A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that is applicable to Pratt & Whitney JT9D-7R4 series turbofan engines was published in the Federal Register on February 27, 2001 (66 FR 12440). That action proposed to require initial and repetitive fluorescent penetrant inspection (FPI) of the high pressure turbine (HPT) 1st stage disk aft lugs, and if the aft lug(s) are cracked, replacement of the HPT 1st stage disk and HPT 1st stage airseals. Also, for certain configuration HPT disk assemblies, this action proposed to require replacement of the HPT 1st stage airseals with newly designed airseals at the next accessibility.
Comments
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.
Clarifications Requested
One commenter addresses four issues:
First, the commenter states that thereis confusion regarding the phrase "before the latest of" which the commenter interprets to mean "whichever comes last." The commenter is correct. The phrase means whichever of the two cyclic limits occurs last.
Secondly, the commenter states that clarification is needed for "initial F.P.I." because there is a difference between FPI as it is proposed in the NPRM and as it is described in applicable Pratt & Whitney service bulletins. The commenter wants to know if the standard SPOP84 full disk FPI inspection at HPT overhaul fulfills the requirements of the NPRM. It is the intent of this AD that the disk lug be inspected for cracks. The full disk FPI covers the requirement.
Thirdly, the commenter states that the NPRM requires that airseal P/N 820121 must be installed on HPT part number (P/N) 787521 (powder metal disks) at the next hot section shop visit as described in Pratt & Whitney (PW) Service Bulletin (SB) JT9D-7R4-72-566. However, the commenter notes that the initial and repetitive inspection requirement of SB JT9D-7R4-72-567 remains unchanged. The commenter requests that the FAA delete the requirement to install the new airseals per SB JT9D-7R4-72-566. The FAA disagrees. The newer airseals offer a significant benefit in life over the older airseals. Though it is not stated explicitly in SB JT9D-7R4-72-567, there are no inspection limits for powder disks with the older sideplates, as it is assumed that they are all removed from service and replaced with the new sideplates per SB JT9D-7R4-72-566. Under this AD, there will be no requirement to inspect the older sideplates as they will be removed from service by paragraph (a) of this rule.
Finally, this commenter and two others note that the compliance for airseal P/N 820121 installation is specified as "at the next hot section shop visit," which is further defined as "any time the HPT rotor is disassembled." However, SB JT9D-7R4-72-566 specifies installation at piece-part opportunity. The FAA agrees and paragraph (e) will be changed to "at disk piece-part opportunity."
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.
Cost Analysis
There are approximately 324 engines of the affected design in the worldwide fleet. The FAA estimates that 47 engines installed on aircraft of U.S. registry would be affected by this proposed AD. Although forced engine removals are not anticipated the first year as a result of this proposed action, a maximum of two removals will be assumed. It would take approximately 86 work hours per engine to accomplish the proposed actions, and the average labor rate is $60 per work hour. Based on these figures, the total labor cost impact of the proposed AD onU.S. operators the first year is estimated to be $24,520. Hardware costs the first year for HPT 1st stage airseals replaced by SB JT9D-7R4-72-566 are estimated to be $128,000, based on replacement costs of $147,110 per disk and $45,143 for sideplates, discounted for average 1/3 life lost at removal. Total combined labor and hardware costs for the first year are therefore estimated to be $140,000.
The following year, it is estimated that inspections will result in a maximum of three engines requiring forced replacement of the HPT 1st stage disk and HPT 1st stage airseals due to cracking. Due to these forced removals, approximately 1/3 of the disk life will be lost. The total combined hardware and labor cost is estimated to be approximately $210,000. The total cost impact of this proposal on U.S. operators in the first two years is expected to be approximately $350,000.
Regulatory Impact
This final 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 final rule.
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 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 final evaluation has been prepared for this action and it 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.
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.
Sec. 39.13 [Amended]
2. Section 39.13 is amended adding a new airworthiness directive to read as follows: