AD 99-22-10

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 General Electric Aircraft Engines (GEAE) Models CF34-1A, -3A, -3A1, and -3A2 turbofan engines was published in the Federal Register on April 5, 1999 (64 FR 16364). That action proposed to require removal from service of forward HPC spools, part number (P/N) 6078T56P01; rear HPC spools, P/N 6087T01P03 and 6087T01P04; and stage 9 HPC disks, P/N 5087T46P01 or 5087T46P02. The affected parts must be removed prior to accumulating cycles in service beyond new, reduced cyclic life limits. Comment Received Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comment received. The commenter supports the rule as proposed. After careful review of the available data, including the comment noted above, the FAA has determined thatair safety and the public interest require the adoption of the rule as proposed. Economic Analysis There are approximately 600 engines of the affected design in the worldwide fleet. The FAA estimates that 28 engines installed on aircraft of US registry will be affected by the requirement within this AD to replace the forward spool. The FAA has calculated the prorated cost for forward spool replacements to be $36,500 per engine, based on the estimated new part cost divided by the original life limit, multiplied by the number of cycles that will be reduced by the AD requirement. Therefore, the FAA estimates the total cost impact for replaced forward spools to be $1,022,000. The FAA estimates that 200 engines installed on aircraft of US registry will be affected by the requirement to replace the stage 9 disk. The FAA has calculated the prorated cost for stage 9 disk replacements to be $3,500 per engine, based on the estimated new part cost divided by the original life limit, multiplied by the number of cycles that will be reduced by the AD requirement. The FAA estimates the total cost impact for replaced stage 9 disks to be $700,000. The FAA estimates that 300 engines installed on aircraft of US registry will be affected by the requirement to replace the rear spool. The FAA has calculated the prorated cost for rear spool replacements to be $8,900 per engine, based on the new part cost divided by the original life limit, multiplied by the number of cycles that will be reduced by the AD requirement. Therefore, the FAA estimates the total cost impact for replaced rear spools to be $2,670,000. The FAA has determined that it will take no additional work hours per engine to remove affected components, as removal would take place at available opportunities. Based on these figures, the total cost impact of the AD on US operators is estimated to be $4,392,000. Regulatory Impact 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." List of Subjects in 14 CFR Part 39 Air Transportation, Aircraft, Aviation safety, Safety. Adoption of the Amendment 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: 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: