[Federal Register Volume 63, Number 117 (Thursday, June 18, 1998)]
[Proposed Rules]
[Pages 33295-33296]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-16271]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 97-ANE-53-AD]
RIN 2120-AA64


Airworthiness Directives; Pratt & Whitney PW4000 Series Turbofan 
Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: This document proposes the adoption of a new airworthiness 
directive (AD) that is applicable to certain Pratt & Whitney (PW) 
PW4000 series turbofan engines not incorporating modifications 
described in certain PW service bulletins listed in the applicability 
section. This proposal would require high pressure compressor (HPC) 
blade tip grinding of the rotor assembly, installation of aluminum 
oxide coated HPC blade tips in stages 9 through 12, modification of HPC 
8th through 14th stage stators, incorporation of 1st stage high 
pressure turbine (HPT) vanes with increased airflow area which also 
requires additional HPT hardware modifications, and incorporation of 
HPC 13th-15th stage zirconium oxide blade tips. This proposal is 
prompted by reports of HPC surge caused by excessive HPC rear stage 
rotor-to-case clearance. The actions specified by the proposed AD are 
intended to prevent HPC surge, which can result in engine power loss at 
a critical phase of flight such as takeoff or climb.

DATES: Comments must be received by August 17, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Regional 
Counsel, Attention: Rules Docket No. 97-ANE-53-AD, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may also be sent 
via the Internet using the following address: ``9-ad-
[email protected]''. Comments sent via the Internet must contain 
the docket number in the subject line. Comments may be inspected at 
this location between 8:00 a.m. and 4:30 p.m., Monday through Friday, 
except Federal holidays.
    The service information referenced in the proposed rule may be 
obtained from Pratt & Whitney, 400 Main St., East Hartford, CT 06108; 
telephone (860) 565-6600, fax (860) 565-4503. This information may be 
examined at the FAA, New England Region, Office of the Regional 
Counsel, 12 New England Executive Park, Burlington, MA.

FOR FURTHER INFORMATION CONTACT: Chris Gavriel, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone (781) 
238-7147, fax (781) 238-7199.

SUPPLEMENTARY INFORMATION:

Comments Invited

    Interested persons are invited to participate in the making of the 
proposed rule by submitting such written data, views, or arguments as 
they may desire. Communications should identify the Rules Docket number 
and be submitted in triplicate to the address specified above. All 
communications received on or before the closing date for comments, 
specified above, will be considered before taking action on the 
proposed rule. The proposals contained in this notice may be changed in 
light of the comments received.
    Comments are specifically invited on the overall regulatory, 
economic, environmental, and energy aspects of the proposed rule. All 
comments submitted will be available, both before and after the closing 
date for comments, in the Rules Docket for examination by interested 
persons. A report summarizing each FAA-public contact concerned with 
the substance of this proposal will be filed in the Rules Docket.
    Commenters wishing the FAA to acknowledge receipt of their comments 
submitted in response to this notice must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 97-ANE-53-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRMs

    Any person may obtain a copy of this NPRM by submitting a request 
to the FAA, New England Region, Office of the Regional Counsel, 
Attention: Rules Docket No. 97-ANE-53-AD, 12 New England Executive 
Park, Burlington, MA 01803-5299.

Discussion

    The Federal Aviation Administration (FAA) has received reports of 
certain Pratt & Whitney (PW) PW4000 series turbofan engine power loss 
events occurring frequently during a critical phase of flight such as 
takeoff or climb. The events have led to the flight crew conducting 
rejected takeoffs and to engine power loss or shutdown events in 
flight. A rejected takeoff could result in the airplane overrunning the 
runway, incurring airplane damage, and injuring airplane occupants. 
Engine power loss or shutdown during takeoff also significantly 
increases crew workload during a critical phase of flight. The 
investigations into these events revealed that they were caused by high 
pressure compressor (HPC) surge that could require crew action to 
recover. Further investigation revealed that the surge results from 
excessive HPC rear stage rotor-to-case clearance. This condition, if 
not corrected, could result in HPC surge, which can result in engine 
power loss at a critical phase of flight such as takeoff.
    The FAA has reviewed and approved the technical contents of the 
following PW Service Bulletins (SB): PW4ENG-72-484, Revision 3, dated 
July 1, 1997, that describes procedures for HPC blade tip grinding at 
the rotor assembly and introduces HPC aluminum oxide blade tip coating 
in stages 9 through 15 compatible with tip grinding; PW4ENG-72-486, 
Revision 1, dated November 23, 1994, that describes procedures for 
modifying HPC 8th through 14th stage stators; PW4ENG-72-514, Revision 
1, dated August 2, 1996, that describe procedures for high pressure 
turbine (HPT) hardware modifications to accommodate the incorporation 
of 1st stage HPT vanes with increased airflow area; and PW4ENG-72-575, 
Revision 1, dated June 30, 1997, that describes procedures for 
incorporating HPC 13th-15th stage zirconium oxide tips.

[[Page 33296]]

    Since an unsafe condition has been identified that is likely to 
exist or develop on other products of this same type design, the 
proposed AD would require grinding of the HPC blade tips at the rotor 
assembly and incorporation of HPC stage 9 through 12 aluminum oxide 
blade tips, modification of HPC 8th through 14th stage stators, 
modification of HPT hardware to accommodate incorporation of 1st stage 
HPT vanes with increased airflow area and incorporation of these vanes, 
and incorporation of HPC 13th through 15th stage zirconium oxide blade 
tips, within 1,400 cycles in service after the effective date of this 
AD, or prior to June 30, 1999, whichever occurs first. The calendar 
end-date was based upon analysis of test data and service experience 
data. The actions would be required to be accomplished in accordance 
with the SBs described previously.
    There are approximately 187 engines of the affected design in the 
worldwide fleet. The FAA estimates that there are currently 61 engines 
installed on aircraft of U.S. registry that would be affected by this 
proposed AD. Required parts would cost approximately $20,000 per 
engine. Based on these figures, the total cost impact of the proposed 
AD, including labor costs, is estimated to be $1,220,000.
    The regulations proposed herein would not have substantial direct 
effects on the States, on the relationship between the national 
government and the States, or on the distribution of power and 
responsibilities among the various levels of government. Therefore, in 
accordance with Executive Order 12612, it is determined that this 
proposal would not have sufficient federalism implications to warrant 
the preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this proposed 
regulation (1) is not a ``significant regulatory action'' under 
Executive Order 12866; (2) is not a ``significant rule'' under the DOT 
Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); 
and (3) if promulgated, will not have a significant economic impact, 
positive or negative, on a substantial number of small entities under 
the criteria of the Regulatory Flexibility Act. A copy of the draft 
regulatory evaluation prepared for this action is contained in the 
Rules Docket. A copy of it may be obtained by contacting the Rules 
Docket at the location provided under the caption ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Safety.

The Proposed Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration proposes to amend 
part 39 of the Federal Aviation Regulations (14 CFR part 39) as 
follows:

PART 39--AIRWORTHINESS DIRECTIVES

    1. The authority citation for part 39 continues to read as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701.


Sec. 39.13  [Amended]

    2. Section 39.13 is amended by adding the following new 
airworthiness directive:

Pratt & Whitney: Docket No. 97-ANE-53-AD.

    Applicability: Pratt & Whitney (PW) Model PW4152, PW4056, 
PW4156, PW4256, PW4052, PW4158, W4060, PW4160, PW4460, PW4050, 
PW4060A, PW4156A, PW4062, PW4462, PW4060C, and PW4650 turbofan 
engines, not incorporating at least one of the modifications 
described in the PW service bulletins (SBs) and listed in items (1) 
through (6), excluding those engines having a (-3) identifier next 
to the engine model number on the engine data plate. These engines 
are installed on but not limited to Boeing 767 and 747 series 
aircraft, McDonnell Douglas MD-11 series aircraft, and Airbus A310 
and A300-600 series aircraft.
    (1) PW4ENG 72-484, Revision 3, dated July 1, 1997, or earlier 
revisions, PW4ENG 72-486, Revision 1, dated November 23, 1994, or 
original issue.
    (2) PW4ENG 72-484, Revision 3, dated July 1, 1997, or earlier 
revisions, PW4ENG 72-575, Revision 1, dated June 30, 1997, or 
original issue, PW4ENG 72-486, Revision 1, dated November 23, 1994, 
or original issue.
    (3) PW4ENG 72-514, Revision 1, dated August 2, 1996, or original 
issue.
    (4) PW4ENG 72-490, Revision 1, dated August 2, 1994, or original 
issue.
    (5) PW4ENG 72-504, Revision 1, dated May 9, 1995, or original 
issue.
    (6) PW4ENG 72-572, dated June 16, 1995.

    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 (b) 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 high pressure compressor (HPC) surge, which can 
result in engine power loss at a critical phase of flight such as 
takeoff, accomplish the following:
    (a) Within 1,400 cycles in service (CIS) after the effective 
date of this AD, or prior to June 30, 1999, whichever occurs first, 
perform the following modifications:
    (1) Incorporate stage 9 through 12 aluminum oxide blade tips and 
grind HPC blade tips at the rotor assembly in accordance with the 
Accomplishment Instructions of PW SB No. PW4ENG-72-484, Revision 3, 
dated July 1, 1997, concurrently with the requirements of paragraph 
(a)(4) of this AD.
    (2) Modify HPC 8th-14th stage stators in accordance with the 
Accomplishment Instructions of PW SB No. PW4ENG-72-486, Revision 1, 
dated November 23, 1994.
    (3) Modify the 1st stage high pressure turbine (HPT) cooling 
duct (TOBI Duct), install a metering plug in the Number 2 bearing 
thrust balance vent tube, and incorporate 1st stage HPT vanes with 
increased airflow area in accordance with the Accomplishment 
Instructions of PW SB No. PW4ENG-72-514, Revision 1, dated August 2, 
1996.
    (4) Incorporate HPC 13th-15th stage zirconium oxide blade tips 
in accordance with the Accomplishment Instructions of PW SB No. 
PW4ENG-72-575, Revision 1, dated June 30, 1997.
    (b) 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 submit their request through an appropriate FAA 
Principal Maintenance Inspector, who may add comments and then send 
it to the Manager, Engine Certification Office.

    Note 2: Information concerning the existence of approved 
alternative methods of compliance with this airworthiness directive, 
if any, may be obtained from the Engine Certification Office.

    (c) Special flight permits may be issued in accordance with 
sections 21.197 and 21.199 of the Federal Aviation Regulations (14 
CFR 21.197 and 21.199) to operate the aircraft to a location where 
the requirements of this AD can be accomplished.

    Issued in Burlington, Massachusetts, on June 11, 1998.
Jay J. Pardee,
Manager, Engine and Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 98-16271 Filed 6-17-98; 8:45 am]
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