[Federal Register Volume 64, Number 77 (Thursday, April 22, 1999)]
[Proposed Rules]
[Pages 19726-19728]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-10054]


 ========================================================================
 Proposed Rules
                                                 Federal Register
 ________________________________________________________________________
 
 This section of the FEDERAL REGISTER contains notices to the public of 
 the proposed issuance of rules and regulations. The purpose of these 
 notices is to give interested persons an opportunity to participate in 
 the rule making prior to the adoption of the final rules.
 
 ========================================================================
 

  Federal Register / Vol. 64, No. 77 / Thursday, April 22, 1999 / 
Proposed Rules  

[[Page 19726]]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NE-22-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. This proposal would establish short term criteria for 
limiting the number of engines with potentially reduced stability on 
each airplane to no more than one engine, would require initial and 
repetitive on-wing or test cell cold takeoff high pressure compressor 
(HPC) stability tests, would require removal of engines from service 
that fail on-wing test acceptance criteria, and would allow a follow-on 
test cell stability test. The AD also establishes required intervals 
for stability testing of the remaining engine with potentially reduced 
stability on the airplane and requirements for reporting test data. 
This proposal is prompted by a report of a dual-engine HPC surge event 
and reports of single-engine HPC surge events during the takeoff and 
climb phases of flight. The actions specified by the proposed AD are 
intended to prevent an HPC surge event, which could result in engine 
power loss at a critical phase of flight such as takeoff or climb.

DATES: Comments must be received by May 24, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation 
Administration (FAA), New England Region, Office of the Regional 
Counsel, Attention: Rules Docket No. 99-NE-22-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: 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 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 99-NE-22-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. 99-NE-22-AD, 12 New England Executive Park, 
Burlington, MA 01803-5299.

Discussion

    The Federal Aviation Administration (FAA) has received a report of 
a dual-engine high pressure compressor (HPC) surge event and several 
reports of single-engine HPC surge events on Pratt & Whitney (PW) 
PW4000 series turbofan engines. The FAA has determined that these HPC 
surges are caused by excessive HPC blade tip-to-stator assembly 
clearances in the aft stages of the HPC. The average maximum clearance 
between the blade tip and the stator assembly is reached during a cold 
engine takeoff approximately 60 seconds after throttle advance from 
idle to takeoff power, as a result of different thermal growth rates of 
the HPC rotor and stator components. The manufacturer's data indicates 
that some PW4000 engines exhibit reduced stability resulting from 
clearances larger than those due to this thermal mismatch alone. 
Testing has indicated that binding of stator assembly segments in the 
HPC outer casing can result in flow path distortion and produce local 
open clearances. These two factors (average maximum clearance and local 
open clearances) combine to produce excessive local blade tip-to-stator 
assembly clearances, which reduce stability and create subsequent 
engine surge.
    The FAA has issued AD 98-23-08, Amendment 39-10873, (63 FR 63391, 
November 13, 1998) which was intended to reduce the rate of single-
engine surges. Although the surge rates for engines that have 
incorporated the requirements of that AD have been reduced, the FAA has 
determined that further improvement is necessary. The investigation of 
engine surge events has determined that the dual-engine HPC surge event 
and several single-engine surge events have occurred on engines that 
meet the requirements of AD 98-23-08.

[[Page 19727]]

    This condition, if not corrected, could result in an HPC surge 
event, which could result in engine power loss at a critical phase of 
flight such as takeoff or climb.
    The FAA has reviewed and approved the technical contents of PW 
Special Instructions (SI) 49F96, dated August 9, 1996, PW SI 7F-96, 
dated January 10, 1996, and PW PW4000 Engine Manual Temporary Revisions 
71-0016, 71-0025, and 71-0030, all dated March 15, 1999, and PW SI 32F-
99, dated March April 13, 1999, which describe procedures for assessing 
the stability of PW4000 engines. Since an unsafe condition has been 
identified that is likely to exist or develop on other Pratt & Whitney 
(PW) PW4000 series turbofan engines of the same type design, the 
proposed AD would require short term criteria for limiting the number 
of engines with potentially reduced stability on each airplane to no 
more than one engine, would require initial and repetitive on-wing or 
test cell cold takeoff high pressure compressor (HPC) stability tests 
for all affected PW4000 series engines, would require removal from 
service of engines that fail on-wing test criteria, and would allow a 
follow-on test-cell stability test. Initial on-wing testing is required 
to limit the number of engines on the aircraft to no more than one 
engine that has exceeded the initial stability threshold. The proposed 
AD also establishes requirements to perform a stability test of the 
remaining engine with potentially reduced stability on the airplane. 
The stability tests are required to be accomplished in accordance with 
the special instructions described previously. This proposed AD has 
been drafted in conjunction with the Transport Aircraft Directorate, to 
coordinate the aircraft level aspects of this compliance plan. Data 
reporting requirements are necessary for this AD to allow continuous 
monitoring of the effectiveness and assumptions of this compliance 
plan. The manufacturer does not receive data on all of the tests that 
are performed, and this data is necessary to continuously monitor this 
plan. Additional rulemaking may be necessary based on the results of 
the data collected.
    There are approximately 2,200 engines of the affected design in the 
worldwide fleet. The FAA estimates that 546 engines installed on 
aircraft of U.S. registry would be affected by this proposed AD. The 
FAA also estimates that, on average, approximately 192 on-wing tests, 
60 test cell stability tests, 11 engine removals, and 19 HPC overhauls 
will be required annually. It is estimated that the cost to industry of 
an on-wing stability test will average $2,000, a test cell stability 
test will average $12,000, an engine removal is approximately $5,000, 
and an HPC overhaul will cost approximately $400,000. Based on these 
figures, the total average annual cost impact of the proposed AD to 
U.S. operators is estimated to be $8,759,000.
    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. 99-NE-22-AD.
    Applicability: Pratt & Whitney PW4050, PW4052, PW4056, PW4060, 
PW4060A, PW4060C, PW4062, PW4152, PW4156, PW4156A, PW4158, PW4160, 
PW4460, PW4462 and PW4650 turbofan engines installed on, but not 
limited to certain models of Boeing 747, Boeing 767, Airbus 
Industrie A300, Airbus Industrie A310, and McDonnell Douglas MD-11 
series airplanes.

    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 (h) 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 a high pressure compressor (HPC) surge event, which 
could result in engine power loss at a critical phase of flight such 
as takeoff or climb, accomplish the following:
    (a) Limit the number of engines on each airplane to no more than 
one untested engine that has exceeded the initial threshold 
specified in Table 1 of this AD, within 1,000 engine cycles in 
service (CIS) from the effective date of this AD or by December 31, 
1999, whichever comes first, by one of the following methods:
    (1) Conduct an initial on-wing stability test on engines listed 
in Table 1 of this AD, which have accumulated cycles equal to or 
greater than the associated initial threshold listed in Table 1 of 
this AD, as follows:
    (i) Perform either a Cool Bodie stability test in accordance 
with PW Special Instructions 7F-96,dated January 10, 1996. Refer to 
Table 2 of this AD for disposition instructions, or;
    (ii) Perform an E1E stability test in accordance with paragraphs 
A through D and F through H of the Run On-Wing E1E Testing section 
of PW Special Instructions 49F-96, dated August 9, 1996. Refer to 
Table 2 of this AD for disposition instructions.
    (iii) For purposes of this AD, the initial threshold for PW4056, 
PW4156, and PW4156A, first run, full-up engines, applies only to 
engines that have incorporated service bulletins PW4ENG 72-474, 72-
477, 72-484, 72-575, 72-485, 72-486, and 72-514 at original 
manufacture, and have had no work performed on the HPC and high 
pressure turbine gas path.
    (2) Remove from service those engines listed in Table 1 of this 
AD with HPC's that have accumulated cycles equal to or greater than 
the initial threshold listed in Table 1 of this AD and replace with 
a serviceable engine that has undergone applicable initial and 
repetitive testing in accordance with paragraphs (a), (b) and (c) of 
this AD.

[[Page 19728]]



                                                     Table 1
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                 Models                        Initial threshold                     Engine manual
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PW4052, PW4152, PW4158, PW4050, PW4650..  2400 HPC cycles since new    50A605, 50A443
                                           or since HPC overhaul.
PW4056,* PW4156,* PW4156A *.............  1700 engine cycles since     50A605, 50A443
                                           new.
PW4056, PW4156, PW4156A.................  1200 HPC cycles since HPC    50A605, 50A443
                                           overhaul.
PW4060, PW4060A, PW4060C, PW4062,         1200 HPC cycles since new    50A605, 50A443,50A822
 PW4160, PW4460, PW4462.                   or since HPC overhaul.
----------------------------------------------------------------------------------------------------------------
 First Run, Full Up Engines.


                                      Table 2.--On-Wing Acceptance Criteria
----------------------------------------------------------------------------------------------------------------
                Test type                         Test result                         Disposition
----------------------------------------------------------------------------------------------------------------
Cool Bodie: In accordance with SI 7F-96,  Pass.......................  Continue in service.
 dated August 9, 1996.
                                          Failure....................  Remove from service or conduct E1E. If
                                                                        <0.02 continue in service. If E1E is 0.02 remove from service, prior
                                                                        to further flight.
E1E: In accordance with SI 49F-96, dated  <0.02......................  Continue in service.
 January 10, 1996.
                                          0.02 but 0.032.                    service. If fail remove engine from
                                                                        service, prior to further flight.
                                          >0.032.....................  Remove from service, prior to further
                                                                        flight.
----------------------------------------------------------------------------------------------------------------

    (b) For engines removed from service in accordance with 
paragraph (a) of this AD, a cold engine fuel spike stability test 
(Testing--20) may be done in accordance with the associated PW 
PW4000 Engine Manual Temporary Revisions 71-0016, 71-0025, and 71-
0030, all dated March 15, 1999, or PW SI 32F-99, dated April 13, 
1999. Engines that pass a test cell stability test may be returned 
to service.
    (c) Repeat stability tests in accordance with paragraph 
(a)(1)(i) or (a)(1)(ii) on engines that meet the acceptance criteria 
of Table 2 of this AD or pass a test cell stability test in 
accordance with paragraph (b) before accumulating 800 CIS since last 
stability test.
    (d) Remove from service engines that do not meet the acceptance 
criteria of Table 2, prior to further flight and replace with a 
serviceable engine that has undergone applicable initial and 
repetetive testing in accordance with paragraphs (a), (b) and (c) of 
this AD.
    (e) Conduct stability tests on the remaining engine on each 
airplane before accumulating 1800 engine CIS after the effective 
date of this AD, or by December 31, 2000, whichever comes first, in 
accordance with paragraph (a) of this AD.
    (f) Engines that have not reached the initial threshold 
specified in Table 1 of this by 1000 engine CIS after the effective 
date of this AD, or by December 31, 1999, whichever comes first, 
must be tested before the engine reaches the initial threshold so 
that no more than one engine per airplane has not been tested. After 
accumulating 1800 CIS or December 31, 2000, whichever comes first, 
the engines must be managed so that all engines have been tested in 
accordance with the initial thresholds specified in Table 1 of this 
AD or the repetitive 800 CIS threshold requirement of this AD.
    (g) After the effective date of this AD, a cold engine fuel 
spike stability test (Testing--20) must be performed in accordance 
with PW Temporary Revision 71-0016, 71-0025, or 71-0030, all dated 
March 15, 1999, or PW SI 32F-99, dated April 13, 1999, before an 
engine can be returned to service after having undergone maintenance 
in the shop, except under any of the following conditions:
    (1) The HPC stage 12 through 14 blade tip clearances were 
restored to the clearances specified in the applicable fits and 
clearances engine manual during the shop visit, or the HPC was 
replaced with a new HPC during the shop visit.
    (2) Less than 800 CIS have passed since the last accomplishment 
of Testing--20, unless a major engine flange was separated during 
the shop visit.
    (3) The shop visit was only for replacement of a line 
replaceable unit, with no other work done, unless a major engine 
flange was separated during the shop visit.

    Note 2: Boeing SB 767-72A0034, dated April 16, 1999, and SB 747-
72A2038, dated April 16, 1999, include instructions similar to those 
contained in this AD, however, these SB's are not approved as 
alternate methods of compliance with this AD.

    (h) 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 3: Information concerning the existence of approved 
alternative methods of compliance with this airworthiness directive, 
if any, may be obtained from the Engine Certification Office.

    (i) Report the results of the stability assessment tests to the 
Manager, Engine Certification Office, 12 New England Executive Park, 
Burlington, MA 01803-5299. Data to be reported includes engine 
serial number, type and date of the test, results of the test 
(include E1E value if applicable), position of engine on the 
airplane, disposition of the engine after the test, time and cycles 
since compressor overhaul, and total time on engine and total cycles 
at the time of the test. Reporting requirements have been approved 
by the Office of Management and Budget (OMB) and assigned OMB 
control number 2120-0056.
    (j) 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 accomplished.

    Issued in Burlington, Massachusetts, on April 14, 1999.
Mark C. Fulmer,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 99-10054 Filed 4-21-99; 8:45 am]
BILLING CODE 4910-13-P