Airworthiness Directives; Pratt & Whitney PW4000 Series Turbofan Engines

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 98-ANE-66-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 proposal would require revisions to the Time Limits

Section (TLS) of the manufacturer's Engine Manuals (EMs) for Pratt &

Whitney (PW) PW4000 series turbofan engines to include required

enhanced inspection of selected critical life-limited parts at each

piece-part exposure. This proposal would also require an air carrier's

approved continuous airworthiness maintenance program to incorporate

these inspection procedures. Air carriers with an approved continuous

airworthiness maintenance program would be allowed to either maintain

the records showing the current status of the inspections using the

record keeping system specified in the air carrier's maintenance

manual, or establish an acceptable alternate method of record keeping.

This proposal is prompted by an FAA study of in-service events

involving uncontained failures of critical rotating engine parts which

indicated the need for improved inspections. The improved inspections

are needed to identify those critical rotating parts with conditions,

that if allowed to continue in service, could result in uncontained

failures. The actions specified by this proposed AD are intended to

prevent critical life-limited rotating engine part failure, which could

result in an uncontained engine failure and damage to the airplane.

DATES: Comments must be received by February 3, 1999.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), New England Region, Office of the Regional

Counsel, Attention: Rules Docket No. 98-ANE-66-AD, 12 New England

Executive Park,

[[Page 59744]]

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 8:00 a.m. and

4:30 p.m., Monday through Friday, except Federal holidays.

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 98-ANE-66-AD.'' The postcard will be date stamped and

returned to the commenter.

Availability of NPRMs

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. 98-ANE-66-AD, 12 New England Executive

Park, Burlington, MA 01803-5299.

Discussion

A recent FAA study analyzing 15 years of accident data for

transport category airplanes identified several failure mode root

causes that can result in serious safety hazards to transport category

airplanes. This study identified uncontained failure of critical life-

limited rotating engine parts as the leading engine-related safety

hazard to airplanes. Uncontained engine failures have resulted from

undetected cracks in rotating parts that initiated and propagated to

failure. Cracks can originate from causes such as unintended excessive

stress from the original design, or they may initiate from stresses

induced from material flaws, handling damage, or damage from machining

operations. The failure of rotating parts can present a significant

safety hazard to the airplanes by release of high energy fragments that

could injure passengers or crew by penetration of the cabin, damage

flight control surfaces, sever flammable fluid lines, or otherwise

compromise the airworthiness of the airplane.

Accordingly, the FAA has developed an intervention strategy to

significantly reduce uncontained engine failures. This intervention

strategy was developed after consultation with industry and will be

used as a model for future initiatives. This intervention strategy is

to conduct enhanced, nondestructive inspections of fan disks which

could most likely result in a safety hazard to the airplane in the

event of a disk fracture. The need for additional rule making is also

being considered by the FAA. Future ADs may be issued introducing

additional intervention strategies to further reduce or eliminate

uncontained engine failures.

Properly focused enhanced inspections require identification of the

parts whose failure presents the highest safety hazard to the airplane,

identifying the most critical features to inspect on these parts, and

utilizing inspection procedures and techniques that improve crack

detection. The FAA, with close cooperation of the engine manufacturers,

has completed a detailed analysis that identifies the most safety

significant parts and features, and the most appropriate inspection

methods.

Critical life-limited high energy rotating parts are currently

subject to some form of recommended crack inspection when exposed

during engine maintenance or disassembly. As a result of this AD, the

inspections currently recommended by the manufacturer will become

mandatory for those parts listed in the compliance section.

Furthermore, the FAA intends that additional mandatory enhanced

inspections resulting from this AD serve as an adjunct to the existing

inspections. The FAA has determined that the enhanced inspections will

significantly improve the probability of crack detection while the

parts are disassembled during maintenance. All mandatory inspections

must be conducted in accordance with detailed inspection procedures

prescribed in the manufacturer's Engine Cleaning, Inspection, and

Repair (CIR) manuals.

Additionally, this AD allows for air carriers operating under the

provisions of 14 CFR part 121 with an FAA-approved continuous

airworthiness maintenance program, and entities with whom those air

carriers make arrangements to perform this maintenance, to verify

performance of the enhanced inspections by retaining the maintenance

records that include the inspections resulting from this AD, provided

that the records include the date and signature of the person

performing the maintenance action. These records must be retained with

the maintenance records of the part, engine module, or engine until the

task is repeated. This will establish a method of record preservation

and retrieval typical to those in existing continuous airworthiness

maintenance programs. Instructions must be included in an air carrier's

maintenance manual providing procedures on how this record preservation

and retrieval system will be implemented and integrated into the air

carrier's record keeping system.

For engines or engine modules that are approved for return to

service by an authorized FAA-certificated entity and that are acquired

by an operator after the effective date of this AD, the mandatory

enhanced inspections need not be accomplished until the next piece-part

opportunity. For example, there is no need for an operator to

disassemble to piece-part level an engine or module returned to service

by an FAA-certificated facility simply because that engine or module

was previously operated by an entity not required to comply with this

AD. Furthermore, the FAA intends for operators to perform the enhanced

inspections of these parts at the next piece-part opportunity following

the initial acquisition, installation, and removal of the part

following the effective date of this AD. For piece parts that have not

been approved for return to service prior to the effective date of this

AD, the FAA does intend that the mandatory enhanced inspections

required by this AD be performed before such parts are approved for

return to service. Piece parts that have been approved for return to

service prior to the effective date of this AD may be installed;

however,

[[Page 59745]]

enhanced inspection will be required at the next piece-part

opportunity.

This proposal would require, within the next 30 days after the

effective date of this AD, revisions to the Time Limits Section (TLS)

of the Engine Manuals for PW4000 series turbofan engines, and, for air

carriers, the approved continuous airworthiness maintenance program.

Pratt & Whitney, the manufacturer of PW4000 series turbofan engines,

used on 14 CFR part 25 airplanes has provided the FAA with a detailed

proposal that identifies and prioritizes the critical life-limited

rotating engine parts with the highest potential to hazard the airplane

in the event of failure, along with instructions for enhanced, focused

inspection methods. The enhanced inspections resulting from this AD

will be conducted at piece-part opportunity, as defined below in the

compliance section, rather than specific time inspection intervals.

There are approximately 1,900 engines of the affected design in the

worldwide fleet. The FAA estimates that 450 engines installed on

airplanes of U.S. registry would be affected by this proposed AD, that

it would take approximately 8 work hours for the fan disk inspection.

The average labor rate is $60 per work hour. Based on these figures,

and using recent shop visit rate data, the total cost impact of the

proposed AD on U.S. operators is estimated to be $70,000 per year.

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 98-ANE-66-AD.

Applicability: Pratt & Whitney PW4050, PW4052, PW4056, PW4060,

PW4060A, PW4062, PW4060C, PW4152, PW4156, PW4156A, PW4158, PW4160,

PW4460, PW4462, PW4164, PW4168, PW4074, PW4074D, PW4077, PW4077D,

PW4084, PW4084D, and PW4090 series turbofan engines, installed on

but not limited to Airbus A300, A310, and A330 series, Boeing 747,

767, 777 series, 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 (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: Required as indicated, unless accomplished

previously.

To prevent critical life-limited rotating engine part failure,

which could result in an uncontained engine failure and damage to

the airplane, accomplish the following:

(a) Within the next 30 days after the effective date of this AD,

revise the manufacturer's Time Limits section of the manufacturer's

Engine Manual, Part Numbers (P/Ns) 50A605, 50A443, 51A342, 50A822,

51A751, and 51A345, as applicable, for Pratt & Whitney PW4050,

PW4052, PW4056, PW4060, PW4060A, PW4062, PW4060C, PW4152, PW4156,

PW4156A, PW4158, PW4160, PW4460, PW4462, PW4164, PW4168, PW4074,

PW4074D, PW4077, PW4077D, PW4084, PW4084D, and PW4090 series

turbofan engines, and for air carrier operations revise the approved

continuous airworthiness maintenance program, by adding the

following:

``MANDATORY INSPECTIONS

(1) Perform inspections of the following parts at each piece-part

opportunity in accordance with the instructions provided in the PW4000

series Engine Cleaning, Inspection, and Repair (CIR) Manuals:

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Manual CIR

Part nomen P/N section Inspection manual

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Hub, LPC Assembly.......................... 50B221 (50B201 Detail)........ 72-31-07 02 51A357

Hub, LPC Assembly.......................... 50B321 (50B301 Detail)........ 72-31-07 02 51A357

Hub, LPC Assembly.......................... 51B321 (51B301 Detail)........ 72-31-07 02 51A357

Hub, LPC Assembly.......................... 52B021 (52B001 Detail)........ 72-31-07 02 51A357

Hub, LPC Assembly.......................... 51B631 (50B601 Detail)........ 72-31-07 02 51A750

Hub, LPC Assembly.......................... 51B821 (51B801 Detail)........ 72-31-07 02 51A750

Hub, LPC Assembly.......................... 52B521 (52B501 Detail)........ 72-31-07 02 51A750

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(2) For the purposes of these mandatory inspections, piece-part

opportunity means:

(i) The part is considered completely disassembled when done in

accordance with the disassembly instructions in the engine

manufacturer's Engine Manual; and

(ii) The part has accumulated more than 100 cycles in service since

the last piece-part opportunity inspection, provided that the part was

not damaged or related to the cause for its removal from the engine.''

(b) Except as provided in paragraph (c) of this AD, and

notwithstanding contrary provisions in section 43.16 of the Federal

Aviation Regulations (14 CFR 43.16), these mandatory inspections

shall be performed only in accordance with the Time Limits

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section of the applicable PW4000 series Engine Manuals.

(c) 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 Engine Certification Office. Operators shall

submit their requests through an appropriate FAA Principal

Maintenance Inspector (PMI), who may add comments and then send it

to the Engine Certification Office.

Note 2: Information concerning the existence of approved

alternative methods of compliance with this airworthiness directive,

if any, may be obtained from the Engine Certification Office.

(d) Special flight permits may be issued in accordance with

sections 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.

(e) The records of the mandatory inspections required as a

result of revising the Time Limits section of the PW4000 series

Engine Manuals and the air carrier's continuous airworthiness

maintenance program as provided by paragraph (a) of this AD shall be

maintained by FAA-certificated air carriers which have an approved

continuous airworthiness maintenance program in accordance with the

record keeping system currently specified in their manual required

by sections 121.369 of the Federal Aviation Regulations (14 CFR

121.369); or, in lieu of the record showing the current status of

each mandatory inspection required by sections 121.380(a)(2)(vi) of

the Federal Aviation Regulations (14 CFR 121.380(a)(2)(vi)),

certificated air carriers may establish an approved alternate system

of record retention that provides a method for preservation and

retrieval of the maintenance records that include the inspections

resulting from this AD, and include the policy and procedures for

implementing this alternate method in the air carrier's maintenance

manual required by sections 121.369 (c) of the Federal Aviation

Regulations (14 CFR 121.369 (c)); however, the alternate system must

be accepted by the appropriate PMI and require the maintenance

records be maintained either indefinitely or until the work is

repeated.

Note 3: These record keeping requirements apply only to the

records used to document the mandatory inspections required as a

result of revising the Time Limits section of the PW4000 series

Engine Manuals as provided in paragraph (a) of this AD, and do not

alter or amend the record keeping requirements for any other AD or

regulatory requirement.

Issued in Burlington, Massachusetts, on October 30, 1998.

David A. Downey,

Assistant Manager, Engine and Propeller Directorate, Aircraft

Certification Service.

[FR Doc. 98-29603 Filed 11-4-98; 8:45 am]

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