AD 96-05-03

This amendment supersedes an existing airworthiness directive (AD), applicable to AlliedSignal Inc. (formerly Garrett Engine Division) TFE731 Series Turbofan Engines, that currently requires inspection of fan rotor disks within certain schedules. This amendment requires initial and repetitive eddy current inspections using an improved, more definitive procedure for detecting fan rotor disk dovetail slot cracks. Also, this amendment adds additional engine models and fan rotor disk part numbers and disallows fluorescent penetrant inspection (FPI) as an alternative inspection method for detecting fan rotor disk dovetail slot cracks. This amendment is prompted after additional analyses revealed that stress levels in the fan rotor disk dovetail slots for the applicable engine models are higher than initially calculated. The actions specified by this AD are intended to prevent uncontained failure of fan rotor disks due to fatigue cracking in the dovetail slots, which can resultin inflight engine shutdowns, severe secondary damage, and fan rotor assembly separation from the engine.

Final rule; request for comments.

96-05-03 AlliedSignal Inc.: Amendment 39-9529. Docket 95-ANE-53. Supersedes AD 91-08-13, Amendment 39-8611.

Applicability: AlliedSignal Inc. (formerly Garrett Engine Division) TFE731-2, -2A, -3, -3A, -3AR, -3B, -3BR, -3C, -3CR, -3D, -3DR, -3R, and -4R series turbofan engines with fan rotor disk part numbers (P/N's) 3072162-1 through -5, 3072816-1, -2, and -3, 3073436-1 through -5, 3073539-(All), and 3074529-(All), where (All) denotes any dash number, installed on but not limited to the following aircraft: Avions Marcel Dassault Falcon 10, 50, 100 series; Learjet 31, 35, 36, and 55 series; Lockheed-Georgia 1329-23 and -25 series; Israel Aircraft Industries 1124 and 1125 series; Cessna 650, Citations III, VI, and VII; Raytheon British Aerospace HS-125 series; and Sabreliner NA-265-65. NOTE: This airworthiness directive (AD) applies to each engine identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the areasubject to the requirements of this AD. For engines that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must use the authority provided in paragraph (b) to request approval from the Federal Aviation Administration (FAA). This approval may address either no action, if the current configuration eliminates the unsafe condition, or different actions necessary to address the unsafe condition described in this AD. Such a request should include an assessment of the effect of the changed configuration on the unsafe condition addressed by this AD. In no case does the presence of any modification, alteration, or repair remove any engine from the applicability of this AD.

Compliance: Required as indicated, unless accomplished previously.

To prevent uncontained failure of fan rotor disks due to fatigue cracking in the dovetail slots, which can result in inflight engine shutdowns, severe secondary damage, and fan rotor assembly separation from the engine, accomplish the following:

(a) Remove and conduct initial and repetitive eddy current inspections for cracks on affected fan rotor disks, and, if necessary, replace cracked fan rotor disks with a serviceable disk, as follows:

(1) Fan rotor disks whose dovetail slots have never been eddy-current inspected must comply with the initial inspection described in paragraphs (3), (4), (5), or (6) of this AD, as applicable. Additionally, all fan rotor disks whose dovetail slots have been previously eddy-current inspected must comply with the repetitive inspections in accordance with paragraphs (7), (8), or (9) of this AD, as applicable.

(2) For paragraphs (3) and (7) of this AD, incorporate new eddy current inspection procedures in accordance with the Accomplishment Instructions (AI) of AlliedSignal Inc. Alert Service Bulletin (ASB) No. TFE731-A72-3432, Revision 5, dated May 31, 1995, within 30 days after the effective dateof this AD. Those fan rotor disks requiring eddy current inspection, prior to the incorporation of the new eddy current procedure, may be inspected in accordance with the AI 's of Allied-Signal Inc. ASB No. TFE731-A72-3432, dated April 11, 1991; Allied-Signal Inc. ASB No. TFE731-A72-3432, Revision 1, dated April 30,1991; Allied-Signal Inc. ASB No. TFE731-A72-3432, Revision 2, dated June 3, 1991; Allied-Signal Inc. ASB No. TFE731-A72-3432, Revision 3, dated October 17, 1991; or AlliedSignal Inc. ASB No. TFE731-A72-3432, Revision 4, dated August 6, 1993.

(3) For engines with Part Number (P/N) 3072162-1 through -4, and P/N 3073436-1 through -4, inspect in accordance with the AI of AlliedSignal Inc. ASB No. TFE731-A72-3432, Revision 5, dated May 31, 1995, as required by Schedule A, using fan rotor disks cycles since new (CSN) on August 16, 1993 (effective date of AD 91-08-13).

