AD 2012-02-07

This AD is effective March 6, 2012.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of February 22, 2011 (76 FR 6323, February 4, 2011).

For service information identified in this AD, contact General Electric Company, GE-Aviation, Room 285, 1 Neumann Way, Cincinnati, OH 45215, phone: (513) 552-3272; email: geae.aoc@ge.com. You may review copies of the referenced service information at the FAA, Engine & Propeller Directorate, 12 New England Executive Park, Burlington, MA. For information on the availability of this material at the FAA, call (781) 238-7125.

Tomasz Rakowski, Aerospace Engineer, Engine Certification Office, FAA, Engine & Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803; phone: (781) 238-7735; fax: (781) 238-7199; email: tomasz.rakowski@faa.gov.

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to supersede AD 2011-02-07, Amendment 39-16580 (76 FR 6323, February 4, 2011) and AD 2011-18-01, Amendment 39-16783 (76 FR 52213, August 22, 2011). Those ADs apply to the specified products. The NPRM published in the Federal Register on October 19, 2011 (76 FR 64844). That NPRM proposed to retain the requirements of AD 2011-02-07 and AD 2011-18-01, except that reporting to the FAA would no longer be required and there would be an optional LPT rotor stage 3 disk removal after a failed HPT blade BSI or a failed engine core vibration survey. That NPRM also proposed to establish a new lower life limit for the LPT rotor stage 3 disk part numbers listed in Table 1 of the proposed AD, and proposed to require removing these disks from service at times determined by a drawdown plan.

We gave the public the opportunity to participate in developing this AD. The following presents the comments received on the proposal and the FAA's response to each comment.

One commenter, The Boeing Company, supports the NPRM (76 FR 64844, October 19, 2011) as written.

One commenter, MTU Maintenance Hannover GmbH, requested that we add a paragraph that allows credit for performing vibration surveys in a test cell, as meeting the AD vibration survey requirements.

We agree. We added paragraph (k)(8) to the AD, which states “Vibration surveys carried out in an engine test cell as part of an engine manual performance run fulfill the vibration survey requirements of paragraphs (k)(2) through (k)(3) of this AD.”

One commenter, Evergreen International Airlines, requested that we add a requirement that two consecutive raw EGT trend data point exceedances must be confirmed by a corresponding shift of other engine parameters to trigger the HPT blade BSI.

We partially agree. We agree that EGT system error should not force a BSI of turbine blades. But we disagree with troubleshooting the EGT raw data points once the EGT system error was ruled out. We added paragraph (o)(4) to the AD to state that, for the purposes of this AD, a raw EGT trend data point above the smoothed average is a confirmed temperature reading over the rolling average of EGT readings that is not a result of EGT system error. We also rearranged the wording in paragraph (iv) in Table 2 of the AD for clarification.

Since we issued the NPRM (76 FR 67844, October 19, 2011), we discovered that, in applicability paragraph (c), engine model CF6-50-E2D was incorrect. We corrected it to read CF6-50E2B in the AD.

We reviewed the relevant data, considered the comments received, and determined that air safety and the public interest require adopting the AD with the changes described previously. We have determined that these minor changes:

• Are consistent with the intent that was proposed in the NPRM (76 FR 64844, October 19, 2011) for correcting the unsafe condition; and

• Do not add any additional burden upon the public than was already proposed in the NPRM.

We also determined that these changes will not increase the economic burden on any operator or increase the scope of the AD.

We estimate that this AD will affect 387 CF6-45 and CF6-50 series turbofan engines installed on airplanes of U.S. registry. We also estimate that it will take about 8 work-hours to perform the HPT blade inspection, 6 work-hours to perform a vibration survey, 4 work-hours to perform an ultrasonic inspection, 2 work-hours to perform an EGT resistance check, 1 work-hour to perform an EGT thermocouple inspection, and 7 work-hours to clean and perform an fluorescent-penetrant inspection of the LPT rotor stage 3 disk for each engine. The average labor rate is $85 per work-hour. The cost estimate for the work just described was covered in the two ADs we are superseding. For this AD, we estimate that a replacement LPT rotor stage 3 disk prorated part cost is $75,000. Based on these figures, we estimate the total cost of this AD to U.S. operators to be $29,025,000.

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.

We have 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 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, 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 14 CFR part 39 as follows:

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