01-7081. Airworthiness Directives; Pratt & Whitney PW4000 Series Turbofan Engines

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 certain models of Pratt & Whitney (PW) PW4000 series turbofan engines. This proposal would require operators to perform initial and repetitive inspections for cracking of high pressure compressor (HPC) front drum rotors based on cycle usage. This proposal would also require the removal from service of any cracked HPC front drum rotors. This proposal is prompted by reports that seven HPC drum rotors have been found cracked on the spacer surface between the 6th and 7th stage disks. The actions specified by the proposed AD are intended to detect premature cracking of the HPC drum rotor that could result in an uncontained engine failure and damage to the airplane.

DATES:

Comments must be received by May 21, 2001.

ADDRESSES:

Submit comments to the Federal Aviation Administration (FAA), New England Region, Office of the Regional Counsel, Attention: Rules Docket No. 2000-NE-49-AD, 12 New England Executive Park, Burlington, MA 01803-5299. Comments may also be sent via the Internet using the following address: “[e-mail]”. 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.

The service information referenced in the proposed rule may be obtained from Pratt & Whitney, 400 Main Street, East Hartford, CT 06108. 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:

Tara Goodman, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington MA 01803-5299; telephone: [phone], fax: [phone].

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-49-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-49-AD, 12 New England Executive Park, Burlington, MA 01803-5299.

Discussion

This proposal is prompted by reports that seven HPC front drum rotors have been found cracked in the axial direction on the spacer surface between the 6th and 7th stage disks. These axial cracks may propagate into the disk and lead to compressor disk fracture, which could result in an uncontained engine failure. The manufacturer is investigating the cause of the cracking. There is currently no terminating action to the repetitive inspection requirements of the proposed AD. This proposed rule may be revised based on the results of the manufacturer's investigation.

Manufacturer's Service Information

The FAA has reviewed and approved the technical contents of PW Alert Service Bulletin (ASB) No. PW4ENG A72-722, dated September 29, 2000. That ASB provides procedures for operators to perform on-wing and off-wing initial and repetitive HPC drum rotor borescope inspections.

Differences Between Manufacturer's Service Information and this AD

Although ASB No. PW4ENG A72-722, dated September 29, 2000, exempts PW4158 engine serial numbers P728534 through P728546, from the inspection requirements, this AD includes those engines in the initial and repetitive inspections and requires replacing any drum rotor that is cracked. The FAA has determined that there is insufficient data to permit the exception of these particular engines from the proposed inspection requirements.

Also, although ASB No. PW4ENG A72-722, dated September 29, 2000, provides procedures for operators to perform off-wing initial and repetitive HPC drum rotor inspections, the off-wing requirements are not mandated by the proposed rule. The FAA has evaluated a 20-year cumulative risk assessment and has determined that an acceptable level of safety will be met by requiring the on-wing inspections at the cyclic intervals detailed in the ASB.

ASB No. PW4ENG A72-722, dated September 29, 2000, states in item 12 of the Accomplishment Instructions for the on-wing inspection that an eddy current nondestructive inspection must be done within five engine cycles of finding a crack indication. The FAA has determined that if confirmation of cracking is necessary, an eddy current inspection must be conducted prior to further flight.

Proposed Actions

Since an unsafe condition has been identified that is likely to exist or develop on other PW4000 series turbofan engines of this same type design, the proposed AD would require operators to perform initial borescope inspections on HPC drum rotors before accumulating 1,500 cycles-since-new (CSN) on the effective date of this AD. This proposed AD would also require thereafter, inspections within 2,200 cycles-since-last-inspection, and the removal from service of any cracked HPC front drum rotor. The compliance intervals were established by analysis of service data and evaluation of a risk analysis. The actions would be required to be accomplished in accordance with the ASB described previously.

Economic Analysis

The FAA estimates that there are 1,970 engines of the affected design in the worldwide fleet, and that 538 engines installed on aircraft of U.S. registry would be affected by this proposed AD. The FAA also estimates that it would take approximately 2.5 work hours per engine to accomplish the proposed on-wing inspection, and that the average labor rate is $60 per work hour. It is estimated that three engines would be found with cracked HPC front drum rotors in the time frame of one year. Approximately 269 engines will be inspected on average per year. The cost of removal and reinstallation of an engine is approximately $10,000, and the cost of replacing the HPC front drum rotor is approximately $750,000. Required replacement parts would cost $356,130 per engine. Based on these figures, the total cost impact per year of the proposed AD for accomplishing initial inspections and replacing HPC front drum rotors, on U.S. operators is estimated to be $3,388,730.

Regulatory Impact

This proposal 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 proposal.

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

[Amended]

2. Section 39.13 is amended by adding the following new airworthiness directive:

Pratt & Whitney: Docket No. 2000-NE-49-AD.

Applicability: This airworthiness directive (AD) applies to Pratt & Whitney (PW) models PW4052, PW4056, PW4060, PW4062, PW4152, PW4156A, PW4158, PW4460, and PW4462 turbofan engines. These engines are installed on but not limited to Boeing 747, 767, McDonnell Douglas MD-11, Airbus Industrie A300, and A310 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 (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 detect premature cracking of the high pressure compressor (HPC) front drum rotor, that could result in an uncontained engine failure and damage to the airplane, accomplish the following:

Initial Inspection

(a) Perform an initial inspection in accordance with the Accomplishment Instructions, On-Wing paragraphs 1 through 13, of PW Alert Service Bulletin (ASB) No. PW4ENG A72-722, dated September 29, 2000, as follows:

(1) Perform an initial inspection of HPC front drum rotors before accumulating 1,500 cycles-since-new.

(2) If the presence of a crack needs to be confirmed, perform an eddy current inspection (ECI) before further flight.

(3) If the presence of a crack is confirmed, remove and replace with a serviceable HPC front drum rotor before further flight.

Repetitive Inspections

(b) Thereafter, perform inspections within 2,200 cycles-since-last-inspection, in accordance with the Accomplishment Instructions, On-Wing paragraphs 1 through 13, of PW ASB No. PW4ENG A72-722, dated September 29, 2000.

(1) If the presence of a crack needs to be confirmed, perform an ECI before further flight.

(2) If the presence of a crack is confirmed, remove and replace with a serviceable HPC front drum rotor before further flight.

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 Federal Aviation Administration (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

(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, Massachusetts, on March 14, 2001.

Mark Liptak,

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