Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan Engines

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-ANE-54; Amendment 39-9102; AD 94-26-06]

Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan

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 Pratt & Whitney (PW) JT9D series turbofan engines.

This action requires initial and repetitive in-shop or on-wing

inspections of the diffuser case rear rail for cracking, and removal,

if necessary, of the diffuser case. This amendment is prompted by

multiple reports of diffuser case rear rail cracking and two reports of

diffuser case rupture. The actions specified in this AD are intended to

prevent diffuser case rupture and an uncontained engine failure.

DATES: Effective January 13, 1995.

The incorporation by reference of certain publications listed in

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

of January 13, 1995.

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

before February 27, 1995.

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-54, 12 New England

Executive Park, Burlington, MA 01803-5299.

The service information referenced in this AD may be obtained from

Pratt & Whitney, 400 Main Street, East Hartford, CT 06108. 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: On September 16, 1993, the Federal Aviation

Administration (FAA) issued airworthiness directive (AD) 93-19-02,

Amendment 39-8695 (58 FR 51212, October 1, 1993), applicable to Pratt &

Whitney (PW) JT9D-3A, -7, -7H, -7A, -7AH, -7F, -7J, -20, and -20J

turbofan engines. That AD requires eddy current inspection and

modification of the diffuser case rear rail, and ultrasonic,

metallographic, and X-ray inspections of specific locations in the

diffuser case. That action was prompted by reports of 2 additional

diffuser case failures that occurred within significantly shorter time

intervals since last inspection than that specified in a previous AD.

That condition, if not corrected, could result in diffuser case rupture

and an uncontained engine failure.

On September 22, 1994, the FAA issued Revision 1 to AD 93-19-02,

Amendment 39-9038 (59 FR 49789, September 30, 1994) to correct an error

in paragraph numbering in the compliance section and allow modification

of diffuser cases in accordance with previous revisions of PW Service

Bulletin No. 5805 as an alternative means of compliance to paragraph

(o) of that AD.

The FAA has determined that the diffuser case on PW JT9D-59A, -70A,

-7Q, and -7Q3 series turbofan engines may also develop cracks in the

rear rail. The diffuser case rear rail is a structural hat section and

stiffens the casing shell under conditions of high pressure and

temperature. The rear rail has developed a cracking problem in service

due to high stresses located adjacent to the strut bosses. These cracks

initiate and propagate in low cycle fatigue (LCF) until the critical

crack length is exceeded. At this point, the cracking mode may change

to rapid tensile, and a rupture may occur.

In an effort to better understand the diffuser case failure mode, a

rig test was performed. This test examined crack initiation and growth

rates in weld-repaired versus non-weld-repaired diffuser cases. Results

of the test established that cracks initiate and propagate more rapidly

in weld-repaired diffuser cases.

In addition, the testing revealed that diffuser case rear rails

that have been modified in accordance with PW Service Bulletin (SB) No.

5768 and SB No. 5654 experience lower rates of crack initiation. Pratt

& Whitney SB 5768 and SB 5654 both provide enhancements to the LCF

characteristics and life of the diffuser case rear rail by removing

electrochemically machined areas on the rear rail, and removing stress

concentrations caused by sharp edges on the rear rail. Incorporation of

PW SB 5768 and SB 5654 provides relaxed intervals for inspection of the

diffuser case rear rail as defined in PW SB No. 5749, Revision 4, dated

May 10, 1993.

To date there have been varying degrees of diffuser case rear rail

cracking on the PW JT9D-59A, -70A, -7Q, and -7Q3 diffuser cases. The

FAA has received multiple reports of in-service cracking. Two reported

cracks measured approximately 5 inches in length, and in two incidents

the diffuser case ruptured. The FAA has determined that these two

incidents may have been prevented if the operators had performed the

inspections described in the SB required by this final rule.

The FAA has reviewed and approved the technical contents of PW SB

No. 5749, Revision 4, dated May 10, 1993, that describes procedures for

in-shop eddy current inspections (ECI) or fluorescent penetrant

inspections (FPI), or on-wing ECI, of the diffuser case rear rail for

cracking.

Since an unsafe condition has been identified that is likely to

exist or develop on other engines of the same type design, this AD is

being issued to prevent diffuser case rupture and an uncontained engine

failure. This AD requires initial and repetitive in-shop ECI or FPI, or

on-wing ECI, of the diffuser case rear rail for cracking, and removal

from service of diffuser cases with cracks that exceed 1.5 inches in

length. 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-54.'' 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:

94-26-06 Pratt & Whitney: Amendment 39-9102. Docket 94-ANE-54.

Applicability: Pratt & Whitney (PW) JT9D-59A, -70A, -7Q, and -

7Q3 series turbofan engines, installed on but not limited to Airbus

A300 series, Boeing 747 series, and McDonnell Douglas DC-10 series

aircraft.

Compliance: Required as indicated, unless accomplished

previously.

To prevent diffuser case rupture and an uncontained engine

failure, accomplish the following:

(a) For diffuser cases that have not been inspected in

accordance with PW Service Bulletin (SB) No. 5749, Revision 3, dated

April 25, 1989, or earlier versions of that SB, prior to the

effective date of this AD, accomplish the following:

(1) If maintenance records indicate that a fluorescent penetrant

inspection (FPI) was performed on the entire diffuser case rear rail

and the diffuser case has accumulated less than 475 cycles in

service (CIS) since that FPI, perform an initial on-wing eddy

current inspection (ECI), or in-shop ECI or FPI, of the diffuser

case rear rail for cracking in accordance with PW SB No. 5749,

Revision 4, dated May 10, 1993, within 500 CIS since the last

diffuser case FPI.

(2) If maintenance records indicate that an FPI was performed on

the entire diffuser case rear rail and the diffuser case has

accumulated 475 or more CIS since that FPI, perform an initial on-

wing ECI, or in-shop ECI or FPI, of the diffuser case rear rail for

cracking in accordance with PW SB No. 5749, Revision 4, dated May

10, 1993, within 25 CIS after the effective date of this AD.

(3) If maintenance records are unavailable, or if it is unknown

when the last FPI was performed on the entire diffuser case rear

rail, perform an initial on-wing ECI, or in-shop ECI or FPI, of the

diffuser case rear rail for cracking in accordance with PW SB No.

5749, Revision 4, dated May 10, 1993, within 25 CIS after the

effective date of this AD.

(4) For diffuser cases introduced into service subsequent to the

effective date of this AD, perform an initial on-wing ECI, or in-

shop ECI or FPI, of the diffuser case rear rail for cracking in

accordance with PW SB No. 5749, Revision 4, dated May 10, 1993,

within the cyclic intervals specified in Table 1 of PW SB No. 5749,

Revision 4, dated May 10, 1993.

(b) For diffuser cases that have been inspected in accordance

with PW SB No. 5749, Revision 3, dated April 25, 1989, or earlier

versions of that SB, prior to the effective date of this AD,

accomplish the following:

(1) Perform an initial on-wing ECI, or in-shop ECI or FPI, of

the diffuser case rear rail for cracking in accordance with PW SB

No. 5749, Revision 4, dated May 10, 1993, within the cyclic

intervals specified in Table 1 of PW SB No. 5749, Revision 4, dated

May 10, 1993.

(2) If maintenance records indicate that the diffuser case has

accumulated more CIS since the last on-wing ECI, or in-shop ECI or

FPI, performed in accordance with PW SB No. 5749, Revision 3, dated

April 25, 1989, or earlier versions of that SB, than the cyclic

intervals specified in Table 1 of PW SB No. 5749, Revision 4, dated

May 10, 1993, perform an initial on-wing ECI, or in-shop ECI or FPI,

of the diffuser case rear rail for cracking in accordance with PW SB

No. 5749, Revision 4, dated May 10, 1993, within 25 CIS after the

effective date of this AD.

(c) If no cracks are found in the diffuser case rear rail during

the initial inspections required by paragraph (a) or (b) of this AD,

as applicable, perform subsequent on-wing ECI, or in-shop ECI or

FPI, of the diffuser case rear rail for cracking in accordance with

PW SB No. 5749, Revision 4, dated May 10, 1993, within the cyclic

intervals specified in Table 1 of PW SB No. 5749, Revision 4, dated

May 10, 1993.

(d) If cracks are found in diffuser case rear rails during the

inspections required by paragraph (a), (b), or (c) of this AD, as

applicable, determine the length of the crack:

(1) If the crack is less than 1.5 inches in length, continue in

service and reinspect in accordance with the Accomplishment

Instructions of PW SB No. 5749, Revision 4, dated May 10, 1993, at

intervals not to exceed 75 CIS since the last inspection.

(2) If the crack is 1.5 inches or greater in length, prior to

further flight remove the diffuser case from service for repair and

replace with a serviceable part.

(e) 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.

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

sections 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.

(g) The actions required by this AD shall be done in accordance

with the following service document:

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Document No. Pages Revision Date

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PW SB No. 5749..................... 1-13 4 May 10, 1993.

Total pages.................... 13

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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 Pratt & Whitney, 400 Main

Street, East Hartford, CT 06108. 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.

(h) This amendment becomes effective on January 13, 1995.

Issued in Burlington, Massachusetts, on December 14, 1994.

Kirk E. Gustafson,

Acting Manager, Engine and Propeller Directorate, Aircraft

Certification Service.

[FR Doc. 94-31870 Filed 12-28-94; 8:45 am]

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