AD 94-23-05

This amendment adopts a new airworthiness directive (AD) that is applicable to AlliedSignal Inc., (formerly Garrett Engine Division) TFE731-3A-200G and -3AR-200G model turbofan engines. This action requires removing from service certain low pressure turbine (LPT) disks, imposing an hourly life limit on the first stage and second stage LPT disks, performing a dimensional inspection of second stage LPT disks at repetitive intervals, and incorporating honeycomb material in the second stage LPT nozzle air seal. This amendment is prompted by reports of LPT disk web separations. The actions specified in this AD are intended to prevent LPT disk web separations, which can result in an uncontained engine failure and damage to the aircraft.

94-23-05 ALLIEDSIGNAL INC.: Amendment 39-9067. Docket 94-ANE-01.
Applicability: AlliedSignal Inc. TFE731-3A-200G and -3AR-200G turbofan engines installed on but not limited to Israel Aircraft Industries, Ltd., 1125 Westwind Astra aircraft.
Compliance: Required as indicated, unless accomplished previously.
To prevent low pressure turbine (LPT) disk web separations, which can result in an uncontained engine failure and damage to the aircraft, accomplish the following:
(a) Remove from service first and second stage LPT disks, with Part Numbers (P/N) 3072351-( ), 3072542-( ), 3074103-1, and 3074105-1, where ( ) denotes any dash number, identified by serial number in the Compliance Sections of AlliedSignal Aerospace Alert Service Bulletin (ASB) No. TFE731-A72-3544, dated October 8, 1993, and AlliedSignal Aerospace ASB No. TFE731-A72-3557, dated May 12, 1994, within 100 hours time in service (TIS) after the effective date of this airworthiness directive (AD), in accordancewith the Accomplishment Instructions of AlliedSignal Aerospace ASB No. TFE731-A72-3544, dated October 8, 1993, and AlliedSignal Aerospace ASB No. TFE731-A72-3557, dated May 12, 1994, and replace with serviceable disks.
(b) Remove first stage LPT disk, P/N 3072351-( ), where ( ) denotes any dash number, and install a serviceable first stage LPT disk in accordance with the Accomplishment Instructions of AlliedSignal Aerospace ASB No. TFE731-A72-3519, Revision 3, dated May 6, 1994, as follows:

Stage 1 LPT Disk

TIS Since New (TSN)
Initial Replacement Schedule
More than 850 hours
Replace within the next 50 hours TIS after the effective date of this AD, or at the next removal of the LPT module, whichever occurs first.
551 to 850 hours
Replace within the next 200 hours TIS after the effective date of this AD, 900 hours TSN, or at the next removal of the LPT module, whichever occurs first.
Less than 551 hours
Replace prior to 750 hours TSN.

(c) Prior to 1,500 hoursTIS after the effective date of this AD, or at the next removal of the LPT module, whichever occurs first, accomplish the following:
(1) Replace the second stage LPT nozzle air seal, P/N 3071878-1, in accordance with the Accomplishment Instructions of AlliedSignal Aerospace SB No. TFE731-72-3530, Revision 1, dated October 8, 1993, with a serviceable nozzle air seal.
(2) Replace or inspect the second stage LPT rotor assembly, P/N 3072541-( ), where ( ) denotes any dash number, and install a serviceable assembly in accordance with the Accomplishment Instructions of AlliedSignal Aerospace ASB No. TFE731-A72-3519, Revision 3, dated May 6, 1994.
(d) Perform subsequent repetitive inspections and remove from service first and second stage LPT disks, and replace with a serviceable disk, as follows:
(1) Remove first stage LPT disks, P/N 3074103-1, prior to accumulating 750 hours TSN, or 3,000 CSN.
(2) Remove first stage LPT disks, P/N 3073733-1, prior to accumulating 1,500 hours TSN, or 3,000 CSN.
(3) Remove second stage LPT disks, P/N 3074105-1 prior to accumulating 4,500 hours TSN, or 3,000 CSN.
(4) Inspect the second stage LPT rotor assembly, P/N 3074106-1, by performing a balance rim dimensional inspection, wire gauge check, and fluorescent penetrant inspection, in accordance with the Engine Light Maintenance Manual, at intervals not to exceed 1500 hours TIS since last inspection.
(e) 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, Los Angeles Aircraft 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, Los Angeles Aircraft Certification Office. NOTE: Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the Los Angeles AircraftCertification Office.
(f) Accomplishment of the requirements of paragraph (c)(1) of this AD in accordance with the original version of AlliedSignal Aerospace SB No. TFE731-72-3530; or the requirements of paragraphs (b) or (c)(2) of this AD in accordance with the original version, Revision 1, or Revision 2 of AlliedSignal Aerospace ASB No. TFE731-A72-3519 constitute acceptable alternative methods of compliance to the applicable requirements of this AD.
(g) 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.
(h) The requirements of this AD shall be accomplished in accordance with the following applicable service documents:

Document No.
Pages
Revision
Date
AlliedSignal
Aerospace
ASB No. TFE731-A72- 3544
Total pages: 10.
1-10
Original
October 8, 1993

AlliedSignal
Aerospace SB No.
TFE731-72-3530
1-2
1
October 8, 1993

3-4
Original
July 2, 1993

5
1
October 8, 1993
Total pages: 8.
6-8
Original
July 2, 1993

AlliedSignal
Aerospace ASB No.
TFE731-A72-3519
Total pages: 8.
1-8
3
May 6, 1994

AlliedSignal
Aerospace
ASB No. TFE731-A72-3557
Total pages: 12.
1-12
Original
May 12, 1994

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 AlliedSignal Inc., Aviation Services Division, Data Distribution, Dept. 64-3/2102-1M, P.O. Box 29003, Phoenix, AZ 85038-9003. 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.
(h) This amendment becomes effective on December 1, 1994.

The Federal Aviation Administration (FAA) has received reports of two low pressure turbine (LPT) disks that failed in the disk web area due to creep fatigue on AlliedSignal Inc. (formerly Garrett Engine Division) Model TFE731-3A-200G turbofan engines. Both disk failures were uncontained. A metallurgical examination of first and second stage LPT disks found that two heat treatment production processes created a microstructure more susceptible to creep fatigue cracking. Both production processes affected AlliedSignal Inc. TFE731-3 series engines' first and second stage LPT disks.
In addition, a field inspection of LPT disks on AlliedSignal Inc. TFE731-3 series turbofan engines revealed that excessive disk growth occurred on AlliedSignal Inc. Model TFE731-3A-200G and TFE731-3AR-200G engines, which are installed on Israel Aircraft Industries, Ltd. (IAI) 1125 Westwind Astra series aircraft. The FAA has determined that the IAI Astra flight profile subjectsthe first and second stage LPT disks to prolonged flight time at or near the maximum continuous inner turbine temperatures limit. Repeated prolonged exposure to high temperatures can cause a more rapid deterioration of the nickel-graphite abradable material on the LPT second stage nozzle air seal than originally anticipated during the certification process of the engine. This deterioration results in increased seal clearance, which contributes to disk growth. This disk growth, also known as creep, resulting either from certain heat treatment production processes, excessive LPT second stage nozzle air seal clearance, or the LPT disk(s) prolonged exposure to elevated operating temperatures, if not corrected, could result in LPT disk web separations, which can result in an uncontained engine failure and damage to the aircraft.
The FAA has reviewed and approved the technical contents of AlliedSignal Aerospace Alert Service Bulletin (ASB) No. TFE731-A72-3519, Revision 3, dated May 6, 1994, that imposes an hourly life limit on first and second stage LPT disks and describes procedures for removal and replacement of these LPT disks; SB No. TFE731-72-3530, Revision 1, dated October 8, 1993, that describes procedures for installing a second stage LPT turbine nozzle that incorporates a honeycomb air seal; and ASB No. TFE731-A72-3544, dated October 8, 1993, and ASB No. TFE731-A72-3557, dated May 12, 1994, that describe procedures for removal and replacement of specific serial numbered first and second stage LPT disks. Certain requirements of this AD may be accomplished using an earlier version of a service bulletin (SB) or ASB than the one cited in the AD. The original version of AlliedSignal Aerospace SB No. TFE731-72-3530 differs only by minor changes that do not impact the technical content of the procedures, and is an acceptable method of compliance to paragraph (c)(1) of this AD. Prior to the effective date of this AD, replacement of LPT disks in accordance with previous revisions of SB No. TFE731-A72-3519 is an acceptable method of compliance to paragraph (b) or (c)(2) of this AD.
Since an unsafe condition has been identified that is likely to exist or develop on other AlliedSignal Inc. TFE731-3A-200G series turbofan engines of the same type design, this AD is being issued to prevent LPT disk web separations, which can result in an uncontained engine failure and damage to the aircraft. This AD requires removing from service certain LPT disks, imposing an hourly life limit on first and second stage LPT disks, performing a dimensional inspection of second stage LPT disks at repetitive intervals, and incorporating honeycomb material in the second stage LPT nozzle air seal. The actions are required to be accomplished in accordance with the service bulletins 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-01." 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: