[Federal Register Volume 64, Number 161 (Friday, August 20, 1999)]
[Rules and Regulations]
[Pages 45426-45433]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-21450]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 99-NE-22-AD; Amendment 39-11263; AD 99-17-16]
RIN 2120-AA64


Airworthiness Directives; Pratt & Whitney PW4000 Series Turbofan 
Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Final rule.

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SUMMARY: This amendment adopts a new airworthiness directive (AD), 
applicable to Pratt & Whitney (PW) PW4000 series turbofan engines, that 
requires short term criteria for limiting

[[Page 45427]]

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-engine 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 amendment 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 this 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: Effective date September 24, 1999. The incorporation by 
reference of certain publications listed in the regulations is approved 
by the Director of the Federal Register as of September 24, 1999.

ADDRESSES: The service information referenced in this AD may be 
obtained from Pratt & Whitney, 400 Main St., East Hartford, CT 06108; 
telephone (860) 565-8770, fax (860) 565-4503. This information may be 
examined at the Federal Aviation Administration (FAA), New England 
Region, Office of the Regional Counsel, 12 New England Executive Park, 
Burlington, MA; or at the Office of the Federal Register, 800 North 
Capitol Street, NW, suite 700, Washington, DC.

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: A proposal to amend part 39 of the Federal 
Aviation Regulations (14 CFR part 39) to include an airworthiness 
directive (AD) that is applicable to Pratt & Whitney PW4000 series 
turbofan engines was published in the Federal Register on April 22, 
1999 (64 FR 19726). That action proposed to 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-engine 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 or test cell stability testing is required to limit the number 
of engines on the airplane to no more than one engine that has exceeded 
the initial threshold. The AD also establishes requirements to perform 
a stability test of the remaining engine with potentially reduced 
stability on the airplane. These tests are performed in accordance with 
Pratt & Whitney (PW) Special Instructions (SI) 49F-96, dated August 9, 
1996; PW SI 7F-96, dated January 10, 1996; PW PW4000 Engine Manual (EM) 
Temporary Revisions (TR) 71-0016, 71-0025, and 71-0030, all dated April 
13, 1999; PW EM 50A605 Section 71-00-00, Testing-20, PW EM 50A443 
Section 71-00-00, Testing -20, and PW EM 50A822, Section 71-00-00, 
Testing -20, all dated June 15, 1999; PW SI 32F-99, dated April 13, 
1999; and PW Cactus Wire C042 G 930902, dated September 2, 1993, which 
describe procedures for assessing the stability of PW4000 engines.
    Interested persons have been afforded an opportunity to participate 
in the making of this amendment. Due consideration has been given to 
the comments received.

Questions About Table Formats

    One commenter notes that the formatting of Tables 1 and 2 as 
published in the Federal Register is somewhat unusual and not to 
standard guidelines. The FAA disagrees. The tables appeared as intended 
when published in the Federal Register. When obtaining the document 
from the Internet, however, if not downloaded in a specific file 
format, the formatting of the document may be lost and the document may 
appear quite different. The problems described are functions of the 
method in which the document is accessed, not in how it was published.

Request to Change Reference to McDonnell Douglas MD-11 to Boeing 
MD-11

    One commenter believes that the reference to the MD-11 airplane is 
incorrect. The NPRM refers to it as the McDonnell Douglas MD-11. The 
commenter notes that the McDonnell Douglas company was bought by the 
Boeing Co., and should therefore be the Boeing MD-11. The FAA does not 
agree. The FAA refers to the product by the name that currently appears 
on the Type Certificate Data Sheet, which is still McDonnell Douglas 
MD-11.

Questions about Applicability of PW4000 Phase 3 Configuration 
Engines

    Several commenters question whether or not PW4000 Phase 3 engines 
are affected by this AD, and request that the proposed rule be modified 
to more clearly identify Phase 3 engines in the applicability section. 
The FAA does not agree. The applicability section of the AD lists those 
model PW4000 engines to which the AD applies. Note 1 reminds operators 
that this AD applies to all products mentioned in the applicability 
section, no matter how modified, altered, or repaired. The AD therefore 
applies to Phase 3 configuration engines of any listed model.
    One commenter noted that the new production PW4056 engines they are 
receiving do not list three of the SB's listed in the definition of 
``first run, full up engines'' in their SB incorporation summaries. The 
FAA agrees. Paragraph (a)(1)(iii) of the AD has been changed to include 
as ``first run, full up engines'' those PW4056, PW4156, and PW4156A 
original manufacture engines that incorporate a (-3) suffix, denoting 
the Phase 3 configuration that incorporates the intent of these SB's.
    One commenter notes that AD 98-23-08 does not affect Phase 3 
engines, and recommends a similar approach for this AD, with a more 
liberal retest interval for the Phase 3 engines. The FAA disagrees. The 
fleet has been thoroughly evaluated to search for any subpopulations 
that exhibit a different wear-out threshold, and to select the most 
appropriate initial threshold for each apparent population. The 
evaluation of the Phase 3 engine population does not justify a distinct 
initial threshold, except in the case of first run, full up PW4056, 
PW4156, and PW4156A engines, which receive unique initial thresholds.
    One commenter suggests that PW SB 72-514 be modified to read ``PW 
72-514 (or 72-504)'', in the definition of first run, full up engines. 
The FAA disagrees. SB 72-514 incorporates the larger HPT nozzle, which 
lowers compressor op-line, increasing surge margin. SB 72-504 
references several SB's, and is the engine manufacturer's documentation 
detailing conversion of a standard PW4052/4056 engine to a Phase 3. As 
they involve the extensive modification of ``used'' engines, converted 
engines do not meet the requirements of a ``first run'' engine. In 
addition, the larger area HPT nozzle is a critical part of the first 
run, full up engine definition, as it offers a significant benefit to 
operability. To include recent shipment engines where these SB's are 
not listed in the SB incorporation paperwork, paragraph (a)(1)(iii) of 
the AD has been changed to include those PW4056, 4156, and 4156A 
original manufacture, first run engines that incorporate a (-3) suffix 
after the data plate engine model designation as

[[Page 45428]]

first run, full up engines for purposes of using that initial threshold 
in Table 1.

Question About Higher Initial Threshold for PW4158 Engines

    One commenter notes that PW4056 engines receive a lower initial 
threshold than did the PW4158 engines, and questions whether or not 
this is in error. The FAA concludes that the PW4158 population 
demonstrates a relatively high cyclic threshold for surge occurrence 
for its thrust rating level. This fleet operates with a high average 
take-off derate level, and based on its demonstrated surge rate, this 
subfleet receives a higher initial threshold.

Requests for Credit for Previously Accomplished Tests

    Several commenters state that the proposed rule is not clear as to 
whether or not credit is allowed for previously accomplished tests, and 
requested that the AD be more specific. The FAA agrees in part. The AD 
states that compliance is ``required as indicated, unless accomplished 
previously.'' Any previously accomplished testing performed in 
accordance with the requirements of this AD is acceptable, and tests 
performed to other than the procedures specified in the AD are not 
acceptable as having previously accomplished the requirements of the 
AD. However, paragraphs (b) and (g) have been changed based on comments 
received. Changes were made to the cold-engine fuel spike test 
definition to cover additional tests performed under the instructions 
supplied in PW Cactus Wire ID C042 G 930902 ZRH, issued September 2, 
1993. This instruction was omitted from the NPRM, and its inclusion in 
this AD will allow acceptance of additional testing performed in the 
past.
    One commenter questions if operators can define engines as either 
tested or untested on the effective date of the AD if previously 
accomplished testing is acceptable. The FAA determines that this 
approach is acceptable. Operators who have done prior acceptable 
testing on engines may take credit for that testing and proceed with 
repetitive testing based on the test schedule defined by the AD, or 
they may ignore the previously accomplished testing and comply with the 
requirements of the AD for initial and repetitive testing as if the 
engines had not been previously tested. The FAA strongly encourages 
operators with previously tested engines that have failed those 
previous stability tests to remove those engines from service 
immediately. The FAA, however, has determined that it is not necessary 
to include a requirement in this AD to remove previously tested engines 
from service based on a failure of the previous test. Surveys indicate 
that few, if any, such engines remain in service, and to include such a 
requirement in the final rule would necessitate a delay in this 
rulemaking.
    In addition, one commenter notes that operators who test more 
frequently than required by the AD will be penalized, as they will, in 
some cases, be forced to remove an engine before the 800 cycle 
repetitive interval, if the engine fails a stability test. The 
commenter requests a time after test failure before which engines 
tested more frequently than the 800-cycle interval must be removed. The 
FAA disagrees. It is not consistent with safe practices to allow an 
engine with known reduced stability to remain in service.

Requests To Exempt Pilot Training Cycles From ``Cycles in Service''

    Two commenters note confusion regarding the term ``Cycles in 
Service.'' They feel that this term should be more clearly defined. One 
requests that pilot training cycles, performed at a reduced thrust 
rating, should not be counted for the purposes of the AD. The FAA 
disagrees. The term ``Cycles in Service'' refers to the standard cycles 
counted for life tracking, and is generally viewed as any flight 
consisting of one takeoff and landing. The FAA has determined not to 
create a separate cycle counting procedure for this AD.

Request for Definition of ``HPC Overhaul''

    Several commenters note that the term ``HPC Overhaul'' needs to be 
defined. The FAA agrees. Paragraph (g) of the AD has been changed to 
use the term ``overhaul'' and a new paragraph has been added to define 
an HPC overhaul as a stage 12 through stage 15 HPC tip clearance 
restoration.
    Several commenters also pointed out that this definition should 
include HPC stages 12 through 15, not 12 through 14. The FAA agrees. 
This final rule has been changed accordingly.
    One commenter requests that the term overhaul be avoided, and that 
repair be substituted in its place. The FAA disagrees. The level of 
work required to perform a stage 12 through stage 15 HPC tip clearance 
restoration is better viewed as an overhaul than a repair. In addition, 
the use of overhaul is consistent with the manufacturer's service 
documentation.

Request To Eliminate the Term ``On-Wing''

    One commenter notes that the words ``on-wing'' should be eliminated 
from paragraph (a)(1), as these tests do not need to be performed on-
wing, as the cold-engine fuel spike test is also acceptable. The FAA 
agrees. The words ``on-wing'' have been removed from paragraph (a)(1).

Request To Add Initial Threshold to Untested Engines Limits

    Several commenters note that certain AD references appear to limit 
the airplane more strictly than intended in that compliance statements 
refer to limiting the airplane to no more than one, or no untested 
engines, without referencing the initial threshold exceedance. The FAA 
agrees. Paragraph (e) has been changed to include reference to the 
initial threshold.

Request To Allow Airplanes To Remain in Revenue Service After Test 
Failure or Exceeding Initial Threshold

    One commenter requests that engines be allowed to remain in revenue 
service for a certain time after a threshold exceedance or test 
failure. The FAA disagrees. This AD is intended to remove from service 
engines identified to have low stability, or potentially reduced 
stability, from service immediately. It would not be consistent to 
allow further usage of engines known to be at a higher potential to 
surge during the takeoff phase of flight in-revenue service.

Request To Allow A Nonrevenue Flight

    Several commenters object to the proposal that requires removing 
engines that fail a stability test or exceed a threshold prior to 
further flight. These commenters note that the stability tests, which 
require running an engine on the ground at high power for extended 
lengths of time, may not be performed at all locations due to noise 
concerns. These commenters request that a nonrevenue flight provision 
be added so that they can return airplanes to a maintenance facility 
where engine removal may be performed after the engine has failed a 
stability test. The FAA agrees in part. As proposed, the provision in 
the AD allowing special flight permits was intended to cover only the 
situation where an engine stability test was overdue and the aircraft 
needed to be moved to a location where that test could be performed. 
The FAA has determined that allowing ferry flights, after an engine 
fails a stability test to move the aircraft to a location where engine 
removal can be performed, is acceptable if the flight is made under 
specified conditions to minimize the risk of engine surge during that 
flight. The special flight provision in the final rule

[[Page 45429]]

has therefore been changed to allow nonrevenue flights after an engine 
fails a stability test. The FAA has determined, however, that ferry 
flights should continue to be handled under the provisions of the 
special flight permit authority contained in part 21. Operators can 
coordinate with the FAA office that oversees their operation to 
minimize the time required to issue a special flight permit.

Request for Clarification of Reporting Requirements

    Several commenters note confusion regarding the reporting 
requirements. The FAA agrees. Paragraph (k) of the final rule, which 
contains the reporting requirement, has been changed to include a time 
limit within which reports must be made and to include an email 
address.
    Several commenters requested that the reporting requirements be 
changed to allow submittal of the data directly to PW. The FAA 
disagrees. The current Office of Management and Budget (OMB) approval 
for reporting requirements in AD's does not cover the submission of 
reports directly to manufacturers. The FAA is working to broaden the 
OMB's approval to cover that situation, but until that new approval is 
in place, reporting must be directly to the FAA. In addition, reporting 
to the FAA will allow the FAA to monitor the consistency of the 
collected test results to past history, verify the assumptions in the 
risk assessment, monitor fleet impact, monitor trends in the surge 
rate, and ensure that the desired level of safety is maintained.

Request for Clarification of How To Select Initial Threshold When 
the Electronic Engine Control (EEC) Programming Plug Is Used

    One commenter notes that engine thrust rating changes can be 
accomplished in accordance with the manufacturer's instructions via the 
EEC programming plug, and requests clarification regarding how to 
select the initial threshold in these cases. The FAA agrees that 
clarification is needed, and has added a new paragraph (a)(3) that 
provides that in those cases where a thrust rating change has been made 
the highest thrust rating selected in the affected HPC overhaul period 
is to be used for determining the initial threshold.

Request To Redefine the Unsafe Condition

    Several commenters feel that the unsafe condition should be defined 
as a dual-engine surge event, and that the AD goes too far in mandating 
safety by requiring that all engines be evaluated, rather than all but 
one engine, as in the airplane manufacturer's service documentation. 
The FAA disagrees. The FAA has concluded that the present single-engine 
surge rate and the increased likelihood of a dual-engine surge event, 
constitute an unsafe condition. Since these surges occur during a 
critical phase of flight (take-off or early climb), they place an extra 
demand on the flight crew during a high-workload period. While an 
airplane may be designed to be able to take-off with one engine 
inoperative, and procedures are in place for engine failures in flight, 
accident history indicates that a high percentage of single-engine 
failures result in accident or incidents due to combination with 
another failure or malfunction. For this reason, this rule addresses 
not only the dual-engine surge, but also the rate of single-engine 
surge.

Request To Allow Boeing Service Bulletin as an Alternate Method of 
Compliance

    One commenter requests that compliance with Boeing service 
bulletins 767-72A0034, dated April 16, 1999, and SB 747-72A2038, dated 
April 16, 1999, be allowed as an alternate method of compliance. The 
FAA does not agree. The Boeing service bulletins allow one engine on an 
airplane to remain untested. Because the FAA has determined that the 
rate of single-engine surge events must also be addressed, allowing one 
engine on an airplane to remain untested would conflict with the goal 
of reducing the rate of single-engine surge events. Therefore, the 
Boeing service bulletins addressing this problem are only for 
reference, and are not approved as an alternate method of compliance.

Request To Tighten the Testing Intervals

    One commenter feels that the proposed rule is not aggressive enough 
in evaluating the PW4000 fleet for low-stability engines, and that more 
aggressive initial and repetitive testing intervals and deadlines need 
to be established. The FAA disagrees. The compliance cyclic thresholds 
and calendar end dates were selected based on a detailed risk analysis 
to evaluate the effectiveness of the fleet management plan. Compliance 
thresholds were established at levels predicted to establish a very low 
rate of surge. The compliance deadlines were selected to minimize risk 
balanced with the logistical complications of achieving fleet-wide 
compliance considering the number of affected engines. This plan was 
carefully evaluated to provide the intended level of safety without 
unnecessarily requiring the grounding of aircraft.

Request To Allow In-situ Borescope Blending of HPC Airfoils for 
Minor Damage

    One commenter notes that the definition of first run, full up 
engines does not allow in-situ borescope blending of the HPC airfoils 
for minor foreign object damage (FOD), and requests that the Final Rule 
be modified to allow this operation. The FAA agrees. Paragraphs 
(a)(iii) and (g)(3) and (g)(4) have been changed to replace ``no work 
performed on the HPC or HPT gaspaths'', to read ``have not had a 
separation of a major engine flange since new, with the exception of 
the `A' or `T' flanges.'' These changes will allow operators to 
consider engines that have undergone only in-situ borescope blending of 
the HPC airfoils for FOD to be a first run, full-up engines, and will 
also allow removal of the inlet and tailpipe.

Request for Definition of Actions To Return an Engine to Service

    One commenter feels that the proposed rule must state required 
action to return a failed engine to service after stability test 
failure. The commenter feels it would be appropriate to require that 
HPC tip clearances on S12 through S15 blades be restored to manual 
limits. The FAA disagrees. The FAA has determined that it is not 
necessary to require blade tip restoration in all cases. The stability 
tests required prior to returning an engine to service will ensure that 
engines that do not receive stage 12 through stage 15 tip clearance 
restoration are adequately assessed before leaving the shop. In 
addition, tip clearance restoration is encouraged by resetting the 
initial threshold interval for those engines having undergone an HPC 
overhaul. HPC tip clearance restoration provides an increase in surge 
margin; however, other actions may also adequately restore surge 
margin, such as installation of the cutback HPT guide vane to lower 
compressor operating line.

Concern About Engine Manual Temporary Revisions

    Two commenters note that the proposed rule references Engine Manual 
Temporary Revisions, and are concerned that once these changes are 
incorporated permanently into the manuals, a noncompliance issue will 
arise. The FAA does not agree. References to Temporary Manual

[[Page 45430]]

Revisions are included in the final rule primarily to allow credit for 
tests conducted previously in accordance with the instructions included 
in those documents. Since the issuance of the NPRM, those Temporary 
Manual Revisions have been incorporated into the Engine Manual, and 
this final rule includes the Engine Manual references as well. Copies 
of the Temporary Manual Revisions should always be available, however, 
through the manufacturer as stated in the AD under ADDRESSES.

Request To Change the Definition of a Shop Visit

    One commenter was concerned that the text omitting the Cold-Engine 
Fuel Spike test requirement in certain cases was too restrictive, and 
that the phrase ``The shop visit was only for replacement of a line 
replaceable unit, with no other work done'' should be expanded to 
include a broader population. The FAA agrees. Paragraph (g)(3) of the 
proposed rule, which appears as paragraph (g)(4) in this final rule, 
has been changed to reference engines that have not had a major flange 
separation.

Request To Include an Engine With an Overhauled HPC as a 
Replacement for an Engine That Has Failed Stability Testing

    Two commenters request that paragraph (d) be modified to include 
engines which have received HPC overhaul as acceptable replacements for 
an engine which has failed a stability assessment test. The FAA agrees. 
The final rule includes a definition of a serviceable engine in 
paragraph (j) to define more clearly return to service requirements and 
the text in paragraphs (a) and (d) has been modified.

Request To Eliminate the Cyclic Limits and Use Only Calendar Dates

    One commenter requests that the final rule be modified to reference 
only calendar end dates, and to omit the cyclic accumulation caps. The 
FAA disagrees. The wearout of the compressor is tied directly to cyclic 
usage and not dates on the calendar. In addition, use of calendar dates 
only to determine initial and repetitive inspection thresholds may 
allow high-usage engines to accumulate excessive wear before being 
evaluated. The FAA will maintain the cyclic limits to ensure that 
engines do not accumulate excessive wear prior to a stability 
assessment.

Request To Eliminate the Calendar End Dates and Use Only the Cyclic 
Limits

    One commenter requests that the final rule be modified to reference 
only the cyclic limits, and to omit the calendar end dates. The FAA 
disagrees. Omission of the calendar end date would allow low usage 
engines to remain in service for an extended period without being 
evaluated. Based on the risk analysis, the FAA has determined that 
calendar end dates are necessary to ensure that all engines are 
evaluated for reduced stability margin by the specified dates, and to 
hasten compliance of low usage engines.

Request To Include Statement About Engines That Are Not Installed 
on Airplanes

    One commenter notes that the AD applies to engines that are both on 
and off the airplane, so the applicability statement should be changed 
to specify ``engines installed on, or intended to be installed on.'' 
The FAA does not agree. The accomplishment instructions of the AD 
address engines in the shop and detail actions that must be taken 
``prior to return to service.'' The phrase ``installed on but not 
limited to'' that appears in the applicability statement of AD's that 
apply to aircraft engines is intended only to provide some information 
as to the types of aircraft on which operators might find the affected 
engines. The phrase does not affect the applicability of the AD and 
does not limit the AD to only those engines installed on the listed 
airplanes. Therefore, it is unnecessary to add the requested phrase to 
the applicability statement.

Concern About the Financial Impact of This AD Upon the Worldwide 
Fleet

    One commenter notes that financial impact quadruples if the 
worldwide fleet, and not just the domestic fleet, is considered. The 
commenter also notes that due to the large number of affected engines, 
and a large time requirement to incorporate corrective action, the 
potential exists for an adverse effect on the airline industry. The FAA 
agrees in part, and has considered the affects on the worldwide fleet 
in determining the necessary required actions to maintain an acceptable 
level of safety. The economic analysis required by Executive Order, 
however, considers only the affects on domestic operators.

Changes to the Economic Analysis

    One commenter questioned the fleet size used for the financial 
impact analysis, and provided a different fleet size for use in the 
calculations. The FAA agrees, and has modified the economic analysis to 
reflect the fleet size provided.

Request for Incorporation of HPC Cutback Stators and HPC Overhaul 
as Terminating Action for This AD

    One commenter requests that the FAA reference incorporation of the 
HPC Cutback Stators and HPC overhaul as terminating action to the 
repetitive testing requirements of this AD. The FAA disagrees. At this 
time, the Cutback HPC Stator configuration has not been certified, and 
therefore cannot be referenced as terminating action. The FAA will 
continue to monitor the fleet-wide trend analysis as inspection results 
are reported and will incorporate terminating action into this AD by 
further rulemaking once that terminating action becomes available.

Question About the Timeliness of This AD

    One commenter notes that this problem has existed since 1992, when 
the first surge event occurred, and that the rate has been steadily 
decreasing to a much lower rate today. The commenter feels that the FAA 
should have issued this kind of AD years ago when the rate was much 
higher. The FAA does not agree. While the FAA does not dispute that 
single engine surge rates may have been higher in the past, until 
recently, surge events were considered independent events, and the 
primary concern was with the dual-engine surge possibility. Because 
statistically, the probability of a dual-engine occurrence for the same 
cause as two single independent events is the square of the single 
engine probability, the probability of a dual-engine occurrence was 
calculated as being extremely remote. However, recent events have 
highlighted the need to re-examine that calculation and it underlying 
assumptions. The FAA now believes that unidentified common causes exist 
that can push reduced surge margin engines into a surge. If multiple 
reduced-surge margin engines are operating on an airplane when these 
yet unidentified influences exist, a multiple engine event is a 
stronger possibility. The FAA views single-engine events as a leading 
contributing factor in accidents when combined with other complicating 
factors such as crew response, other failures, etc. The FAA has 
focussed more strongly on defects that affect the critical phases of 
flight where crew workload is high and which have a high rate of 
occurrence. For this reason, and due to an event which occurred last 
year involving a single engine PW4000 surge and crew response, the FAA 
issued AD 98-23-08

[[Page 45431]]

to address that issue, and is now issuing this AD to address the 
overall single-engine surge rate, as well as the dual-engine event 
concern.

Concern About the Reliability of the E1E Test

    One commenter expresses concern regarding the implementation of the 
E1E test, believing it to be an unreliable tool in determining whether 
or not an engine is prone to a Group 3 surge. The FAA does not agree. 
The E1E test, the Cool Bodie test, and the Cold-Engine Fuel Spike tests 
have statistically proven themselves strong indicators of the 
likelihood of an engine to surge in subsequent service. While 
individual engines may provide different test results, the PW4000 fleet 
as a whole shows a strong correlation between these evaluations and the 
likelihood of a subsequent Group 3 surge event.

Request To Allow a Retest After Water Washing an Engine That Failed 
the Initial Tests

    One commenter requests that engines which fail an E1E test be 
allowed a second test opportunity after a water wash is performed. The 
FAA does not agree. The database upon which the correlations were based 
comes from a sampling of status engines in the fleet. Those engines 
were not typically water washed prior to accomplishing the test. It is 
unknown whether allowing such a retest would invalidate the assumptions 
upon which the management plan was based. It is also unknown how long 
any benefit derived from the water-washing might be expected to last 
before returning to the prior unwashed level.

Editorial Changes for Clarity

    One commenter requests that the word ``untested'' be replaced with 
``not previously tested'' in the Final Rule. The FAA agrees. The word 
``untested'' has been changed to ``has not been previously tested'' in 
paragraph (a) of this AD.

Administrative Changes and Corrections

    Several minor format, typographical and administrative corrections 
were incorporated as appropriate.
    After careful review of the available data, including the comments 
noted above, the FAA has determined that air safety and the public 
interest require the adoption of the rule with the changes described 
previously. The FAA has determined that these changes will neither 
increase the economic burden on any operator nor increase the scope of 
the AD.
    There are approximately 1,975 engines of the affected design in the 
worldwide fleet. The FAA estimates that 495 engines installed on 
airplane of U.S. registry would be affected by this proposed AD. The 
FAA also estimates that, on average, approximately 190 on-wing tests, 
74 test cell stability tests, 16 engine removals, and 22 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 $10,148,000.
    The regulations adopted herein will 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 final 
rule does not have sufficient federalism implications to warrant the 
preparation of a Federalism Assessment.
    For the reasons discussed above, I certify that this action (1) is 
not a ``significant regulatory action'' under Executive Order 12866; 
(2) is not a ``significant rule'' under DOT Regulatory Policies and 
Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action 
and it is contained in the Rules Docket. A copy of it may be obtained 
from the Rules Docket at the location provided under the caption 
ADDRESSES.

List of Subjects in 14 CFR Part 39

    Air transportation, Aircraft, Aviation safety, Incorporation by 
reference, Safety.

Adoption of the Amendment

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the Federal Aviation Administration amends 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:

99-17-16  Pratt & Whitney: Amendment 39-11263. Docket 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 engine that has not been previously tested and has exceeded the 
initial threshold specified in Table 1 of this AD, within 1,000 HPC 
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 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 Instruction 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 not had a separation of a major engine flange, 
with the exception of the ``A'' flange or the ``T'' flange, since 
new. PW4056, PW4156, and PW4156A original manufacture engines that 
have a (-3) suffix after the data plate engine model

[[Page 45432]]

designation, denoting the ``Phase 3'' configuration, are allowed to 
use the PW4056, PW4156, and PW4156A first run, full up engine 
initial threshold in Table 1 if, since new, they have not had a 
separation of a major engine flange, with the exception of the ``A'' 
flange or ``T'' flange.
    (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.
    (3) When a thrust rating change has been made in accordance with 
the manufacturer's instructions utilizing the Electronic Engine 
Control (EEC) programming plug in the affected HPC overhaul period, 
the initial threshold associated with the highest thrust rating must 
be utilized.

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


                  Table 2.--On-Wing Acceptance Criteria
------------------------------------------------------------------------
          Test type                Test result           Disposition
------------------------------------------------------------------------
Cool Bodie..................  Pass................  Continue in service.
In accordance with SI 7F-96,  Failure.............  Remove from service
 dated January 10, 1996.                             or conduct E1E. If
                                                     <0.020 continue in
                                                     service. If E1E is
                                                     0.020
                                                     remove from
                                                     service, prior to
                                                     further flight.
E1E.........................  <0.020..............  Continue in Service.
In accordance with SI 49F-    0.020 but  Conduct Cool Bodie,
 96, dated August 9, 1996.     0.032.     if pass continue in
                                                     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 PW4000 
Engine Manual (EM) Temporary Revisions (TR's) 71-0016, 71-0025, and 
71-0030, all dated March 15, 1999, or PW4000 EM 50A443, 50A822, or 
50A605, Section 71-00-00, Testing-20, pages 1301-1316, dated June 
15, 1999, or PW SI 32F-99, dated April 13, 1999. Cold-Engine fuel 
spike testing using a surge margin analysis control (SMAC) full 
authority digital electronic control (FADEC) P/N 50D341-SKX13041, P/
N 50D341-SKX02, or P/N 53D063-SK07, and performed in conjunction 
with PW Cactus Wire C042 G 930902 ZRH, dated September 02, 1993,will 
also be acceptable for meeting the testing requirements of this AD. 
Engines must pass this test cell stability test to 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.
    (e) Conduct stability tests on the remaining engines on each 
airplane that exceed the initial threshold defined in Table 1 of 
this AD 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) or (b) of this AD.
    (f) Engines that have not reached the initial threshold 
specified in Table 1 of this AD 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 that has 
exceeded its initial threshold 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; PW EM 50A605 Section 71-00-00, Testing-20, PW EM 
50A443 Section 71-00-00, Testing-20, and PW EM 50A822, Section 71-
00-00, Testing 20, all dated June 15, 1999; or PW SI 32F-99, dated 
April 13, 1999; or PW Cactus Wire C042 G 930902 ZRH, dated September 
02, 1993 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 was overhauled, or replaced with an overhauled HPC, 
or
    (2) The HPC was replaced with an HPC that is new from production 
with no time in service, or
    (3) Less than 800 CIS have passed since the last accomplishment 
of Testing-20, unless a major engine flange, except the ``A'' flange 
or the ``T'' flange, was separated during the shop visit, or
    (4) The shop visit was only for replacement of a line 
replaceable unit, with no other work done, unless a major engine 
flange, except the ``A'' flange or the ``T'' 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 requests 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) Special flight permits may be issued in accordance with 
Sec. Sec. 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, provided that in 
the case where an aircraft has an engine that has failed a stability 
assessment the following conditions are made part of the special 
flight permit:
    (1) The engine must be operated for at least 20 minutes at 
Ground Idle prior to initiating the takeoff, or for 5 minutes at 1.2 
Engine Pressure Ratio (EPR);
    (2) If applicable, the Environmental Control System (ECS) bleed 
must be shut off prior to setting takeoff power, and left off until 
5 minutes after power set;
    (3) The affected engine must be operated at the appropriate 
minimum approved derated thrust for safe takeoff and climb in order 
to minimize the risk of a takeoff surge; and
    (4) Only one engine per airplane may have failed a stability 
assessment to perform this flight.
    (j) For the purposes of this AD, the following definitions 
apply:

[[Page 45433]]

    (1) An HPC overhaul is defined as whenever the HPC stage 12 
through 15 blade tip clearances are restored to the clearances 
specified in the applicable fits and clearances section of the 
engine manual during the shop visit.
    (2) A serviceable engine is defined as an engine that either:
    (i) Has not exceeded the initial threshold specified in Table 1 
of this AD, or
    (ii) Has passed a stability test performed in accordance with 
paragraphs (a)(1)(i) or (a)(1)(ii) or (b) or (g) of this AD within 
the last 800 CIS.
    (k) Report the results of the stability assessment tests to the 
Manager, Engine Certification Office, 12 New England Executive Park, 
Burlington, MA 01803-5299, or by electronic mail to 
``Robert.G[email protected].'' Data to be reported includes:
    (1) Engine serial number;
    (2) Type and date of the test;
    (3) Results of the test (include E1E value if applicable);
    (4) Position of engine on the airplane;
    (5) Disposition of the engine after the test; and
    (6) Time and cycles since compressor overhaul, total time on 
engine, and total cycles at the time of the test.
    Results are due to the FAA New England Office within 60 days of 
test date, or for previously accomplished tests for which 
retroactive credit is taken, within 60 days of the effective date of 
this AD.
    Reporting requirements have been approved by the Office of 
Management and Budget (OMB) and assigned OMB control number 2120-
0056.
    (l) The stability assessment tests shall be done in accordance 
with the following Pratt & Whitney service documentation:

----------------------------------------------------------------------------------------------------------------
        Document No.                     Pages                     Revision                      Date
----------------------------------------------------------------------------------------------------------------
SI 7F-96....................  All.......................  Original..................  January 10, 1996.
SI 32F-99...................  All.......................  Original..................  April 13, 1999.
SI 49F-96...................  All.......................  Original..................  August 9, 1996.
TR 71-0016..................  All.......................  Original..................  March 15, 1999.
TR 71-0025..................  All.......................  Original..................  March 15, 1999.
TR 71-0030..................  All.......................  Original..................  March 15, 1999.
EM 50A443, Section 71-00-00.  All.......................  Original..................  June 15, 1999.
EM 50A605, Section 71-00-00.  All.......................  Original..................  June 15, 1999.
EM 50A822, Section 71-00-00.  All.......................  Original..................  June 15, 1999.
PW Cactus Wire: C042 G        All.......................  Original..................  September 2, 1993.
 930902 ZRH.
Total pages: 108
----------------------------------------------------------------------------------------------------------------

This incorporation by reference was approved by the Director of the 
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 
51. Copies may be obtained from Pratt & Whitney, 400 Main St., East 
Hartford, CT 06108; telephone (860) 565-8770, fax (860) 565-4503. 
Copies may be inspected at the FAA, New England Region, Office of 
the Regional Counsel, 12 New England Executive Park, Burlington, MA; 
or at the Office of the Federal Register, 800 North Capitol Street, 
NW, suite 700, Washington, DC.
    (m) This amendment becomes effective on September 24, 1999.

    Issued in Burlington, Massachusetts, on August 12, 1999.
Kirk E. Gustafson,
Acting Manager, Engine and Propeller Directorate, Aircraft 
Certification Service.
[FR Doc. 99-21450 Filed 8-19-99; 8:45 am]
BILLING CODE 4910-13-U