Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan Engines

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-ANE-04]

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 certain Pratt & Whitney

JT9D series turbofan engines, that currently requires initial and

repetitive eddy current inspection (ECI) or fluorescent penetrant

inspection (FPI) for cracks in first stage high pressure turbine (HPT)

disk cooling air holes. This action would require initial and

repetitive FPI for cracks in cooling air holes of additional first

stage HPT disks, and replacement with serviceable parts. In addition,

this action would require initial and repetitive FPI for cracks in tie

bolt holes of certain other affected second stage HPT disks installed

in PW JT9D series turbofan engines. This proposal is prompted by

reports of a cracked cooling air hole on one first stage HPT disk, and

a cracked tie bolt hole on one second stage HPT disk. The actions

specified by the proposed AD are intended to prevent turbine disk

failure due to cooling air hole or tie bolt hole cracking, which could

result in an uncontained engine failure and damage to the aircraft.

DATES: Comments must be received by May 19, 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. 97-ANE-04, 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 Assistant Chief

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

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:

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 97-ANE-04.'' 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. 97-ANE-04, 12 New

[[Page 12980]]

England Executive Park, Burlington, MA 01803-5299.

Discussion

On January 3, 1991, the Federal Aviation Administration (FAA)

issued airworthiness directive AD 91-04-10, Amendment 39-6859 (56 FR

5343, February 11, 1991), applicable to Pratt & Whitney (PW) JT9D

series turbofan engines, to require initial and repetitive eddy current

inspection (ECI) or fluorescent penetrant inspection (FPI) of first

stage high pressure turbine (HPT) disk cooling air holes, and removal

from service of disks that have developed cracks. That action was

prompted by six reports of first stage HPT disks that developed cracks

in service. That condition, if not corrected, could result in turbine

disk failure due to cooling hole cracking, which could result in an

uncontained engine failure and damage to the aircraft.

Since the issuance of that AD, PW produced improved first stage HPT

disks, Part Number (P/N) 840301, installed on JT9D-59A, 70A, 7Q, and

7Q3 engines, that utilized enhanced manufacturing processes that were

intended to preclude improper machining. In addition, PW introduced

procedures for rework of four existing disks, P/Ns 768001, 792701,

812901, 819801, into disks with improved hole surface processing, P/Ns

840401, 840501, 840601, and 840701, believed to eliminate damaged

material. Both the improved and reworked disks share the possibility of

improper machining resulting in damaged material microstructure. The

FAA has since received reports that one improved first stage HPT disk

installed in a PW JT9D-7Q series turbofan engine, and one second stage

HPT disk installed in a PW JT9D-7R4E1 (AI-500) series turbofan engine,

have developed cracks in service. These cracks were discovered within

the cooling holes of the first stage HPT disk and within the tie bolt

holes of the second stage HPT disk. These cracks were found during

routine FPI of the cooling holes and tie bolt holes carried out during

engine shop visits. Engineering review of the structural load

conditions within the cooling holes and tie bolt holes concluded that

all cracking had initiated and propagated in low cycle fatigue (LCF).

Metallurgical analysis of these two cracked disks revealed a severely

worked outer surface layer of material within the holes. The material

microstructure at this worked layer manifested itself as distorted,

elongated grains. The FAA has determined that this condition is the

result of improper machining of the cooling and tie bolt holes during

the disk manufacturing process.

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 91-04-10 to require initial and

repetitive FPI for cracks in cooling air holes of affected first stage

HPT disks, and, if necessary, replacement with serviceable parts. In

addition, this proposed AD would require initial and repetitive FPI for

cracks in tie bolt holes of all affected second stage HPT disks.

Finally, this proposed AD would require reporting findings of cracked

turbine disks.

There are approximately 881 engines of the affected design in the

worldwide fleet. The FAA estimates that 236 engines installed on

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

FAA estimates a total of 3 HPT disks would be found cracked, and the

approximate cost for a new HPT disk is $200,000. Operators average

approximately 1,800 cycles in service per year. For the PW JT9D-59A, -

70A, -7Q, and 7Q3 fleet, the FAA estimates 10.28 inspections over a 20

year period. For the PW JT9D-7R4D, -7R4D1, 7R4E, and -7R4E1 (AI-500)

fleet, the FAA estimates 6.0 inspections over a 20 year period. The

estimated time to accomplish an inspection would be 0.5 work hours, and

the average labor rate is $60 per work hour. The estimated cost to

inspect the PW JT9D-59A, -70A, -7Q, and -7Q3 fleet of 136 engines over

a 20 year period is $41,942. The estimated cost to inspect the PW JT9D-

7R4D, -7R4D1, 7R4E, and -7R4E1 (AI-500) fleet of 100 engines is

$18,000. Based on these figures, the total cost impact of the proposed

AD on U.S. operators is estimated to be $659,942.

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

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 removing amendment 39-6859 (56 FR

5343, February 11, 1991) and by adding a new airworthiness directive to

read as follows:

Pratt & Whitney: Docket No. 97-ANE-04. Supersedes AD 91-04-10,

Amendment 39-6859.

Applicability: Pratt & Whitney (PW) JT9D-59A, -70A, -7Q, -7Q3, -

7R4D, -7R4D1, 7R4E, and -7R4E1 (AI-500) series turbofan engines,

installed on but not limited to Airbus Industrie A300 and A310,

Boeing 747 and 767, and McDonnell Douglas DC-10 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 (d) 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 turbine disk failure due to cooling hole or tie bolt

hole cracking, which could result in an uncontained engine failure

and damage to the aircraft, accomplish the following:

(a) For first stage high pressure turbine (HPT) disks, Part

Numbers (P/Ns) 768001, 792701, 812901, 819801, 840501, 840401,

840701, 840601, and 840301, installed in PW

[[Page 12981]]

JT9D-59A, -70A, -7Q, and -7Q3 engines, accomplish the following:

(1) Disks that have not been fluorescent penetrant inspected or

eddy current inspected since introduction into service, perform an

initial fluorescent penetrant inspection (FPI) for cracks in all 40

cooling air holes in accordance with PW Turbojet Engine Standard

Practices Manual, P/N 585005, Chapter/Section 70-33, using Special

Process Operation Procedure (SPOP) 84, as follows:

(i) Disks with 3,500 cycles since new (CSN) or more on the

effective date of this AD, inspect prior to accumulating 5,000 CSN,

or within 1,500 cycles in service (CIS) after the effective date of

this AD, whichever occurs later.

(ii) Disks with less than 3,500 CSN on the effective date of

this AD, inspect prior to accumulating 5,000 CSN.

(2) Disks that have been reoperated in accordance with PW SB No.

5815, Revision 2, dated July 31, 1992, or prior revisions, that have

not been fluorescent penetrant inspected or eddy current inspected

since reoperation, perform an initial FPI for cracks in all 40

cooling air holes in accordance with PW Turbojet Engine Standard

Practices Manual, P/N 585005, Chapter/Section 70-33, using SPOP 84,

as follows:

(i) Disks with 3,500 CIS or more since reoperation on the

effective date of this AD, inspect prior to accumulating 5,000 CIS

since reoperation, or within 1,500 CIS after the effective date of

this AD, whichever occurs later.

(ii) Disks with less than 3,500 CIS since reoperation on the

effective date of this AD, inspect prior to accumulating 5,000 CIS

since reoperation.

(3) Disks that have been fluorescent penetrant inspected, or

eddy current inspected, since introduction into service or since re-

operation, in accordance with PW SB No. 5744, Revision 3, dated

March 31, 1993, or prior revisions, or PW JT9D-7Q, -7Q3 Engine

Manual, P/N 777210, 72-51-00, Inspection -03, or PW JT9D-59A, -70A

Engine Manual, P/N 754459, 72-51-00, Heavy Maintenance Check -03,

perform an FPI for cracks in all 40 cooling air holes, prior to

accumulating 3,500 CIS since last FPI or ECI, or within 250 CIS

after the effective date of this AD, whichever occurs later, in

accordance with PW Turbojet Engine Standard Practices Manual, P/N

585005, Chapter/Section 70-33, using SPOP 84.

(4) Thereafter, perform FPI for cracks in all 40 cooling air

holes at intervals not to exceed 3,500 CIS since last FPI, in

accordance with PW Turbojet Engine Standard Practices Manual, P/N

585005, Chapter/Section 70-33, using SPOP 84.

(5) Prior to further flight, remove from service cracked disks,

and replace with serviceable parts.

(b) For second stage HPT disks, P/N 5001802-01, installed in PW

JT9D-7R4D, -7R4D1, 7R4E, and -7R4E1 (AI-500) engines, accomplish the

following:

(1) Disks that have not been fluorescent penetrant inspected

since introduction into service, perform an initial FPI for cracks

in all 30 tie bolt holes in accordance with PW Turbojet Engine

Standard Practices Manual, P/N 585005, Chapter/Section 70-33, using

SPOP 84, as follows:

(i) Disks with 6,000 CSN or more on the effective date of this

AD, inspect prior to accumulating 8,000 CSN, or within 2,000 CIS

after the effective date of this AD, whichever occurs later.

(ii) Disks with less than 6,000 CSN on the effective date of

this AD, inspect prior to accumulating 8,000 CSN.

(2) Disks that have been fluorescent penetrant inspected since

introduction into service, perform an FPI for cracks in all 30 tie

bolt holes, prior to accumulating 6,000 CIS since last FPI, or

within 250 CIS after the effective date of this AD, whichever occurs

later, in accordance with PW Turbojet Engine Standard Practices

Manual, P/N 585005, Chapter/Section 70-33, using SPOP 84.

(3) Thereafter, perform FPI for cracks in all 30 tie bolt holes

at intervals not to exceed 6,000 CIS since last FPI, in accordance

with PW Turbojet Engine Standard Practices Manual, P/N 585005,

Chapter/Section 70-33, using SPOP 84.

(4) Prior to further flight, remove from service cracked disks,

and replace with serviceable parts.

(c) Report findings of cracked turbine disks within 48 hours

after inspection to 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, Internet:

``Daniel.K[email protected]''. Reporting requirements have been

approved by the Office of Management and Budget and assigned OMB

control number 2120-0056.

(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 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.

(e) 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 inspection requirements of this AD can be accomplished.

Issued in Burlington, Massachusetts, on March 13, 1997.

James C. Jones,

Acting Manager, Engine and Propeller Directorate, Aircraft

Certification Service.

[FR Doc. 97-6889 Filed 3-18-97; 8:45 am]

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