Airworthiness Directives; Pratt & Whitney JT8D Series Turbofan Engines

SUMMARY: This document proposes the supersedure of an existing

airworthiness directive (AD), applicable to certain Pratt & Whitney

(PW) JT8D series turbofan engines, that currently requires initial and

repetitive inspections of certain front compressor fan hubs and

shotpeening of the forward and aft rim to web radius. This action would

reduce the initial inspection interval for front compressor fan hubs

installed in all positions of all applicable aircraft, establish a

compliance end-date, and clarify the wording of the compliance

requirements. This proposal is prompted by a report of a front

compressor fan hub fracture installed in a Boeing 737 aircraft that

resulted in the release of fan blades and portions of the hub outer

rim. The actions specified by the proposed AD are intended to prevent

fracture of the front compressor fan hub, which can result in an

uncontained engine failure and damage to the aircraft.

DATES: Comments must be received by January 20, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), New England Region, Office of the Assistant Chief

Counsel, Attention: Rules Docket No. 94-ANE-21, 12 New England

Executive Park, Burlington, MA 01803-5299. 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, Technical Publications Department, M/S

132-30, 400 Main Street, East Hartford, CT 06108. This information may

be examined at the FAA, New England Region, Office of the Assistant

Chief Counsel, 12 New England Executive Park, Burlington, MA.

FOR FURTHER INFORMATION CONTACT: Mark A. Rumizen, Aerospace Engineer,

Engine Certification Office, FAA, Engine and Propeller Directorate, 12

New England Executive Park, Burlington, MA 01803-5299; telephone (617)

238-7137, fax (617) 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 94-ANE-21.'' 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 Assistant Chief Counsel,

Attention: Rules Docket No. 94-ANE-21, 12 New England Executive Park,

Burlington, MA 01803-5299.

Discussion

On July 15, 1993, the Federal Aviation Administration (FAA) issued

Airworthiness Directive (AD) 93-14-14, Amendment 39-8638 (58 FR 39644,

July 26, 1993), applicable to Pratt & Whitney (PW) JT8D series turbofan

engines, to require initial and repetitive inspections for cracks, and

removal from service, if necessary, of certain front compressor fan

hubs. Front compressor fan hubs installed on engines in the No. 2

position on Boeing 727 aircraft must be inspected according to a more

aggressive schedule than other installations. In addition, that AD

requires shotpeening of the forward and aft rim to web radius area of

hubs that pass the inspections. That action was prompted by reports of

two front compressor fan hub fractures on engines operating in the No.

2 position on Boeing 727 aircraft. That condition, if not corrected,

could result in a fracture of the front compressor fan hub, which can

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

Since the issuance of that AD, the FAA has received a report of a

front compressor fan hub fracture on a PW JT8D engine installed on a

Boeing 737 aircraft. The examination of the failed hardware revealed

the failure mechanism to be identical to that described in AD 93-14-14.

The analysis conducted for that AD concluded that the vibratory stress

environment that caused fan hub fractures was the most severe for

engines installed in the No. 2 position on Boeing 727 aircraft.

Therefore, the FAA addressed this population in a more aggressive

manner than engines installed in other aircraft, or in the No. 1 or No.

3 position on Boeing 727 aircraft. The FAA determined that a similar,

but less severe stress environment existed in engines installed in

other aircraft or positions other than the No. 2 position in the Boeing

727 aircraft, and inspection and shotpeening requirements were

specified for these engines in AD 93-14-14. Since the failure of the

fan hub installed in the Boeing 737 aircraft, the FAA has reassessed

the risk analysis for all installations and determined that the

predicted risk level should be reduced. Therefore, the FAA proposes to

supersede AD 93-14-14 with a reduced initial fan hub inspection

requirement for engines installed in all positions of all applicable

aircraft, by requiring engines removed from the Boeing 727 aircraft No.

2 position to adhere to the Boeing 727 aircraft No. 2 position

inspection requirements, and by establishing a compliance end-date.

The FAA has received comments from operators that the wording of

paragraph (b)(4) of AD 93-14-14 is confusing. The FAA has revised the

wording to emphasize that the repetitive inspection is required at the

next opportunity when the front compressor fan hub is accessible at the

detail level in the shop only after accumulating 2,500 additional

cycles in service (CIS) since the last inspection.

In addition, the FAA has revised the wording in paragraph (d) that

defines a shop visit as an engine removal for engine maintenance that

cannot be performed while installed in the aircraft.

Since publication of AD 93-14-14, PW has issued Alert Service

Bulletin (ASB) No. 6104, Revision 3, dated June 16, 1994, that

describes the reduced initial inspection intervals for the applicable

engine installations.

Since an unsafe condition has been identified that is likely to

exist or develop on other products of this same type design, the

proposed AD would supersede AD 93-14-14 to reduce the initial

inspection interval for front compressor fan hubs installed in all

positions of all applicable aircraft, revise the compliance

requirements for repositioned engines, establish a compliance end-date,

and clarify the wording of the compliance requirements.

The FAA estimates that 1475 engines installed on aircraft of U.S.

registry and 690 domestic uninstalled engines would be affected by this

proposed AD, that it would take approximately 12 work hours per engine

to accomplish the proposed actions, and that the average labor rate is

$55 per work hour. Based on these figures, the total cost impact of the

proposed AD on U.S. operators is estimated to be $1,428,900.

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. App. 1354(a), 1421 and 1423; 49 U.S.C.

106(g); and 14 CFR 11.89.

Sec. 39.13 [Amended]

2. Section 39.13 is amended by removing amendment 39-8638 (58 FR

39644, July 26, 1993) and by adding a new airworthiness directive to

read as follows:

Pratt & Whitney: Docket No. 94-ANE-21. Supersedes AD 93-14-14,

Amendment 39-8638.

Applicability: Pratt & Whitney (PW) Model JT8D-9, -9A, -11, -15,

-15A, -17, -17A, -17R, and -17AR turbofan engines containing front

compressor fan hub Part Number (P/N) 817401 with the following

serial numbers: J78892 through J80538, K32019 through K34018, L32197

through L34133, or M05722 through M07296; and all serial numbers of

fan hubs P/N 594301, 640601, 743301, 749801, 750101, 791801, and

806001. These engines are installed on but not limited to Boeing 727

and 737 series, and McDonnell Douglas DC-9 series aircraft.

Compliance: Required as indicated, unless accomplished

previously.

To prevent fracture of the front compressor fan hub, which can

result in an uncontained engine failure and damage to the aircraft,

accomplish the following:

(a) For front compressor fan hubs installed in engines in the

No. 2 position on Boeing 727 aircraft on or after the effective date

of this airworthiness directive (AD), inspect and shotpeen the front

compressor fan hub in accordance with Appendix A, Appendix B, and

Attachment 1 (NDIP-764) of PW Alert Service Bulletin (ASB) No. 6104,

Revision 3, dated June 16, 1994, as follows:

(1) Initially inspect the front compressor fan hub as follows:

----------------------------------------------------------------------------------------------------------------

Total Part Cycles (TPC) on the

effective date of this AD Initial inspection interval

----------------------------------------------------------------------------------------------------------------

Over 18,001 TPC.................. Inspect at the next shop visit, or within 300 cycles in service (CIS) after

the effective date of this AD, whichever occurs first.

16,501 to 18,000 TPC............. Inspect at the next shop visit, or within 500 CIS after the effective date of

this AD, whichever occurs first.

15,001 to 16,500 TPC............. Inspect at the next shop visit, or within 750 CIS after the effective date of

this AD, whichever occurs first.

13,501 to 15,000 TPC............. Inspect at the next shop visit, or within 1,000 CIS after the effective date

of this AD, whichever occurs first.

10,501 to 13,500 TPC............. Inspect at the next shop visit, or within 1,500 CIS after the effective date

of this AD, whichever occurs first.

Less than 10,501 TPC............. Inspect at the next shop visit but not to exceed 12,000 TPC, or by the

compliance end-date, whichever occurs first.

----------------------------------------------------------------------------------------------------------------

(2) Engines removed from the No. 2 position on Boeing 727

aircraft and reinstalled in aircraft or positions other than the No.

2 position on Boeing 727 aircraft after the effective date of this

AD must adhere to the initial inspection interval specified in

paragraph (a)(1) of this AD. Inspect and shotpeen front compressor

fan hubs on these repositioned engines in accordance with paragraph

(a)(1) of this AD.

(3) Remove front compressor fan hubs from service if cracks are

found during the inspection process and replace with a serviceable

hub.

(4) Shotpeen the front compressor fan hubs that pass the

inspections required by paragraph (a)(1) of this AD, in accordance

with Appendix B of PW ASB No. 6104, Revision 3, dated June 16, 1994,

prior to returning the hub to service.

(5) Thereafter, inspect, shotpeen, and remove from service, if

necessary, front compressor fan hubs that are reinstalled in the No.

2 position of Boeing 727 aircraft, in accordance with Appendix A,

Appendix B, and Attachment 1 (NDIP-764), as applicable, of PW ASB

No. 6104, Revision 3, dated June 16, 1994, as follows:

(i) For hubs that were last inspected and shotpeened with

greater than 12,000 TPC upon inspection, inspect and shotpeen at the

first shop visit after 2,500 CIS since last inspection, but prior to

the accumulation of 8,000 CIS since last inspection.

(ii) For hubs that were last inspected and shotpeened with less

than or equal to 12,000 TPC upon inspection, inspect and shotpeen at

the first shop visit after 2,500 CIS since last inspection, or prior

to accumulating 12,000 TPC, whichever occurs later, but not to

exceed 8,000 CIS since last inspection.

(6) Engines removed from the No. 2 position on Boeing 727

aircraft and reinstalled in aircraft or positions other than the No.

2 position on Boeing 727 aircraft prior to reaching the repetitive

inspection interval specified in paragraph (a)(5) of this AD must be

inspected as follows:

(i) For the next inspection, inspect in accordance with

paragraph (a)(5) of this AD; and

(ii) Thereafter, inspect and shotpeen in accordance with

paragraph (b)(4) of this AD.

(b) For front compressor fan hubs installed in engines that are

installed in aircraft or positions other than the No. 2 position on

Boeing 727 aircraft on the effective date of this AD, inspect and

shotpeen the front compressor fan hubs in accordance with Appendix

A, Appendix B, and Attachment 1 (NDIP-764) of PW ASB No. 6104,

Revision 3, dated June 16, 1994, as follows:

(1) Initially inspect the front compressor fan hub at the next

shop visit after the effective date of this AD, but not later than

the compliance end-date.

(2) Remove front compressor fan hubs from service if cracks are

found during the inspection process and replace with a serviceable

hub.

(3) Shotpeen the front compressor fan hubs that pass the

inspection requirements specified in paragraph (b)(1) of this AD, in

accordance with Appendix B of PW ASB No. 6104, Revision 3, dated

June 16, 1994, prior to returning the hub to service.

(4) Thereafter, upon accumulating 2,500 addition CIS since the

last inspection, inspect, shotpeen, and remove from service, if

necessary, front compressor fan hubs that are not reinstalled in the

No. 2 position on Boeing 727 aircraft, in accordance with Appendix

A, Appendix B, and Attachment 1 (NDIP-764) of PW ASB No. 6104,

Revision 3, dated June 16, 1994, when the front compressor fan hub

is accessible at the detail level in the shop.

(5) Thereafter, inspect, shotpeen, and remove from service, if

necessary, front compressor fan hubs that are reinstalled in the No.

2 position of Boeing 727 aircraft after the effective date of this

AD in accordance with paragraph (a)(5) of this AD.

(c) Inspect and shotpeen front compressor fan hubs that were

inspected and shotpeened in accordance with Appendix A, Appendix B,

and Attachment 1 (NDIP-764) of PW ASB No. 6104, dated December 21,

1992, PW ASB No. 6104, Revision 1, dated May 21, 1993, or PW ASB No.

6104, Revision 2, dated June 18, 1993, prior to the effective date

of this AD in accordance with paragraphs (a)(5) or (b)(4) of this

AD, as applicable.

(d) For the purpose of this AD, the compliance end-date

referenced in paragraphs (a)(1) and (b)(1) of this AD is defined as

December 31, 1999, or 6,000 TPC after the effective date of this AD,

whichever occurs later.

(e) For the purpose of this AD, a shop visit is defined as an

engine removal for engine maintenance that cannot be performed while

installed in the aircraft, and that entails separation of pairs of

mating (lettered) engine flanges or the removal of a compressor

disk, hub, or spool, or removal of a turbine disk.

(f) For the purpose of this AD, accessibility of a front

compressor fan hub at the detail level in the shop is defined as

engine maintenance that entails separation of the front compressor

fan hub from the front compressor and removal of the fan blades.

(g) Report the front compressor fan hub part number, total time,

and total cycles in service for each hub that passes the inspections

defined in this AD, within 60 days after the inspection, to the

Manager, Engine Certification Office, Engine and Propeller

Directorate, Aircraft Certification Service, FAA, 12 New England

Executive Park, Burlington, Massachusetts, 01803-5299; fax (617)

238-7199. For any hub that is found cracked, submit the information

requested in paragraph B of Part 4, of the Accomplishment

Instructions of PW ASB No. 6104, Revision 3, dated June 16, 1994,

within 60 days after the inspection to the Manager, Engine

Certification Office, at the address identified above. The reporting

requirements of this AD terminate one year after the effective date

of this AD. Information collection requirements contained in this

regulation have been approved by the Office of Management and Budget

(OMB) under the provision of the Paperwork Reduction Act of 1980 (44

U.S.C. 3501-3520) and have been assigned OMB Control Number 2120-

0056.

(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. The

request should be forwarded through an appropriate FAA Principal

Maintenance Inspector, who may add comments and then send it to the

Manager, Engine Certification Office.

Note: 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

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 November 14, 1994.

James C. Jones,

Acting Manager, Engine and Propeller Directorate, Aircraft

Certification Service.

[FR Doc. 94-28634 Filed 11-18-94; 8:45 am]

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