[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: ``engineprop@faa.dot.gov''. 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.Kerman@faa.dot.gov''. 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
