[Federal Register Volume 59, Number 64 (Monday, April 4, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-7786]


[[Page Unknown]]

[Federal Register: April 4, 1994]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-ANE-03; Amendment 39-8863, AD 94-07-05]

 

Airworthiness Directives; General Electric Company CT58 Series 
Turboshaft Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule, request for comments.

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SUMMARY: This amendment adopts a new airworthiness directive (AD) that 
is applicable to General Electric Company (GE) CT58-110 and -140 series 
turboshaft engines. This action supersedes priority letter AD 93-10-09 
that currently requires inspection of the forward and aft cooling plate 
locating groove or channel (rabbet groove) of stage 1 and stage 2 
turbine wheels for cracks and minimum radii, and replacement, if 
necessary, with serviceable turbine wheels. In addition, that AD 
reduces the cyclic life limit of certain stage 1 and stage 2 turbine 
wheels based on the cycles since new and the rabbet groove radius. This 
action retains the inspection requirements of the current priority 
letter AD, but adds an additional eddy current inspection of the stage 
1 and stage 2 turbine wheels, accelerates the inspection schedule, 
reduces the cyclic life limit of certain stage 1 and stage 2 turbine 
wheels below the published limits and those imposed by the priority 
letter AD, and provides for the removal from service of certain stage 1 
and stage 2 turbine wheels. This amendment is prompted by an extensive 
analytical study performed by GE as a result of an uncontained stage 2 
turbine wheel failure on a GE Model CT58-140-1 turboshaft engine. The 
actions specified by this AD are intended to prevent an uncontained 
engine failure and damage to the aircraft.

DATES: Effective April 19, 1994.
    The incorporation by reference of certain publications listed in 
the regulations is approved by the Director of the Federal Register as 
of April 19, 1994.
    Comments for inclusion in the Rules Docket must be received on or 
before June 3, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Assistant Chief 
Counsel, Attention: Rules Docket No. 94-ANE-03, 12 New England 
Executive Park, Burlington, MA 01803-5299.
    The service information referenced in this AD may be obtained from 
General Electric Company, 1000 Western Ave., Lynn, MA 01910. This 
information may be examined at the FAA, New England Region, Office of 
the Assistant Chief Counsel, 12 New England Executive Park, Burlington, 
MA; or at the Office of the Federal Register, 800 North Capitol Street, 
NW., suite 700, Washington, DC.

FOR FURTHER INFORMATION CONTACT: Robert J. Ganley, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone (617) 
238-7138; fax (617) 238-7199.

SUPPLEMENTARY INFORMATION: On May 20, 1993, the Federal Aviation 
Administration (FAA) issued priority letter airworthiness directive 
(AD) 93-10-09, applicable to General Electric Company (GE) CT58 series 
turboshaft engines, which requires inspection of the forward and aft 
cooling plate locating rabbet groove or channel of stage 1 and stage 2 
turbine wheels for cracks and minimum radii, and replacement, if 
necessary, with serviceable turbine wheels. In addition, that AD 
reduces the cyclic life limit of stage 1 and stage 2 turbine wheels to 
4,200 cycles since new (CSN) for wheels with 3,000 or less CSN on the 
effective date of that AD, and that, upon inspection, have a rabbet 
groove radius of less than 0.010 inches. That action was prompted by an 
investigation into a stage 2 uncontained turbine wheel failure on a GE 
Model CT58-140-1 turboshaft engine. That condition, if not corrected, 
could result in an uncontained engine failure and damage to the 
aircraft.
    Since the issuance of that priority letter AD, the FAA received the 
results of an extensive analytical study performed by GE as a result of 
the noted stage 2 turbine wheel failure. The study indicates that a 
crack initiated in the inboard radius of the rabbet groove on the 
forward side of the wheel. The fatigue crack propagated 360 deg. around 
the wheel, and approximately 300 deg. of the wheel departed in the 
failure. The wheel failure has been attributed to an under minimum 
radius that results in reduced low cycle fatigue capability. The 
results of this study also indicate that the minimum calculated lives 
for certain stage 1 and stage 2 turbine wheels, regardless of the 
forward and aft rabbet groove radii, are significantly lower than the 
published limits and those imposed by the priority letter AD.
    The FAA has reviewed and approved the technical contents of GE CT58 
Service Bulletin (SB) No. A72-126 (CEB-206), Revision 2, dated August 
31, 1993, that describes the revised inspection requirements, 
accelerated inspection schedule, and the removal from service of 
certain stage 1 and stage 2 turbine wheels.
    Since an unsafe condition has been identified that is likely to 
exist or develop on other engines of this same type design, this AD 
supersedes priority letter AD 93-10-09 to add an additional eddy 
current inspection requirement, accelerate the inspection schedule, and 
provide for the removal from service of certain stage 1 and stage 2 
turbine wheels. The priority letter AD referred to the stage 1 and 
stage 2 turbine wheels as high pressure turbine disks. In order to be 
consistent with the SB described previously, the terminology has been 
changed in this final rule to turbine wheel. The actions are required 
to be accomplished in accordance with the SB described previously.
    Since a situation exists that requires the immediate adoption of 
this regulation, it is found that notice and opportunity for prior 
public comment hereon are impracticable, and that good cause exists for 
making this amendment effective in less than 30 days.

Comments Invited

    Although this action is in the form of a final rule that involves 
requirements affecting flight safety and, thus, was not preceded by 
notice and an opportunity for public comment, comments are invited on 
this rule. Interested persons are invited to comment on this 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 under the caption ADDRESSES. All 
communications received on or before the closing date for comments will 
be considered, and this rule may be amended in light of the comments 
received. Factual information that supports the commenter's ideas and 
suggestions is extremely helpful in evaluating the effectiveness of the 
AD action and determining whether additional rulemaking action would be 
needed.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the rule that might 
suggest a need to modify the 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 that 
summarizes each FAA-public contact concerned with the substance of this 
AD 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 94-ANE-03.'' The postcard will be date stamped and 
returned to the commenter.
    The regulations adopted herein will 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 final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    The FAA has determined that this regulation is an emergency 
regulation that must be issued immediately to correct an unsafe 
condition in aircraft, and is not a ``significant regulatory action'' 
under Executive Order 12866. It has been determined further that this 
action involves an emergency regulation under DOT Regulatory Policies 
and Procedures (44 FR 11034, February 26, 1979). If it is determined 
that this emergency regulation otherwise would be significant under DOT 
Regulatory Policies and Procedures, a final regulatory evaluation will 
be prepared and placed in the Rules Docket. A copy of it, if filed, may 
be obtained from the Rules Docket at the location provided under the 
caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends 14 CFR part 
39 of the Federal Aviation Regulations as follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); 
and 14 CFR 11.89.


Sec. 39.13  [Amended]

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

94-07-05  General Electric Company: Amendment 39-8863. Docket No. 
94-ANE-03.

    Applicability: General Electric Company (GE) CT58-110 and -140 
series turboshaft engines installed on but not limited to Boeing 
Vertol 107 series, and Sikorsky S61 and S62 series aircraft.
    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent an uncontained engine failure and damage to the 
aircraft, accomplish the following:
    (a) For stage 1 turbine wheels, Part Number (P/N) 4002T17P01 and 
4002T17P02, and stage 2 turbine wheels, P/N 4002T96P01 and 
4002T96P02, that have not previously accomplished GE CT58 Service 
Bulletin (SB) No. A72-126 (CEB-206), Revision 1, dated December 5, 
1969, inspect the wheels in accordance with paragraphs 2.A or 2.B; 
and 2.D, 2.E, and 2.F of GE CT58 SB No. A72-126 (CEB-206), Revision 
2, dated August 31, 1993, as follows, or remove the wheels from 
service prior to August 1, 1994, and replace with a serviceable 
part, whichever occurs earlier:
    (1) For wheels utilized in repetitive heavy lift (RHL) or 
external lift operation:
    (i) For wheels that have accumulated less than 500 hours time 
since new (TSN) on the effective date of this airworthiness 
directive (AD), inspect the wheels prior to accumulating 900 hours 
TSN.
    (ii) For wheels that have accumulated 500 hours TSN or more on 
the effective date of this AD, inspect the wheels at the next engine 
shop visit, or prior to accumulating 400 hours time in service (TIS) 
after the effective date of this AD, whichever occurs earlier.
    (2) For wheels utilized in non-RHL operation:
    (i) For wheels that have accumulated less than 1,500 hours TSN 
on the effective date of this AD, inspect the wheels prior to 
accumulating 2,000 hours TSN.
    (ii) For wheels that have accumulated 1,500 hours TSN or more on 
the effective date of this AD, inspect the wheels at the next engine 
shop visit, or prior to accumulating 600 hours TIS after the 
effective date of this AD, whichever occurs earlier.
    (b) For stage 1 turbine wheel, P/N 4002T17P04, and stage 2 
turbine wheel, P/N 4002T96P04, inspect the wheels in accordance with 
paragraphs 2.D and 2.E of GE CT58 SB No. A72-126 (CEB-206), Revision 
2, dated August 31, 1993, and the inspection schedule outlined in 
paragraph (a)(1) and (a)(2) of this AD, as applicable, or remove the 
wheels from service prior to August 1, 1994, and replace with a 
serviceable part, whichever occurs earlier.
    (c) For wheels inspected in accordance with paragraph (a) of 
this AD, accomplish the following:
    (1) Prior to further flight, remove from service cracked wheels, 
wheels that do not meet the required web thickness limits, or wheels 
that have a cooling plate locating groove or channel (rabbet groove) 
radius less than 0.006 inches, and replace with a serviceable part.
    (2) Prior to further flight, mark wheels that have a rabbet 
groove radius of 0.006 inches or greater, by marking the part with 
the number ``CEB 206, REV 2'' in accordance with paragraph 2.H of GE 
CT58 SB No. A72-126 (CEB-206), Revision 2, dated August 31, 1993.
    (d) For wheels inspected in accordance with paragraph (b) of 
this AD, accomplish the following:
    (1) Prior to further flight, remove from service cracked wheels, 
and replace with a serviceable part.
    (2) Prior to further flight, mark wheels with the number ``CEB 
206, REV 2'' in accordance with paragraph 2.H of GE CT58 SB No. A72-
126 (CEB-206), Revision 2, dated August 31, 1993.
    (e) For stage 1 turbine wheels, P/N 4002T17P02 and 4002T17P04, 
and stage 2 turbine wheels, P/N 4002T96P02 and 4002T96P04, that have 
previously accomplished GE CT58 SB No. A72-126 (CEB-206), Revision 
1, dated December 5, 1969, eddy current inspect (ECI) and 
fluorescent penetrant inspect (FPI) the wheels in accordance with GE 
CT58 SB No. A72-126 (CEB-206), Revision 2, dated August 31, 1993, as 
follows, or remove the wheels from service and replace with a 
serviceable part in accordance with paragraph (g)(1) or (g)(2) of 
this AD, as applicable, whichever occurs earlier:
    (1) For wheels utilized in RHL or external lift operation, 
inspect wheels in accordance with the inspection limits defined in 
Table 1 of GE CT58 SB No. A72-126 (CEB-206), Revision 2, dated 
August 31, 1993, or prior to 400 hours TIS after the effective date 
of this AD, whichever occurs later.
    (2) For wheels utilized in non-RHL operation, inspect wheels in 
accordance with the inspection limits defined in Table 1 of GE CT58 
SB No. A72-126 (CEB-206), Revision 2, dated August 31, 1993, or 
prior to 600 hours TIS after the effective date of this AD, 
whichever occurs later.
    (f) For wheels inspected in accordance with paragraph (e) of 
this AD, accomplish the following:
    (1) Prior to further flight, remove from service cracked wheels, 
and replace with a serviceable part.
    (2) Prior to further flight, mark wheels with the number ``CEB 
206, REV 2'' in accordance with paragraph 2.H of GE CT58 SB No. A72-
126 (CEB-206), Revision 2, dated August 31, 1993.
    (g) For wheels marked in accordance with paragraph (c)(2), 
(d)(2), or (f)(2) of this AD:
    (1) For wheels that have a rabbet groove radius less than 0.013 
inches, remove from service prior to August 1, 1994, and replace 
with a serviceable part.
    (2) For wheels that have a rabbet groove radius of 0.013 inches 
or greater, remove from service in accordance with the inspection 
limits defined in Table 1 of GE CT58 SB No. A72-126 (CEB-206), 
Revision 2, dated August 31, 1993, or prior to August 1, 1994, 
whichever occurs later, and replace with a serviceable part.
    (3) ECI and FPI wheels in accordance with GE CT58 SB No. A72-126 
(CEB-206), Revision 2, dated August 31, 1993, as follows:
    (i) For wheels utilized in RHL or external lift operation, 
reinspect wheels at intervals not to exceed 1,000 hours TIS since 
the last inspection.
    (ii) For wheels utilized in non-RHL operation, reinspect wheels 
at intervals not to exceed 2,000 hours TIS since the last 
inspection.
    (iii) Prior to further flight, remove from service cracked 
wheels, and replace with a serviceable part.
    (h) Remove from service within 400 hours TIS after the effective 
date of this AD, stage 1 turbine wheels, P/N 278D978P002, 
37D400498P101, 37D400307P101, 37D400010P101, 37D400227P101, 
3018T97P02, 3018T97P03, and 3018T97P04; and stage 2 turbine wheels, 
P/N 278D979P002, 37D400499P101, 37D400228P102, 37D400004P102, 
3018T98P01, 3018T98P02, 3018T98P03, and 3018T98P04, and replace with 
serviceable parts.
    (i) For the purpose of this AD, the following definitions apply:
    (1) An engine shop visit is defined as the induction of an 
engine into a shop for maintenance involving the separation of any 
major flange.
    (2) RHL operation is defined as more than ten lift-carry-drop 
cycles per hour TIS without landing, or more than ten takeoffs and 
landings per hour TIS.
    (3) External lift operation is defined as up to ten lift-carry-
drop cycles per hour TIS without landing, or up to ten takeoffs and 
landings per hour TIS.
    (4) Non-RHL operation is defined as carrying passengers or 
internal cargo.
    (5) A serviceable part is defined as stage 1 turbine wheel, P/N 
4002T17P02 TF3, and stage 2 turbine wheel, P/N 4002T96P02 TF3.
    (j) 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: Information concerning the existence of approved 
alternative methods of compliance with this airworthiness directive, 
if any, may be obtained from the Engine Certification Office.

    (k) Special flight permits may be issued in accordance with FAR 
21.197 and 21.199 to operate the aircraft to a location where the 
requirements of this AD can be accomplished.
    (l) The inspection and replacement shall be done in accordance 
with the following service bulletin: 

------------------------------------------------------------------------
         Document No.            Page    Revision           Date        
------------------------------------------------------------------------
GE CT58 SB No. A72-126 (CEB-      1-28           2  Aug. 31, 1993.      
 206).                                                                  
                               --------                                 
    Total Pages...............     28                                   
------------------------------------------------------------------------

This incorporation by reference was approved by the Director of the 
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 
51. Copies may be obtained from General Electric Company, 1000 
Western Ave., Lynn, MA 01910. Copies may be inspected at the FAA, 
New England Region, Office of the Assistant Chief Counsel, 12 New 
England Executive Park, Burlington, MA; or at the Office of the 
Federal Register, 800 North Capitol Street, NW., suite 700, 
Washington, DC.
    (m) This amendment supersedes priority letter AD 93-10-09, 
issued May 20, 1993.
    (n) This amendment becomes effective on April 19, 1994. Issued 
in Burlington, Massachusetts, on March 23, 1994.
Marc Bouthillier,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 94-7786 Filed 4-1-94; 8:45 am]
BILLING CODE 4910-13-P