AD 97-25-10 R1

On November 28, 1997, the Federal Aviation Administration (FAA) issued AD 97-25-10, Amendment 39-10234 (62 FR 64514, December 8, 1997), applicable to certain Pratt & Whitney (PW) JT9D series turbofan engines, to require initial and repetitive fluorescent penetrant inspections (FPI) for cracks in cooling air holes of affected first stage high pressure turbine (HPT) disks, and, if necessary, replacement with serviceable parts. In addition, that airworthiness directive (AD) requires initial and repetitive FPI for cracks in tie bolt holes of all affected second stage HPT disks. Finally, that action requires reporting findings of cracked turbine disks. That action was prompted by reports of a cracked cooling air hole on one first stage HPT disk, and a cracked tie bolt hole on one second stage HPT disk. That condition, if not corrected, could result in turbine disk failure due to cooling air hole or tie bolt hole cracking, which could result in an uncontainedengine failure and damage to the aircraft. Since the issuance of that AD, the FAA received questions regarding clarifying the inspection procedures for second stage HPT disk tiebolt holes. In addition, one commenter requested that the 48 hour time requirement to notify the FAA that a cracked disk is found be changed to 10 working days. The commenter explained that 48 hours is not practical if a cracked disk is found over a holiday weekend. The FAA concurs, and has changed this revision to the final rule AD to include a 10 working day reporting requirement. Also, based on new data and subsequent re-evaluation of the risk analysis since publication of the existing AD, the FAA has determined that the repetitive inspection interval for first stage HPT disks may be extended. This revision to the final rule AD includes the extended inspection interval. The FAA has reviewed and approved the technical contents of PW Service Bulletin (SB) No. JT9D-7R4-72-536, Revision 2, dated April 30, 1998, that describes procedures for FPI for cracks in tie bolt holes of all affected second stage HPT disks. Since an unsafe condition has been identified that is likely to exist or develop on other engines of this same type design, this AD revises AD 97-25-10 to call out the second stage HPT hub assembly by part number (P/N) in addition to the hub P/N for clarification of affected parts, and reference a SB that does not change any of the requirements in the AD, but better explains the inspection procedures that are referenced in the current AD. The actions are required to be accomplished in accordance with PW SB No. JT9D-7R4-72-536, Revision 2, dated April 30, 1998. Since the issuance of that AD, the FAA received a request to increase the inspection interval for first stage HPT disks. The FAA has determined, by review of risk analysis, that extending the inspection interval provides an adequate margin of safety. Since a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days. Comments Invited Although this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications should identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the ADaction and determining whether additional rulemaking action would be needed. Comments are specifically invited on the overall regulatory, economic, environmental, and energy aspects of the rule that might suggest a need to modify the 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 that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket. Commenters wishing the FAA to acknowledge receipt of their comments submitted in response to this notice must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 97-ANE-04." The postcard will be date stamped and returned to the commenter. 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. The FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, 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, 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 removing Amendment 39-10234 (62 FR 64514, December 8, 1997) and by adding a new airworthiness directive, Amendment 39-10652, to read as follows: