[Federal Register Volume 65, Number 249 (Wednesday, December 27, 2000)]
[Proposed Rules]
[Pages 81780-81782]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-32879]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2000-NE-25-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 Pratt & Whitney (PW) PW4000 series 
turbofan engines with 2nd stage high pressure turbine (HPT) air seal 
assembly part number (P/N) 50L976 or P/N 50L960 installed. This 
proposal would require operators to recalculate 2nd stage HPT air seal 
assembly cycles-in-service, based on flight hour-to-cycle ratio usage. 
This proposal would also require upon recalculation, initial and 
repetitive on-wing borescope inspections of 2nd stage HPT air seal 
assemblies for cracks based on the newly calculated service life. This 
proposal would also require the removal from service of any cracked 
seal assemblies, and the removal of seal assemblies at or before newly 
calculated service life limits. This proposal is prompted by reports 
that thirteen 2nd stage HPT air seal assemblies have been found cracked 
in the rim area. The actions specified by the proposed AD are intended 
to prevent 2nd stage HPT air seal assembly fracture that could result 
in an uncontained engine failure.

DATES: Comments must be received by February 26, 2001.

ADDRESSES: Submit comments to the Federal Aviation Administration 
(FAA), New England Region, Office of the Regional Counsel, Attention: 
Rules Docket No. 2000-NE-25-AD, 12 New England Executive Park, 
Burlington, MA 01803-5299. Comments may also be sent via the Internet 
using the following address: ``[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

[[Page 81781]]

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 Street, East Hartford, CT 06108. 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: Tara Goodman, Aerospace Engineer, 
Engine Certification Office, FAA, Engine and Propeller Directorate, 12 
New England Executive Park, Burlington MA 01803-5299; telephone: (781) 
238-7130, 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 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 action 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 action must submit a self-addressed, 
stamped postcard on which the following statement is made: ``Comments 
to Docket Number 2000-NE-25-AD.'' The postcard will be date stamped and 
returned to the commenter.

Availability of NPRM's

    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. 2000-NE-25-AD, 12 New England Executive 
Park, Burlington, MA 01803-5299.

Discussion

    This proposal is prompted by reports that thirteen 2nd stage HPT 
air seal assemblies have been found cracked in the rim area. The 
current design 2nd stage HPT air seal assemblies are operating in a 
temperature environment that is hotter than the manufacturer 
anticipated. Investigation shows that the crack initiation and 
propagation result from thermal mechanical fatigue. Investigation also 
revealed that the length of the flight, or mission cycle affects the 
service life limit of the 2nd stage HPT air seal assembly. Therefore in 
recalculating the service life of 2nd stage HPT air seal assemblies, 
this AD requires operators to determine, on a monthly basis, the flight 
hour-to-cycle-ratio for the hours and cycles accumulated that month, 
and then to apply the appropriate initial inspection threshold and 
repetitive cyclic inspection interval. Cracking of the 2nd stage HPT 
air seal assembly, if not corrected, could result in seal fracture and 
uncontained engine failure. The manufacturer has informed the FAA that 
the 2nd stage HPT air seal assembly is currently being redesigned, and 
that upon completion of the certification, the installation of the new 
design will act as terminating action to the repetitive inspection 
requirements of the proposed AD. This proposed rule may be revised 
based on the new design.

Service Information

    The FAA has reviewed and approved the technical contents of PW 
Alert Service Bulletin (ASB) No. PW4G-112-A72-233, dated August 25, 
2000. These contents describe procedures for operators to: (1) 
Determine, on a monthly basis, the flight hour-to-cycle ratio for the 
hours and cycles accumulated that month. (2) Apply the appropriate 
initial inspection threshold and repetitive cyclic inspection interval. 
(3) Recalculate the service life of 2nd stage HPT air seals. (4) 
Determine the appropriate inspection interval. The ASB also includes 
procedures for the removal from service of any cracked 2nd stage HPT 
seal assemblies or the removal of 2nd stage HPT seal assemblies at or 
before the newly calculated service life limits.

Proposed Actions

    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 recalculation of service lives of 2nd stage 
HPT air seal assemblies, and the initial and repetitive on-wing 
borescope inspections of 2nd stage HPT air seal assemblies for cracks. 
The proposed action would also require the removal from service of any 
cracked seal assemblies, or the removal of seal assemblies at or before 
the calculated service life limits. The actions would be required to be 
accomplished in accordance with the ASB described previously.

Economic Analysis

    The FAA estimates that there are 233 engines of the affected design 
in the worldwide fleet, and that 96 engines installed on aircraft of 
U.S. registry would be affected by this proposed AD. The FAA also 
estimates that it would take approximately 2.3 work hours per engine to 
accomplish the proposed on-wing borescope inspection, and that the 
average labor rate is $60 per work hour. The FAA estimates that 
approximately 47% of the certified life of the affected parts will be 
lost. Required parts would cost $235,950 per engine. Based on these 
figures, the total cost impact of the proposed AD on U.S. operators is 
estimated to be $10,659,312.

Regulatory Impact

    This proposal does not have federalism implications, as defined in 
Executive Order 13132, because it would not have a substantial direct 
effect 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. Accordingly, 
the FAA has not consulted with state authorities prior to publication 
of this proposal.
    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:

[[Page 81782]]

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. 2000-NE-25-AD.
    Applicability: This airworthiness directive (AD) is applicable 
to Pratt & Whitney (PW) models PW4074, PW4077, PW4077D, and PW4090 
turbofan engines with 2nd stage high pressure turbine (HPT) air seal 
assembly part number (P/N) 50L976 or P/N 50L960 installed. These 
engines are installed on but not limited to Boeing 777 series 
airplanes.

    Note 1: This 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 (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 air seal assembly failure that could 
result in uncontained engine failure, accomplish the following:

Calculation of Service Limits

    (a) Within 30 days of the effective date of this AD, and then 
each calendar month thereafter, determine the hour-to-cycle ratio of 
2nd stage HPT air seal assemblies based on the hours and cycles 
accumulated in the previous month in accordance with Paragraph 1 of 
the Accomplishment Instructions for air seal management of PW Alert 
Service Bulletin (ASB) No. PW4G-112-A72-233, dated August 25, 2000.

Borescope Inspections

    (b) For 2nd stage HPT air seal assemblies, determine the initial 
inspection time and repetitive inspection interval in cycles, in 
accordance with Paragraph 2 of the Accomplishment Instructions for 
air seal management of PW ASB No. PW4G-112-A72-233, dated August 25, 
2000. Perform borescope inspections of the 2nd stage HPT air seal 
assembly for cracks, and remove HPT air seal assemblies from service 
if cracked, in accordance with the On-Wing Procedure section of 
Accomplishment Instructions of PW ASB No. PW4G-112-A72-233, dated 
August 25, 2000.

New Cycle Limits

    (c) Determine new cycle limits for 2nd stage HPT air seal 
assemblies in accordance with Paragraph 3 of the Accomplishment 
Instructions for air seal management of PW ASB No. PW4G-112-A72-233, 
dated August 25, 2000, and remove from service 2nd stage HPT air 
seal assemblies prior to exceeding those limits.

Alternative Methods of Compliance

    (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 (ECO). 
Operators shall submit their request through an appropriate Federal 
Aviation Administration (FAA) Principal Maintenance Inspector, who 
may add comments and then send it to the Manager, ECO.

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

Special Flight Permits

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

    Issued in Burlington, Massachusetts, on December 15, 2000.
David A. Downey,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 00-32879 Filed 12-26-00; 8:45 am]
BILLING CODE 4910-13-P