Airworthiness Directives; Pratt & Whitney JT8D Series Turbofan Engines

Proposed Rules

Federal Register

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Proposed Rules

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 96-ANE-32]

RIN 2120-AA64

Airworthiness Directives; Pratt & Whitney JT8D Series Turbofan

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 Pratt & Whitney JT8D-1, -1A, -1B,

-7, -7A, -7B, -9, -9A, -11, -15, - 17, and -17R series turbofan

engines. This proposal would require initial and repetitive fluorescent

penetrant and eddy current inspections of 4th stage low pressure

turbine (LPT) hubs for cracks, and, if necessary, replacement with

serviceable parts. This proposal is prompted by a report of an

uncontained 4th stage LPT blade release. The actions specified by the

proposed AD are intended to prevent a 4th stage LPT blade release due

to hub cracking, which can result in an uncontained engine failure and

damage to the aircraft.

DATES: Comments must be received by March 10, 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. 96-ANE-32, 12 New England

Executive Park, Burlington, MA 01803-5299. 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 Pratt & Whitney, Publication Department, Supervisor

Technical Publications Distribution, M/S 132-30, 400 Main St., East

Hartford, CT 06108; telephone (860) 565-7700, fax (860) 565-4503

03-5299. 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 Pratt & Whitney, Publication Department, Supervisor

Technical Publications Distribution, M/S 132-30, 400 Main St., East

Hartford, CT 06108; telephone (860) 565-7700, fax (860) 565-4503. 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

re 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 96-ANE-32.'' 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. 96-ANE-32, 12 New England Executive Park,

Burlington, MA 01803-5299.

Discussion

The Federal Aviation Administration (FAA) has received a report of

an uncontained engine failure on a Pratt & Whitney (PW) JT8D-15

turbofan engine. On January 30, 1996, this engine, installed on a

Boeing Model 727-200 aircraft, experienced an uncontained 4th stage low

pressure turbine (LPT) blade release during takeoff roll. The aircraft

sustained damage to the vertical stabilizer and the engine cowling.

Inspection of the engine revealed that the LPT blade release resulted

from a radial fracture of the 4th stage LPT hub. The investigation

determined that the failure was due to a crack which initiated in and

propagated in low cycle fatigue from an inclusion located in the hub

bore. This condition, if not corrected, could result in a 4th stage LPT

blade release due to hub cracking, which can result in an uncontained

engine failure and damage to the aircraft

lted

from a radial fracture of the 4th stage LPT hub. The investigation

determined that the failure was due to a crack which initiated in and

propagated in low cycle fatigue from an inclusion located in the hub

bore. This condition, if not corrected, could result in a 4th stage LPT

blade release due to hub cracking, which can result in an uncontained

engine failure and damage to the aircraft.

Further investigation revealed that a certain population of PW JT8D

4th stage LPT hubs may contain inclusions of aluminum/titanium

carbonitrides rich in cerium and lanthanum in the hub bore that may

initiate a crack in the bore, and if undetected, may propagate,

resulting in a hub fracture and LPT blade release. The cause of the

inclusion occurred during the material melting process where a small

amount of slag created during the desulfurization/deoxidization process

of the vacuum induction melt survived a subsequent melt and was not

detected by the required nondestructive test inspections for this

material/part. The FAA has determined that material produced prior to

April 31, 1983, has more susceptibility to inclusions, whereas

subsequent to that date process improvements have been implemented to

produce material that is less susceptible to inclusions. Due to these

process improvements, the FAA has identified certain 4th stage LPT hubs

produced prior to April 1983 that have a greater potential for

contamination. Prior to the uncontained engine failure on January 30,

1996, the FAA received reports of two previous incidents of cracks in

the 4th stage LPT hub due to inclusions that were discovered during

routine shop visits.

The FAA has reviewed and approved the technical contents of PW

Alert Service Bulletin (ASB) No. A6274,

ubstantial 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:

Pratt & Whitney: Docket No. 96-ANE-32.

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:

Pratt & Whitney: Docket No. 96-ANE-32.

Applicability: Pratt & Whitney (PW) Models JT8D-1, -1A, -1B, -7,

-7A, -7B, 9, -9A, -11, -15, -17, and -17R turbofan engines, with 4th

stage low pressure turbine (LPT) hubs identified by serial number

(S/N) in Table A of PW Alert Service Bulletin (ASB) No. A6274,

Revision 1, dated December 97, 1996. These engines are installed on

but not limited to Boeing 727 and 737 series, and McDonnell Douglas

DC-9 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 (b) 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 4th stage LPT blade failure due to hub cracking,

which can result in an uncontained engine failure and damage to the

aircraft, accomplish the following:

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 4th stage LPT blade failure due to hub cracking,

which can result in an uncontained engine failure and damage to the

aircraft, accomplish the following:

(a) Perform fluorescent penetrant inspection (FPI) and eddy

current inspection (ECI) of affected 4th stage LPT hubs for cracks,

in accordance with Paragraph 2A of PW ASB No. A6274, Revision 1,

dated December 9, 1996, as follows:

(1) Inspect at the next time after the effective date of this AD

that the hub is removed from the module and has been debladed.

(2) Thereafter, inspect each time the hub is removed from the

module and has been debladed.

(3) Remove from service any cracked 4th stage LPT hub and

replace with a serviceable part.

(b) 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.

Issued in Burlington, Massachusetts, on January 2, 1997.

Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification

Service.

[FR Doc. 97-469 Filed 1-8-97; 8:45 am]

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