SCHEDULE A

Fan Rotor Disk (CSN)
Initial Inspection Schedule

Greater than 2,800
Within the next 50 cycles in service (CIS) after August 16, 1993 (effective date of AD 91-08-13).

2,301 through 2,800
Within the next 100 CIS after August 16, 1993 (effective date of AD 91-08-13), or prior to 2,850 CSN, whichever occurs first.

1,601 through 2,300
Within the next 200 CIS after August 16, 1993 (effective date of AD 91-08-13) or prior to 2,400 CSN, whichever occurs first.
1,600 or less
Prior to accumulating 1,800 CSN.

(4) For engines with P/N's 3072162-5, 3073436-5, 3073539-1, and 3074529-1, inspect in accordance with the AI of AlliedSignal Inc. ASB No. TFE731-A72-3432, Revision 5, dated May 31, 1995, as required by Schedule B, using fan rotor disk CSN on the effective date of this AD.

SCHEDULE B

Fan Rotor Disk CSN
Initial Inspection Schedule
Greater than 1,600
Within the next 200 CIS after the effective date of this AD.
1,600 or less
Prior to accumulating 1,800 CSN.

(5) For engines with P/N's 3072816-1 and -2, inspect in accordance with theAI of AlliedSignal Inc. ASB No. TFE731-A72-3445, Revision 2, dated May 31, 1995, as required by Schedule C, using fan rotor disk CSN on the effective date of this AD.

SCHEDULE C

Fan Rotor Disk CSN
Initial Inspection Schedule
Greater than 2,800
Within 50 CIS after the effective date of this AD.

2,301 to 2,800
Within 100 CIS after the effective date of this AD, or prior to 2,850 CSN, whichever occurs first.
2,300 or less
Prior to accumulating 2,400 CSN

(6) For engines with P/N 3072816-3, inspect in accordance with the AI of AlliedSignal Inc. ASB No. TFE731-A72-3445, Revision 2, dated May 31, 1995, as required by Schedule D, using fan rotor disk CSN on the effective date of this AD.

SCHEDULE D

Fan Rotor Disk CSN
Initial Inspection Schedule
Greater than 2,200
Within 200 CIS after the effective date of this AD.
2,200 or less
Prior to accumulating 2,400 CSN.

(7) For engines with P/N 3072162-1, -2, -3, and -4, P/N 3073436-1, -2, -3,and -4, thereafter inspect in accordance with the AI of AlliedSignal Inc. ASB No. TFE731-A72-3432, Revision 5, dated May 31, 1995, at every Major Periodic Inspection (MPI), as defined in the applicable engine maintenance manual, or prior to accumulating 1,300 CIS since last eddy current inspection, whichever occurs first.

(8) For engines with P/N's 3072162-5, 3073436-5, 3073539-(All), and 3074529-(All), where (All) denotes any dash number, thereafter inspect in accordance with the AI of AlliedSignal Inc. ASB No. TFE731-A72-3432, Revision 5, dated May 31, 1995, as required by Schedule E.

SCHEDULE E

Fan Rotor Disk CIS Since Previous Eddy Current Inspection
Repetitive Inspection Schedule
Greater than 1,100
Within 200 CIS after the effective date of this AD.
1,100 or less
Every engine MPI or prior to accumulating 1,300 CIS since last eddy current inspection, whichever occurs first.

(9) For engines with P/N 3072816-1, -2, and -3, thereafter inspect in accordancewith the AI of AlliedSignal Inc. ASB No. TFE731-A72-3445, Revision 2, dated May 31, 1995, as required by Schedule F.

SCHEDULE F

Fan Rotor Disk CIS Since Previous Eddy Current Inspection
Repetitive Inspection Schedule
Greater than 1,100
Within 200 CIS after the effective date of this AD
1,100 or less
Every engine MPI or prior to accumulating 1,300 CIS since last eddy current inspection, whichever occurs first.

(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, 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 Aircraft 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.

(d) The actions required by this AD shall be done in accordance with the following service documents:

Document No.
Pages
Revision
Date
Allied-Signal Inc. ASB No. TFE731-A72-3432
1-16
Original
April 11, 1991
Total pages: 16.

Allied-Signal Inc. ASB No. TFE731-A72-3432
1-22
1
April 30, 1991
Total pages: 22.

Allied-Signal Inc. ASB No. TFE731-A72-3432
1-20
2
June 3, 1991
Total pages: 20.

Allied-Signal Inc. ASB No. TFE731-A72-3432
1-22
3
October 17, 1991
Total pages: 22.

AlliedSignal Inc. ASB No. TFE731-A72-3432
1-16
4
August 6, 1993
Total pages: 16.

AlliedSignal Inc. ASB No. TFE731-A72-3432
1-14
5
May 31, 1995
Total Pages: 14.

AlliedSignal Inc. ASB No. TFE731-A72-3445
1-14
2
May 31, 1995
Total Pages: 14.

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 Aerospace, Attn: Data Distribution, M/S 64-3/2101-201, P.O. Box 29003, Phoenix, AZ 85038-9003; telephone (602) 365-2493, fax (602) 365-5577. 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 April 2, 1996.

On July 15, 1993, the Federal Aviation Administration (FAA) issued airworthiness directive (AD) 91-08-13, Amendment 39-8611 (58 FR 40732, July 30, 1993), to require inspection of fan rotor disks within certain schedules installed on AlliedSignal Inc. (formerly Garrett Engine Division) Model TFE731-2, -3, and -3R turbofan engines. That action was prompted by a report of an in-service uncontained failure of the first stage fan rotor disk in which a segment of the fan rotor disk rim and five fan blades departed the engine. Metallurgical examination of the fractured fan rotor disk determined that a fatigue crack had initiated in the area of the aft acute corner of one of the dovetail slots in the fan rotor disk. Failure of this fan rotor disk occurred at 3,300 cycles which was less than the then FAA-approved life limit of 4,100 cycles. That condition, if not corrected, could result in uncontained failure of fan rotor disks due to fatigue cracking in the dovetail slots, which can result in inflight engine shutdowns, severe secondary damage, and fan rotor assembly separation from the engine.

Since the issuance of that AD, the FAA has determined from additional analyses that stress levels in the fan rotor disk dovetail slots for the applicable engine models are higher than initially calculated. Also, additional TFE731 series engine models have similar stress levels. From fan rotor disk dovetail slot eddy-current inspection data, the FAA has determined that 8 (or 1%) of those TFE731-3A, -3AR, -3B, -3BR, -3C, -3CR, and -4R fan rotor disks inspected exhibited fatigue cracking and were removed from service. Moreover, similar eddy-current inspection data from the TFE731-2, -3, and -4 series engines has indicated that crack detectability from a one-time eddy-current inspection is between 80-90 percent, which is not as high as previously evaluated. Therefore, the FAA has determined that initial and repetitive eddy-current inspections mustbe performed using an improved, more definitive procedure. Furthermore, the FAA has determined that fluorescent penetrant inspection (FPI) is not adequate to detect fan rotor disk dovetail slot cracks. Accordingly, this AD disallows FPI as an alternative inspection method for detecting fan rotor disk dovetail slot cracks.

The FAA has reviewed and approved the technical contents of Allied-Signal Inc. Alert Service Bulletin (ASB) No. TFE731-A72-3432, dated April 11, 1991; Allied-Signal Inc. ASB No. TFE731-A72-3432, Revision 1, dated April 30,1991; Allied-Signal Inc. ASB No. TFE731-A72-3432, Revision 2, dated June 3, 1991; Allied-Signal Inc. ASB No. TFE731-A72-3432, Revision 3, dated October 17, 1991; AlliedSignal Inc. ASB No. TFE731-A72-3432, Revision 4, dated August 6, 1993; AlliedSignal Inc. ASB No. TFE731-A72-3432, Revision 5, dated May 31, 1995, and AlliedSignal Inc. ASB No. TFE731-A72-3445, Revision 2, dated May 31, 1995. These ASB's describe procedures for initial and repetitive eddy current inspections of fan rotor disks for cracks.

Since an unsafe condition has been identified that is likely to exist or develop on other engines of this same type design, this AD supersedes AD 91-08-13 to require initial and repetitive eddy current inspections using an improved, more definitive procedure for detecting fan rotor disk dovetail slot cracks. In addition, this amendment adds: the TFE731-2A, -3A, -3AR, -3B, -3BR, -3C, -3CR, -3D, -3DR, and -4R engines models to the Applicability section; adds fan rotor disk part numbers 3072161-5, 3073436-5, 3072816-1, -2, and -3, 3073539-(All), and 3074529-(All), where (All) denotes any dash number, to the Compliance section; and disallows FPI as an alternative inspection method for detecting fan rotor disk dovetail slot cracks. These actions are required to be accomplished in accordance with the ASB's 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 whetheradditional 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 95-ANE-53." 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 39Air 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 USC 106(g), 40113, 44701.

39.13 - [AMENDED]
2. Section 39.13 is amended by removing Amendment 39-8611, (58 FR 40732, July 30, 1993), and by adding a new airworthiness directive, Amendment 39-9529, to read as follows: