AD 2008-08-12

This AD is effective May 19, 2008.

The Director of the Federal Register approved the incorporation by reference of certain publications listed in this AD as of May 19, 2008.

For service information identified in this AD, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.

Barbara Mudrovich, Aerospace Engineer, Cabin Safety and Environmental Systems Branch, ANM-150S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 917-6477; fax (425) 917-6590.

We issued a notice of proposed rulemaking (NPRM) to amend 14 CFR part 39 to include an airworthiness directive (AD) that would apply to all Boeing Model 757 airplanes. That NPRM was published in the Federal Register on December 17, 2007 (72 FR 71275). That NPRM proposed to require repetitive inspections of the anchor tab of the bulkhead seal assemblies of the wing thermal anti-ice (TAI) system for cracks at certain outboard stations of the left and right wings, and corrective action if necessary. That NPRM also proposed to provide for optional terminating action for the repetitive inspections.

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

Boeing concurs with the contents of the NPRM.

Northwest Airlines (NWA) asks that the repetitive inspection intervals specified in the NPRM be changed from 6,000 flight hours to 24 months. NWA states that because the NPRM already allows up to 36 months after the airplane has accumulated 20,000 total flight hours to accomplish the initial check, an acceptable level of safety would be maintained if repetitive intervals coincide with operator-scheduled heavy check intervals not to exceed 24 months. NWA adds that if repetitive inspections are at the proposed 6,000-flight-hour intervals, the inspections would need to be accomplished in a line environment. NWA asks that we allow the repetitive inspections to be done during heavy maintenance checks where specialized personnel are available in a controlled environment more conducive to performing the work.

We do not agree to extend the compliance time for the repetitive inspections. Based on data from the manufacturer, we find that a 6,000-flight-hour interval is appropriate. We do not currently have data or analysis, nor did NWA provide any, that can support such an extension of the compliance time. We have determined that the 6,000-flight-hour compliance time is appropriate given the probability of crack initiation, crack growth characteristics, and the ability of operators to integrate the required actions into established maintenance practices. However, according to the provisions of paragraph (i) of this AD, we may approve requests to adjust the compliance time if the request includes data that prove that the new compliance time would provide an acceptable level of safety. We have made no change to the AD in this regard.

NWA also states that the work-hour estimate specified in the Costs of Compliance section of the NPRM is underestimated. NWA states that the 2-hour estimate for the inspections is well below the estimate provided by Boeing Special Attention Service Bulletins 757-30-0021 and 757-30-0022, both Revision 1, both dated June 13, 2007, as referenced in the NPRM. NWA adds that an accurate estimate for accomplishing the inspections is 8 work hours (2 work hours per support) when access is provided at a heavy maintenance check.

From this comment, we infer that NWA would like us to increase the work-hour estimate given in the NPRM. We do not agree. The cost information below describes only the direct costs of the specific actions required by this AD. Based on the best data available, the manufacturer provided the number of work hours (2) necessary to do the required inspections, as specified in the service bulletins. This number represents the time necessary to perform only the actions actually required by this AD. We recognize that, in doing the actions required by an AD, operators might incur incidental costs in addition to the direct costs. The cost analysis in AD rulemaking actions, however, typically does not include incidental costs such as the time required to gain access and close up, time necessary for planning, or time necessitated by other administrative actions. Those incidental costs, which might vary significantly among operators, are almost impossible to calculate. We have made no change to the AD in this regard.

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

There are about 929 airplanes of the affected design in the worldwide fleet. This AD affects about 530 airplanes of U.S. registry. The inspection takes about 2 work hours per airplane, at an average labor rate of $80 per work hour. Based on these figures, the estimated cost of the AD for U.S. operators is $84,800, or $160 per airplane, per inspection cycle.

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), 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.

You can find our regulatory evaluation and the estimated costs of compliance in the AD Docket.

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: