[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]
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