Federal Aviation Administration (FAA), DOT.
We are adopting a new airworthiness directive (AD) for all Boeing Model 757 airplanes. This AD requires 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. This AD also provides optional terminating action for the repetitive inspections. This AD results from reports of cracks found at the anchor tab of the bulkhead seal assemblies of the wing TAI system. In one incident, the anchor tab and bulkhead seal assembly had separated because of the cracks. We are issuing this AD to prevent failure of the anchor tab of the bulkhead seal assembly, which in icing conditions could result in insufficient airflow to the wing TAI system, subsequent ice on the wings, and consequent reduced controllability of the airplane.
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.
Examining the AD Docket
You may examine the AD docket on the Internet at http://www.regulations.gov; or in person at the Docket Management Facility 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 address for the Docket Office (telephone 800-647-5527) is the Document Management Facility, U.S. Department of Transportation, Docket Operations, M-30, West Building, Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.Start Further Info
FOR FURTHER INFORMATION CONTACT:
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.End Further Info End Preamble Start Supplemental Information
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 Start Printed Page 19994terminating action for the repetitive inspections.
We gave the public the opportunity to participate in developing this AD. We considered the comments received.
Support for the NPRM
Boeing concurs with the contents of the NPRM.
Request To Extend Compliance Time
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.
Request To Increase Work Hour Estimate
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.
Costs of Compliance
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.
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.
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.Start List of Subjects
List of Subjects in 14 CFR Part 39End List of Subjects
Adoption of the AmendmentStart Amendment Part
Accordingly, under the authority delegated to me by the Administrator, the FAA amendsEnd Amendment Part Start Part
PART 39—AIRWORTHINESS DIRECTIVESEnd Part Start Amendment Part
1. The authority citation for part 39 continues to read as follows:End Amendment Part
2. The FAA amends § 39.13 by adding the following new AD:End Amendment Part
2008-08-12 Boeing: Amendment 39-15464. Docket No. FAA-2007-0339; Directorate Identifier 2007-NM-182-AD.
(a) This airworthiness directive (AD) is effective May 19, 2008.
(c) This AD applies to all Boeing Model 757-200, -200PF, -200CB, and -300 series airplanes, certificated in any category.Start Printed Page 19995
(d) This AD results from reports of cracks found at the anchor tab of the bulkhead seal assemblies of the wing thermal anti-ice (TAI) system. In one incident, the anchor tab and bulkhead seal assembly had separated because of the cracks. We are issuing this AD to prevent failure of the anchor tab of the bulkhead seal assembly, which in icing conditions could result in insufficient airflow to the wing TAI system, subsequent ice on the wings, and consequent reduced controllability of the airplane.
(e) You are responsible for having the actions required by this AD performed within the compliance times specified, unless the actions have already been done.
Repetitive Inspections/Corrective Action
(f) At the applicable times specified in paragraph 1.E., “Compliance,” of Boeing Special Attention Service Bulletin 757-30-0021 or 757-30-0022, both Revision 1, both dated June 13, 2007, as applicable; except where the service bulletins specify starting the compliance time “ * * * from the date on this service bulletin,” this AD requires starting the compliance time from the effective date of this AD: Perform detailed inspections for cracks of the anchor tab of the bulkhead seal assemblies of the wing TAI system at certain outboard stations of the left and right wings by doing all the actions, including all applicable corrective actions, in accordance with the Accomplishment Instructions of the applicable service bulletin. Do all applicable corrective actions before further flight.
Optional Terminating Action
(g) Installing a new duct anchor support bracket adjacent to the bulkhead seal assemblies in accordance with Part 2 of the Accomplishment Instructions of Boeing Special Attention Service Bulletin 757-30-0021 or 757-30-0022, both Revision 1, both dated June 13, 2007, as applicable, ends the repetitive inspections required by paragraph (f) of this AD.
Credit for Actions Done According to Previous Issue of Service Information
(h) Actions accomplished before the effective date of this AD in accordance with Boeing Special Attention Service Bulletins 757-30-0021 and 757-30-0022, both dated August 15, 2006, are considered acceptable for compliance with the corresponding actions specified in this AD.
Alternative Methods of Compliance (AMOCs)
(i)(1) The Manager, Seattle Aircraft Certification Office, FAA, has the authority to approve AMOCs for this AD, if requested in accordance with the procedures found in 14 CFR 39.19.
(2) To request a different method of compliance or a different compliance time for this AD, follow the procedures in 14 CFR 39.19. Before using any approved AMOC on any airplane to which the AMOC applies, notify your appropriate principal inspector (PI) in the FAA Flight Standards District Office (FSDO), or lacking a PI, your local FSDO.
Material Incorporated by Reference
(j) You must use Boeing Special Attention Service Bulletin 757-30-0021, Revision 1, dated June 13, 2007; or Boeing Special Attention Service Bulletin 757-30-0022, Revision 1, dated June 13, 2007; as applicable; to do the actions required by this AD, unless the AD specifies otherwise.
(2) For service information identified in this AD, contact Boeing Commercial Airplanes, P.O. Box 3707, Seattle, Washington 98124-2207.
(3) You may review copies of the service information incorporated by reference at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html.Start Signature
Issued in Renton, Washington, on April 3, 2008.
Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. E8-7662 Filed 4-11-08; 8:45 am]
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