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###### Department of Transportation

###### Federal Aviation Administration 

          - 14 CFR Part 39 
          - [Docket No. 2000-NE-24-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 Pratt & Whitney Canada (P&WC) Model PW305 and PW305A turbofan engines. This proposal would require removing stage 4 low pressure turbine (LPT) disks from service before exceeding new, lower cyclic life limits. This proposal is prompted by the results of a spin pit test analysis which indicate that the stage 4 LPT disk does not have full published life. The actions specified by the proposed AD are intended to prevent LPT disk failure resulting from premature cracking of the LPT disks, which could result in an uncontained engine failure and damage to the airplane. 

# DATES:

Comments must be received by December 18, 2000. 

# ADDRESSES:

Submit comments to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 2000-NE-24-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 8:00 a.m. and 4:30 p.m., Monday through Friday, except Federal holidays. 

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:

James Rosa, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone: (781) 238-7152; fax (781) 238-7199. 

# 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 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-24-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-24-AD, 12 New England Executive Park, Burlington, MA 01803-5299. 

## Discussion 

Transport Canada, which is the airworthiness authority for Canada, recently notified the FAA that an unsafe condition may exist on P&WC model PW305 and PW305A turbofan engines. P&WC ran a spin test and found earlier than expected indications of crack initiation. As a result of this test, Transport Canada advises that there is a possibility of premature failure of the stage 4 LPT disks, part numbers (P/N's) 30A1457 and 30A1499. This condition, if not corrected, could cause a failure of the stage 4 LPT disk, that could result in an uncontained engine failure and damage to the airplane. To prevent a premature failure of the stage 4 LPT disk, this proposal would decrease the current life limit of these disks from 5,000 to 4,000 cycles-in-service (CIS). 

## Bilateral Airworthiness Agreement 

This engine model is manufactured in Canada and is type certificated for operation in the United States under the provisions of § 21.29 of the Federal Aviation Regulations (14 CFR 21.29) and the applicable bilateral airworthiness agreement. Pursuant to this bilateral airworthiness agreement, Transport Canada has kept the FAA informed of the situation described above. The FAA has examined the findings of Transport Canada, reviewed all available information, and determined that AD action is necessary for products of this type design that are certificated for operation in the United States. To prevent premature failure of the stage 4 LPT disk used in the model PW305 and PW305A engines, Transport Canada issued airworthiness directive (AD) CF-99-28 in order to ensure the airworthiness of these P&WC engines in Canada. 

## Proposed Actions 

Since an unsafe condition has been identified that is likely to exist or develop on other products of this same type design, the proposed AD would require removing certain stage 4 LPT disk P/N's 30A1457 and 30A1499 from service, before exceeding new lower cyclic life limit of 4000 CIS, and replacing them with serviceable parts. The new life limits are based on spin test analysis results that indicate that the LPT disks do not have full published lives. 

## Economic Analysis 

                    There are currently 358 engines in the domestic fleet containing the affected stage 4 LPT disks, P/N's 30A1457 and                           ( print page 69259)                        30A1499, and a total of 484 engines in the worldwide fleet. The total cost to the domestic fleet to remove and replace these disks at the new life limit of 4000 CIS, rather than the former life limit of 5000 CIS, is estimated to be $6,331,015.                 

## 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:

**Pratt & Whitney Canada:**                                 Docket No. 2000-NE-24-AD.                             

*Applicability:*                                 Pratt & Whitney Canada (P&WC) Model PW305 and PW305A turbofan engines, with stage 4 low pressure turbine (LPT) disks, part numbers (P/N's) 30A1457 and 30A1499. These engines are installed on but not limited to British Aerospace BAe. 125 1000A, BAe. 125 1000B, Hawker 1000 and Learjet 60 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:*                                 Required as indicated, unless accomplished previously.                             

To prevent premature LPT disk failure due to cracking of the LPT disks, which could result in an uncontained engine failure and damage to the airplane, accomplish the following: 

## New Stage 4 LPT Life Limit 

(a) Remove stage 4 LPT disks, P/N's 30A1457 and 30A1499, prior to exceeding the new life limit of 4000 cycles-in-service (CIS). 

(b) Except for the provisions of paragraph (c) of this AD, no parts, identified by P/N in paragraph (a) of this AD, that exceed the new life limit of 4000 CIS, may be installed. 

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

# Note 2:

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

## Ferry Flights 

(d) Special flight permits may be issued in accordance with §§ 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, MA, on November 9, 2000. 

David A. Downey, 

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

[FR Doc. 00-29379 Filed 11-15-00; 8:45 am] 

BILLING CODE 4910-13-U