Determine hours time in service (TIS) and cycles in service 
(CIS) in accordance with the improved methodology described in GE 
Aircraft Engines Service Bulletin (SB) No. (CT58) A72-162 (CEB-258), 
Revision 5, dated May 12, 1994.
    (b) For engines that have engaged in repeated heavy lift (RHL) 
operations, as defined in paragraph (e) of this AD, accomplish the 
following:
    (1) For compressor rear shafts, Part Numbers (P/N's) 4000T29P01/
P03, 5016T95P01/P04, and 5013T86P03, accomplish the following:
    (i) For compressor rear shafts, with either 2,975 or more hours 
TIS, or 9,550 or more CIS, on the effective date of this AD, remove 
compressor rear shafts and replace with a serviceable compressor 
rear shaft at the next light overhaul or next exposure of compressor 
rear shafts after the effective date of this AD, whichever occurs 
first.
    (ii) For all other compressor rear shafts, remove compressor 
rear shafts and replace with a serviceable compressor rear shaft, 
prior to accumulating 3,000 hours TIS, or 9,600 CIS, whichever 
occurs first.
    (iii) For all compressor rear shafts, remove from service and 
replace with a serviceable, redesigned compressor rear shaft, P/N 
5016T95P06, not later than December 31, 1997.
    (2) Initially inspect the ten rotating parts specified in 
paragraph (d) of this AD for cracks at the times specified in sub-
paragraphs (i) and (ii) of this paragraph, and, thereafter, inspect 
at each light overhaul or major overhaul until the parts are retired 
from service. Perform the inspections in accordance with the 
procedures described in GE Aircraft Engines SB No. (CT58) 72-181, 
CEB284, Revision 1, dated November 29, 1995. Prior to further 
flight, replace parts found cracked during these inspections with 
serviceable parts.
    (i) For parts with greater than the baseline time in service 
(TIS) on the effective date of this AD, inspect at the earliest 
occurrence of the following after the effective date of this AD: the 
next light overhaul, the next major overhaul, or the next exposure 
of the affected parts.
    (ii) For parts with less than or equal to the baseline TIS on 
the effective date of this AD, inspect within 1,000 hours TIS from 
the listed baseline TIS.
    (c) For engines that have never engaged in RHL operations, 
accomplish the following:
    (1) For compressor rear shafts, P/N's 4000T29P01/P03, 
5016T95P01/P04, and 5013T86P03, remove compressor rear shafts and 
replace with a serviceable compressor rear shaft, prior to 
accumulating 9,600 CIS, or 9,000 hours TIS, whichever occurs first. 
Prior to December 31, 1999, replace compressor rear shafts with a 
serviceable, redesigned compressor rear shaft, P/N 5016T95P06.
    (2) Initially inspect the ten rotating parts specified in 
paragraph (d) of this AD for cracks at the times specified in sub-
paragraphs (i) and (ii) of this paragraph, and, thereafter, at each 
light overhaul or major overhaul until the parts are retired from 
service. Perform the inspections in accordance with the procedures 
described in GE Aircraft Engines SB No. (CT58) 72-181, CEB284, 
Revision 1, dated November 29, 1995. Prior to further flight, 
replace parts found cracked during these inspections with 
serviceable parts.
    (i) For parts with greater than the baseline TIS on the 
effective date of this AD, inspect at the earliest occurrence of the 
following after the effective date of this AD: the next light 
overhaul, the next major overhaul, or the next exposure.
    (ii) For parts with less than or equal to the baseline TIS on 
the effective date of this AD, inspect within 2,000 hours TIS from 
the listed baseline hours.
    (d) For the purpose of performing the inspections required by 
paragraphs (b)(2) and

[[Page 15863]]

(c)(2) of this AD, the following baseline TIS are established:
    (i) For compressor rotor spool assemblies, P/N's 6010T57G04 and 
6010T57G08, whether or not used in RHL operations, baseline is 2,000 
hours TIS.
    (ii) For turbine front shafts, P/N's 5003T35P01 and 573D358P002, 
whether or not utilized in RHL operation, baseline is 1,000 hours 
TIS.
    (iii) For turbine coupling shafts, P/N's 4001T26P01 and 
278D987P002, if utilized in RHL operation, baseline is 1,000 hours 
TIS; if never utilized in RHL operations, baseline is 2,000 hours 
TIS.
    (iv) For turbine rear shafts, P/N's 4005T29P01 and 
37D400244P101, whether or not utilized in RHL operation, baseline is 
2,000 hours TIS.
    (v) For Stage 1 front cooling plates, P/N's 37C300055P101, 
whether or not utilized in RHL operation, baseline is 1,000 hours 
TIS.
    (vi) For Stage 1 aft cooling plates, P/N's 3002T25P01 and 
645C334P002, whether or not utilized in RHL operation, baseline is 
1,000 hours TIS.
    (vii) For Stage 2 front cooling plates, P/N's 3000T88P02 and 
645C332P002, whether or not utilized in RHL operation, baseline is 
1,000 hours TIS.
    (viii) For Stage 2 aft cooling plates, P/N's 3002T27P01 and 
645C336P002, whether or not utilized in RHL operation, baseline is 
1,000 hours TIS.
    (ix) For Stage 1 turbine wheels, P/N 4002T17P02 TF3, if utilized 
in RHL operation, baseline is 1,000 hours TIS; if never utilized in 
RHL operation, baseline is 2,000 hours TIS.
    (x) For Stage 2 turbine wheels, P/N 4002T96P02 TF3, if utilized 
in RHL operation, baseline is 1,000 hours TIS; if never utilized in 
RHL operation, baseline is 2,000 hours TIS.
    (e) For the purpose of this AD, the following definitions apply:
    (1) RHL operation is defined as performing more than 10 lift-
carry-drop cycles per hour TIS without landing, or more than 10 
takeoffs and landings per hour TIS.
    (2) Light overhaul is defined as scheduled engine maintenance 
that allows the engine to continue in service until scheduled major 
overhaul time is reached.
    (3) Major overhaul is defined as scheduled engine maintenance 
including complete engine inspections and tests with repair or 
replacement of parts or components as necessary.
    (f) 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. The 
request should be forwarded 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.

    (g) 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 inspection requirements of this AD can be accomplished.

    Issued in Burlington, Massachusetts, on March 27, 1997.
James C. Jones,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 97-8475 Filed 4-2-97; 8:45 am]
BILLING CODE 4910-13-U 1