Discussion
We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 by adding an AD that would apply to the specified products. The NPRM was published in the Federal Register on January 7, 2014 (79 FR 763). The NPRM proposed to correct an unsafe condition for the specified products. The MCAI states:
There have been in-service events involving the perforation of PT6A small series engine cases as a result of the loss of integrity of Power Turbine (PT) Containment Rings under failure loads. Perforation of engine cases has been seen to result from the liberation of PT blades and from fracture/displacement of the PT Containment Ring itself.
Comments
We gave the public the opportunity to participate in developing this AD. We considered the comments received.
Request To Add Engine Models to the List of Applicable Engines
Friend Aircare requested that we add the engine models listed in P&WC Service Bulletin (SB)No. 12076, Revision 3, dated January 17, 1992, to the applicability of this AD because that SB requires the same modification to the PT containment ring assembly.
We agree. We revised paragraph (c) of this AD by adding certain serial numbers of the following P&WC engine models: PT6A-11, PT6A-11AG, PT6A-15AG, PT6A-110, PT6A-112, and PT6A-121. We revised paragraph (e) of this AD to specify use of either P&WC SB No. 12076, Revision 3, dated January 17, 1992; or P&WC SB No. PT6A-72-A1427, Revision 3, dated January 27, 2012, as applicable. We revised paragraph (f) of this AD by adding credit for corrective actions taken in accordance with P&WC SB No. 12076, Revision 2, dated April 24, 1991, or earlier versions.
Request To Exclude Engines Used on Single-Engine Aircraft
Reabe Spraying Services, Inc. requested that we exclude from applicability engines used on single-engine aircraft, or aircraft where the engine has nothing alongside of it that would sustain damage from releaseof debris.
We disagree. We consider the uncontained release of engine hardware to be an unsafe condition. We did not change this AD.
Request To Withdraw the NPRM
Dynamic Aviation requested that the FAA withdraw the NPRM (79 FR 763, January 7, 2014). Dynamic Aviation has not experienced any PT disk blade failure in 16 years and 800,000 flight hours.
We disagree. There have been in-service events involving the perforation of PT6A series engine cases as a result of the loss of integrity of the PT containment rings under failure loads. Perforation of engine cases has been seen to result from the liberation of PT blades and from fracture/displacement of the PT containment ring itself. We consider the release of engine hardware to be an unsafe condition. This AD requires the incorporation of P&WC SB No. 12076, Revision 3, dated January 17, 1992, or P&WC SB No. PT6A-72-A1427, Revision 3, dated January 27, 2012, as applicable, to prevent uncontained events. We did not change this AD.
Requests To Extend the Period of Compliance
Dynamic Aviation requested that we change the compliance time from within 24 months after the effective date of this AD, to within 36 to 48 months after the effective date of this AD. Dynamic Aviation said the extended compliance period would better allow the complete modification of all engines.
Ameriflight LLC requested that we reconsider the period of compliance to allow a longer, more realistic timeframe for compliance.
We agree. The compliance period can be increased without an appreciable risk effect. We revised paragraph (e)(2) of this AD to read, ``Within 48 months after the effective date of this AD, modify the existing PT containment ring.''
Request To More Accurately Estimate the Time Required To Modify an Engine
Several entities requested that the estimated time and costs of compliance for completing the requirements of this AD more accurately reflect the actual time required to modify an engine.
We agree. In the NPRM (79 FR 763, January 7, 2014), we based our estimate of 3 hours to modify an engine on original equipment manufacturer service information. Further analysis indicates this estimate is inadequate. We increased the estimated hours required to modify an engine from 3 hours to 20 hours.
Conclusion
We reviewed the available data, including the comments received, and determined that air safety and the public interest require adopting this AD with the changes described previously. We determined that these changes will not increase the economic burden on any operator or increase the scope of this AD.
Costs of Compliance
We estimate that this AD affects 1,000 engines installed on airplanes of U.S. registry. We estimate that it will take about 20 hours per engine to comply with this AD. The average labor rate is $85 per hour. Required parts cost about $1,655 per engine. Based on these figures, we estimate the cost of this AD on U.S. operators to be$3,355,000.
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 of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action.
Regulatory Findings
We determined that 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 this AD:
(1) Is not a ``significant regulatory action'' under Executive Order 12866,
(2) Is not a ``significant rule'' under the DOT Regulatory Policies and
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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.