Airworthiness Directives; General Electric Company CT58 Series Turboshaft Engines

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:

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Document No. Page Revision Date

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GE CT58 SB No. A72-126 (CEB- 1-28 2 Aug. 31, 1993.

206).

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Total Pages............... 28

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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]

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