[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: 94-24200]
[[Page Unknown]]
[Federal Register: October 13, 1994]
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DEPARTMENT OF TRANSPORTATION
14 CFR Part 39
[Docket No. 93-ANE-83; Amendment 39-9036; AD 94-20-08]
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, and installation of an improved No.
6 bearing scavenge pump bracket bushing. 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 on 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 24, 1993, the Federal Aviation
Administration (FAA) issued airworthiness directive (AD) 93-06-05,
Amendment 39-8530 (58 FR 31902, June 1, 1993), applicable to Pratt &
Whitney (PW) JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -17,
and -17R 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-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -
11, -15, -17, and -17R engines that contain fan exhaust inner front
duct segment assemblies that are installed in accordance with PW Alert
Service Bulletin (ASB) No. 6039, Revision 2, dated May 4, 1992, or
earlier revisions of PW ASB No. 6039, and either (a) PW honeycomb third
stage outer airseal Part Number (P/N) 801931, 802097, 797594, or
798279; or (b) Pyromet Industries, Inc., honeycomb third stage outer
airseal P/N PI9336; or (c) McClain International, Inc., honeycomb third
stage outer airseal P/N M2433; or (d) a turbine case shield assembly
installed in accordance with PW ASB No. 6039, Revision 2, dated May 4,
1992, or earlier revisions of PW ASB No. 6039; or (e) 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.
A proposal to amend part 39 of the Federal Aviation Regulations (14
CFR part 39) by superseding AD 93-06-05 was published in the Federal
Register on December 28, 1993 (58 FR 68572). 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-
1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -17, and -17R engines
that 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 (a) PW
honeycomb third stage outer airseal P/N 801931, 802097, 797594, or
798279; or (b) Pyromet Industries, Inc., honeycomb third stage outer
airseal P/N PI9336; or (c) McClain International, Inc., honeycomb third
stage outer airseal P/N M2433; or (d) 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 (e) 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.
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 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.
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.
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 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 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 the FAA's economic analysis should
account for the costs to implement AD 93-06-05 and other safety
concerns since they are directed at reducing the safety concern
addressed by the proposed rule. AD 93-06-05 requires LPT blade torque
check inspections. The FAA does not concur. The proposed rule maintains
the inspection requirements of AD 93-06-05, but only until the
installation of the containment hardware, which is ultimately required
for all engines in accordance with the compliance schedule. Therefore,
the inspections continue only as options, and only the mandated
hardware installation is used to compute the direct costs of this AD.
Further, since inspections are not mandated for engines that have
containment hardware installed, only the cost of either the inspection
or containment hardware applies for any given engine. The containment
hardware cost, the higher of the two, was used on the assumption that
an operator would install the hardware rather than continue with the
optional inspection program.
One commenter states that the modifications required by PW SB No.
5748, LPT vane cluster cut-back, are not applicable to the engine
models specified in this AD. This requirement should be eliminated from
the AD. The FAA concurs. The modification of the LPT vane clusters in
accordance with PW SB No. 5748, is not required for the ``non-A'' JT8D
engine models and therefore has been eliminated from this AD.
One commenter states 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 PP/N M2533 as an
acceptable installation.
One commenter states that a one-year extension of the compliance
end date to December 31, 1999, should be granted. The FAA concurs. A
one-year extension of the compliance end date has been granted to
adjust for the time required to review the comments to the NPRM and
process the Final Rule.
One commenter states that only engines removed for shop visits on
or after the AD effective date will be required to comply with the AD,
and therefore AD compliance would not be required for engines already
undergoing a shop visit as of the AD effective date. The FAA concurs,
but no revision of the AD is required because the wording in the
proposed rule accounts for this situation.
One commenter states 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 is not applicable to
the engine models specified in this AD, and therefore has eliminated
this requirement. 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.
One commenter states 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 states that the -15A/-17A models were the only engine
group to have the initial steel duct modification incorporated during
manufacture in accordance with PW SB No. 5697. These engines, together
with a limited number of retrofitted engines, will be the only ones
able to take advantage of the associated industry support program. The
FAA has no comment on the extent or application of any support program
which may offset some of the costs of the hardware required by this
airworthiness directive. While some operators may receive discounts on
the cost of the containment hardware, the economic analysis is computed
on the assumption that no discount or warranty program is available.
Therefore, this comment is beyond the scope of the AD or its economic
analysis.
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 that
risk analysis accounted for both high and low utilization operations.
However, determining the hourly and cyclic equivalent to the compliance
end date specified in the AD, the FAA has determined that the fleet
average utilization rate can be applied to low utilization operators.
The FAA has added the hourly and cyclic equivalents to the AD.
One commenter states the PW JT8D-17R 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-17R 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.
One commenter concurs with the rule as proposed.
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 paragraphs (a)(1) and (a)(1)(iii) 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 6,000 engines installed on aircraft of U.S.
registry will be affected by this AD, that it will take 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 $44,730,000.
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 39-8530 (58 FR
31902, June 7, 1993) and by adding a new airworthiness directive,
Amendment 39-9036, to read as follows:
94-20-08 Pratt & Whitney: Amendment 39-9036. Docket No. 93-ANE-83.
Supersedes AD 93-06-05, Amendment 39-8530.
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.
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 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,
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. 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,
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) 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: 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 installations shall be done in accordance with the
following service documents:
------------------------------------------------------------------------
Document No. Pages Revision Date
------------------------------------------------------------------------
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.
------------------------------------------------------------------------
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. 94-24200 Filed 10-12-94; 8:45 am]
BILLING CODE 4910-13-P
