AD 94-18-06

This amendment adopts a new airworthiness directive (AD) that is applicable to Textron Lycoming LTS101 series turboshaft and LTP101 series turboprop engines. This action requires a one-time removal of 321 No. 2 bearings with serial numbers from suspect manufacturing lots, and replacement with serviceable parts. This amendment is prompted by reports of three in- service bearing failures. The actions specified in this AD are intended to prevent engine power loss and inflight engine shutdown due to No. 2 bearing failure, which could result in possible loss of the aircraft.

Final rule; request for comments.

94-18-06 Textron Lycoming: Amendment 39-9019. Docket 94-ANE-20.
Applicability: Textron Lycoming LTS101 series turboshaft and LTP101 series turboprop engines incorporating No. 2 bearings, Part Number (P/N) 4-301-362-01 that have serial numbers 3- 740 through 3-839, 3-1288 through 3-1361, and 4-534 through 4-680. These engines are installed on but not limited to Aerospatiale AS350 and SA-366 series, Bell 222 series, and MBB BK117 series helicopters; and Airtractor AT302, Piaggio P166, Cessna 421 (STC), and Page Thrush airplanes.
NOTE: Affected bearings, or kits P/N T05K21714, incorporating those bearings, would have been shipped from Textron Lycoming or an approved Service Facility after September 20, 1993.
Compliance: Required as indicated, unless accomplished previously.
To prevent engine power loss and inflight engine shutdown due to No. 2 bearing failure, which could result in possible loss of the aircraft, accomplish the following:
(a) For engines installed onsingle-engine aircraft and twin-engine aircraft with both engines having affected bearings, prior to further flight remove No. 2 bearings in accordance with Textron Lycoming Alert Service Bulletin (ASB) No. A-LT101-72-50-0163, Revision 1, dated March 8, 1994, and replace with serviceable parts.
(b) For engines installed on all other aircraft, within 25 hours time in service (TIS) after the effective date of this airworthiness directive (AD) remove No. 2 bearings in accordance with Textron Lycoming ASB No. A-LT101-72-50-0163, Revision 1, dated March 8, 1994, and replace with serviceable parts.
(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 appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Engine Certification Office. NOTE: Information concerningthe existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Engine Certification Office.
(d) The removal and replacement of the No. 2 bearings shall be done in accordance with the following service document:

Document No.
Pages
Revision
Date
Textron Lycoming ASB No. A-LT101- 72-50-0163
1-3
1
March 8, 1994
Total pages: 3.

This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Textron Lycoming, Stratford Division, 550 Main Street, Stratford, CT 06497. Copies may be inspected at the FAA, New England Region, Office of the Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.
(e) This amendment becomes effective on September 26, 1994.

The Federal Aviation Administration (FAA) has received reports of three in-service bearing failures on Textron Lycoming LTS101 series turboshaft engines. Investigation revealed that three manufacturing lots totaling 321 No. 2 bearings were manufactured with roller cages either undercut or staked improperly, thereby increasing the bearing cage stress levels. The bearings from the incident engines exhibited circumferential fractures spanning across the cage cross web sections. The bearings were the winged design, which incorporates features to improve lubrication.
The FAA has determined through analysis that the fractures were caused due to high cycle fatigue, as no material defects have been found. The failures were caused by an increased stress level at the cross web area, the location of maximum tensile stress of the cage, with crack initiation at the corners of the cross web. Textron Lycoming has determined that two manufacturing lots, with 100 bearings and 147 bearings each, were undercut at the inner diameter (ID) of cage roller pockets to remove burrs after broaching. This undercutting operation removed up to 0.020 inch from the cross web area thickness, about 25% of the total thickness. The two bearing failures were from the lot of 100 undercut-cage bearings. In addition, Textron Lycoming has found that a separate lot of 74 bearings had cage cross webs deformed as the result of an improperly fitted spacer of a staking tool. This condition, if not corrected, could result in engine power loss and inflight engine shutdown due to No. 2 bearing failure, which could result in possible loss of the aircraft.
The FAA has reviewed and approved the technical contents of Textron Lycoming Alert Service Bulletin (ASB) No. A-LT101-72-50-0163, Revision 1, dated March 8, 1994, that describes procedures for removal and replacement of affected No. 2 bearings.
Since an unsafe condition has been identified that is likely to exist or develop on other Textron Lycoming LTS101 series turboshaft and LTP101 series turboprop engines of the same type design, this airworthiness directive (AD) is being issued to prevent engine power loss and inflight engine shutdown due to No. 2 bearing failure. This AD requires a one-time removal of 321 No. 2 bearings with serial numbers from suspect manufacturing lots, and replacement with serviceable parts. For engines installed on single-engine aircraft and twin-engine aircraft with two affected bearings, the bearings must be removed and replaced prior to further flight. For engines installed on all other aircraft, the bearings must be removed and replaced prior to the next 25 hours time in service (TIS). This timetable is empirically based on the early failure times, on the unpredictable nature of the high cycle fatigue mode, and on the lack of advance warning of failure. At this time, the FAA has not determined an analytically predicted failure time. The compliance timetable of prior to further flight for the single-engine aircraft or twin-engine aircraft with two affected bearings provides for more conservatism based on the possibility of complete loss of engine power. The actions are required to be accomplished in accordance with the alert service bulletin described previously.
Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days. Comments Invited
Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this 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 under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed.
Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the 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 that summarizes each FAA-public contact concerned with the substance of this AD 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-20." The postcard will be date stamped and returned to the commenter.
The regulations adopted herein will 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 final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.
The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES." List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 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. 39.13 - [AMENDED]
2. Section 39.13 is amended by adding the following new airworthiness directive: