AD 94-23-04

This amendment adopts a new airworthiness directive (AD), applicable to Garrett Turbine Engine Company ATF3 series turbofan engines, that requires a one-time inspection for cracks of the curvic and bore area of the high pressure turbine (HPT) rotor assembly disk, and replacement, if necessary, with a serviceable disk. This amendment is prompted by several reports of cracks discovered during routine inspections of HPT rotor assembly disks. The actions specified by this AD are intended to prevent an uncontained failure of the HPT rotor assembly disk.

Final rule.

94-23-04 Garrett Turbine Engine Company: Amendment 39-9066. Docket 93-ANE-39.
Applicability: Garrett Turbine Engine Company Model ATF3-6 and -6A turbofan engines equipped with high pressure turbine (HPT) rotor assembly disk, Part Number (P/N) 3001765-1 and -2, listed by serial numbers in Table 1 of Allied-Signal Aerospace Company, Garrett Engine Division, Alert Service Bulletin (ASB) No. ATF3-A72-6184, Revision 1, dated January 11, 1993. These engines are installed on but not limited to Dassault Aviation Falcon Jet Falcon Series G (Falcon 20G/HU-25) and Mystere-Falcon 200 aircraft.
Compliance: Required as indicated, unless accomplished previously.
To prevent an uncontained failure of the HPT rotor assembly disk, accomplish the following:
(a) For engines with 1550 or more HPT rotor assembly disk cycles since new (CSN) on the effective date of this AD, perform a one-time inspection for cracks of the curvic and bore area of the HPT rotor assembly disk, and replace if necessary, with a serviceable disk, in accordance with Allied-Signal Aerospace Company, Garrett Engine Division, ASB No. ATF3-A72-6184, Revision 1, dated January 11, 1993, within 50 cycles in service (CIS) after the effective date of this AD.
(b) For engines with less than 1550 HPT rotor assembly disk CSN on the effective date of this AD, perform a one-time inspection for cracks of the curvic and bore area of the HPT rotor assembly disk, and replace if necessary, with a serviceable disk, in accordance with Allied-Signal Aerospace Company, Garrett Engine Division, ASB No. ATF3-A72-6184, Revision 1, dated January 11, 1993, within 300 CIS after the effective date of this AD, or prior to accumulating 1600 CSN, whichever occurs first.
(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, 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.
(d) 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.
(e) The inspection, and replacement, if necessary, shall be done in accordance with the following alert service bulletin:

Document No.
Pages
Revision
Date
Allied-Signal Aerospace Company, Garrett Engine Division, ASB No. ATF3-A72-6184
1-6
1
January 11, 1993
Total Pages: 6.

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 Propulsion Engines, 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.
(f) This amendment becomes effective on February 6, 1995.

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 Garrett Turbine Engine Company Model ATF3-6 and -6A turbofan engines was published in the Federal Register on February 11, 1994 (59 FR 6603). That action proposed to require a one-time inspection for cracks of the curvic and bore area of high pressure turbine (HPT) rotor assembly disks listed by serial number in Table 1 of Allied-Signal Aerospace Company, Garrett Engine Division, Alert Service Bulletin (ASB) No. ATF3-A72-6184, Revision 1, dated January 11, 1993.
Interested persons have been afforded an opportunity to participate in the making of this amendment. No comments were received on the proposal or the Federal Aviation Administration's (FAA) 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 75 Garrett Turbine Engine Company Model ATF3-6 and -6A turbofan engines of the affected design in the worldwide fleet. The FAA estimates that 2 engines installed on aircraft of U.S. registry will be affected by this AD, that it will take approximately 220 work hours per engine to accomplish the required actions, and that the average labor rate is $55 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $24,200.
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 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: