AD 2014-07-02

This AD is effective May 8, 2014.

Robert Morlath, Aerospace Engineer, Engine Certification Office, FAA, Engine & Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803; phone: (781) 238-7154; fax: (781) 238-7199; email: robert.c.morlath@faa.gov.

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2012-26-14, Amendment 39-17309 (78 FR 2195, January 10, 2013), (“AD 2012-26-14”). AD 2012-26-14 applied to the specified products. The NPRM published in the Federal Register on November 19, 2013 (78 FR 69316). The NPRM proposed to continue to require removal from service of certain HP compressor stages 1 to 6 rotor disc assemblies before exceeding certain thresholds. The NPRM also proposed to restrict the applicability to engines exposed to silver-plated nuts, and to remove the terminating action statement required by AD 2012-26-14.

We gave the public the opportunity to participate in developing this AD. We considered the comments received.

RRD requested that we include the installation of a new HP compressor stages 1 to 6 rotor disc assembly with silver-free nuts, part number (P/N) U755872, as a necessary terminating action to the parts removal requirements of this AD, because this would eliminate the unsafe condition caused by silver nut corrosion.

We disagree. The flight cycle limits imposed by this AD on engines operating with silver-plated nuts provide an acceptable level of safety. Requiring operators to purchase a new HP compressor stages 1 to 6 rotor disc assembly and new silver-free nuts would be an undue economic burden. If an operator chooses to install a new HP compressor stages 1 to 6 rotor disc assembly and silver-free nuts, P/N U755872, this AD would no longer apply to that engine. We did not change this AD.

RRD requested that instead of requiring a one-time replacement of the HP compressor stages 1 to 6 rotor disc assembly installed with silver-plated nuts, we require replacement of the P/Ns at intervals published in European Aviation Safety Agency (EASA) AD 2012-0230, Initial Issue, dated October 30, 2012.

We disagree. Our proposed AD did not require a one-time replacement. This AD requires, for any HP compressor stages 1 to 6 rotor disc assembly that has ever been installed with silver-plated nuts, replacement at the cyclic limits stated in paragraphs (e)(1) and (e)(2) of this AD, which are equivalent to the cyclic limits stated in EASA AD 2012-0230, Initial Issue, dated October 30, 2012. We did not change this AD.

RRD requested that we update references to service bulletins (SBs) to the most recent versions.

We disagree. We do not reference any SBs in this AD. We did not change this AD.

We reviewed the available data, including the comments received, and determined that air safety and the public interest require adopting the AD as proposed.

We estimate that this AD affects 255 engines installed on airplanes of U.S. registry. We also estimate that it will take about 20 hours per engine to comply with this AD. The average labor rate is $85 per hour. Prorated parts life will cost about $13,500 per engine. Based on these figures, we estimate the cost of this AD on U.S. operators to be $3,876,000.

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.

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.

Accordingly, under the authority delegated to me by the Administrator, the FAA amends part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

1. The authority citation for part 39 continues to read as follows:

2. The FAA amends § 39.13 by removing airworthiness directive (AD) 2012-26-14, Amendment 39-17309 (78 FR 2195, January 10, 2013) and adding the following new AD: