[Federal Register Volume 62, Number 53 (Wednesday, March 19, 1997)]
[Proposed Rules]
[Pages 12979-12981]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-6889]


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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]
BILLING CODE 4910-13-U