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

DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 39

[Docket No. 93-ANE-43]

Airworthiness Directives; Rolls-Royce, plc Spey Series Turbofan

Engines

AGENCY: Federal Aviation Administration, DOT.

ACTION: Notice of proposed rulemaking (NPRM).

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

SUMMARY: This document proposes the adoption of a new airworthiness

directive (AD) that is applicable to Rolls-Royce, plc Spey series

turbofan engines. This proposal would require a one-time inspection of

stage 1 and stage 2 high pressure turbine (HPT) and low pressure

turbine (LPT) steel disks for cracks and corrosion pitting. This

proposal is prompted by a report of a stage 7 high pressure compressor

steel disk found cracked due to corrosion. The actions specified by the

proposed AD are intended to prevent an HPT or LPT steel turbine disk

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

uncontained engine failure.

DATES: Comments must be received by March 14, 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-43, 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 the proposed rule 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-43.'' 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-43, 12 New England Executive Park,

Burlington, MA 01803-5299.

Discussion

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

authority for the United Kingdom, recently 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 of a steel stage 7 high pressure

compressor disk installed in an R-R Spey 506-14D engine. The crack had

originated from a corrosion pit that apparently had been present at the

disk's entry into service. Subsequent investigation revealed that

engine failure due to disk burst was imminent.

The CAA has determined that steel stage 1 and stage 2 high pressure

turbine (HPT) and low pressure turbine (LPT) disks could also contain

corrosion pitting that could have been present since original

manufacture. Rolls-Royce, plc has informed the FAA that all turbine

disks installed in Spey engine models type certificated in the United

States are made of steel. This condition, if not corrected, could

result in an HPT or LPT steel turbine disk burst due to cracking

attributed to corrosion, which may result in an uncontained engine

failure.

Testing and further analysis indicate that to ensure that steel

stage 1 and stage 2 HPT and LPT disks do not operate under prolonged

exposure to levels of corrosion greater than the overhaul manual

limits, at least one inspection is required after 40% of the disk

cyclic life is expended in order for the disk to continue in service

and to reliably attain full disk cyclic life. Rolls-Royce, plc has

issued Service Bulletin No. Sp72-1044, dated September 1992, that

specifies a one-time inspection of steel stage 1 and stage 2 HPT and

LPT disks for cracks and corrosion pitting. 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.

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 AD action

is necessary for products of this type design that are certificated for

operation in the United States.

Since an unsafe condition has been identified that is likely to

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

type design registered in the United States, the proposed AD would

require a one-time inspection of steel stage 1 and stage 2 HPT and LPT

disks for cracks and corrosion pitting once the disks have completed at

least 40% of their published Group ``A'' cyclic life limits as

specified in the applicable overhaul manual. These disks must be

inspected in accordance with the applicable overhaul manual during the

engine's next shop visit for either HPT or LPT overhaul after the

effective date of this AD. Accomplishment of this inspection will allow

stage 1 and stage 2 HPT and LPT disks to complete the remainder of

their current published cyclic life limits.

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

registry would be affected by this proposed AD and that the average

labor rate is $55 per work hour. The FAA estimates that it would take

no additional work hours per engine to accomplish the proposed actions

to the HPT's as the inspection is performed during scheduled overhauls.

Approximately 80% of the engines will require an additional 25 work

hours of extra access, inspection, and rebuild time to perform the

required LPT inspection. Based on these figures, the total cost impact

of the proposed AD on U.S. operators is estimated to be $189,750.

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-43.

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 series and Fokker F28 series

aircraft.

Compliance: Required as indicated, unless accomplished

previously.

To prevent a high pressure turbine (HPT) or low pressure turbine

(LPT) steel turbine disk burst due to cracking attributed to

corrosion, which may result in an uncontained engine failure,

accomplish the following:

(a) Perform a one-time inspection for cracks and corrosion

pitting in steel stage 1 and stage 2 HPT disks that on the effective

date of this airworthiness directive (AD) have completed 40% or more

of their published Group ``A'' lives, in accordance with the

procedures and schedule described in R-R Service Bulletin (SB) No.

Sp72-1044, dated September 1992, at the next shop visit after the

effective date of this AD.

(b) Perform a one-time inspection for cracks and corrosion

pitting in steel stage 1 and stage 2 HPT disks that on the effective

date of this AD have completed less than 40% of their published

Group ``A'' lives, in accordance with the procedures and schedule

described in R-R SB No. Sp72-1044, dated September 1992, at the

first shop visit after completing 40% of their published Group ``A''

lives.

(c) Perform a one-time inspection for cracks and corrosion

pitting in steel stage 1 and stage 2 LPT disks that on the effective

date of this AD have completed 40% or more of their published Group

``A'' lives, in accordance with the procedures and schedule

described in R-R SB No. Sp72-1044, dated September 1992, at the next

shop visit after the effective date of this AD.

(d) Perform a one-time inspection for cracks and corrosion

pitting in steel stage 1 and stage 2 LPT disks that on the effective

date of this AD have completed less than 40% of their published

Group ``A'' lives, in accordance with the procedures and schedule

described in R-R SB No. Sp72-1044, dated September 1992, at the

first shop visit after completing 40% of their published Group ``A''

lives.

(e) Replace with a serviceable part, disks that do not meet the

inspection requirements described in section 72-50 of the applicable

R-R Spey Engine Overhaul Manual, prior to return to service.

(f) Mark disks that meet the inspection requirements described

in section 72-50 of the applicable R-R Spey Engine Overhaul Manual

in accordance with R-R SB No. Sp72-1044, dated September 1992, prior

to return to service.

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

engine removal where engine maintenance entails removal of either

HPT or LPT disks for the purposes of scheduled disk inspections.

(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 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 27, 1993.

Jay J. Pardee,

Acting Manager, Engine and Propeller Directorate, Aircraft

Certification Service.

[FR Doc. 94-00586 Filed 01-10-94; 8:45 am]

BILLING CODE 4910-13-P