Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan Engines

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 94-ANE-54]

RIN 2120-AA64

Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan

Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the supersedure of an existing

airworthiness directive (AD), applicable to Pratt & Whitney (PW) JT9D

series turbofan engines, that currently 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 action

would reduce the allowable crack length, reduce the inspection

intervals, and introduce an improved inspection method. This proposal

is prompted by a report of an additional diffuser case rupture, and

improved understanding of crack propagation rates. The actions

specified by the proposed AD are intended to prevent diffuser case

rupture, an uncontained engine failure, and damage to the aircraft.

DATES: Comments must be received by March 12, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), New England Region, Office of the Regional

Counsel, Attention: Rules Docket No. 94-ANE-54, 12 New England

Executive Park, Burlington, MA 01803-5299. Comments may also be sent

via the Internet using the following address: ``9-ad-

[email protected]''. Comments sent via the Internet must contain the

docket number in the subject line. 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, 400 Main St., East Hartford, CT 06108;

telephone (860) 565-6600, fax (860) 565-4503. This information may be

examined at the FAA, New England Region, Office of the Regional

Counsel, 12 New England Executive Park, Burlington, MA.

: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, 400 Main St., East Hartford, CT 06108;

telephone (860) 565-6600, fax (860) 565-4503. This information may be

examined at the FAA, New England Region, Office of the Regional

Counsel, 12 New England Executive Park, Burlington, MA.

FOR FURTHER INFORMATION CONTACT: Peter White, Aerospace Engineer,

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

New England Executive Park, Burlington, MA 01803-5299; telephone (781)

238-7128, fax (781) 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.

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.

Availability of NPRMs

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 94-ANE-54.'' 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 Regional Counsel,

Attention: Rules Docket No. 94-ANE-54, 12 New England Executive Park,

Burlington, MA 01803-5299.

Discussion

On December 29, 1994, the Federal Aviation Administration (FAA)

issued airworthiness directive AD 94-26-06, Amendment 39-9102 (59 FR

67176, December 29, 1994), applicable to Pratt & Whitney (PW) JT9D-59A,

-70A, -7Q, and -7Q3 series turbofan engines, to require 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.

That action was prompted by multiple reports of diffuser case rear rail

cracking and two reports of diffuser case rupture. That condition, if

not corrected, could result in diffuser case rupture, uncontained

engine failure, and damage to the aircraft.

Since the issuance of that AD, the FAA has received a report of an

additional diffuser case rupture. Based on new information regarding

crack propagation rates on repaired diffuser cases, on-wing and in-shop

findings of additional cracked diffuser cases and further refinement of

inspection techniques the manufacturer has significantly changed the

inspection program.

The FAA has reviewed and approved the technical contents of PW JT9D

Service Bulletin (SB) No. 5749, Revision 8, dated October 30, 1998,

that describes procedures for initial and repetitive in-shop and on-

wing fluorescent penetrant inspections (FPI) and eddy current

inspections (ECI) of diffuser case rear rails for cracks. PW JT9D SB

No

turer has significantly changed the

inspection program.

The FAA has reviewed and approved the technical contents of PW JT9D

Service Bulletin (SB) No. 5749, Revision 8, dated October 30, 1998,

that describes procedures for initial and repetitive in-shop and on-

wing fluorescent penetrant inspections (FPI) and eddy current

inspections (ECI) of diffuser case rear rails for cracks. PW JT9D SB

No. 5749, Revision 8, dated October 30, 1998, references PW JT9D SB No.

5654, dated January 21, 1986, that describes procedures for blending

and polishing the rear rail top surface to remove electrochemical

machining (ECM) marks and fatigued material; and PW JT9D SB No. 5768,

Revision 6, dated March 23, 1995, that describes procedures for skim

cutting the diffuser case rear rail top surface to remove

electrochemical machining (ECM) marks and fatigued material; and PW

JT9D SB No. 6197, Revision 1, dated March 23, 1995, that describes

procedures for skim cutting fatigued material from the rear rail top

surface. PW JT9D SB No. 5749, Revision 8, dated October 30, 1998,

varies the initial and repetitive inspection intervals based on the

incorporation of these SBs referenced above, and the parts' age in

cycles.

Since an unsafe condition has been identified that is likely to

exist or develop on other products of this same type design, the

proposed AD would supersede AD 94-26-06 to reduce the allowable crack

length, reduce the inspection intervals, and introduce an improved

inspection method. Initial and repetitive intervals would vary

depending upon rail improvement SB incorporation--higher inspection

intervals are allowed after surface finish improvements of the rear

rail top surface to remove ECM marks, fatigued material, and sharp

edges have been incorporated. The actions would be required to be

accomplished in accordance with the appropriate SBs described

previously.

There are approximately 566 engines of the affected design in the

worldwide fleet

SB incorporation--higher inspection

intervals are allowed after surface finish improvements of the rear

rail top surface to remove ECM marks, fatigued material, and sharp

edges have been incorporated. The actions would be required to be

accomplished in accordance with the appropriate SBs described

previously.

There are approximately 566 engines of the affected design in the

worldwide fleet. The FAA estimates that 157 engines installed on

aircraft of U.S. registry would be affected by this proposed AD, that

it would take approximately 29 work hours per engine to accomplish the

proposed actions, and that the average labor rate is $60 per work hour.

Based on these figures, the total cost impact of the proposed AD on

U.S. operators is estimated to be $273,180.

The regulations proposed herein would 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

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

d, 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 diffuser case rupture, an uncontained engine failure,

and damage to the aircraft, accomplish the following:

(a) Perform initial and repetitive fluorescent penetrant

inspections (FPI) or eddy current inspections (ECI) of diffuser case

rear rails for cracks in accordance with the Accomplishment

Instructions of PW JT9D (SB) No. 5749, Revision 8, dated October 30,

1998, as follows:

(1) For engines on-wing that have not had the diffuser case rear

rail FPI or ECI inspected using the procedures referenced in PW JT9D

SB No. 5749, Revision 4, dated April 25, 1989; Revision 5, dated

September 29, 1995; Revision 6, dated May 8, 1998; Revision 7, dated

August 19, 1998; or Revision 8, dated October 30, 1998; Section 2,

Part 1A (1)-(3), accomplish the following:

(i) Perform an initial on-wing inspection within 25 cycles of

the effective date of this AD in accordance with Section 2, Part 2

of PW JT9D SB No. 5749, Revision 8, dated October 30, 1998.

(ii) Thereafter, except as provided in paragraph (a)(4) of this

AD, perform on-wing inspections in accordance with the time

requirements listed in Section 2, Part 2 of PW JT9D SB No. 5749,

Revision 8, dated October 30, 1998.

ial on-wing inspection within 25 cycles of

the effective date of this AD in accordance with Section 2, Part 2

of PW JT9D SB No. 5749, Revision 8, dated October 30, 1998.

(ii) Thereafter, except as provided in paragraph (a)(4) of this

AD, perform on-wing inspections in accordance with the time

requirements listed in Section 2, Part 2 of PW JT9D SB No. 5749,

Revision 8, dated October 30, 1998.

(2) For engines on-wing that have had the diffuser case rear

rail FPI or ECI inspected using the procedures referenced in PW JT9D

SB No. 5749, Revision 4, dated April 25, 1989; Revision 5, dated

September 29, 1995; Revision 6, dated May 8, 1998; Revision 7, dated

August 19, 1998; or Revision 8, dated October 30, 1998; Section 2,

Part 1 A (1)-(3), perform initial and repetitive on-wing inspections

in accordance with PW JT9D SB 5749, Revision 8, dated October 30,

1998, within the time requirements listed in Section 2, Part 2 of

that SB, except as provided in paragraph (a)(4) of this AD.

(3) Remove from service diffuser cases that do not meet the

return to service criteria stated in PW JT9D SB No. 5749, Revision

8, dated October 30, 1998, Section 2, Part 2 D, and replace with

serviceable parts.

(4) For engines that are overdue for an inspection on the

effective date of this AD, accomplish the required inspection within

25 cycles in service of the effective date of this AD.

(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.

Operators shall submit their requests 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.

ne Certification Office.

Operators shall submit their requests 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.

(c) 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.

Issued in Burlington, Massachusetts, on January 5, 1999.

David A. Downey,

Assistant Manager, Engine and Propeller Directorate, Aircraft

Certification Service.

[FR Doc. 99-492 Filed 1-8-99; 8:45 am]

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