AD 96-18-13

This amendment adopts a new airworthiness directive (AD), applicable to AlliedSignal Inc. (formerly Garrett Engine Division) TFE731 series turbofan engines, that requires removing certain fan rotor disks from service in accordance with a drawdown schedule, and would establish new fan rotor disk life limits. 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 the fan rotor disk 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.

Final rule.

96-18-13 AlliedSignal Inc.: Amendment 39-9737. Docket 95-ANE-55.
Applicability: AlliedSignal Inc. (formerly Garrett Engine Division) Models TFE731-2, -2A, -3, -3A, -3AR, -3B, -3BR, -3C, -3CR, -3D, -3DR, -3R, and -4R turbofan engines, 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 series and 1125 Westwind series; Cessna Model 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 area subject 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 request approval for an alternative method of compliance in accordance with paragraph (d) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.
Compliance: Required as indicated, unless accomplished previously.
To prevent uncontained failure of the fan rotor disk 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) For engines equipped with fan rotor disks, part numbers (P/N's) 3072162-5, 3073436-5, 3073539-(All), and 3074529-(All), where (All) denotes any dash number, remove fan rotor disks from service and install a serviceable disk in accordance with the Accomplishment Instructions of AlliedSignal Engines Alert Service Bulletin (ASB) No. TFE731-A72-3569, dated May 31, 1995, as required by the following schedule:

Fan Rotor Disk Cycles Since New (CSN) on the Effective Date of this AD
Required Fan Rotor Disk Retirement (Remove From Service)
3,600 or less
Not to exceed the new life limit of 4,100 CSN.
3,601 to 5, 500
Within the next 500 cycles after the effective
date of this AD or prior to reaching 5,700 CSN,
whichever occurs first.
5,501 or greater
Within the next 200 cycles after the effective
date of this AD, not to exceed 7,100 CSN.

(b) For engines equipped with fan rotor disks, P/N 3072816-(All), where (All) denotes any dash number, remove fan rotor disks from service and install a serviceable disk in accordance with Accomplishment Instructions of AlliedSignal Engines ASB No. TFE731-A72-3570, dated May 31, 1995, as required by the following schedule:

Fan Rotor Disk CSN on the Effective Date of this AD
Required Fan Rotor Disk Retirement (Remove From Service)3,850 or less
Not to exceed the new life limit of 4,600 CSN.
3,851 to 6,000
Within the next 750 cycles after the effective date of this AD, or prior to reaching 6,500 CSN, whichever occurs first.
6,001 or greater
Within the next 500 cycles after the effective date of this AD, not to exceed 10,000 CSN.

(c) A serviceable part is one that has not exceeded the life limits established by this AD.
(d) 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 CertificationOffice.
(e) 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.
(f) The actions required by this AD shall be done in accordance with the following AlliedSignal Engines ASBs:

Document No
Pages
Revision
Date
TFE731-A72-3569
1-8
Original
May 31, 1995
Total Pages: 8.

TFE731-A72-3570
1-8
Original
May 31, 1995
Total Pages: 8.

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.
(g) This amendment becomes effective on November 12, 1996.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to AlliedSignal Inc. (formerly Garrett Engine Division) TFE731 series turbofan engines was published in the Federal Register on March 22, 1996 (61 FR 11790). That action proposed to require removing certain fan rotor disks from service in accordance with a drawdown schedule and would establish new fan rotor disk life limits in accordance with AlliedSignal Engines Alert Service Bulletin (ASB) No. TFE731- A72-3569, dated May 31, 1995, and ASB No. TFE731-A72-3570, dated May 31, 1995.
Interested persons have been afforded an opportunity to participate in the making of this amendment. No comments were received on the proposal or the FAA's determination of the cost to the public. The FAA has determined that air safety and the public interest require the adoption of the rule as proposed.
There are approximately 5,000 engines of the affected design in the worldwide fleet. The FAA estimates that 2,500 engines installed on aircraft of U.S. registry will be affected by this AD, that it will take approximately 16 work hours per engine to accomplish the required actions, and that the average labor rate is $60 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $2,400,000.
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.
For the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866;(2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it 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 USC 106(g), 40113, 44701. 39.13 - [AMENDED]2. Section 39.13 is amended by adding the following new airworthiness directive: