Airworthiness Directives; General Electric Aircraft Engines CT7 Series Turboprop Engines

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-ANE-07; Amendment 39-8972; AD 94-15-01]

Airworthiness Directives; General Electric Aircraft Engines CT7

Series Turboprop 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 Aircraft Engines (GE) CT7 series

turboprop engines. This action requires a one-time ultrasonic

inspection of a suspect population of propeller shafts for

metallurgical defects, and if necessary, replacement with a serviceable

part. This amendment is prompted by a report of an inflight propeller

separation due to a metallurgical defect. The actions specified in this

AD are intended to prevent failure of the propeller shaft, which can

result in separation of the propeller from the propeller shaft and

possible damage to the aircraft.

DATES: Effective August 4, 1994.

The incorporation by reference of certain publications listed in

the regulations is approved by the Director of the Federal Register as

of August 4, 1994.

Comments for inclusion in the Rules Docket must be received on or

before September 19, 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-07, 12 New England

Executive Park, Burlington, MA 01803-5299.

The service information referenced in this AD may be obtained from

General Electric Aircraft Engines, 1000 Western Avenue, 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: Daniel Kerman, Aerospace Engineer,

Engine Certification Office, FAA, Engine and Propeller Directorate, 12

New England Executive Park, Burlington, MA 01803-5299; telephone (617)

238-7130, fax (617) 238-7199.

SUPPLEMENTARY INFORMATION: The Federal Aviation Administration (FAA)

has determined that certain propeller shafts on General Electric

Aircraft Engines (GE) CT7 series turboprop engines may have a

metallurgical defect that could cause separation of the propeller from

the propeller shaft. The FAA's investigation has revealed this

population of propeller shafts may contain a metallurgical defect known

as a pipe inclusion, which developed during manufacture of the shaft.

This defect typically forms during the process of melting the ingot

used to form the shaft and positions itself at either end of the ingot.

During this phase of the manufacturing process cropping both ends of

the ingot normally ensures complete removal of such defects. The FAA

has determined, however, that for five heat lots of material, pipe

inclusions may not have been completely removed from the material used

to form the propeller shaft. The FAA has determined that suspect

material was used to manufacture approximately 326 propeller shafts.

The FAA received a report of a propeller separating from a SAAB-

SCANIA SF340 series aircraft inflight following severe vibration. The

FAA's investigation revealed that the propeller shaft separated due to

a pipe inclusion defect positioned in a high stress location of the

propeller shaft. That defect initiated a crack which propagated to

failure. This condition, if not corrected, could result in failure of

the propeller shaft, which can result in separation of the propeller

from the propeller shaft and possible damage to the aircraft.

The FAA has reviewed and approved the technical contents of GE

(CT7-TP Series) Service Bulletin (SB) No. A72-350, Revision 3, dated

June 9, 1994, that describes procedures for a one-time ultrasonic

inspection of the propeller shaft flange outer diameter (OD) fillet

radius and inner diameter (ID) bore for detection of subsurface

defects. In addition, Table 3 of this SB lists by propeller gearbox

serial number (S/N) a certain population of suspect propeller shafts to

be identified by internal markings during a one-time borescope

inspection. Those propeller shafts with markings identified as suspect

in accordance with this SB must be ultrasonically inspected prior to

further flight.

Since an unsafe condition has been identified that is likely to

exist or develop on other GE CT7 series turboprop engines of the same

type design, this airworthiness directive (AD) is being issued to

prevent separation of the propeller from the propeller shaft, which

could result in damage to the aircraft. This AD requires a one-time

ultrasonic inspection of the propeller shaft flange OD fillet radius

and ID bore on a suspect population of propeller shafts for subsurface

metallurgical defects, and if necessary, replacement with a serviceable

part. This inspection must be performed at the next shop visit after

the effective date of this AD, or prior to October 31, 1994, whichever

occurs first. The FAA has determined that the compliance end-date of

October 31, 1994, will be necessary to ensure timely inspection of all

propeller shafts and thus minimize the potential for additional

propeller shaft failures. The actions are required to be accomplished

in accordance with the service bulletin 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-07.'' 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 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. App. 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:

94-15-01 General Electric Aircraft Engines: Amendment 39-8972.

Docket 94-ANE-07.

Applicability: General Electric Aircraft Engines (GE) Models

CT7-5A2, -5A3, -7A, -7A1, -9B, -9B1, -9B2, -9C, -9D turboprop

engines, with propeller gearboxes listed by serial number in GE

(CT7-TP Series) Service Bulletin (SB) No. A72-350, Revision 3, dated

June 9, 1994. These engines are installed on but not limited to

Construcciones Aeronauticas, SA (CASA) CN-235 series and SAAB-SCANIA

SF340 series aircraft.

Compliance: Required as indicated, unless accomplished

previously.

To prevent failure of the propeller shaft, which can result in

separation of the propeller from the propeller shaft and possible

damage to the aircraft, accomplish the following:

(a) Perform a one-time ultrasonic inspection of the propeller

shaft flange outer diameter (OD) fillet radius and inner diameter

(ID) bore for subsurface metallurgical defects, and replace, if

necessary, with a serviceable part, at the next shop visit after the

effective date of this AD, or prior to October 31, 1994, whichever

occurs first. Perform the ultrasonic inspection, and replacement, if

necessary, in accordance with GE (CT7-TP Series) SB No. A72-350,

Revision 3, dated June 9, 1994, on propeller shafts listed by

propeller gearbox serial number (S/N) in Table 2 of that SB.

(b) Perform a one-time borescope inspection to identify all

markings on the propeller shaft at the next shop visit after the

effective date of this AD, or prior to October 31, 1994, whichever

occurs first. Perform the borescope inspection in accordance with GE

(CT7-TP Series) SB No. A72-350, Revision 3, dated June 9, 1994, on

propeller shafts listed by propeller gearbox S/N in Table 3 of that

SB, and before further flight, proceed as follows:

(1) For those propeller shafts that are determined to be

suspect, perform a one-time ultrasonic inspection, and replace, if

necessary with serviceable parts, in accordance with the

Accomplishment Instructions of GE (CT7-TP Series) SB No. A72-350,

Revision 3, dated June 9, 1994.

(2) For those propeller shafts that are determined not to be

suspect, no further action is required.

(c) For the purpose of this AD, a shop visit is defined as the

induction of the engine into the shop for maintenance, or separation

of the propeller for maintenance.

(d) 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.

(e) Special flight permits may be issued in accordance with

Sec. Sec. 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.

(f) The inspections, and replacement, if necessary, shall be

done in accordance with the following service document:

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Revision

Document No. Pages Date

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GE (CT7-TP Series) SB No. A72-350. 1-40 3 June 9, 1994.

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Total pages: 40.

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 Aircraft Engines, 1000

Western Avenue, 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.

(g) This amendment becomes effective on August 4, 1994.

Issued in Burlington, Massachusetts, on July 8, 1994.

Michael H. Borfitz,

Acting Manager, Engine and Propeller Directorate, Aircraft

Certification Service.

[FR Doc. 94-17328 Filed 7-19-94; 8:45 am]

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