Airworthiness Directives; General Electric Aircraft Engines CT7 Series Turboprop Engines

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-ANE-07; Amendment 39-9011; AD 94-17-16]

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 supersedes an existing airworthiness directive

(AD), applicable to General Electric Aircraft Engines (GEAE) CT7 series

turboprop engines, that currently 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 extends the compliance time for the required

ultrasonic inspection on certain propeller shafts. This amendment is

prompted by information indicating that the equipment necessary to

perform the ultrasonic inspection is less available than originally

assumed. The actions specified by 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 September 15, 1994.

The incorporation by reference of certain publications listed in

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

of September 15, 1994.

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

before October 31, 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, 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: On July 8, 1994, the Federal Aviation

Administration (FAA) issued airworthiness directive (AD) 94-15-01,

Amendment 39-8972 (59 FR 36930, July 20, 1994), applicable to General

Electric Aircraft Engines (GEAE) CT7 series turboprop engines, to

require a one-time ultrasonic inspection of the propeller shaft flange

outer diameter (OD) fillet radius and inner diameter (ID) bore on a

suspect population of propeller shafts for subsurface metallurgical

defects, and if necessary, replacement with a serviceable part. That

action was prompted by the determination that certain propeller shafts

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

Aircraft S340 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.

Since the issuance of that AD, the FAA has determined that

ultrasonic inspection equipment was assumed to be more available than

has proven to be, based on input received by the manufacturer. The

manufacturer reported that there are many operators that would

experience difficulty gaining access to the ultrasonic inspection

equipment in a timely manner given the current AD's compliance

requirements, which could result in unscheduled grounding of aircraft.

Therefore, the FAA is extending the compliance time for ultrasonic

inspection of those propeller shafts first identified by borescope

inspection in paragraph (b) of this AD to be suspect. In the current

AD, paragraph (b) requires operators to ultrasonically inspect suspect

propeller shafts identified by borescope inspection prior to further

flight. This supersedure will extend the compliance time for ultrasonic

inspection to the next shop visit following the borescope inspection,

or October 31, 1994, whichever occurs first. This compliance time is

identical to the compliance time described in paragraph (a) of this AD,

applicable to propeller shafts already suspected to have a

metallurgical defect. By matching the compliance time of paragraph (b)

of this AD to paragraph (a) of this AD, there is no reduction in the

level of airworthiness of the inspection requirements of this AD.

In addition, the FAA has revised the shop visit definition

described in paragraph (c) of this AD to eliminate the separation of

propeller criterion, which could lead to forced unscheduled ultrasonic

inspections of the propeller shaft without ultrasonic inspection

equipment available, and to specify the induction of the propeller

gearbox into the overhaul shop rather than the engine, because it is

not necessary to remove the engine to perform the inspections required

by this AD.

The FAA has reviewed and approved the technical contents of GEAE

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

June 8, 1994, that describes procedures for a one-time ultrasonic

inspection of the propeller shaft flange 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 the next shop visit following

the borescope inspection, or October 31, 1994, whichever occurs first.

Since the inspection procedures have not changed in Revision 3 of GEAE

(CT7-TP Series) SB No. A72-350, inspections performed in accordance

with previous revisions of this SB constitute acceptable alternate

methods of compliance to the inspections required by this AD.

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 AD 94-15-01 to require 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. 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 removing Amendment 39-8972, (59 FR

36930, July 20, 1994), and by adding a new airworthiness directive,

Amendment 39-9011, to read as follows:

94-17-16 General Electric Aircraft Engines: Amendment 39-9011.

Docket 94-ANE-07. Supersedes AD 94-15-01, Amendment 39-8972.

Applicability: General Electric Aircraft Engines (GEAE) Models

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

engines, with propeller gearboxes listed by serial number in GEAE

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

June 8, 1994. These engines are installed on but not limited to

Construcciones Aeronauticas, SA (CASA) and Industri Pesawat Terbang

Nusantara (IPTN) CN-235 series and SAAB Aircraft S340 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

defective propeller shafts with serviceable parts, 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

replace defective propeller shafts with serviceable parts, in

accordance with GEAE (CT7-TP Series) SB No. A72-350, Revision 3,

dated June 8, 1994, on propeller shafts listed by propeller gearbox

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

(b) At the next shop visit after the effective date of this AD,

or prior to October 31, 1994, whichever occurs first, perform a one-

time borescope inspection to identify all markings on the propeller

shaft, in accordance with GEAE (CT7-TP Series) SB No. A72-350,

Revision 3, dated June 8, 1994, on propeller shafts listed by

propeller gearbox S/N in Table 3 of that SB; and proceed as follows:

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

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

defective propeller shafts with serviceable parts, at the next shop

visit after the borescope inspection required by paragraph (b) of

this AD, or October 31, 1994, whichever occurs first, in accordance

with the Accomplishment Instructions of GEAE (CT7-TP Series) SB No.

A72-350, Revision 3, dated June 8, 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 propeller gearbox into the overhaul shop 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 shall be done in accordance

with the following service documents:

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Document No. Pages Revision Date

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GEAE (CT7-TP Series) SB No. A72-350................. 1-40 3 June 8, 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 September 15, 1994.

Issued in Burlington, Massachusetts, on August 16, 1994.

Mark C. Fulmer,

Acting Manager, Engine and Propeller Directorate, Aircraft

Certification Service.

[FR Doc. 94-20591 Filed 8-30-94; 8:45 am]

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