[Federal Register: March 24, 1998 (Volume 63, Number 56)]
[Proposed Rules]               
[Page 14055-14057]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr24mr98-24]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-ANE-02-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 PW4000 
series turbofan engines. This proposal would require fluorescent 
penetrant and eddy current inspections of 2nd stage high pressure 
turbine (HPT) rotating airseals for cracks, removal from service of 
cracked parts, incorporation of improved 2nd stage HPT rotating 
airseals, and modification of 2nd stage ring segments and vane clusters 
to increase cooling flow and reduce stress as terminating action to the 
inspection requirements. This proposal is prompted by reports of 2nd 
stage HPT rotating airseal cracking. The actions specified by the 
proposed AD are intended to prevent 2nd stage HPT rotating airseal 
cracking, which could result in an uncontained engine failure and 
damage to the aircraft.

DATES: Comments must be received by May 26, 1998.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Regional 
Counsel, Attention: Rules Docket No. 98-ANE-02-AD, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may also be sent 
via the Internet using the following address: ``9-ad-
engineprop@faa.dot.gov''. 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: Peter White, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington, MA 01803-5299; telephone (781) 
238-7128, 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

[[Page 14056]]

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 98-ANE-02-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. 98-ANE-02-AD, 12 New England Executive 
Park, Burlington, MA 01803-5299.

Discussion

    The Federal Aviation Administration (FAA) has received reports of 
2nd stage high pressure turbine (HPT) rotating airseal cracking on 
Pratt & Whitney (PW) Models PW4052, PW4056, PW4060, PW4060A, PW4062, 
PW4152, PW4156A, PW4158, PW4460, PW4462, PW4164, and PW4168 turbofan 
engines. These reports of rotating air seal cracking led to the 
issuance of PW Alert Service Bulletin (ASBs) that describe procedures 
for inspecting airseals on uninstalled engines. Results of these 
inspections revealed a widespread cracking problem affecting all of 
these engine models. Further investigation revealed that the HPT 
airseals crack due to low cycle fatigue in at least three distinct 
locations. The causes of these cracks are a combination of excessive 
thermal and mechanical loading. This condition, if not corrected, could 
result in HPT airseal cracking, which could result in an uncontained 
engine failure and damage to the aircraft.
    The FAA has reviewed and approved the technical contents of PW ASBs 
No. PW4ENG A72-628, Revision 1, dated February 17, 1998, and No. PW4G-
100-A72-80, Revision 1, dated February 17, 1998, that describe 
procedures for fluorescent penetrant inspections (FPI) and eddy current 
inspections (ECI) of HPT airseals for cracks; and PW Service Bulletins 
(SBs) No. PW4ENG 72-636, dated May 16, 1997, No. PW4G-100-72-93, dated 
May 22, 1997, No. PW4ENG 72-637, dated May 16, 1997, and No. PW4G-100-
72-94, dated May 22, 1997, that describe procedures for modification of 
2nd stage ring segments and vane clusters, and incorporation of 
improved HPT airseals.
    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, at the next hot section shop visit and all 
subsequent hot section shop visits after the effective date of this AD, 
FPI and ECI of HPT airseals for cracks, and removal from service of 
cracked parts. Within 6 years after the effective date of this AD, this 
AD would require modification of 2nd stage ring segments and vane 
clusters, and incorporation of improved HPT airseals, as terminating 
action to the inspection requirements. The calendar end-date was 
determined based upon risk analysis, review of service data, industry 
capability and parts availability. The actions would be required to be 
accomplished in accordance with the service documents described 
previously.
    There are approximately 1,720 engines of the affected design in the 
worldwide fleet. The FAA estimates that 350 engines installed on 
aircraft of U.S. registry would be affected by this proposed AD, and 
that it would take no additional time to accomplish the proposed 
actions. Required parts would cost approximately $57,200 per engine. In 
addition, these parts will have consumed some portion of their life 
limits at the time of their removal, so this full cost burden will not 
be realized. Based on these figures, assuming an average part removal 
time of 7,000 cycles, the total cost impact of the proposed AD on U.S. 
operators is estimated to be $10,677,333. Pratt & Whitney has advised 
the FAA that it has an Industry Support Program that will reimburse 
operators for unconsumed life in parts that are retired early for 
cracking. This should eliminate the majority of the financial burden to 
the operators.
    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. 98-ANE-02-AD.
    Applicability: Pratt & Whitney Models PW4052, PW4056, W4060, 
PW4060A, PW4062, PW4152, PW4156A, PW4158, PW4460, W4462, PW4164, and 
PW4168 turbofan engines, with 2nd stage high pressure turbine (HPT) 
rotating airseals, Part Numbers (P/N) 50L156 or 50L195, installed. 
These engines are installed on but not limited to Boeing 747 and 767 
series, McDonnell Douglas MD-11 series, and Airbus Industrie A300, 
A310, and A330 series aircraft.

    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

[[Page 14057]]

this AD is affected, the owner/operator must request approval for an 
alternative method of compliance in accordance with paragraph (d) of 
this AD. The request should include an assessment of the effect of 
the modification, alteration, or repair on the unsafe condition 
addressed by this AD; and, if the unsafe condition has not been 
eliminated, the request should include specific proposed actions to 
address it.

    Compliance: Required as indicated, unless accomplished 
previously.
    To prevent 2nd stage HPT rotating airseal cracking, which could 
result in an uncontained engine failure and damage to the aircraft, 
accomplish the following:
    (a) At the next hot section shop visit after the effective date 
of this AD, and at each subsequent hot section shop visit, 
fluorescent penetrant inspect and eddy current inspect 2nd stage HPT 
rotating airseals for cracks, remove from service cracked airseals, 
and replace with serviceable parts, in accordance with Pratt & 
Whitney Alert Service Bulletins No. PW4ENG A72-628, Revision 1, 
dated February 17, 1998, and No. PW4G-100-A72-80, Revision 1, dated 
February 17, 1998.
    (b) For the purpose of this AD, a hot section shop visit is 
defined as any time the HPT module is disassembled.
    (c) Within 6 years after the effective date of this AD, modify 
2nd stage ring segments and vane clusters, and install improved 2nd 
stage HPT rotating airseals in accordance with Pratt & Whitney 
Service Bulletins No. PW4ENG 72-636, dated May 16, 1997, No. PW4G-
100-72-93, dated May 22, 1997, No. PW4ENG 72-637, dated May 16, 
1997, and No. PW4G-100-72-94, dated May 22, 1997. Performance of 
these modifications and installation of the improved 2nd stage HPT 
rotating airseal constitutes terminating action to the inspection 
requirements of this AD.
    (d) An alternative method of compliance or adjustment of the 
compliance time that provides an acceptable level of safety may be 
used if approved by the Manager, Engine Certification Office. 
Operators shall 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.

    (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.

    Issued in Burlington, Massachusetts, on March 17, 1998.
Jay J. Pardee,
Manager, Engine and Propeller Directorate, Aircraft Certification 
Service.
[FR Doc. 98-7559 Filed 3-23-98; 8:45 am]
BILLING CODE 4910-13-P