[Federal Register Volume 62, Number 235 (Monday, December 8, 1997)]
[Rules and Regulations]
[Pages 64514-64517]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-31965]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 97-ANE-04; Amendment 39-10234; AD 97-25-10]
RIN 2120-AA64
Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan
Engines
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
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[[Page 64515]]
SUMMARY: This amendment supersedes 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
amendment requires initial and repetitive FPI for cracks in cooling air
holes of additional first stage HPT disks, and replacement with
serviceable parts. In addition, this amendment requires 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 amendment 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 this 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: Effective January 12, 1998.
ADDRESSES: The service information referenced in this AD 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. This
information may be examined at the Federal Aviation Administration
(FAA), New England Region, Office of the Assistant Chief Counsel, 12
New England Executive Park, Burlington, MA 01803-5299; or at the Office
of the Federal Register, 800 North Capitol Street, NW., suite 700,
Washington, DC.
FOR FURTHER INFORMATION CONTACT: Tara Goodman, Aerospace Engineer,
Engine Certification Office, FAA, Engine and Propeller Directorate, 12
New England Executive Park, Burlington, MA 01803-5299; telephone (781)
238-7130, fax (781) 238-7199.
SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal
Aviation Regulations (14 CFR part 39) by superseding airworthiness
directive (AD) 91-04-10, Amendment 39-6859 (56 FR 5343, February 11,
1991), applicable to Pratt & Whitney (PW) JT9D series turbofan engines,
was published in the Federal Register on March 19, 1997 (62 FR 12979).
That action proposed to require initial and repetitive fluorescent
penetrant inspections (FPI) for cracks in cooling air holes of affected
first stage high pressure turbine (HPT) disks, and, if necessary,
replacement with serviceable parts. In addition, the action proposed to
require initial and repetitive FPI for cracks in tie bolt holes of all
affected second stage HPT disks. Finally, that action proposed to
require reporting findings of cracked turbine disks.
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the comments received.
One commenter states that since the root cause of the crack which
was found on the cooling hole of the improved disk, part number (P/N)
840301, was caused by improper tooling application (use of reamer
instead of a carbide insert) at the specified supplier, only the
suspect supplier and lots should be affected by the AD. The commenter
maintains that if the FAA suspects PW's qualified carbide insert
machining process, every maintenance process requiring the
manufacturer's qualification should always require FAA qualification in
future. The Federal Aviation Administration (FAA) does not concur. The
improved disk, P/N 840301, is manufactured with the new reamer tooling
method; however, a disk of this P/N was found with cooling hole
cracking. The reamer method was introduced by manufacturers to preclude
abusive machining that was found using the carbide insert method.
Investigation has shown that both the carbide insert method and the
reamer method are subject to the same abusive machining phenomenon. The
FAA approves manufacturing and maintenance processes, which are updated
as necessary.
The same commenter requests that the FAA and PW develop an
inspection procedure that can detect not only a crack but detect
whether a severely worked layer of material exists or not, so that
unnecessary repetitive inspections can be minimized by removing those
disks. The FAA does not concur. It is not possible to detect 100% of
the possible cracking conditions in the field using current inspection
methods. Therefore, repetitive inspections are necessary for disks that
are in service because cracking can propagate in fatigue from a layer
of severely worked material resulting from the manufacturing process.
The same commenter requests the FAA extend the initial inspection
requirement for disks that have been previously inspected, noting that
the AD as proposed would allow 1,500 cycles in service (CIS) before
initial inspection for disks never inspected while only 250 CIS for
disks that have been inspected but that have accumulated more than
3,500 CIS since last inspection. The FAA does not concur. The current
AD, effective in 1991, requires repetitive inspections of disks
installed in JT9D-59A, -70A, -7Q, and -7Q3 engines at intervals not to
exceed 3,500 CIS. Therefore, the example cited by the commenter should
not occur, as disks installed in JT9D-59A or -7Q engines should never
exceed 3,500 CIS since last inspection. Only if a disk installed in a
JT9D-7R4 engine had exceeded 3,500 CIS since last inspection would the
requirement to inspect no later than 250 CIS after the effective date
of this AD apply. This inspection requirement was considered in the
risk analysis and the FAA has determined that it is necessary. The
commenter does not indicate how many JT9D-7R4 engines might be affected
by the 250 CIS initial inspection requirement. Individual operators can
apply for an adjustment to that compliance time under paragraph (d) of
the AD.
One commenter states that the mandated use of FPI does not provide
all possible assurance that defective HPT disks will be removed from
service. The commenter believes that eddy current inspection, or a
combination of the two methods, would clearly provide a greater
probability of crack detection. The FAA does not concur. The first
stage turbine cooling air holes and second stage tie bolt holes have
low aspect ratios. The FAA has determined that FPI of low aspect ratio
holes is adequate for detecting cracks in these locations.
One commenter states that there appears to be anomalies in the
requirements for disks that have been in service for over 6,000 cycles
since new (CSN), as stated in paragraph (b)(1)(i) of the compliance
section. The commenter maintains that as the paragraph reads in the
proposed rule, this inspection will always occur later than
accumulating 8,000 CSN if CSN is greater than 6,000 on the effective
date of the AD. The FAA concurs and has changed this paragraph to
require inspection within 2,000 CIS if a disk has over 6,000 CSN on the
effective date of the AD.
The same commenter suggests that at next engine shop visit would be
sufficient as an interval for cooling hole and tie bolt hole
inspections. The FAA does not concur. Since the timing of engine shop
visits varies widely between operators, the use of shop visits to
define inspection intervals in ADs does not provide adequate
objectivity on which to assess the effectiveness of the required
actions in addressing the unsafe condition. The FAA has determined that
a maximum of 2,000 CIS interval is required.
[[Page 64516]]
Subsequent to the publication of the proposed rule, two JT9D-7R4D/E
operators indicated that the 6,000 CIS re-inspection interval for
second stage turbine hub tie bolt hole mismachining would require them
to remove engines prematurely due to their high cycle utilization rate.
The FAA has determined through a review of risk analysis that the
additional risk involved in extending the re-inspection interval from
6,000 CIS to 8,000 CIS is sufficiently low and has changed the re-
inspection interval accordingly.
In addition, the manufacturer has recommended that Special Process
Operation Procedure (SPOP) 70 be used in lieu of SPOP 84 in order to
permit the inspection of the second stage turbine hub tie bolt holes
when the second stage turbine rotor is removed from the HPT module
assembly without necessitating the removal of the second stage turbine
blades. The FAA concurs and has changed the reference to the inspection
procedure accordingly.
After careful review of the available data, including the comments
noted above, the FAA has determined that air safety and the public
interest require the adoption of the rule with the changes described
previously. The FAA has determined that these changes will neither
increase the economic burden on any operator nor increase the scope of
the AD.
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.
For the reasons discussed above, I certify that this action (1) Is
not a ``significant regulatory action'' under Executive Order 12866;
(2) is not a ``significant rule'' under DOT Regulatory Policies and
Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action
and it is contained in the Rules Docket. A copy of it 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. 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,
Amendment 39-10234, to read as follows:
97-25-10 Pratt & Whitney: Amendment 39-10234. Docket 97-ANE-04
Supersedes airworthiness directive (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 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 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, 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
Service Bulletin (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, 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
reoperation, 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, 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, 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, SPOP
70, as follows:
(i) Disks with 6,000 CSN or more on the effective date of this
AD, inspect within 2,000 CIS after the effective date of this AD.
[[Page 64517]]
(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 8,000 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, SPOP 70.
(3) Thereafter, perform FPI for cracks in all 30 tie bolt holes
at intervals not to exceed 8,000 CIS since last FPI, in accordance
with PW Turbojet Engine Standard Practices Manual, P/N 585005,
Chapter/Section 70-33, SPOP 70.
(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 Tara Goodman, Aerospace Engineer, Engine
Certification Office, FAA, Engine and Propeller Directorate, 12 New
England Executive Park, Burlington, MA 01803-5299; telephone (781)
238-7130, fax (781) 238-7199, Internet:
``Tara.Goodman@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.
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 method of compliance with this AD, 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 requirements of this AD can be accomplished.
(f) This amendment becomes effective on January 12, 1998.
Issued in Burlington, Massachusetts, on November 28, 1997.
Jay J. Pardee,
Manager, Engine and Propeller Directorate,
Aircraft Certification Service.
[FR Doc. 97-31965 Filed 12-5-97; 8:45 am]
BILLING CODE 4910-13-U
