[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: 

------------------------------------------------------------------------
     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.                                                        
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                                                         
------------------------------------------------------------------------

    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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