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 July 11, 2014 (79 FR 40018). The NPRM proposed to correct an unsafe condition for the specified products. The MCAI states:
A Trent engine experienced an engine internal fire, caused by combustion of carbon deposits inside the high/intermediate (HP/IP) oil vent tubes. The consequent chain of events resulted in the failure of the IP turbine disk drive arm. Similar engine architecture exists on Trent 800 series engines.
This condition, if not corrected, could lead to uncontained multiple turbine blade failures or an IP turbine disk burst, possibly resulting in damage to, and reduced control of, the aeroplane.
Prompted by these findings, an Intermediate Pressure Turbine Overspeed System (IPTOS) protection scheme has been developed for Trent 800 engines installed on Boeing 777 aeroplanes.
For the reasons described above, this AD requires introduction of the IPTOS protection function by installation of a new software standard (B7.2) in the engine electronic controller (EEC), which will protect against IP turbine overspeed when IP shaft failure is detected.
Since we issued the NPRM (79 FR 40018, July 11, 2014), we issued a supplemental NPRM (79 FR 70475, November 26, 2014) to amend the costs of compliance and to more clearly state certain compliance requirements. Since we issued the supplemental NPRM, we changed paragraph (e) of this AD for clarity.
Comments
We gave the public the opportunity to participate in developing this AD. We considered the comments received.
Request To Modify the Installation Prohibition Paragraph
American Airlines (AA) requested that we modify the Installation Prohibition paragraph (f) to allow installation of an EEC with a software standard earlier than B7.2, and coincidenton-wing upgrade of the software standard to B7.2 or later, but prohibit operation of an engine that incorporates a software standard earlier than B7.2. AA states that the EEC original equipment manufacturer does not update the software as part of a component shop visit.
We agree. We modified the Installation Prohibition paragraph (f) to allow installation of an EEC with a software standard earlier than B7.2, but to prohibit operation of an engine with a software standard earlier than B7.2.
Conclusion
We reviewed the available data, including the comment 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 about 140 engines installed on airplanes of U.S. registry. We also estimate that it would take about 2 hours perengine to
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comply with this AD. 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 $23,800.
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 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.