[Federal Register Volume 59, Number 197 (Thursday, October 13, 1994)]
[Unknown Section]
[Page 0]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-24201]
[[Page Unknown]]
[Federal Register: October 13, 1994]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 93-ANE-72; Amendment 39-9037; AD 94-20-09]
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 certain Pratt & Whitney (PW) JT8D series turbofan
engines, that currently requires initial and repetitive inspections of
installed third and fourth stage low pressure turbine (LPT) blade sets
for blade shroud crossnotch wear, and removal of blade sets found with
excessively worn blade shroud crossnotches. This amendment continues to
require inspections, and removal, if necessary, of blade sets, but also
requires, as a terminating action to the inspections: installation of
improved LPT containment hardware, installation of an improved No. 6
bearing scavenge pump bracket bushing, and modification and remarking
with a new identification number third and fourth stage LPT vanes with
a reduced platform leading edge dimension. This amendment is prompted
by reports of additional uncontained engine failures since publication
of the current AD, and the availability of improved LPT containment
hardware. The actions specified by this AD are intended to prevent
damage to the aircraft resulting from engine debris following an LPT
blade or shaft failure.
DATES: Effective November 14, 1994.
The incorporation by reference of certain publications listed in
the regulations is approved by the Director of the Federal Register as
of November 14, 1994.
ADDRESSES: The service information referenced in this AD may be
obtained from Pratt & Whitney, 400 Main Street, East Hartford, CT
06108. 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: Mark A. Rumizen, Aerospace Engineer,
Engine Certification Office, FAA, Engine and Propeller Directorate, 12
New England Executive Park, Burlington, MA 01803-5299; telephone (617)
238-7137, fax (617) 238-7199.
SUPPLEMENTARY INFORMATION: On May 4, 1992, the Federal Aviation
Administration (FAA) issued AD 92-10-05, Amendment 39-8239 (57 FR
23050, June 1, 1992), applicable to Pratt & Whitney (PW) JT8D-15A, -
17A, and -17AR engines, to require initial and repetitive inspections
of the third and fourth stage low pressure turbine (LPT) blade sets for
excessively worn blade shroud crossnotches, and the removal of blade
sets found with excessively worn blade crossnotches. That AD is not
applicable, however, to PW JT8D-15A, -17A, and -17AR engines that
contain the third and fourth stage LPT containment hardware installed
in accordance with PW Alert Service Bulletin (ASB) No. 6039, Revision
1, dated February 20, 1992.
A proposal to amend part 39 of the Federal Aviation Regulations (14
CFR part 39) by superseding AD 92-10-05, Amendment 39-8239 (57 FR
23050, June 1, 1992), was published in the Federal Register on December
28, 1993 (58 FR 68570). That action proposed to continue to require
repetitive inspections of installed third and fourth stage LPT blade
sets for blade shroud crossnotch wear, and removal of blade sets found
with excessively worn blade shroud crossnotches. These inspections are
not required, however, for PW JT8D-15A, -17A, and -17AR engines that
contain the third and fourth stage LPT containment hardware installed
in accordance with PW ASB No. 6039, Revision 3, dated October 15, 1993,
or earlier revisions.
That notice of proposed rulemaking (NPRM) also proposed to require,
however, for all engines, installation of improved third stage LPT
containment hardware at the next access to the third stage LPT air
sealing ring, but not later than December 31, 1998; installation of the
improved fourth stage LPT containment hardware at the next shop visit,
but not later than December 31, 1998; installation of the improved No.
6 bearing scavenge pump bracket bushing at the next shop visit, but not
later than December 31, 1998; and modification and remarking with a new
identification number third and fourth stage LPT vanes with a reduced
platform leading edge dimension at the next shop visit, but not later
than December 31, 1998. The installation of improved containment
hardware would serve as terminating action for the repetitive
inspections.
The actions would be required to be accomplished in accordance with
the following service documents: PW ASB No. A5913, Revision 6, dated
October 15, 1993, that 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 modification and remarking with a new identification number
third and fourth stage LPT vanes with a reduced platform leading edge
dimension.
Interested persons have been afforded an opportunity to participate
in the making of this amendment. Due consideration has been given to
the comments received.
The FAA received several comments that state that inspections and
modifications are available that address the root cause of shaft
fractures and blade failures, whereas the installation of the
containment hardware does not, and should therefore not be mandated.
The FAA does not concur. Currently available inspections and
modifications only protect against known failure modes, whereas the
containment hardware will diminish the severity of all failure modes,
both known and unknown, by protecting the aircraft from damage due to
uncontained engine debris.
One commenter states that the FAA's economic analysis does not
reflect the true cost of the containment hardware. The FAA does not
concur. The intent of the economic analysis is to quantify the total
direct cost to operators of the proposed rule. The analysis does,
however, account for engines currently equipped with the required
parts, and the price for the required parts quoted in the proposed rule
is actually an average value that reflects costs for these engines.
One commenter states that the FAA's economic analysis does not
account for the increased fuel costs resulting from the added weight of
the containment hardware. The economic analysis reflects the direct
costs of performing the requirements of the AD. Since the FAA has
determined that the AD is required to correct an unsafe condition found
in engines of this type design, and, therefore, operators must perform
the requirements of the AD in order to ensure the continued
airworthiness of the engines they operate, a comparison of the costs of
operating the engine with and without the required containment hardware
would not be proper.
One commenter states that the definition of shop visit stated in
the proposed rule encompasses many types of minor or peripheral
maintenance activities where installation of the containment hardware
cannot be accomplished, thus causing a forced induction into an
overhaul facility. The FAA concurs. The shop visit definition has been
revised to address this commenter's concern.
One commenter states that adopting separate rules for separate
groupings of PW JT8D engine models in Docket Nos. 93-ANE-72 and 93-ANE-
83 is not justified since both address the same safety concern. In
addition, separating into two separate rules also avoids a major rule
classification and thereby reduces the economic impact of each separate
action. The FAA does not concur. The FAA issues airworthiness
directives based on product type design, not based on a failure mode,
the result of a failure mode, or the description of a safety concern.
Therefore, it is quite possible, as in this case, that more than one AD
will address the same or very similar issues as they apply to more than
one type design or more than one variant of a type design. In addition,
in this case, each AD docket number cited by the commenter proposed to
supersede an existing AD. Therefore, the AD's need to remain separate
to maintain consistency with the superseded AD's in order to simplify
the tracking of compliance by PW JT8D operators. Further, the economic
impact of both rules combined would amount to approximately
$51,000,000, which is far below the threshold for declaring a combined
AD a significant regulatory action under Executive Order 12886 or a
significant rule under existing DOT regulatory policy.
The FAA received several comments that state that the FAA should
evaluate PW JT8D engine models separately to determine if all models
require the proposed actions to be accomplished, or if some models can
be exempted from compliance due to differences in design or
demonstrated operational safety. The FAA does not concur. Design
differences between the various PW JT8D engine models were evaluated
and no significant differences, other than low pressure rotor speed in
the higher rated engines, were revealed that could impact containment
capability. The increased low pressure rotor speeds are protected for
in the design of the higher rated engines with the addition of a
turbine shield, and the historical event data does not indicate that
these higher low pressure rotor speeds result in a greater number of
uncontained failures.
One commenter states that an alternative to the compliance end date
of December 31, 1998, should be expressed in hours and cycles, with
performance required as whichever occur later, to accommodate low
utilization operators. The FAA concurs. The FAA performed a risk
analysis to determine the inspection interval requirements and hourly
and cyclic equivalents to the compliance end date were derived from
that risk analysis. The FAA has added the hourly and cyclic equivalents
to the AD.
The FAA received several comments that state that the compliance
requirements should be revised to minimize economic impact due to major
engine disassembly. Specifically, modification of the LPT vane cluster
assemblies and installation of the No. 6 bearing scavenge pump bracket
bushing could entail major engine disassembly depending on the scope of
work performed at the next shop visit occurring after the effective
date of the AD. The FAA concurs in part. The FAA has determined that
the modification of the LPT vane cluster assemblies can be accomplished
at the next part access and still meet safety objectives. However, the
compliance requirements for the installation of the No. 6 bearing
scavenge pump bracket bushing is still required at the next shop visit
to achieve the desired level of safety.
The FAA received several comments that state that PMA 3rd stage
outer air seal, Part Number (P/N) M2533, manufactured by McClain
International, should be an acceptable alternative installation to the
corresponding PW part, P/N 811962. The FAA concurs. Third stage turbine
outer air seal, P/N M2533, has been granted FAA PMA approval, and
therefore meets all applicable Federal Aviation Regulations and is
directly interchangeable with PW P/N 811962. The AD has been revised to
specify P/N M2533 as an acceptable installation.
One commenter states the PW JT8D-17R and -17AR engines should be
exempted from the requirement to install the thicker third stage
turbine outer air seal because these engines are already configured
with a turbine shield for containment protection. The FAA does not
concur. The PW JT8D-17AR engines require additional containment
protection due to higher rated low pressure rotor speeds on these
engine models. Therefore, both the thicker third stage turbine outer
air seal and the turbine shield are required for these engine models.
The FAA received two comments that state that additional costs
could be incurred due to lack of availability of the parts required by
this AD. The FAA does not concur. The FAA has coordinated this AD
closely with PW to ensure the availability of the required parts. In
addition, PMA parts are specified in this AD as an acceptable
alternative for PW parts.
One commenter concurs with the rule as proposed.
The FAA has extended the compliance end date to December 31, 1999,
in order to maintain consistency with AD 94-20-08, Docket No. 93-ANE-
83. In addition, the compliance requirement for modification of the LPT
vane cluster assemblies has been revised to exempt engines that
incorporate PW SB No. 5859, Revision 3, dated January 22, 1991, or
earlier revisions.
In addition, the FAA has determined that inspections of the third
and fourth stage LPT blade sets in accordance with the procedures and
intervals described in PW ASB No. 5913, Revision 5, dated August 10,
1992; or PW ASB No. 5913, Revision 4, dated February 20, 1992,
constitute acceptable alternative methods of compliance for the
inspections required by paragraph (a)(1) of this AD.
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 FAA estimates that 944 engines installed on aircraft of U.S.
registry will be affected by this AD, that it will take approximately
an average of 4 work hours, based on fleet configuration mix, per
engine to accomplish the required actions, and that the average labor
rate is $55 per work hour. Required parts will cost approximately
$7,235 per engine. Based on these figures, the total cost impact of the
AD on U.S. operators is estimated to be $7,037,520.
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. App. 1354(a), 1421 and 1423; 49 U.S.C.
106(g); and 14 CFR 11.89.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by removing Amendment 39-8239 (57 FR
23050, June 1, 1992) and by adding a new airworthiness directive,
Amendment 39-9037, to read as follows:
94-20-09 Pratt & Whitney: Amendment 39-9037. Docket 93-ANE-72.
Supersedes AD 92-10-05, Amendment 39-8239.
Applicability: Pratt & Whitney (PW) Model JT8D-15A, -17A, and -
17AR turbofan engines, installed on but not limited to Boeing 737
and 727 series aircraft, and McDonnell Douglas DC-9 series aircraft.
Compliance: Required as indicated, unless accomplished
previously.
To prevent damage to the aircraft resulting from engine debris
following a low pressure turbine (LPT) blade or shaft failure,
accomplish the following:
(a) For engines that do not contain PW honeycomb third stage
outer airseal, Part Number (P/N) 801931, 802097, 797594, or 798279,
or Parts Manufacturer Approval honeycomb third stage outer airseal
P/N PI9336 or P/N M2433, and 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, 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 the
requirements of Part 2 of the Accomplishment Instructions of PW ASB
No. A5913, Revision 6, dated October 15, 1993, as follows:
(i) Initially inspect the blade shroud crossnotches of the third
stage LPT blade set when specified in paragraph (a)(1)(i)(A) or
(a)(1)(i)(B) of this AD, whichever occurs later, as follows:
(A) Inspect within 3,000 cycles or 3,000 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 the 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 500 cycles or 500 hours time in service,
whichever occurs first, after the effective date of this AD.
(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, as follows:
(A) Inspect within 3,000 cycles or 3,000 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 the last blade shroud crossnotch
repair that was accomplished per the requirements specified in
Section 72-53-13 of the PW JT8D Engine Manual P/N 481672; or
(B) Inspect within 500 cycles or 500 hours time in service,
whichever occurs first, after the effective date of this AD.
(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;
but not later than December 31, 1999, 8,000 hours time in service
after the effective date of this AD, or 7,000 cycles after the
effective date of this AD; whichever occurs latest, install the
improved inner front fan exhaust duct and associated hardware in
accordance 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 the effective date of this AD, but not later than
December 31, 1999, 8,000 hours time in service after the effective
date of this AD or 7,000 cycles after the effective date of this AD,
whichever occurs latest, 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: 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,
but not later than December 31, 1999, 8,000 hours time in service
after the effective date of this AD or 7,000 cycles after the
effective date of this AD, whichever occurs latest, 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) For engines that do not incorporate PW SB No. 5859, Revision
3, dated January 22, 1991, or earlier revisions, accomplish the
following: at the next accessibility to the third and fourth stage
LPT vane cluster assemblies after the effective date of this AD, but
not later than December 31, 1999, 8,000 hours time in service after
the effective date of this AD or 7,000 cycles after the effective
date of this AD, whichever is latest, remove material from the inner
platform leading edge on third and fourth stage LPT vane and vane
cluster assemblies, and reidentify these modified vanes in
accordance with the Accomplishment Instructions of PW SB No. 5748,
Revision 5, dated August 3, 1993.
(6) Accomplishment of the installations and modification
required by paragraphs (a)(2), (a)(3), (a)(4), and (a)(5) of this AD
constitutes terminating action to the inspections required by
paragraph (a)(1) of this AD.
(b) For engines that do contain PW honeycomb third stage outer
airseal, P/N 801931, 802097, 797594, or 798279, or Parts
Manufacturer Approval honeycomb third stage outer airseal P/N PI9336
or P/N M2433, and 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, perform the
installations and modifications required by paragraphs (a)(2),
(a)(3), (a)(4), and (a)(5) 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 requirements 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: 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 inspections and modification shall be done in accordance
with the following service bulletins:
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Document No. Pages Revision Date
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PW ASB No. A5913....... 1 6............ October 15, 1993.
2 4............ February 20, 1992.
3-8 6............ October 15, 1993.
9 4............ February 20, 1992.
10 6............ October 15, 1993.
11 4............ February 20, 1992.
12 6............ October 15, 1993.
Appendix A............. 1 6............ October 15, 1993.
2-3 5............ August 10, 1992.
4 2............ September 28, 1990.
5 6............ October 15, 1993.
6 Original..... April 2, 1990.
7 2............ September 28, 1990.
8-14 Original..... April 2, 1990.
Total pages: 26
PW ASB No. A6110....... 1 1............ October 15, 1993.
2 Original..... March 19, 1993.
3-59 1............ October 15, 1993.
Total pages: 59
PW ASB No. A6131....... 1-13 Original..... August 24, 1993.
Total pages: 13.
PW SB No. 5748......... 1 5............ August 3, 1993.
2 2............ September 15, 1988.
3-4 5............ August 3, 1993.
5-10 2............ September 15, 1988.
11-12 5............ August 3, 1993.
13-16 2............ September 15, 1988.
17-18 4............ October 3, 1989.
Total pages: 18
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This incorporation by reference was approved by the Director of
the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR
part 51. Copies may be obtained from Pratt & Whitney, 400 Main
Street, East Hartford, CT 06108. 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 November 14, 1994.
Issued in Burlington, Massachusetts, on September 22, 1994.
Mark C. Fulmer,
Acting Manager, Engine and Propeller Directorate, Aircraft
Certification Service.
[FR Doc. 94-24201 Filed 10-12-94; 8:45 am]
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