AD 97-02-11

Effective March 5, 1997.

The incorporation by reference of certain publications listed in the regulations is approved by the Director of the Federal Register as of March 5, 1997.

The service information referenced in this AD 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 at the Federal Aviation Administration (FAA), New England Region, Office of the Assistant Chief Counsel, 12 New England Executive Park, Burlington, MA; or at the Office of the Federal Register, 800 North Capitol Street, NW., Suite 700, Washington, DC.

Diane Cook, Aerospace Engineer, Engine Certification Office, FAA, Engine and Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803-5299; telephone (617) 238-7134, fax (617) 238-7199.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to Pratt & Whitney (PW) JT8D-200 series turbofan engines was published in the Federal Register on October 4, 1996 (61 FR 51847). That action proposed to require cleaning, initial and repetitive eddy current inspections (ECI) and fluorescent penetrant inspections (FPI) for cracks of tierod and counterweight holes; removing bushings; initial and repetitive ECI and FPI of bushed holes for cracks; and, if necessary, replacing with serviceable parts. The compliance requirements allow selection of inspection schedules depending on fan hub S/Ns listed in PW Alert Service Bulletin (ASB) No. A6272, dated September 24, 1996, and includes an inspection schedule for those fan hubs whose S/Ns are not listed in the ASB. In addition, the proposed AD requires reporting the number of initial inspections and the findings of cracked fan hubs.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

One commenter states that the Notice of Proposed Rulemaking (NPRM) as written was confusing and subject to interpretation, and offered a number of editorial suggestions. The FAA reviewed the suggestions and concurs in part with the changes.

The commenter states that the applicability should be expressed to the lowest practical level by including the phrase ``front compressor front hub (fan hub)'' and its corresponding part number in the applicability statement. The FAA concurs. The applicability section in this final has been revised to read ``* * * engines with front compressor front hub (fan hub) Part Number 5000501-01 installed''.

The commenter states that a stronger statement regarding the initial inspections for fan hubs with less than 4,000 cycles since new (CSN) was needed. The commenter suggests adding the intent of the first note on page 8 of PW ASB No. A6272, dated September 24, 1996, which requires inspection after the fan hub has accumulated more than 4,000 cycles in service. This change would eliminate the need for paragraph (a) of the proposed rule. The FAA concurs. The structure of the compliance section in this final rule has been modified to include the initial 4,000 CSN inspection requirement in the beginning of each of two compliance paragraphs. Paragraph (a) of this final rule will cover coolant channel drilled (CCD) fan hubs identified by S/N in the SB, and paragraph (b) for inspection of all other affected fan hubs. For each population of hubs, the initial inspection must not be completed until the fan hub has accumulated more than 4,000 CSN.

The commenter states that paragraph (c) of the NPRM is vague and should specify what is to be reported. The FAA concurs and has added the requirement of reporting in accordance with Accomplishment Instructions, Paragraph F, of Attachment 1 to PW ASB No. A6272, dated September 24, 1996, to this final rule.

The commenter states that paragraph (a) and Table 1 of the NPRM do not clearly indicate that the operator is to choose one of the three options in Table 1 and stick with the corresponding reinspection interval. The commenter suggests adding ``or'' after options 1 and 2 in Table 1 and adding a note to require that the operator follow the initial and repetitive requirements of the option chosen. The FAA concurs in part. The ``or'' has been added as suggested. The original proposal contained such a requirement in proposed paragraph (b)(1)(i), which has been carried over into new paragraph (a)(2). Operators must follow the repetitive inspection interval corresponding to the selected initial inspection time.

The commenter states that the time limit for reporting in paragraph (c) of the NPRM is unreasonable because its administrative personnel do not work on weekends and during holiday periods. The commenter recommends a 10 day limit for reporting. The FAA does not concur. A 48 hour period should be adequate and is a standard reporting requirement time limit in ADs. The AD does not require that only administrative personnel submit the report to the FAA.

Two commenters, including the National Transportation Safety Board, state that they agree with the NPRM's proposed initial and repetitive inspection program on the population of hubs that were produced using the CCD procedure, based on the investigation that indicates that these hubs may have a higher risk of abusive machining damage. However, since the commenters do not agree that CCD hubs are the only suspect fan hubs, the commenters do not agree with the proposed inspection program for the remaining hub population. The NPRM proposed to inspect the remaining population (those hubs not CCD) when the hub assembly is stripped to the piece part level. The commenters are concerned that this proposal may allow hubs to be initially inspected as late as 10,000 cycles in service (CIS) after the effective date of this AD. The commenters believe that these hubs are of nearly equal concern as the fan hubs produced by CCD and the proposed interval is too long to detect all potential cracks before they may be expected to propagate to failure. The commenters propose that inspection/reinspection occur at the next shop visit for all of those hubs that have between 10,000 and 15,000 CIS since new regardless of the type of drill used during manufacture.

The FAA does not concur at this time. The FAA's analysis of this problem indicates that hubs manufactured using coolant-channel drills are more susceptible to work hardened areas in the tierod and counterweight holes that could serve as a crack origin. The FAA concludes, therefore, that it is logical to treat these two distinct populations of compressor hubs differently in terms of when operators must perform the required inspections. Requiring all hubs to be inspected according to the CCD schedule is not supported by the available data. The investigation, however, continues and should any additional data become available, the FAA may initiate further rulemaking as required.

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes described previously. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

There are approximately 2,624 engines of the affected design in the worldwide fleet. The FAA estimates that 1,279 engines installed on aircraft of U.S. registry will be affected by this AD, that it will take approximately 20 work hours per engine for 360 engines to disassemble, remove, inspect, and reassemble engines, and 4 work hours per engine for 919 engines to inspect at piece-part exposure, and that the average labor rate is $60 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $862,560.

The regulations adopted herein will not have substantial direct effects 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. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant the preparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (1) is not a ``significant regulatory action'' under Executive Order 12866; (2) is not a ``significant rule'' under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (3) 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 final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption ADDRESSES.

Air Transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

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

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