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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 2000-NE-41-AD] 
          - RIN 2120-AA64 

# AGENCY:

Federal Aviation Administration, DOT. 

# ACTION:

Notice of proposed rulemaking (NPRM).

# SUMMARY:

This document proposes the adoption of a new airworthiness directive (AD) that is applicable to Rolls-Royce (RR) Corporation (formerly Allison Engine Company) AE 3007A and AE 3007C model engines with high pressure turbine (HPT) 1st to 2nd stage turbine spacer part number (P/N) 23058369 installed. This proposal would require removal and replacement of the HPT 1st to 2nd stage turbine spacer P/N 23058369 before it reaches its new reduced engine cycle life limit. This proposal is prompted by the results of a detailed component analysis that indicates that the HPT 1st to 2nd stage turbine spacer stresses are higher than predicted. The actions specified by the proposed AD are intended to prevent HPT 1st to 2nd stage turbine spacer failure which could result in an uncontained engine failure and damage to the airplane. 

# DATES:

Comments must be received by April 23, 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-41-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may also be submitted to the Rules Docket by using the following Internet address: “9-ane-adcomment@faa.gov.” Comments may be inspected at this location between 8:00 a.m. and 4:30 p.m., Monday through Friday, except Federal holidays. 

# FOR FURTHER INFORMATION CONTACT:

Michael Downs, Aerospace Engineer, Chicago Aircraft Certification Office, FAA, Small Airplane Directorate, 2300 E. Devon Ave., Des Plaines, IL 60018; telephone (847) 294-7870, fax (847) 294-7834. 

# 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 proposal must submit a self-addressed, stamped postcard on which the following statement is made: “Comments to Docket Number 2000-NE-41-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-41-AD, 12 New England Executive Park, Burlington, MA 01803-5299.                           ( print page 11127)    

## Discussion 

The manufacturer's original analysis of the HPT 1st to 2nd stage turbine spacer P/N 23058369 low-cycle fatigue life computed a cleared life of 20,000 cycles. When the part number was reanalyzed for low-cycle fatigue life, it was determined that the stress concentration factor in the cooling slots was incorrect and the stresses associated with the forward cooling slots were higher than predicted. The updated analysis indicates that the low-cycle fatigue life limit of P/N 23058369 should be reduced from 20,000 cycles to 9,400 cycles. 

Since an unsafe condition has been identified that is likely to exist or develop on other RR AE 3007A and AE 3007C model engines of the same type design, the proposed AD would require removal and replacement of HPT 1st to 2nd stage turbine spacer P/N 23058369 before it reaches its new reduced engine cycle life limit. This condition, if not corrected, could result in HPT 1st to 2nd stage turbine spacer failure, which could result in an uncontained engine failure and damage to the airplane. 

## Economic Impact

There are approximately 378 engines of the affected design in the worldwide fleet. The FAA estimates that 300 engines installed on 150 airplanes of U.S. registry would be affected by this proposed AD. It will take approximately 13 work hours per engine to accomplish the removal and replacement of the affected HPT 1st to 2nd stage spacer. The 13 work hours cited include teardown and rebuilding from the module level, but not engine removal. Engines are rarely scheduled off-wing solely for the purpose of replacement of time-expired components.The average labor rate is $60 per work hour. Required parts will cost approximately $10,012 per engine. Based on these figures, the FAA estimates the total cost impact of the proposed AD on U.S. operators, to be $3,237,600. Because most of the fleet field parts are below the new value, special scheduling should not be required. 

## 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 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 adding the following new airworthiness directive:

**Rolls-Royce Corporation:**                                 Docket No. 2000-NE-41-AD.                            

*Applicability:*                                 This AD is applicable to Rolls-Royce (RR) Corporation (formerly Allison Engine Company) AE 3007A and AE 3007C model engines with high pressure turbine (HPT) 1st to 2nd stage turbine spacer part number ­(P/N) 23058369 installed. These engines are installed on but not limited to Empresa Brasileira de Aeronautica S.A. (EMBRAER) EMB-145 and Cessna 750 series airplanes.                             

# Note 1:

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 (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 accomplished previously. 

To prevent HPT 1st to 2nd stage turbine spacer-failure, which could result in an uncontained engine failure and damage to the airplane, accomplish the following: 

## New Reduced Engine Cycle Life Limit 

(a) For all RR Corporation AE 3007A and AE 3007C model engines with HPT 1st to 2nd stage turbine spacer, P/N 23058369 installed, remove spacer before reaching the new reduced engine cycle life limit of 9,400 cycles and replace with a serviceable part. 

(b) Revise the airworthiness limitations section of the Instruction for Continued Airworthiness, as follows: P/N 23058369=9,400 cycles. 

## 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, Chicago Aircraft Certification Office. Operators shall submit their request through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Chicago Aircraft Certification Office (ACO). 

# Note 2:

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

## Special Flight Permits 

(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.

Issued in Burlington, Massachusetts, on February 13, 2001. 

Jay J. Pardee, 

Manager, Engine and Propeller Directorate, Aircraft Certification Service.

[FR Doc. 01-4393 Filed 2-21-01; 8:45 am] 

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