[Federal Register Volume 62, Number 182 (Friday, September 19, 1997)]
[Rules and Regulations]
[Pages 49137-49140]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 97-24798]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 97-ANE-07; Amendment 39-10135; AD 97-19-14]
RIN 2120-AA64
Airworthiness Directives; Pratt & Whitney JT8D Series Turbofan
Engines
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
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SUMMARY: This amendment supersedes an existing airworthiness directive
(AD), applicable to 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 amendment keeps the compliance actions of the current AD
intact but changes the compliance time for LPT containment hardware
installation from the current calendar end-date to December 31, 1998,
for engines that contain suspect 4th stage hubs identified by serial
number. This amendment 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 this AD are intended to
prevent damage to the aircraft resulting from engine debris following
an LPT blade, shaft, or hub failure.
DATES: Effective October 24, 1997.
The incorporation by reference of PW Alert Service Bulletin No.
A6131, Revision 1, dated May 16, 1995; PW Alert Service Bulletin No.
A6131, Revision 2, dated July 28, 1997; PW Alert Service Bulletin No.
A6274, Original, dated November 7, 1996; and PW Alert Service Bulletin
No. A6274, Revision 1, dated December 9, 1996, is approved by the
Director of the Federal Register as of October 24, 1997.
The incorporation by reference of all other publications listed in
the regulations was previously approved as of November 14, 1994 (59 FR
51842, October 13, 1994).
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 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: Christopher Spinney, Aerospace
Engineer, Engine Certification Office, FAA, Engine and Propeller
Directorate, 12 New England Executive Park, Burlington, MA 01803-5299;
telephone (781) 238-7175, fax (781) 238-7199.
SUPPLEMENTARY INFORMATION: A proposal to amend part 39 of the Federal
Aviation Regulations (14 CFR part 39) by superseding 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, was published in the Federal Register
on April 1, 1997 (62 FR 15437). That action proposed 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. The proposal would have
reduced the compliance time for LPT containment hardware installation
from the current calendar end-date to December 31, 1998.
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due
[[Page 49138]]
consideration has been given to the comments received.
Eight commenters state that the more stringent compliance times
should only be applicable to those engines that have a suspect 4th
stage LPT hub installed. Otherwise, the proposed AD imposes an undue
burden to operators, since the proposed AD does not specifically
address the threat of the 4th stage hub suspect population. The
commenters offer several alternatives, such as withdrawal of the NPRM,
writing a stand alone AD, changing the compliance paragraph, and adding
a paragraph to NPRM Docket No. 96-ANE-32. The FAA concurs with the
comments and is changing the compliance paragraph accordingly. This
final rule contains a new compliance schedule, which is intended to
meet the threat of an blade release due to the failure of the 4th stage
LPT hub. The threat of a 4th hub failure has been isolated to a suspect
population of hubs listed in PW Alert Service Bulletin No. A6274,
Revision 1, dated December 9, 1996.
Two commenters state that the third stage turbine air sealing ring
should not have the more stringent compliance times, as the third stage
turbine air sealing ring does not affect 4th stage LPT containment,
which is why the compliance end-date is being moved up. The FAA
concurs. The third stage turbine air sealing ring does not contribute
to the containment of 4th stage LPT blades, therefore the FAA has
removed the more stringent compliance times for the third stage turbine
air sealing ring in this final rule. The FAA has also relaxed the
compliance time for the improved No. 6 bearing scavenge pump bracket
bushing, as this part also does not contribute to the containment of
4th stage LPT blades released due to a 4th stage hub fracture.
One commenter states that the AD cannot be complied with on
schedule as the replacement hardware is not available. The FAA does not
concur. The manufacturer has advised the FAA that there are no current
or foreseen shortages of hardware that will slow down operators'
ability to comply with the AD.
One commenter states that the proposed rule should be withdrawn, as
the risk is within acceptable limits without any further action and the
actions described in NPRM Docket No. 96-ANE-32 are adequate to prevent
future occurrences of uncontained failures from this cause. The FAA
does not concur. While not yet published, the actions proposed in NPRM
Docket No. 96-ANE-32 would, if adopted, minimize the threat of an
uncontained blade release due to a hub fracture. The FAA has also
evaluated the risk and crack growth analysis data and field experience
for the 4th stage LPT hub and the data supports the conclusion that the
failure mechanism is the loss of a 4th stage LPT blade and that the hub
field management program must address non-containment of the LPT blade
as well as the inspection of the LPT hub for cracks. The FAA feels the
added measure of security offered by the improved containment is
warranted in this case. However, the FAA agrees the more aggressive
containment schedule should only apply to those hubs at highest risk of
failing and releasing a blade as outlined in the compliance section
described in previous responses to comments.
One commenter states that accomplishment of the actions described
in PW ASB No. A6131, Revision 1, dated May 16, 1995, should be an
acceptable alternative method of compliance to the AD's reference of
the Original version of the ASB. The FAA concurs and has added
reference to Revision 1 to the compliance section of this final rule.
One commenter states concern that the same containment hardware
will be required for engines required to accomplish the actions
described in AD 94-20-09 covering ``A'' model engines. The FAA does not
concur. The suspect hubs are not approved for installation on ``A''
model engines; therefore, a similar condition does not exist for the
``A'' models.
Three commenters support the rule as proposed.
In addition, the FAA has reviewed and approved the technical
contents of PW ASB No. A6274, Revision 1, dated December 9, 1996, and
Original, dated November 7, 1996, that describe procedures for
repetitive inspections of affected LPT hubs; and PW ASB No. A6131,
Revision 2, dated July 28, 1997, that describes procedures for
installation of the improved No. 6 bearing scavenge pump bracket
bushing.
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 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 new AD alters 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 will result in no additional economic impact.
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 39-9036 (59 FR
51842, October 15, 1994) and by adding a new airworthiness directive to
read as follows:
97-19-14 Pratt & Whitney: Amendment 39-10135. Docket 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.
[[Page 49139]]
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. A5913, Revision 5, dated
August 10, 1992; or PW ASB No. A5913, 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 (SB) 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 the effective date of this AD,
install the improved inner front fan exhaust duct and associated
hardware in accordance with Part A of the Accomplishment
Instructions of PW ASB A6110, Revision 1, dated October 15, 1993, as
follows:
(i) For engines that have a 4th stage LPT hub installed with a
serial number listed in PW ASB A6274, Table A, dated November 7,
1996, or Revision 1, dated December 9, 1996, install the improved
inner front fan exhaust duct before December 31, 1998, or 8,000
hours time in service since November 14, 1994, or 7,000 cycles in
service since November 14, 1994, whichever occurs first.
(ii) For engines that do not have a 4th stage LPT hub installed
with a serial number listed in PW ASB A6274, Table A, dated November
7, 1996, or Revision 1, dated December 9, 1996, install the improved
inner front fan exhaust duct before December 31, 1999, or 8,000
hours time in service since November 14, 1994, or 7,000 cycles in
service since November 14, 1994, whichever occurs latest.
(3) At the next access to the third stage turbine air sealing
ring, install the improved third stage turbine air sealing ring and
associated hardware in accordance with Part B of the Accomplishment
Instructions of PW ASB A6110, Revision 1, dated October 15, 1993.
The installation of the improved third stage turbine air sealing
ring must occur no later than December 31, 1999, or 8,000 hours time
in service since November 14, 1994, or 7,000 cycles in service since
November 14, 1994, whichever occurs latest.
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 the effective date of this AD,
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, or Revision 1, dated May 16, 1995, or
Revision 2, dated July 28, 1997. The installation of the improved
No. 6 bearing scavenge pump bracket bushing must be accomplished no
later than December 31, 1999, or 8,000 hours time in service since
November 14, 1994, or 7,000 cycles since November 14, 1994,
whichever occurs latest.
(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.
Operators shall forward their requests 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 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) The actions required by this AD shall be done in accordance
with the following PW service documents:
[[Page 49140]]
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Document No. Pages Revision Date
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ASB No. A5913...................... 1-12 6................... October 15, 1993.
Total pages: 12.
ASB No. A6110...................... 1-59 1................... October 15, 1993.
Total pages: 59.
ASB No. A6131...................... 1-13 Original............ August 24, 1993.
Total pages: 13.
ASB No. A6131...................... 1-14 1................... May 16, 1995.
Total pages: 14.
ASB No. A6131...................... 1-21 2................... July 28, 1997.
Total pages: 21.
ASB No. A6274...................... 1, 2 1................... December 9, 1996.
3, 4 Original............ November 7, 1996.
5 1................... December 9, 1996.
6-22 Original........... November 7, 1996.
23 1................... December 9, 1996.
Total pages: 23.
ASB No. A6274...................... 1-23 Original............ November 7, 1996.
Attachment NDIP-889................ 1-39 Original............ November 1, 1996.
Total pages: 62.
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This incorporation by reference of PW ASB No. A5913, Revision 6,
dated October 15, 1993; and PW ASB No. A6110, Revision 1, dated
October 15, 1993; was previously approved by the Director of the
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part
51 as of November 14, 1994 (59 FR 51842, October 13, 1994). Copies
may be obtained from Pratt & Whitney, 400 Main St., East Hartford,
CT 06108; telephone (860) 565-6600, fax (860) 565-4503. Copies may
be inspected at the FAA, New England Region, Office of the Assistant
Chief Counsel, 12 New England Executive Park, Burlington, MA; or at
the Office of the Federal Register, 800 North Capitol Street, NW.,
suite 700, Washington, DC.
(g) This amendment becomes effective on October 24, 1997.
Issued in Burlington, Massachusetts, on September 10, 1997.
Mark C. Fulmer,
Acting Manager, Engine and Propeller Directorate, Aircraft
Certification Service.
[FR Doc. 97-24798 Filed 9-18-97; 8:45 am]
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