AD 2008-16-18

This AD becomes effective September 15, 2008. The Director of the Federal Register approved the incorporation by reference of certain publications listed in this AD as of September 15, 2008.

The Docket Operations office is located at Docket Management Facility, U.S. Department of Transportation, 1200 New Jersey Avenue, SE., West Building Ground Floor, Room W12-140, Washington, DC 20590-0001.

Jason Yang, Aerospace Engineer, Engine Certification Office, FAA, Engine & Propeller Directorate, 12 New England Executive Park, Burlington, MA 01803; e-mail: jason.yang@faa.gov; telephone (781) 238-7747; fax (781) 238-7199.

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an AD that would apply to the specified products. That NPRM was published in the Federal Register on October 24, 2007 (72 FR 60293). That NPRM proposed to correct an unsafe condition for the specified products. The Civil Aviation Authority (CAA), which is the aviation authority for the United Kingdom, has issued United Kingdom Airworthiness Directive G-2006-0002, dated February 13, 2006, to correct an unsafe condition for the specified products. The CAA AD states:

A population of HP turbine discs that were manufactured between 1989-1999 and which were subject to possible machining anomalies, were believed to have an increased chance of suffering from cooling air hole cracking, compared to the general fleet population of HP turbine discs. As a result of this risk, Rolls-Royce issued Non-Modification Service Bulletin (NMSB) 72-C816, recommending in-service inspections of the subject discs.

Recently an RB211 HP turbine disc has been found with a crack which had propagated further than expected from the risk model that was used to establish the original inspection defined in the above NMSB; This has led to the need for a revision of the original inspection requirements.

An HP turbine disc fracture would be uncontained and create a potential unsafe condition. Accordingly, this AD introduces revised inspection requirements to reflect the increased risk of HP turbine disc cracking and potential disc fracture.

You may obtain further information by examining the CAA AD in the AD docket.

We gave the public the opportunity to participate in developing this AD. We considered the comment received. The commenter supports the NPRM.

We changed the paragraph layering in paragraph (e) of the regulatory text to clarify the requirements for disks that have a serial number in Table 1 of this AD and disks that don't have a serial number in Table 1 of this AD.

We reviewed the available data, including the comment received, and determined that air safety and the public interest require adopting the AD with the change described previously. We determined that this change will not increase the economic burden on any operator or increase the scope of the AD.

We estimate that this AD will affect 72 engines of U.S. registry. We also estimate that it will take about 10 work-hours per product to comply with this AD. The average labor rate is $80 per work-hour. Required parts will cost about $15,000 per product. Based on these figures, we estimate the total cost of the proposed AD to U.S. operators to be $1,137,600. Our cost estimate is exclusive of possible warranty coverage.

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 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); and

3. 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.

We prepared a regulatory evaluation of the estimated costs to comply with this AD and placed it in the AD docket.

You may examine the AD docket on the Internet at http://www.regulations.gov; or in person at the Docket Operations office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The AD docket contains this AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Operations office (telephone (800) 647-5527) is provided in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

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:

2. The FAA amends § 39.13 by adding the following new AD: