Discussion
We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to certain CFM CFM56-7B series turbofan engines. The NPRM published in the Federal Register on May 1, 2015 (80 FR 24856). The NPRM was prompted by a report of an uncommanded IFSD on a CFM CFM56-7B engine following rupture of the 73-tooth gearshaft located in the engine AGB. The NPRM proposed to require MCD inspection of the affected gearshafts until removal.
Comments
We gave the public the opportunity to participate in developing this AD. The following presents the comments received on the NPRM (80 FR 24856, May 1, 2015) and the FAA's response to each comment.
Request To Add CFM56-3 Engines to Applicability
CFM requested that we add CFM56-3 engines to this AD, as the CFM56- 3 engines share the same 73-tooth and 41-tooth gearshafts as the CFM56- 7B engines.
We agree. We revised the applicability of this AD byadding CFM56-3 engines.
Request To Clarify Discussion of IFSDs
CFM commented that the NPRM (80 FR 24856, May 1, 2015) incorrectly indicated that multiple instances of uncommanded IFSDs occurred on CFM56-7B engines following rupture of the 73-tooth gearshaft when only one IFSD actually occurred. CFM requested that this AD be revised to reflect that only one IFSD occurred following rupture of the 73-tooth gearshaft.
We agree. We revised the Summary, Discussion, and Unsafe Condition sections of this final rule to reflect the occurrence of one IFSD following rupture of the 73-tooth gearshaft in the CFM56-7B's AGB.
Request To Clarify Inspection Requirement
CFM commented that the NPRM (80 FR 24856, May 1, 2015) did not clearly specify that the MCD inspection is of the AGB/TGB.
We agree. We revised the Summary and the Compliance sections of this final rule to reflect that the required inspection is an ``AGB/TGB MCD inspection.''
Request To Clarify Relevant Service Information
CFM requested that we specify in the Relevant Service Information section of the NPRM (80 FR 24856, May 1, 2015) that the referenced service bulletins (SBs) describe the procedures for removal of the affected 73-tooth and 41-tooth gearshafts and also list the affected gearshafts by serial number (S/N).
We disagree. This AD does not include a ``Relevant Service Information'' section. We are, however, incorporating this SB by reference and it is available on the Internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2015- 0277. We did not change this AD.
Request To Clarify Proposed AD Requirements
CFM commented that the Proposed AD Requirements section should be revised to be consistent with the compliance and mandatory terminating action paragraphs in this AD.
We disagree. This AD incorporates changes produced as a result of the comments received, as permitted by the Administrative Procedures Act (APA) (Pub. L. 79-404,5 U.S.C. 551, et. seq.). To take the action the commenter suggests would be contrary to the APA. We did not change this AD.
Request To Allow Use of Later Revisions to SBs
CFM requested that we include a provision in this AD to allow for use of later revisions to CFM SB No. CFM56-7B S/B 72-0964, Revision 1, dated December 15, 2014, and SB No. CFM56-7B S/B 72-0965, dated December 16, 2014.
We disagree. We do not know the content of future revisions of SBs and, therefore, cannot approve them before publication. We did not change this AD.
Request To Revise Description of Laboratory Analysis
CFM requested we change the wording in the Compliance section of this AD from ``particles lab analysis'' to ``laboratory analysis.''
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We agree. The term ``laboratory analysis'' is more accurate. We revised the term ``particles lab analysis'' to read ``laboratory analysis'' in the Compliance section of this AD.
Request To Include Serial Numbers of Affected Gearshafts
CFM requested that we include the S/Ns of the affected 73-tooth and 41-tooth gearshafts in this AD instead of referencing the SBs. CFM indicated that CFM56-3 operators may not have access to the CFM56-7B SBs.
We disagree. Operators have access to CFM SB No. CFM56-7B S/B 72- 0964, Revision 1, dated December 15, 2014, in the AD docket on the Internet at http://www.regulations.gov by searching for and locating Docket No. FAA-2015-0277, or by requesting the SB from CFM. We did not change this AD.
Request To Limit Applicability by Engine Serial Number
Sun Country Airlines requested that the Applicability of this AD be limited to CFM56-7B engines with engine S/Ns listed in Appendix A of CFM SB No. CFM56-7B S/B 72-0964 and CFM56-7B engines that have the 73- tooth gearshafts listed in Appendix B of CFM SB No. CFM56-7B S/B 72- 0964 installed post-production. Sun Country Airlines noted that the applicability of the NPRM (80 FR 24856, May 1, 2015) could be misconstrued to mean to include all CFM56-7B engines unless it is proven that they do not have the affected 73-tooth or 41-toth gearshafts.
We disagree. CFM identified the affected population of gearshafts by gearshaft S/N and by the engine S/N on which it was installed. However, an affected gearshaft may now be installed on an engine with an S/N not listed in Appendix A. To address the latter population, those engines with a gearshaft that has been installed on an unknown engine, we identified the affected population of 73-tooth and 41-tooth gearshafts by gearshaft part number and S/N. We did not change this AD.
Request To Clarify That Applicability Is by Gearshaft Serial Number
Delta Air Lines (Delta) requested that we clarify that the applicability of the AD is by gearshaft S/N rather than by engine S/N.
We agree. We revised the Applicability paragraph of this AD to read: ``This AD applies to all CFM International S.A. (CFM) CFM56-7B and CFM56-3 engines with a 73-tooth or 41-tooth gearshaft installed in the accessory gearbox (AGB), that has a gearshaft serial number in Appendix A or Appendix B of CFM Service Bulletin (SB) No. CFM56-7B S/B 72-0964, Revision 1, dated December 15, 2014.''
Request To Verify Affected Gearshafts Have Been Removed From Service and Reduce the Scope of Applicability
Delta requested that we verify which gearshafts have been removed from service per the proposed requirements of the NPRM (80 FR 24856, May 1, 2015). Delta further asked that we reduce the applicability to only those affected gearshafts that remain in service.
We disagree. This AD will ensure that all affected gearshafts are removed from service and that gearshafts already removed from service are not returned to service. We did not change this AD.
Support for the NPRM
The Boeing Company and an anonymous commenter expressed support for the NPRM (80 FR 24856, May 1, 2015) as proposed.
Conclusion
We reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting this AD with the changes described previously.
We also determined that these changes will not increase the economic burden on any operator or increase the scope of this AD.
Related Service Information Under 1 CFR Part 51
We reviewed CFM SB No. CFM56-7B S/B 72-0964, Revision 1, dated December 15, 2014. The service information describes procedures for removal of affected 73-tooth and 41-tooth gearshafts. This service information is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section of this AD.
Costs of Compliance
We estimate that this AD will affect about 67 engines installed on airplanes of U.S. registry. We also estimate that it will take about 1 hour per engine to do the inspection and 8 hours per engine to replace each affected gearshaft. We estimate thirty-six 73-tooth gearshafts and forty 41-tooth gearshafts will need replacement at a cost of $12,480 and $7,680 per part, respectively. The average labor rate is $85 per hour. Based on these figures, we estimate the cost of this AD on U.S. operators to be $813,855.
Authority for This Rulemaking
Title 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, section 106, describes the authority of the FAA Administrator. Subtitle VII: Aviation Programs, describes in more detail the scope of the Agency's authority.
We are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701: ``General requirements.'' Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices, methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope ofthat authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.
Regulatory Findings
This AD will not have federalism implications under Executive Order 13132. This AD will 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.
For the reasons discussed above, I certify that this AD:
(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),
(3) Will not affect intrastate aviation in Alaska to the extent that it justifies making a regulatory distinction, and
(4) 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.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.