A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an AD that is applicable to certain SN PW models PW4164, PW4168, and PW4168A turbofan engines was published in the Federal Register on September 20, 2002 (67 FR 59215). That action proposed to require operators to initially and repetitively borescope-inspect 14th and 15th stage rubstrips located on the 13th and 14th stage stator set for wear in accordance with Pratt & Whitney Alert Service Bulletin (ASB) PW4G-100-A72-170, Revision 2, dated June 24, 2002. That action also proposed that installation of an HPC inner rear case assembly in accordance with Pratt & Whitney service bulletin (SB) No. PW4G-100-72-159, Revision 1, dated July 12, 2000, be terminating action for the repetitive borescope inspections of this AD.
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.
Terminating Action Too Specifically Tied to SB
One commenter states that the proposed terminating action to modify or repair the HPC inner rear case hook recognizes only one method of compliance, which is in accordance with PW SB PW4G-100-72-159. The commenter requests the addition of Chromalloy Florida Repair Procedure 00-CFL-039-0 as an approved method to repair the HPC inner rear case.
The FAA agrees. Therefore, the terminating action of the final rule includes both PW SB PW4G-100-72-159 and Chromalloy Florida Repair Procedure 00-CFL-039-0, as approved methods to modify or replace the HPC inner rear case.
Include HPC Inner Rear Case Assembly P/N 58H559-01
One commenter suggests including HPC inner rear case assembly P/N 58H559-01 as an installation option to installing HPC inner rear case assembly P/N 58H026-01, because P/N 58H559-01 also introduces the rear hook made from Haynes 242 material, as specified in PW SB No. PW4G-100-72-187.The FAA agrees. Therefore, SB PW4G-100-72-187, which incorporates an HPC inner rear case assembly with an improved durability rear hook, is added as an additional method for terminating action for the repetitive borescope inspections of this AD.
Allow for Engines Already Inspected
The same commenter suggests that another category be added to Table 1 that makes allowances for engines already inspected per ASB PW4G-100-A72-170 before the effective date of this AD. The proposal as-written has no condition stated for engines already inspected per ASB PW4G-100-A72-170.
The FAA agrees. However, instead of modifying Table 1, a paragraph has been added to the final rule that states that engines borescope-inspected before the effective date of this AD, in accordance with PW ASB PW4G-100-A72-170, Revision 1, dated November 21, 2001, or Revision 2, dated June 24, 2002, must perform actions in accordance with the wear limits and disposition instructions of this AD.
Change Replacement Wording and Supply Definition Paragraph
The same commenter suggests that the last phrase in paragraph (c)(2) be changed from requiring the replacement of the engine with an engine not affected by this AD, to requiring the replacement of the engine with a "non-worn'' engine. The commenter also suggests supplying a definition for the term "non-worn'' engine. The commenter's reason for this suggestion is that he believes that engines that do not exhibit wear should be acceptable replacements, rather than mandating as acceptable replacements only engines that have incorporated the new material hooks.
The FAA partially agrees. The risk analysis assumes that all engines containing HPC inner rear case rear hooks made from Greek Ascoloy would be inspected at least every 600 cycles-in-service (CIS) after the effective date of this AD. The intent of the AD is to remove engines showing wear of the HPC inner rear case rear hook before a surge event is caused. Therefore, paragraph(c) is rewritten to require the replacement of "engines with HPC inner rear case hook wear beyond limits'' with "a serviceable engine''. A definition of serviceable engine has also been added.
Delete Paragraphs for Borescope Inspections of Uninstalled Engines
The same commenter suggests deleting the paragraphs for borescope inspections of uninstalled engines, because the wear limits are already covered previously in the compliance section.
The FAA agrees. The risk analysis treats uninstalled and installed engines equally by using an average utilization rate. These paragraphs as originally proposed may result in misinterpretation. Therefore, these paragraphs are deleted from the final rule.
ASB PW4G-100-A72-170 Revised
Although the proposal incorporated the Accomplishment Instructions of ASB PW4G-100-A72-170, Revision 2, dated June 24, 2002, by reference, this final rule incorporates the Accomplishment Instructions of ASB PW4G-100-A72-170, Revision 3, dated January 31, 2003 by reference. Revision 3 of ASB PW4G-100-A72-170 includes changes for clarification purposes and does not affect the original intent of the ASB. These changes include treating installed and uninstalled engines alike as discussed in the preceding comments, adding P/N 58H559-01 to the new material list, and simplifying Table 1.
Move Applicability Information
For clarification, the FAA has deleted paragraph (a) as it appeared in the proposal and has expanded the Applicability paragraph in the final rule to state that this AD is applicable to PW models PW4164, PW4168, and PW4168A turbofan engines, serial numbers P733301 through P733500 that have HPC inner case assembly P/N 53H272-01 which incorporates an HPC inner case rear hook susceptible to excessive wear.
Change to Table 1
Table 1 has been simplified to eliminate redundant and potentially confusing information. The compliance categories for "engines with between 900 and 1,500 CSN or CSR'' and "engines withover 1,500 CSN or CSR'' have been combined.
Tables 2 and 3 added
Tables 2 and 3 have been added to clarify the repetitive borescope inspection and removal schedules as outlined in ASB PW4G-100-A72-170. This information was referenced previously and does not constitute additional compliance requirements.
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.
Economic Analysis
There are approximately 90 Pratt & Whitney models PW4164, PW4168, and PW4168A turbofan engines of the affected design in the worldwide fleet. The FAA estimates that 21 engines installed on airplanes of U.S. registry would be affected by this AD. The FAA also estimates that it would take approximately 3 work hours per engine to perform the inspection, and that the average labor rate is $60 per work hour. Assuming an average accumulation of 100 cycles-in-service per month per engine, the FAA estimates an average of two borescope inspections be required per engine per year. Parts cost is not included in this analysis, as this AD requires inspection. Based on these figures, the total cost of the AD to U.S. operators is estimated to be $7,560.
Regulatory Analysis
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 regulatoryaction'' 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) 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, Incorporation by reference, 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 a new airworthiness directive to read as follows: