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###### Department of Transportation

###### Federal Aviation Administration

          - 14 CFR Part 39
          - [Docket No. 2001-NE-19-AD]
          - RIN 2120-AA64

# AGENCY:

Federal Aviation Administration, DOT.

# ACTION:

Notice of proposed rulemaking (NPRM).

# SUMMARY:

The Federal Aviation Administration (FAA) proposes to adopt a new airworthiness directive (AD) that is applicable to General Electric Company CF6-50 and CF6-80C2 turbofan engines. This proposal would require replacement of certain existing CF6-50 and CF6-80C2 shrouds with new design shrouds. This proposal is prompted by 37 low pressure turbine (LPT) uncontained events on the CF6-50 and 24 on the CF6-80C2 engine models since 1993, and the development and certification of newly designed shrouds that will improve LPT containment capability. The actions specified by the proposed AD are intended to prevent uncontained engine failure and possible airplane damage.

# DATES:

Comments must be received by July 16, 2001.

# ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 2001-NE-19-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 General Electric Company via Lockheed Martin Technology Services, 10525 Chester Road, Suite C, Cincinnati, Ohio 45215, telephone: (513) 672-8400; fax: (513) 672-8422. 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:

Karen Curtis, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone: (781) 238-7192, 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 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 2001-NE-19-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. 2001-NE-19-AD, 12 New England Executive Park, Burlington, MA 01803-5299.

## Discussion

Since 1993, the General Electric CF6 turbofan engine has experienced a number of low pressure turbine (LPT) failures in which debris from the engine has escaped from the engine case and nacelle. The engine shroud is part of the containment system intended to prevent such debris from an LPT failure from threatening the aircraft. For the CF6-50 engine model, there have been 16 such events where the debris escaped the engine case, 12 where the debris escaped both the case and nacelle, and nine where the debris escaped the case and nacelle and impacted the aircraft. The CF6-80C2 has experienced 16 events where the debris escaped the engine case, six where the debris escaped the case and nacelle, and two where the debris impacted the aircraft.

Many different upstream failures have led to the secondary breakup and separation of LPT blades, and resulted in low energy LPT case penetrations. High pressure turbine (HPT) blade failures, HPT nozzle failures, and fan mid shaft separations due to high pressure compressor airduct failures have been the leading causes for uncontained LPT failures for these engine models. In addition, multiple shroud repairs can lead to reduced shroud backsheet thickness and result in reduced containment system capability.

The manufacturer has developed, and the FAA has certified, newly designed shrouds that will improve LPT contaiment capability and enhance engine safety. Although the manufacturer and the FAA have also designed and certified design improvements to address the known upstream failure modes, not all such failure modes can be anticipated and therefore improved LPT containment capability is necessary to protect the airplane from debris from an LPT failure, and enhance safety for these engine models.

This proposal would require replacement of certain existing CF6-50 and CF6-80C2 shrouds with new design shrouds.

## Manufacturer's Service Information

                    The FAA has reviewed and approved the technical contents of GE Aircraft                           ( print page 27476)                        Engines Service Bulletin (GEAE SB) CF6-80C2 S/B 72-1006, dated April 11, 2001 and GEAE SB CF60-50 S/B 72-1170, dated May 7, 1999, that specify part numbers and procedures for the removal and replacement of the shrouds.                

## 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 General Electric Company CF6-50 and CF6-80C2 turbofan engines of the same type design, the proposed AD would require replacement of certain existing CF6-50 and CF6-80C2 shrouds with new design shrouds at the next shroud piece part exposure, but no later than December 31, 2006. The actions would be required to be accomplished in accordance with the service bulletins described previously.

## Economic Impact

There are approximately 5,055 GE CF6-50 and CF6-80C2 turbofan engines of the affected design in the worldwide fleet. The FAA estimates that 1,106 engines installed on airplanes of U.S. registry would be affected by this proposed AD. Because this proposal calls for the replacement of shrouds at piece part exposure, the FAA does not expect that additional labor costs will be accrued beyond that normally required to remove the existing shroud. New shrouds will cost approximately $63,250 for the CF6-50 engines, and $87,020 for the CF6-80C2 engines. Based on these figures, the total cost to retrofit all installed US registered engines is estimated to be $85,096,038 over a five year period, or $17,019,207 annually.

## 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:

**General Electric Company:**                                 Docket No. 2001-NE-19-AD.                            

*Applicability:*                                 This airworthiness directive (AD) is applicable to General Electric Company (GE) CF6-50 and CF6-80C2 turbofan engines These engines are installed on, but not limited to DC-10-15, DC-10-30, MD11, 747, 767, A300 and A310 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 uncontained engine failure and possible airplane damage, do the following:                            

(a) Remove existing Stage 2, 3 and 4 low pressure turbine (LPT) CF6-80C2 shrouds and replace with new design part numbers (P/N's) 2083M12G01, 2083M13G01, and 2083M14G01, respectively, in accordance with GE Aircraft Engines Service Bulletin (GEAE SB) CF6-80C2 S/B 72-1006, dated April 11, 2001, at the next shroud piece part exposure, but no later than December 31, 2006.

(b) Remove existing Stage 1, 2, 3 and 4 LPT CF6-50 shrouds and replace with new design P/N's 1822M35G01, 1822M36G01, 1822M36G02, and 1822M37G01, respectively, in accordance with GEAE SB CF6-50 S/B 72-1170, dated May 7, 1999, at the next shroud piece part exposure, but no later than December 31, 2006.

## 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, 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.

(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 May 11, 2001.

Francis A. Favara,

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

[FR Doc. 01-12425 Filed 5-16-01; 8:45 am]

BILLING CODE 4910-13-P