[Federal Register Volume 66, Number 226 (Friday, November 23, 2001)]
[Proposed Rules]
[Pages 58689-58691]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 01-29191]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 2001-NE-25-AD]
RIN 2120-AA64


Airworthiness Directives; Pratt & Whitney 4000 Series Turbofan 
Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: The Federal Aviation Administration (FAA) proposes to adopt a 
new airworthiness directive (AD) that is applicable to Pratt & Whitney 
(PW) PW4090, PW4090-3, PW4074D, PW4077D, PW4090D, and PW4098 turbofan 
engines with 15th stage high pressure compressor (HPC) disks having 
certain part numbers (P/N's). This proposal would require initial and 
repetitive borescope inspections of 15th stage HPC disks for cracks in 
the knife edges, eddy current inspections (ECI's) of blade loading 
slots if required, and removal of cracked disks. In addition, this 
proposal would require the removal from service of these P/N disks, at 
a new lower cyclic life limit. This proposal is prompted by two reports 
of 15th stage HPC disks with cracks in the outer rim front rail of the 
blade loading slots, and in the front forward and middle knife edges. 
The actions specified by the proposed AD are intended to prevent 15th 
stage HPC disk failures from cracks, which could result in an 
uncontained engine failure.

DATES: Comments must be received by January 22, 2002.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Regional 
Counsel, Attention: Rules Docket No. 2001-NE-25-AD, 12 New England 
Executive Park, Burlington, MA 01803-5299. Comments may be inspected at 
this location, by appointment, between 8:00 a.m. and 4:30 p.m., Monday 
through Friday, except Federal holidays. 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. 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, by appointment, at the FAA, New England Region, Office 
of the Regional Counsel, 12 New England Executive Park, Burlington, MA.

FOR FURTHER INFORMATION CONTACT: Jason Yang, Aerospace Engineer, Engine 
Certification Office, FAA, Engine and

[[Page 58690]]

Propeller Directorate, 12 New England Executive Park; telephone (781) 
238-7747, 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 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 2001-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. 2001-NE-25-AD, 12 New England Executive 
Park, Burlington, MA 01803-5299.

Discussion

    In March of 2001, the FAA received two reports from the 
manufacturer of two factory engines with cracks in the 15th stage HPC 
disk blade loading slot outer rim front rail, and in the front forward 
and middle knife edges. The manufacturer's investigation results 
revealed that the crack initiations were caused by thermo-mechanical 
fatigue. Due to these investigation results, this proposal would 
require initial borescope inspections of 15th stage HPC disks P/N 
56H015 and 57H715 for cracks in the knife edges and blade loading 
slots, eddy current inspections (ECI's) within 25 cycles-in-service 
from the time of borescope inspection of blade loading slots if 
required, and removal of cracked disks. Repetitive borescope 
inspections at intervals of no more than 1,000 cycles-in-service since 
last inspection are also required. In addition, this proposal would 
require the removal from service of these P/N disks, at a new lower 
cyclic life limit of 8,000 cycles-since-new (CSN). The actions 
specified by the proposed AD are intended to prevent 15th stage HPC 
disk failures from cracks, which could result in an uncontained engine 
failure. Currently there is no terminating action for the repetitive 
inspections due to cracking of 15th stage HPC disks, P/N's 56H015 and 
57H715. This condition, if not corrected, could result in disk rupture 
and uncontained engine failure.

Manufacturer's Service Information

    The FAA has reviewed and approved the technical contents of PW 
Service Bulletin (SB) PW4G-112-A72-242, dated May 1, 2001 that 
describes procedures for initial and repetitive borescope inspections 
of 15th stage HPC disks for cracks in the front forward and middle 
knife edges, ECI's of front rail of the blade loading slots that have 
suspect cracks, within 25 cycles-in-service from time of initial 
borescope inspection, and the removal of cracked disks. In addition, 
the SB requires the removal from service of disks at a new lower cyclic 
life limit of 8,000 hours CSN.

Differences Between This AD and the Manufacturer's Service 
Information

    Pratt & Whitney (PW) SB PW4G-112-A72-242, dated May 1, 2001, 
requires that for disks removed from engines in a maintenance facility 
for HPC rotor maintenance, that includes rotor tip grinding, the 
inspection specified in Engine Cleaning, Inspection, and Repair Manual, 
Chapter/Section 72-35-92, Inspection/Check-02 must be done on disks 
with 2,000 CSN or less. The SB also requires that disks removed from 
engines, with more than 2,000 CSN be replaced with a serviceable disk. 
PW has informed the FAA that to help reduce the operators' cost of 
replacing disks, PW may supply replacement disks at no cost, to be 
installed at the time disks with more than 2,000 CSN are removed for 
maintenance. This proposed AD addresses only inspections, replacement, 
and new cyclic life limit of installed disks.

FAA's Determination of an Unsafe Condition and Proposed Actions

    Since an unsafe condition has been identified that is likely to 
exist or develop on other PW PW4090, PW4090-3, PW4074D, PW4077D, 
PW4090D, and PW4098 turbofan engines of the same type design with 15th 
stage HPC disks P/N's 56H015 and 57H715, the proposed AD would require 
initial and repetitive borescope inspections of 15th stage HPC disks 
for cracks in the front forward and middle knife edges, ECI's of blade 
loading slots that have suspect cracks or cracks, within 25 cycles-in-
service from time of initial borescope inspection, and the removal of 
cracked disks. In addition, the proposed AD would require the removal 
from service of disks at a new lower cyclic life limit of 8,000 hours 
CSN.

Economic Analysis

    There are approximately 160 PW4090, PW4090-3, PW4074D, PW4077D, 
PW4090D, and PW4098 turbofan engines of the affected design in the 
worldwide fleet. The FAA estimates that 70 engines installed on 
airplanes of U.S. registry would be affected by this proposed AD. The 
FAA also estimates that it would take approximately 2.5 work hours per 
engine to accomplish an initial borescope inspection, and that the 
average labor rate is $60 per work hour. Required parts for a borescope 
inspection would cost approximately $9 per engine. Based on these 
figures, the total cost effect for the initial borescope inspection for 
U.S. operators is estimated to be $11,130. Assuming that all 70 engines 
would require 15th stage HPC disk replacement, and that a replacement 
disk costs approximately $65,000, the total disk cost effect of the 
proposed AD on U.S. operators is estimated to be $4,550,000.

Regulatory Analysis

    This proposed rule 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 proposed rule.
    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

[[Page 58691]]

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. 2001-NE-25-AD.
    Applicability: This airworthiness directive (AD) is applicable 
to Pratt & Whitney (PW) PW4090, PW4090-3, PW4074D, PW4077D, PW4090D, 
and PW4098 turbofan engines with 15th stage high pressure compressor 
(HPC) disks part numbers (P/N's) 56H015 or 57H715. These engines are 
installed on, but not limited to Boeing 777 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 (c) 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: Compliance with this AD is required as indicated, 
unless already done.
    To prevent 15th stage HPC disk failures from cracks, which could 
result in an uncontained engine failure, do the following:

Initial Inspection

    (a) Perform an initial inspection for cracks in the front rail 
of the blade loading slots and front forward and middle knife edges 
of the 15th stage HPC disk, and replace disk in accordance with 
paragraphs 1.A. through 1.E.(4) of, ``For Engines Installed on 
Aircraft''; or paragraphs 2.A. through 2.E.(4) of, ``For Engines 
Removed From the Aircraft'', of the Accomplishment Instructions of 
PW Service Bulletin PW 4G-112-A72-242, dated May 1, 2001, and the 
following Table 1:

            Table 1.--15th Stage HPC Disk Initial Inspection
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           Action                      If:                  Then:
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(1) Borescope-inspect disk,   (i) Borescope         Replace the disk
 within 4,600 cycles-since-    inspection shows a    with a serviceable
 new (CSN) or before 90 days   crack in any knife    disk before further
 after the effective date of   edge area..           flight.
 this AD, whichever occurs
 later..
  ..........................  (ii) Borescope        Perform an eddy
                               inspection shows a    current inspection
                               suspect crack in      (ECI) to confirm
                               any loading slot..    crack within the
                                                     next 25 cycles-in-
                                                     service (CIS), and
                                                     if cracked replace
                                                     with a servicable
                                                     disk before further
                                                     flight.
------------------------------------------------------------------------

Repetitive Inspections

    (b) Perform repetitive inspections in accordance with the 
inspection procedures in paragraph (a) of this AD at intervals of no 
more than 1,000 CIS since the last inspection.

New Cyclic Life Limit

    (c) This AD establishes a new cyclic life limit for 15th stage 
HPC disks P/N's 56H015 and 57H715 of 8,000 cycles-since-new (CSN). 
Thereafter, except as provided in paragraph (d) of this AD, no 
alternative cyclic life limit may be approved for 15th stage HPC 
disks P/N's 56H015 and 57H715.

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 must submit their request through an appropriate 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 
Secs. 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 done.


    Issued in Burlington, Massachusetts, on November 14, 2001.
Donald E. Plouffe,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 01-29191 Filed 11-21-01; 8:45 am]
BILLING CODE 4910-13-U