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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 2000-NE-53-AD] 
          - RIN 2120-AA64 

# AGENCY:

Federal Aviation Administration, DOT. 

# ACTION:

Notice of proposed rulemaking (NPRM). 

# SUMMARY:

The Federal Aviation Administration (FAA) proposes to supersede two existing airworthiness directives (ADs), applicable to Honeywell International Inc. (formerly AlliedSignal Inc. and Garrett Turbine Engine Co.) TFE731-2, -3, and -4 series turbofan engines. Those AD's currently require removing certain fan rotor discs from service in accordance with a drawdown schedule, and establishing new fan rotor disc life limits. This proposal would require stricter life limits for certain fan rotor discs. This proposal is prompted by the availability of an improved fan rotor disc and by a reduction in the probability of fan rotor disc failure by terminating the life of the older, high-stressed, fan rotor disc. The actions specified in the proposed AD are intended to prevent failure of the fan disc due to fatigue cracking in the dovetail slots, which could result in in-flight engine shutdown, uncontained engine failure, and damage to the airplane.

# DATES:

Comments must be received by July 2, 2001. 

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 2000-NE-53-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may also be sent via the Internet using the following address: “9-ane-adcomment@faa.gov”. Comments sent via the Internet must contain the docket number in the subject line. Comments may be inspected at this location between 8 a.m. and 4:30 p.m., Monday through Friday, except Federal holidays. The service information referenced in the proposed rule may be obtained from Honeywell Engines and Systems (formerly AlliedSignal Inc. and Garrett Turbine Engine Co.) Technical Publications and Distribution, M/S 2101-201, P.O. Box 52170, Phoenix, AZ 85072-2170; telephone: (602) 365-2493 (General Aviation), (602) 365-5535 (Commercial Aviation), fax: (602) 365-5577 (General Aviation), (602) 365-2832 (Commercial Aviation). This information may be examined at the FAA, New England Region, Office of the Regional Counsel, 12 New England Executive Park, Burlington, MA.

# FOR FURTHER INFORMATION CONTACT:

Joseph Costa, Aerospace Engineer, Los Angeles Aircraft Certification Office, FAA, Transport Airplane Directorate, 3960 Paramount Blvd., Lakewood CA 90712-4137; telephone: (562) 627-5246; fax: (562) 627-5210. 

# SUPPLEMENTARY INFORMATION:

## Comments Invited

Interested persons are invited to participate in the making of the proposed 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 above. All communications received on or before the closing date for comments, specified above, will be considered before taking action on the proposed rule. The proposals contained in this action may be changed in light of the comments received. 

Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the proposed 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 summarizing each FAA-public contact concerned with the substance of this proposal will be filed in the Rules Docket. 

Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this action must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2000-NE-53-AD.” The postcard will be date stamped and returned to the commenter.

## Availability of NPRM's 

                    Any person may obtain a copy of this NPRM by submitting a request to the FAA, New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 2000-NE-53-AD, 12 New                           ( print page 21897)                        England Executive Park, Burlington, MA 01803-5299.                 

## Discussion 

On May 22, 1986, the FAA issued AD 86-11-05, Amendment 39-5325 (51 FR 2025, June 4, 1986), and on August 26, 1996, the FAA issued AD 96-18-13, Amendment 39-9737 (61 FR 47806, September 11, 1996). These AD's require removing certain fan rotor discs from service in accordance with drawdown schedules based on the fan rotor disc's accumulated cycles-since-new (CSN). These AD's also establish new fan rotor disc life cycle limits at 4,100 CSN or 4,600 CSN, depending on the respective disc part number. That action was prompted after additional analyses revealed that stress levels in the dovetail slots of the affected fan rotor discs were higher than initially calculated. The requirements of that AD are intended to prevent failure of the fan disc due to fatigue cracking in the dovetail slots, resulting in in-flight engine shutdown, uncontained engine failure, and damage to the airplane. In addition, to further reduce the probability of a fatigue failure and separation of in-service fan rotor discs, the FAA issued AD 96-05-03, Amendment 39-9529 (61 FR 10881, March 18, 1996) and AD 96-04-01, Amendment 39-9512 (61 FR 7690, February 29, 1996), which require initial and repetitive eddy current inspections of the dovetail slots. Within the past ten years, 400 fan discs have been removed from service for unacceptable eddy current inspection indications. Service experience has shown that the crack detection capability of this eddy current inspection procedure remains between 80-90 percent. Since AD 86-11-05, AD 96-18-13, AD 96-05-03, and AD 96-04-01 were issued, the FAA has determined that approximately 1,400 affected fan rotor discs remain in service, and has concluded that an accelerated removal schedule of affected fan rotor discs at next access or prior to December 31, 2002, is necessary to further reduce the probability of fan rotor disc failures. 

## Manufacturer's Service Information 

The FAA has reviewed and approved the technical contents of Honeywell International Inc. Alert Service Bulletin TFE731-A72-3668, dated October 25, 2000, that describes fan rotor disc replacement procedures, and references other documents for instructions on replacement, with the redesigned fan rotor discs. 

## FAA's Determination of an Unsafe Condition and Proposed Actions 

Since an unsafe condition has been identified that is likely to exist or develop on other Honeywell International Inc. (formerly AlliedSignal Inc. and Garrett Turbine Engine Co.) TFE731-2, -3, and -4 series turbofan engines of this same type design, the proposed AD would require replacing fan rotor discs part numbers (P/N's) 3072162-All, 3072816-All, 3073436-All, 3073539-All, and 3074529-All (where All denotes all dash numbers). 

## Economic impact 

There are approximately 1,400 engines with affected discs in the worldwide fleet. The FAA estimates that 1,100 engines installed on aircraft of U.S. registry would be affected by this proposed AD. The FAA also estimates that it would take approximately one work hour per engine to accomplish the proposed action during a normally scheduled fan rotor disc removal period, and approximately six work hours per engine to accomplish the proposed action during an unscheduled fan rotor disc removal period, and that the average labor rate is $60 per work hour. Required parts would cost approximately $20,400 per engine. Based on these figures, the total cost impact of the proposed AD on U.S. operators is estimated to be $22,509,000. 

## Regulatory Impact 

This proposed rule does not have federalism implications, as defined in Executive Order 13132, because it would not have a substantial direct effect 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. Accordingly, the FAA has not consulted with state authorities prior to publication of this proposed rule. 

                    For the reasons discussed above, I certify that this proposed regulation (1) is not a “significant regulatory action” under Executive Order 12866; (2) is not a “significant rule” under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) if promulgated, 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 copy of the draft regulatory evaluation prepared for this action is contained in the Rules Docket. A copy of it may be obtained by contacting the Rules Docket at the location provided under the caption                     **ADDRESSES.**

# List of Subjects in 14 CFR Part 39

      - Air transportation
      - Aircraft
      - Aviation safety
      - Safety

## The Proposed Amendment 

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration (FAA) proposes to amend 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. 106(g), 40113, 44701. 

§ 39.13

2. Section 39.13 is amended by removing Amendment 39-5325 (51 FR 2025, June 4, 1986) and Amendment 39-9737, (61 FR 47806, September 11, 1996) and by adding a new airworthiness directive, to read as follows: 

**Honeywell International Inc.:**                                 Docket No. 2000-NE-53-AD. Supersedes AD 86-11-05, Amendment 39-5325 and AD 96-18-13, Amendment 39-9737.                            

*Applicability:*                                 This airworthiness directive (AD) is applicable to Honeywell International Inc. (formerly AlliedSignal Inc. and Garrett Turbine Engine Co.) TFE731-2, -3, and -4 series turbofan engines, with fan rotor discs part numbers (P/N's) 3072162-All, 3072816-All, 3073436-All, 3073539-All, and 3074529-All (where All denotes all dash numbers). These engines are installed on, but not limited to, Avions Marcel Dassault Falcon 10, 50, and 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 airplanes.                             

# Note 1:

This 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 (c) 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 

Compliance with this AD is required as indicated, unless already done. 

                                To prevent failure of the fan disc due to fatigue cracking in the dovetail slots, which could result in in-flight engine shutdown,                                       ( print page 21898)                                    uncontained engine failure, and damage to the airplane, do the following:                             

(a) Remove fan rotor discs P/N's 3072162-All, 3072816-All, 3073436-All, 3073539-All, and 3074529-All (where All denotes all dash numbers), and replace with serviceable fan rotor discs at next access to the fan rotor disc, at the next scheduled fan rotor disc inspection, or prior to December 31, 2002, whichever occurs earliest. Fan rotor disc replacement information is available in Honeywell International Inc. Alert Service Bulletin TFE731-A72-3668, dated October 25, 2000. 

## Definitions 

(b) For the purpose of this AD, the following definitions apply: 

(1) Access to the fan rotor disc is whenever the fan shaft is unstretched. 

(2) A serviceable disc is a disc that does not have a P/N listed in this AD. 

## Alternative Methods of Compliance 

(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 (LAACO). Operators shall submit their request through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, LAACO. 

# Note 2:

Information concerning the existence of approved alternative methods of compliance with this airworthiness directive, if any, may be obtained from the LAACO.

## Special Flight Permits 

(d) Special flight permits may be issued in accordance §§ 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished. 

Issued in Burlington, Massachusetts, on April 24, 2001. 

Donald E. Plouffe, 

Acting Manager, Engine and Propeller Directorate, Aircraft Certification Service. 

[FR Doc. 01-10890 Filed 5-1-01; 8:45 am] 

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