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 July 28, 1998 (63 FR 40216). That action proposed to require, within the next 30 days after the effective date of this AD, revisions to the Time Limits Section (TLS) of the PW JT8D-200 Turbofan Engine Manual, and, for air carriers, the approved continuous airworthiness maintenance program. The manufacturer of JT8D-200 series turbofan engines has provided the Federal Aviation Administration (FAA) with a detailed proposal that identifies and prioritizes the critical life-limited rotating engine parts with the highest potential to hazard the airplane in the event of failure, along with instructions for enhanced, focused inspection methods. The enhanced inspections resulting from this AD will be conducted at piece-part opportunity, as defined in this AD, rather than specific inspection intervals.
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 supports the measures outlined in the proposed rule.
Several commenters ask that the FAA clarify the record keeping aspects of the mandatory inspections resulting from the required changes to the Original Equipment Manufacturer's manual and operator's continuous airworthiness maintenance program. Two commenters believe that paragraph (e) of the proposed rule is unclear and suggests that certain preamble language be added to it for clarity and that it be revised by eliminating the word "or" from the first sentence and beginning a second sentence with "In lieu of the record.." Two commenters state that the AD should be revised to clearly specify which types of maintenance records must be retained (i.e., inspection results, defect reporting requirements, date of performed maintenance, signature of the person performing the maintenance). These commenters believe that these revisions are necessary in order to avoid potential differences in interpretation between the air carriers and the FAA. And, one commenter states that the AD should clarify that there is no need for a special form to comply with the AD record keeping requirements. The FAA concurs in part. Generally, record keeping requirements are addressed in other regulations and this AD does not change those requirements. In order to allow flexibility from operator to operator, the FAA does not concur that the AD itself specify the precise nature of the records that will result from the required changes to the manufacturer's manual and operator's maintenance program. The FAA has, however, revised Paragraph (e) of this AD to clarify record keeping aspects of the new mandatory inspections.
One commenter requests that the FAA link the conduct of mandatoryinspections on whether the subject part was removed from an engine while the engine was installed on the airplane or while the engine was removed and in an overhaul shop. The commenter wishes to exempt those parts that are removed from installed engines from the focused inspections. The FAA does not concur. The mandatory inspections are based on a single trigger. The trigger is a part being completely disassembled using the engine manual instructions (piece-part opportunity), and is not dependent on whether an engine is installed on the airplane. This final rule mandates that the definition of piece-part opportunity appears in the mandatory section of each affected engine manual. This final rule further mandates that an operator's continuous airworthiness maintenance program be modified to capture those engine manual changes.
One commenter suggests that language be added to the requirements adding a minimum cycles in service threshold after which mandatory inspections would be applicable. The FAA does not concur. The FAA is aware that cracks can be missed during part inspections and that each time a part is processed through an inspection line, the probability of detecting a crack is increased. Commonly used on-condition maintenance plans make it likely that a given part could be returned to service for thousands of cycles without the need for additional focused inspection. Recognizing two opposing aspects of part removal and inspection, i.e., a need for a brief exemption period following conduct of mandatory inspections and the benefits of increased frequency of inspection, FAA established the 100 cycle threshold. No consideration for crack growth time was given in the choice of this number nor was time-since-new (TSN) considered as a possible reason for exempting parts from focused inspection. It is based strictly on keeping the frequency of mandatory inspection as high as practical and therefore increasing the probability of crack detection while providing a brief window of exemption from mandatory inspection if certain conditions are met. Therefore, the 100 cycle limit will remain in the compliance section of the AD and no exemption will be allowed for low TSN parts.
One commenter states that the mandatory manual chapters were modified to require new inspection requirements prior to issuance of the final rule AD and that FAA should provide written notification to Flight Standards Offices that the inspections proposed in the proposed rule are not mandatory until the establishment of an effectivity date in a published final rule AD. Some confusion between Operators, Manufacturers and Principal Maintenance Inspectors was created when the mandatory manual sections were modified prior to the release of a final rule AD. The FAA concurs in part. The manuals were modified prior to issuance of the final rule to minimize implementation delays from lengthy original equipment manufacturer EM revision cycles. FAA will attempt a higher levelof coordination of timing the manual revisions so that the revisions follow final rule ADs in the future. Such a notice, however, is beyond the scope of this AD and may well cause additional confusion rather than clarify the present situation.
One commenter suggested that the parts requiring focused inspection be identified by "all" rather than by specific part number. The FAA does not concur. The FAA intentionally allowed each manufacturer to choose a format that fits their products manual. Identification of parts requiring mandatory inspections has been accomplished by either part number identification or use of the word "all". Part number identification was chosen by some manufacturers since the processes and procedures needed to conduct new inspections were not yet developed for all parts of a certain type, i.e., fan disks/hubs. The FAA wants the manufacturers to have flexibility in managing how their manuals are structured within Air Transport Association code requirement.One commenter states that a "spot focused" fluorescent-penetrant inspection (FPI) should be performed in the rivet area of the fan hub instead of removing rivets, the air seal, and the compressor duct to inspect the fan hub. The commenter believes that rivet removal and replacement may induce stresses and cause cracks. The FAA does not concur. Inspection of the entire fan hub (i.e., bore, all holes, fillet radii, rim slot bottom, upper lug surface, pressure face of dovetail slots) is needed to detect all possible crack indications. Although few cracks have been detected thus far, there is concern that other high stress areas (e.g. dovetail slots) may be affected. Furthermore, removal of the assembled parts (air seal and compressor duct) will provide assurance that liquids for inspection and cleaning will not become entrapped in the titanium hub.
One commenter states that the phrase "by or related to the cause of its removal from the engine" should be added for clarification to paragraph (2)(b) of Inspection Requirements, paragraph A, in the Compliance Section. The FAA concurs and the phrase has been added.
One commenter states that the affected assembly part number (P/N) in the Compliance Section, paragraph B, Parts Requiring Inspection Table, is in error and should be 5000421-01. The FAA concurs and the P/N has been revised.
One commenter states that AD 97-17-04 compliance requirements relative to the JT8D Engine Manual, P/N 773128, 72-33-31 Insp-02, as specified in the proposed rule should be clarified. The FAA does not concur that a change needs to be made to the AD, but offers the following explanation for clarification purposes. The inspection requirements of AD 97-17-04 remain intact and are not affected by this AD. While the inspection techniques are similar, this AD will require inspections at every piece-part opportunity without having to remove bushings. AD 97-17-04 requires inspections with bushings removed at fixed inspection intervals depending on part serial number.
One commenter states that an existing alternative method of compliance (AMOC) for removal of C1 hub bushings prior to eddy current inspection should be allowed for this AD. The FAA does not concur. Because this AD does not require the removal of bushings at every piece-part opportunity, no AMOC for an alternate bushing removal procedure is required.
One commenter states that the PW JT8D-200 Turbofan Engine Manual section reference in the Parts Requiring Inspection table is in error and should read 72-33-31. The FAA concurs and the table has been revised.
No comments were received on the economic analysis contained in the proposed rule. Based on that analysis, the FAA has determined that the annual per engine cost of $240 does not create a significant economic impact on small entities.
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.
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: