Airworthiness Directives; Rolls-Royce, plc Spey Series Turbofan Engines

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 93-ANE-31]

Airworthiness Directives; Rolls-Royce, plc Spey 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 Rolls-Royce, plc (R-R) Spey series

turbofan engines. This document proposes to supersede Telegraphic AD

T89-02-52, which superseded Telegraphic AD T88-22-51. Telegraphic AD

T88-22-51 reduced cyclic life limits for seventh stage high pressure

compressor (HPC) disk from 40,000 total part cycles in service (TPC) to

35,000 TPC for the R-R Spey Model 506-14 and -14D engines. Telegraphic

AD T89-02-52 currently requires repetitive inspections or further

reduced cyclic life limits for seventh stage HPC disks. This proposal

would increase the AD's effectivity to include additional R-R Spey

engine models, eliminate the option for repetitive inspections, and

further reduce the cyclic life limits. This proposal is prompted by

further investigation into disk bore cracking that was caused by

corrosion. The actions specified by the proposed AD are intended to

prevent a seventh stage HPC disk burst due to cracking attributed to

corrosion, which may result in an uncontained engine failure.

DATES: Comments must be received by February 10, 1994.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

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

Counsel, Attention: Rules Docket No. 93-ANE-31, 12 New England

Executive Park, Burlington, MA 01803-5299. Comments may be inspected at

this location between 8 a.m. and 4:30 p.m., Monday through Friday,

except Federal holidays.

The service information referenced in this AD may be obtained from

the Service Manager, Spey engines, Rolls-Royce, plc, East Kilbride,

Glasgow G74 4PY, Scotland. 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: John Fisher, Aerospace Engineer,

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

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

238-7149, 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 93-ANE-31.'' 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. 93-ANE-31, 12 New England Executive Park,

Burlington, MA 01803-5299.

Discussion:

The Civil Aviation Authority (CAA), which is the airworthiness

authority of the United Kingdom, notified the Federal Aviation

Administration (FAA) that an unsafe condition may exist on Rolls-Royce,

plc (R-R) Spey series turbofan engines. The CAA advises that they have

received a report of a three-inch crack extending radially outward from

the bore on a seventh stage high pressure compressor (HPC) disk

installed in a R-R Spey Model 506-14D engine. The crack originated from

a corrosion pit that apparently had been present at the disk's entry

into service. Investigation indicated that failure of the engine due to

disk burst was imminent. That condition, if not corrected, could result

in a seventh stage HPC disk burst due to cracking attributed to

corrosion, which may result in an uncontained engine failure.

This engine model is manufactured in the United Kingdom and is type

certificated for operation in the United States under the provisions of

Sec. 21.29 of the Federal Aviation Regulations and the applicable

bilateral airworthiness agreement. Pursuant to this bilateral

airworthiness agreement, the CAA has kept the FAA informed of the

situation described above. The FAA has examined the findings of the

CAA, reviewed all available information, and determined that

airworthiness directive (AD) action is necessary for products of this

type design that are certificated for operation in the United States.

On October 20, 1988, the FAA issued Telegraphic AD T88-22-51, which

reduced cyclic life limits for seventh stage HPC disks from 40,000

total part cycles in service (TPC) to 35,000 TPC for the R-R Spey Model

506-14 and -14D engines. On January 26, 1989, the FAA issued

Telegraphic AD T89-02-52, which supersedes Telegraphic AD T88-22-51,

and currently requires repetitive inspections or further reduced cyclic

life limits for seventh stage HPC disks.

Since the issuance of these two previous AD's, further

investigation of the cracked disk revealed that the crack originated

from a corrosion pit that could have been present at the disk's entry

into service. A testing program investigated the effects of corrosion

on seventh stage HPC disks, and as a result of this investigation, disk

cyclic life has been reevaluated, assuming the possible presence of

corrosion at entry into service. To account for the possible presence

of corrosion, this proposed AD would further reduce the cyclic life

limit, and would require removing from service seventh stage HPC disks

that exceed the revised cyclic life limits following the schedule

established in this AD.

This revised limit reduces the cyclic life limit below the point

that intermediate, repetitive inspections are practical; therefore,

this AD does not provide for repetitive inspections. In addition, this

AD would increase the effectivity to include additional R-R Spey engine

models not affected by the previous Telegraphic AD's.

Rolls-Royce issued Mandatory Service Bulletin No. Sp72-1034,

Revision 1, dated May 4, 1990, that describes the revised cyclic life

limits for seventh stage HPC disks, and the additional R-R Spey engine

models affected. The CAA classified this service bulletin as mandatory

in order to assure the airworthiness of these R-R Spey series turbofan

engines in the United Kingdom.

Since an unsafe condition has been identified that is likely to

exist or develop on other R-R Spey series turbofan engines of this same

type design installed on aircraft registered in the United States, the

proposed AD would supersede Telegraphic AD T89-02-52 to increase the

AD's effectivity to include additional R-R Spey engine models,

eliminate the option for repetitive inspections of seventh stage HPC

disks, further reduce the cyclic life limits, and require removing from

service disks that exceed the revised cyclic life limits following the

schedule established in this AD. The actions are required to be

accomplished in accordance with the service bulletin described

previously.

The FAA estimates that 173 engines installed on aircraft of U.S.

registry would be affected by this proposed AD, and that it would not

take any additional work hours per engine to accomplish the proposed

actions. Replacement parts, prorated for the reduced life, would cost

approximately $1,718 per engine. Based on these figures, the total cost

impact of the proposed AD on U.S. operators is estimated to be

$297,214.

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 14

CFR part 39 of the Federal Aviation Regulations 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 adding the following new

airworthiness directive:

Rolls-Royce, plc: Docket No. 93-ANE-31

Applicability: Rolls-Royce, plc (R-R) Spey 506-14 series, 511-14

series, and 555-15 series turbofan engines installed on but not

limited to British Aerospace BAC 1-11 and Fokker F28 aircraft.

Compliance: Required as indicated, unless accomplished

previously.

To prevent a seventh stage high pressure compressor (HPC) disk

burst due to cracking attributed to corrosion, which may result in

an uncontained engine failure, accomplish the following:

(a) For seventh stage HPC disks that on the effective date of

this airworthiness directive (AD) exceed the revised cyclic life

limits described in R-R Service Bulletin (SB) Sp72-1034, Revision 1,

dated May 4, 1990, remove from service and replace with a

serviceable part within 60 days after the effective date of this AD.

(b) For seventh stage HPC disks that on the effective date of

this AD do not exceed the revised cyclic life limits described in R-

R SB Sp72-1034, Revision 1, dated May 4, 1990, remove from service

and replace with a serviceable part: either prior to exceeding the

revised cyclic life limits, or within 60 days after the effective

date of this AD, whichever occurs later.

(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 Manager, Engine Certification Office. The

request should be forwarded through an 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.

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

21.197 and 21.199 to operate the airplane to a location where the

requirements of this AD can be accomplished.

Issued in Burlington, Massachusetts, on December 29, 1993.

Jay J. Pardee,

Acting Manager, Engine and Propeller Directorate, Aircraft

Certification Service.

[FR Doc. 94-00587 Filed 01-10-94; 8:45 am]

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