Airworthiness Directives; Textron Lycoming LTS101 Series Turboshaft and LTP101 Series Turboprop Engines

DEPARTMENT OF TRANSPORTATION

14 CFR Part 39

[Docket No. 94-ANE-64]

Airworthiness Directives; Textron Lycoming LTS101 Series

Turboshaft and LTP101 Series Turboprop 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 Textron Lycoming LTS101 series

turboshaft and LTP101 series turboprop engines. This proposal would

require replacement of cast material axial compressor rotors with

wrought material axial compressor rotors that have improved fatigue

characteristics and material properties. This proposal is prompted by

36 reports of axial compressor blade failures on cast rotors. The

actions specified by the proposed AD are intended to prevent engine

power loss and inflight engine shutdown.

DATES: Comments must be received by February 3, 1995.

ADDRESSES: Submit comments in triplicate to the Federal Aviation

Administration (FAA), Office of the Assistant Chief Counsel, Attention:

Rules Docket No. 94-ANE-64, 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 Textron Lycoming, 550 Main Street, Stratford, CT 06497. 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: Eugene Triozzi, Aerospace Engineer,

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

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

238-7131, 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-64.'' 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-64, 12 New England Executive Park,

Burlington, MA 01803-5299.

Discussion

The Federal Aviation Administration (FAA) has determined that cast

material axial compressor rotors in Textron Lycoming LTS101 series

turboshaft and LTP101 series turboprop engines are susceptible to high

cycle fatigue (HCF) failure. The FAA has received 36 reports of axial

compressor blade failures on cast material axial compressor rotors

installed in these engines. Metallurgical evaluation of these failed

rotors found that cracks originated from porosity, inclusions, or

pitting erosion. This condition, if not corrected, can result in engine

power loss and inflight engine shutdown.

Statistical analysis shows decreasing failure probability with

increasing rotor time in service. In addition, engine testing has

identified blade excitation frequencies that occur within the engine

operating range that could contribute to HCF failure. The wrought rotor

design has improved material properties and increased HCF margin. This

proposed airworthiness directive (AD) requires replacement of cast

material axial compressor rotors with wrought material axial compressor

rotors.

The FAA has reviewed and approved the technical contents of Textron

Lycoming Service Bulletin No. LT 101-72-30-0088, Revision 5, dated

September 25, 1992, that describes procedures and schedules for

replacing cast material axial compressor rotors with wrought material

axial compressor rotors.

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 require replacing cast material axial compressor

rotors with wrought material axial compressor rotors that have improved

fatigue characteristics and material properties. The actions would be

required to be accomplished in accordance with the service bulletin

described previously.

There are approximately 200 engines of the affected design in the

worldwide fleet. The FAA estimates that 100 engines installed on

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

it would take approximately 50 work hours per engine to accomplish the

proposed actions, and that the average labor rate is $60 per work hour.

Required parts would cost approximately $6,500 per engine, on a

prorated cost basis. Based on these figures, the total cost impact of

the proposed AD on U.S. operators is estimated to be $955,000.

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 ``major rule'' under Executive Order 12291; (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 adding the following new

airworthiness directive:

Textron Lycoming: Docket No. 94-ANE-64.

Applicability: Textron Lycoming LTS101 turboshaft and LTP101

turboprop engines installed on but not limited to Aerospatiale AS

350 and SA366G, Bell 222, and Messerschmitt Bolkow-Blohm (MBB) BK117

helicopters; Piaggio P166-DL3 and Airtractor AT302 airplanes.

Compliance: Required as indicated, unless accomplished

previously.

To prevent engine power loss and inflight engine shutdown,

accomplish the following:

(a) Remove from service Part Numbers (P/N) 4-101-006-20, -21, -

24, -26, -35, -36, and -40 cast material axial compressor rotors, as

follows:

(1) For axial compressor rotors P/N 4-101-006-35 with serial

number suffix ``E,'' remove in accordance with Textron Lycoming

Service Bulletin (SB) No. LT 101-72-30-0088, Revision 5, dated

September 25, 1992, within 50 hours time in service (TIS), or 60

days after the effective date of this AD, whichever occurs first.

(2) For axial compressor rotors P/N 4-101-006-35 with serial

number suffix other than ``E,'' and all other axial compressor

rotors with P/N listed in paragraph (a) of this airworthiness

directive (AD), remove in accordance with Textron Lycoming SB No. LT

101-72-30-0088, Revision 5, dated September 25, 1992, as follows:

(i) For axial compressor rotors that have accumulated 600 hours

or less TIS since new, remove within 100 hours TIS, or 120 days

after the effective date of this AD, whichever occurs first.

(ii) For axial compressor rotors that have accumulated more than

600 but less than or equal to 1,200 hours TIS since new, remove

within 300 hours TIS, or 240 days after the effective date of this

AD, whichever occurs first.

(iii) For axial compressor rotors that have accumulated more

than 1,200 but less than or equal to 2,400 hours TIS since new,

remove within 600 hours TIS, or 360 days after the effective date of

this AD, whichever occurs first.

(iv) For axial compressor rotors that have accumulated more than

2,400 hours TIS since new, remove within 1,200 hours TIS, or 720

days after the effective date of this AD, whichever occurs first.

(3) Replace with a serviceable wrought material axial compressor

rotor P/N 4-101-006-28, -32, -39, or -41, as applicable, in

accordance with Textron Lycoming SB No. LT 101-72-30-0088, Revision

5, dated September 25, 1992.

(b) 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 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.

(c) 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 aircraft to a location where

the requirements of this AD can be accomplished.

Issued in Burlington, Massachusetts, on December 27, 1994.

Jay J. Pardee,

Manager, Engine and Propeller Directorate, Aircraft Certification

Service.

[FR Doc. 95-64 Filed 1-3-95; 8:45 am]

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