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 CFM International (CFMI) CFM56-5C2/G, -5C3/G, and -5C4 series turbofan engines was published in the Federal Register on March 26, 1996 (61 FR 13110). That action proposed to require a reduction of the low cycle fatigue (LCF) retirement lives for certain high pressure turbine rotor (HPTR) front shafts, HPTR front air seals, HPTR disks, booster spools, and low pressure turbine rotor (LPTR) stage 3 disks.
Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.
Two commenters object to the use of an AD to accomplish life limit changes, and suggest instead that operators incorporate the new limits into their FAA-approved maintenance programs. One commenter argues that the use of the AD process places unnecessary burdens on operators through additional record keeping. That commenter suggests alternatively that if the FAA does issue the AD, a new paragraph be added that states that incorporating the requirements of paragraphs (a) through (f) into an operator's maintenance program should be considered compliance with the AD and that after making that incorporation the AD would no longer apply. The FAA does not concur. Service life limits that appear as airworthiness limitations at the time of type certification can be changed to more restrictive limits only by way of rulemaking through an AD. A change to one operator's maintenance program alone will not mandate new, more restrictive, life limits for other operators. While these new limits may have appeared in service instructions or manuals before an AD is published, the FAA must complete the change by publishing the final rule AD. The FAA believes that recording the AD and its accomplishment is no more burdensome on operators than makingchanges to their maintenance program to specifically incorporate the same changes. Under the commenter's proposal, additional record keeping may be necessary to ensure that purchasers or other users of that operator's aircraft, who may not have FAA-approved maintenance programs, comply with the new, more restrictive limits. The FAA also does not concur with the commenter's proposed new paragraph which provides that once the changes are incorporated into a maintenance program the requirements of the AD would no longer apply, including the requirement that the changes may not be further adjusted without FAA approval. The FAA believes that these changes to life limits must be finalized in the form of an AD, and that no changes to the proposed AD are necessary.
Two commenters note that the booster spool life of 13,800 cycles identified in paragraph (d) of the AD is 1,200 cycles since new (CSN) less than the Chapter 05 life noted in Revision 3 of the CFM56-5C Engine Shop Manual (ESM), dated December 1, 1995. The FAA does not concur. An initial booster spool life for the CFM56-5C2/G, -5C3/G, and -5C4 series engines of 13,900 CSN was introduced by Temporary Revision (TR) TR-05-003, dated October 7, 1994. Temporary Revision TR- 05-007, dated October 28, 1994, reduced the life to 13,000 CSN. The FAA has revised paragraph (d) of this final rule to state a life of 13,000 CSN to be consistent with current published life.
Two commenters note that the LPTR stage 3 disk life of 8,630 cycles identified in paragraph (e) of the AD is 930 CSN higher than the Chapter 05 life stated in Revision 3 of the CFM56-5C ESM, dated December 1, 1995. The FAA does not concur. An initial LPTR stage 3 disk life for the CFM56-5C2/G, -5C3/G, and -5C4 series engines of 9,200 CSN was introduced by TR-05-004, dated October 7, 1994. Temporary Revision TR-05-008, dated October 28, 1994, reduced the life to 7,000 CSN. The FAA has revised paragraph (e) of this final rule to state a life of7,000 CSN to be consistent with the current published life.
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.
There are approximately 10 engines of the affected design in the worldwide fleet. The manufacturer has advised the FAA that there are no engines installed on U.S. registered aircraft that would be affected by this AD. Therefore, there is no associated cost impact on U.S. operators as a result of this AD. However, should an affected engine be imported on an aircraft and placed on the U.S. registry in the future, it would not take any additional work hours per engine to accomplish the proposed actions. Assuming that the parts cost is proportional to the reduction of the LCF retirement lives, the required parts would cost approximately $25,736 per engine. Based on these figures, the total cost impact of the AD is estimated to be $25,736 per engine.
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, 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 USC 106(g), 40113, 44701. 39.13 - [AMENDED]
2. Section 39.13 is amended by adding the following new airworthiness directive: