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Proposed Rule

Airworthiness Directives; Pratt & Whitney JT8D Series Turbofan Engines

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Information about this document as published in the Federal Register.

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AGENCY:

Federal Aviation Administration, DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

The Federal Aviation Administration (FAA) proposes to supersede an existing airworthiness directive (AD), that is applicable to Pratt & Whitney JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -15A, -17, -17A, -17R, and -17AR turbofan engines. That AD currently requires a determination of the utilization rate and protective coating type of the 7th, 8th, 9th, 10th, 11th, and 12th stage high pressure compressor (HPC) disks, and removal, inspection for corrosion, and recoating of those HPC disks based on utilization rate. This proposal would require removal and replacement of protective coating of 7th, 8th, 9th, 10th, 11th, and 12th stage HPC disks, initial and repetitive inspections for corrosion pits and cracks, and removal from service as required. This proposal is prompted by operator reports of cracks found on several JT8D steel HPC disks since the existing AD was published. The actions specified in the proposed AD are intended to prevent fracture of the HPC disks, which can result in uncontained release of engine fragments, inflight engine shutdown, and airframe damage.

DATES:

Comments must be received by March 25, 2003.

ADDRESSES:

Submit comments in triplicate to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 97-ANE-05-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may be inspected at this location, by appointment, between 8 a.m. and 4:30 p.m., Monday through Friday, except Federal holidays. 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.

The service information referenced in the proposed rule may be obtained from Pratt & Whitney, 400 Main St., East Hartford, CT 06108; telephone (860) 565-6600, fax (860) 565-4503. This information may be examined, by appointment, at the FAA, New England Region, Office of the Regional Counsel, 12 New England Executive Park, Burlington, MA.

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FOR FURTHER INFORMATION CONTACT:

Christopher Spinney, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone (781) 238-7175; fax (781) 238-7199.

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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 97-ANE-05-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. 97-ANE-05-AD, 12 New England Executive Park, Burlington, MA 01803-5299.

Discussion

On May 29, 1998, the FAA issued AD 98-12-07, Amendment 39-10563 (63 FR 31340, June 9, 1998), to supersede AD 94-20-01, Amendment 39-9020 (59 FR 49175, September 27, 1994). AD 98-12-07 requires a determination of the utilization rate and protective coating type of the 7th, 8th, 9th, 10th, 11th, and 12th stage HPC disks, and removal, inspection for corrosion, and recoating of those HPC disks based on utilization rate, and shortens the inspection interval for certain low utilization disks. That action was prompted by a report of an additional uncontained 9th stage HPC disk failure due to corrosion pitting. That condition, if not corrected, could result in uncontained release of engine fragments, inflight engine shutdown, and airframe damage.

Since that AD was issued, operators have found cracks on various JT8D steel HPC disks. Some of these cracks originate in the tierod hole area of the disk. The inspection intervals in AD 98-12-07 do not account for risk of fractures originating from tierod hole areas. This proposal is a result of a complete re-assessment of the risks associated with a disk fracture due to a corrosion pit. Since the tierod hole corrosion does not correlate well with the utilization rate of the disks, that calculation has been eliminated from the proposal. Also, because the thin-webbed 9th stage disk represents a higher risk of fracture than other part numbers, a tighter inspection interval has been assigned to those parts.

Manufacturer's Service Information

The FAA has reviewed and approved the technical contents of Pratt & Whitney Alert Service Bulletin (ASB) No. A6431, dated November 27, 2002, that describes procedures for initial and repetitive inspections to detect corrosion on HPC disks, and removal Start Printed Page 3476from service of HPC disks corroded beyond serviceable limits. This ASB supersedes ASB No. 6038, referenced in AD 98-12-07.

Differences Between This Proposal and the Manufacturer's Service Information

Although PW ASB No. A6431 dated November 27, 2002, refers to the ASB issuance date for computing compliance intervals, this proposal calls for computing compliance intervals based on the effective date of the AD.

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 Pratt & Whitney JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -15A, -17, -17A, -17R, and -17AR turbofan engines of this same type design, the proposed AD would supersede AD 98-12-07 to require removal and replacement of coating of 7th, 8th, 9th, 10th, 11th, and 12th stage HPC disks, initial and repetitive inspections for corrosion pits and cracks, and removal from service as required. The actions are required to be done in accordance with the alert service bulletin described previously.

Economic Analysis

At the time of publication of AD 98-12-07, there were approximately 11,119 engines of the affected design in the worldwide fleet. The FAA estimated that 6,815 engines installed on aircraft of U.S. registry were affected by AD 94-20-01, and 2 work hours would be necessary to determine the utilization rate and type of surface treatment. Based on domestic fleetwide data, the FAA estimated that approximately 8.7% or 593 engines were considered to have low utilization rates. Approximately 8.6 work hours would be required to remove these engines from the aircraft, 500 work hours to tear down, deblade, and to reassemble the engine, and 8.6 work hours to reinstall the reassembled engines. The FAA estimated 69% of the removed engines would require scrapping the disks. The FAA assumed that 3 disks per engine may require replacement, and the cost of a new disk would be approximately $7,000. The average labor rate is $60 per work hour. Based on these figures, the total cost of AD 94-20-01 on U.S. operators was estimated to be $ 14,279,542. The cost increase between AD 94-20-01 and the superseding AD, AD 98-12-07 was based on the increased inspections of some low utilization disks. The FAA estimated 31% of the low utilization disks required an additional inspection. The cost of these additional inspections was estimated to be $4,426,658. The cost increase between AD 98-12-07 and this proposal is based on the increased domestic fleet size that will be effected by this proposal. The FAA currently estimates the domestic fleet of engines affected by this AD to be 1,800 engines. This is an increase of 1,023 engines or 1.32 times the total number of engines effected by the two previous AD's. The total cost of the previous two AD's was $18,706,200, therefore, the total cost of this AD is $24,692,184, and the cost increase associated with this proposal is $5,985,985.

Regulatory Analysis

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.

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List of Subjects in 14 CFR Part 39

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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:

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PART 39—AIRWORTHINESS DIRECTIVES

1. The authority citation for part 39 continues to read as follows:

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Authority: 49 U.S.C. 106(g), 40113, 44701.

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[Amended]

2. Section 39.13 is amended by removing Amendment 39-10563, (63 FR 31340 June 9, 1998), and by adding a new airworthiness directive:

Pratt & Whitney: Docket No. 97-ANE-05-AD. Supersedes AD 98-12-07, Amendment 39-10563.

Applicability: This airworthiness directive (AD) is applicable to Pratt & Whitney (PW) JT8D-1, -1A, -1B, -7, -7A, -7B, -9, -9A, -11, -15, -15A, -17, -17A, -17R, and -17AR turbofan engines. These engines are installed on, but not limited to Boeing 737 and 727 series, and McDonnell Douglas DC-9 series 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 (d) 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 fracture of the 7th, 8th, 9th, 10th, 11th, and 12th stage high pressure compressor (HPC) disks, which can result in uncontained release of engine fragments, inflight engine shutdown, and airframe damage, do the following:

(a) Perform initial and repetitive inspections of HPC disks for corrosion pits and cracks after stripping the protective coating in accordance with the intervals and procedures specified in the compliance section and accomplishment instructions of PW Alert Service Bulletin (ASB) No. 6431, dated November 27, 2002.

(b) Before further flight, replace HPC disks found with corrosion pits or cracks beyond serviceable limits as defined by PW ASB No. 6431, dated November 27, 2002.

(c) For the purposes of this AD, use the effective date of this AD for computing compliance intervals whenever PW ASB No. A6431, dated November 27, 2002, refers to the issuance date of the ASB.

Alternative Methods of Compliance

(d) 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 must 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.

Special Flight Permits

(e) Special flight permits may be issued in accordance with §§ 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 Start Printed Page 3477and 21.199) to operate the airplanes to a location where the requirements of this AD can be done.

Start Signature

Issued in Burlington, Massachusetts, on January 16, 2003.

Francis A. Favara,

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

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[FR Doc. 03-1543 Filed 1-23-03; 8:45 am]

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