[Federal Register Volume 62, Number 62 (Tuesday, April 1, 1997)]
[Proposed Rules]
[Pages 15437-15439]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-8164]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 97-ANE-07]
RIN 2120-AA64
Airworthiness Directives; Pratt & Whitney JT8D 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
JT8D series turbofan engines, that currently requires inspections of
low pressure turbine (LPT) blade sets for blade shroud crossnotch wear,
and removal, if necessary. In addition, the current AD requires, as a
terminating action to the inspections, installation of improved LPT
containment hardware, and installation of an improved No. 6 bearing
scavenge pump bracket bushing. This action would keep the compliance
actions of the current AD intact but change the compliance time for
full compliance from the current calendar end-date to December 31,
1998. This proposal is prompted by a report of a fourth stage hub
manufacturing defect that led to the failure of the hub and subsequent
release of LPT blades. The actions specified by the proposed AD are
intended to prevent damage to the aircraft resulting from engine debris
following an LPT blade, shaft, or hub failure.
DATES: Comments must be received by May 1, 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-07, 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: Christopher Spinney, Aerospace
Engineer, Engine Certification Office, FAA, Engine and Propeller
Directorate, 12 New England Executive Park, Burlington, MA 01803-5299;
telephone (617) 238-7175, 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-07.'' 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-07, 12 New England Executive Park,
Burlington, MA 01803-5299.
Discussion
On September 22, 1994, the Federal Aviation Administration (FAA)
issued airworthiness directive AD 94-20-08, Amendment 39-9036 (59 FR
51842, October 15, 1994), applicable to Pratt & Whitney (PW) JT8D-1, -
1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -17, and -17R series turbofan
engines, to require inspections of low pressure turbine (LPT) blade
sets for blade shroud crossnotch wear, and removal, if necessary. In
addition, the current AD requires, as a terminating action to the
inspections, installation of improved LPT containment hardware, and
installation of an improved No. 6 bearing scavenge pump bracket
bushing. That action was prompted by reports of uncontained engine
failures. That condition, if not corrected, could result in damage to
the aircraft resulting from engine debris following an LPT blade,
shaft, or hub failure.
Since the issuance of that AD, the FAA has developed a two-part
risk management plan intended to address the threat of blade release
due to fourth stage LPT hub failure. One part of the management plan is
a proposed rule, Docket No. 96-ANE-32 (62 FR 1299, January 9, 1997),
which proposes the initial and repetitive inspections and removal from
service of defective disks in a suspect population. The other part of
the risk management plan is this proposed AD, which reduces the threat
of uncontainment by changing the compliance date of the current AD, 94-
20-08. The current AD addresses two threats to uncontainment in a blade
failure and a shaft fracture by requiring initial and repetitive
inspections of worn shroud crossnotches on third and fourth stage LPT
blades until improved containment hardware can be installed. To address
the threat of shaft fracture, the improved containment hardware
installation is required, as well as an improved No. 6 bearing scavenge
pump bracket bushing to provide for better rotor meshing. The
compliance deadline for incorporating the improved containment hardware
and the bearing bracket bushing is currently December 31, 1999, or
7,000 cycles since November 14, 1994, or 8,000 hours since November 14,
1994, whichever occurs later. To address the additional threat of
uncontainment in the form of a fourth stage LPT hub fracture, which
results in a blade release, the calendar end-date for completing
compliance to the requirements of the superseded AD is changed to
December 31, 1998, or 7,000 cycles since November 14, 1994, or 8,000
hours since November 14, 1994, whichever occurs first.
The FAA has reviewed and approved the technical contents of the
following service documents: PW ASB No. A5913, Revision 6, dated
October 15, 1993, that
[[Page 15438]]
describes the third and fourth stage LPT blade set inspection
procedures and replacement requirements; PW ASB No. A6110, Revision 1,
dated October 15, 1993, that describes procedures for installation of
improved LPT containment hardware; PW ASB No. A6131, dated August 24,
1993, that describes procedures for installation of an improved No. 6
bearing scavenge pump bracket bushing; and PW SB No. 5748, Revision 5,
dated August 3, 1993, that describes procedures for removing material
from the inner platform leading edge on third and fourth stage LPT vane
and vane cluster assemblies, and remarking these modified vanes with
new identification numbers.
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 94-20-08 to keep the compliance actions
of the current AD intact but change the compliance time for full
compliance from the current calendar end-date to December 31, 1998.
The FAA has determined that the changes to the AD would neither
increase the scope of the required actions over the current AD, nor
increase the economic burden on operators over the costs of complying
with the current AD. While the proposed new AD would alter the
compliance times, operators should still be able to perform the
required actions at scheduled maintenance. Therefore the FAA has
determined that this new AD would result in no additional economic
impact.
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 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by removing amendment 39-9036 (59 FR
51842, October 15, 1994) and by adding a new airworthiness directive to
read as follows:
Pratt & Whitney: Docket No. 97-ANE-07. Supersedes AD 94-20-08,
Amendment 39-9036.
Applicability: Pratt & Whitney (PW) JT8D-1, -1A, -1B, -7, -7A, -
7B, -9, -9A, -11, -15, -17, and -17R turbofan engines, installed on
but not limited to Boeing 737 and 727 series aircraft, and McDonnell
Douglas DC-9 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 damage to the aircraft resulting from engine debris
following a low pressure turbine (LPT) blade, shaft, or hub failure,
accomplish the following:
(a) For engines that do not contain fan exhaust inner front duct
segment assemblies that are installed in accordance with PW Alert
Service Bulletin (ASB) No. 6039, Revision 3, dated October 15, 1993,
or earlier revisions of PW ASB No. 6039, and either PW honeycomb
third stage outer airseal Part Number (P/N) 801931, 802097, 797594,
or 798279; or Pyromet Industries, Inc., honeycomb third stage outer
airseal P/N PI9336; or McClain International, Inc., honeycomb third
stage outer airseal P/N M2433; or a turbine case shield assembly
installed in accordance with PW ASB No. 6039, Revision 3, dated
October 15, 1993, or earlier revisions of PW ASB No. 6039; or a
third stage blade set that has third stage turbine blades that were
installed in accordance with PW SB No. 5331, dated October 27, 1982,
accomplish the following:
(1) Conduct initial and repetitive inspections on installed
third and fourth stage LPT blade sets, and remove and replace with
serviceable blade sets, as necessary, in accordance with Part 1 of
the Accomplishment Instructions of PW ASB No. A5913, Revision 6,
dated October 15, 1993; or PW ASB No. 5913, Revision 5, dated August
10, 1992; or PW ASB No. 5913, Revision 4, dated February 20, 1992,
as follows:
(i) Initially inspect the blade shroud crossnotches of the third
stage LPT blade set when specified in paragraphs (a)(1)(i)(A) or
(a)(1)(i)(B) of this AD, whichever occurs later. Engines that
contain a third stage blade set that have third stage turbine blades
that were installed per the requirements specified in PW Service
Bulletin No. 5331, dated October 27, 1982, do not require the third
stage blade set inspection.
(A) Inspect within 6,000 cycles or 6,000 hours time in service,
whichever occurs first, since new, since the last blade shroud
crossnotch inspection specified in Section 72-53-12 of PW JT8D
Engine Manual P/N 481672, or since last blade shroud crossnotch
repair that was accomplished per the requirements specified in
Section 72-53-12 of PW JT8D Engine Manual P/N 481672; or
(B) Inspect within 1,000 cycles or 1,000 hours time in service
since November 14, 1994, whichever occurs first.
(ii) Initially inspect the blade shroud crossnotches of the
fourth stage LPT blade set when specified in paragraph (a)(1)(ii)(A)
or (a)(1)(ii)(B) of this AD, whichever occurs later. Engines that
contain fan exhaust inner front duct segment assemblies that were
installed per the requirements of PW ASB No. 6039, Revision 3, dated
October 15, 1993, or earlier revisions of PW ASB No. 6039, do not
require the fourth stage blade set inspection.
(A) Inspect within 6,000 cycles or 6,000 hours time in service,
whichever occurs first, since new, since the last blade shroud
crossnotch inspection specified in Section 72-53-13 of PW JT8D
Engine Manual P/N 481672, or since last blade shroud crossnotch
repair that was accomplished per the requirements specified in
Section 72-53-13 of PW JT8D Engine Manual P/N 481672; or
(B) Inspect within 1,000 cycles or 1,000 hours time in service
since November 14, 1994, whichever occurs first.
(iii) Thereafter, inspect the third and fourth stage LPT blade
sets in accordance with the procedures and intervals specified in PW
ASB No. A5913, Revision 6, dated October 15, 1993;
(2) At the next shop visit after November 14, 1994; but not
later than December 31, 1998, or 8,000 hours time in service since
November 14, 1994, or 7,000 cycles since November 14, 1994,
whichever occurs first, install the improved inner front fan exhaust
duct and associated hardware in accordance
[[Page 15439]]
with Part A of the Accomplishment Instructions of PW ASB No. A6110,
Revision 1, dated October 15, 1993.
(3) At the next access to the third stage turbine air sealing
ring after November 14, 1994, but not later than December 31, 1998,
or 8,000 hours time in service since November 14, 1994, or 7,000
cycles since November 14, 1994, whichever occurs first, install the
improved third stage turbine air sealing ring and associated
hardware in accordance with Part B of the Accomplishment
Instructions of PW ASB No. A6110, Revision 1, dated October 15,
1993.
Note 2: Third stage turbine outer air seal, P/N M2533, is an
acceptable alternative to PW P/N 811962 for compliance with this
paragraph.
(4) At the next shop visit after November 14, 1994, but not
later than December 31, 1998, or 8,000 hours time in service since
November 14, 1994, or 7,000 cycles since November 14, 1994,
whichever occurs first, install the improved No. 6 bearing scavenge
pump bracket bushing in accordance with the Accomplishment
Instructions of PW ASB No. A6131, dated August 24, 1993.
(5) Accomplishment of the installations required by paragraphs
(a)(2), (a)(3), and (a)(4) of this AD constitutes terminating action
to the repetitive inspections required by paragraph (a)(1) of this
AD.
(b) For engines that do contain fan exhaust inner front duct
segment assemblies that are installed in accordance with PW ASB No.
6039, Revision 3, dated October 15, 1993, or earlier revisions of PW
ASB No. 6039, and either PW honeycomb third stage outer airseal P/N
801931, 802097, 797594, or 798279; or Pyromet Industries, Inc.,
honeycomb third stage outer airseal P/N PI9336; or McClain
International, Inc., honeycomb third stage outer airseal P/N M2433;
or a turbine case shield assembly installed in accordance with PW
ASB No. 6039, Revision 3, dated October 15, 1993, or earlier
revisions of PW ASB No. 6039; or a third stage blade set that has
third stage turbine blades that were installed in accordance with PW
SB No. 5331, dated October 27, 1982, perform the installations
required by paragraphs (a)(2), (a)(3), and (a)(4) of this AD, at the
times specified in those respective paragraphs.
(c) For the purpose of this AD, a shop visit is defined as an
engine removal, where engine maintenance entails separation of pairs
of major mating engine flanges or the removal of a disk, hub, or
spool at a maintenance facility that is capable of compliance with
the instructions of this AD, regardless of other planned
maintenance, except for field maintenance type activities performed
at this maintenance facility in lieu of performing them on-wing or
at another peripheral facility.
(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 3: 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 requirements of this AD can be accomplished.
Issued in Burlington, Massachusetts, on March 24, 1997.
James C. Jones,
Acting Manager, Engine and Propeller Directorate, Aircraft
Certification Service.
[FR Doc. 97-8164 Filed 3-31-97; 8:45 am]
BILLING CODE 4910-13-U
