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AGENCY:

Federal Aviation Administration (FAA), DOT.

ACTION:

Notice of proposed rulemaking (NPRM).

SUMMARY:

We propose to adopt a new airworthiness directive (AD) for all McDonnell Douglas Model MD-90-30 airplanes. This proposed AD would require repetitive inspections for cracks of the upper aft skin panels on the horizontal stabilizer, and related investigative and corrective actions if necessary. This proposed AD results from a report of cracks found in the aft skin panels on the upper right side of the horizontal stabilizer at the aft inboard corner. We are proposing this AD to detect and correct cracks in the fail-safe structure that may not be able to sustain limit load, which could result in the loss of overall structural integrity of the horizontal stabilizer.

DATES:

We must receive comments on this proposed AD by May 7, 2009.

ADDRESSES:

You may send comments by any of the following methods:

• Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the instructions for submitting comments.
• Fax: 202-493-2251.
• Mail: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590.
• Hand Delivery: U.S. Department of Transportation, Docket Operations, M-30, West Building Ground Floor, Room W12-140, 1200 New Jersey Avenue, SE., Washington, DC 20590, between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays.

For service information identified in this AD, contact Boeing Commercial Airplanes, Attention: Data & Services Management, 3855 Lakewood Boulevard, MC D800-0019, Long Beach, California 90846-0001; telephone 206-544-5000, extension 2; fax 206-766-5683; e-mail dse.boecom@boeing.com; Internet https://www.myboeingfleet.com. You may review copies of the referenced service information at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington. For information on the availability of this material at the FAA, call 425-227-1221 or 425-227-1152.

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 proposed AD, the regulatory evaluation, any comments received, and other information. The street address for the Docket Office (telephone 800-647-5527) is in the ADDRESSES section. Comments will be available in the AD docket shortly after receipt.

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FOR FURTHER INFORMATION CONTACT:

Roger Durbin, Aerospace Engineer, Airframe Branch, ANM-120L, FAA, Los Angeles Aircraft Certification Office, 3960 Paramount Boulevard, Lakewood, California 90712-4137; telephone (562) 627-5233; fax (562) 627-5210.

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SUPPLEMENTARY INFORMATION:

Comments Invited

We invite you to send any written relevant data, views, or arguments about this proposed AD. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2009-0160; Directorate Identifier 2008-NM-176-AD” at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this proposed AD. We will consider all comments received by the closing date and may amend this proposed AD because of those comments.

We will post all comments we receive, without change, to http://www.regulations.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive about this proposed AD.

Discussion

We have received a report that one operator found two instances of a crack in the aft skin panel on the upper right side of the horizontal stabilizer at the aft inboard corner. The airplanes had accumulated 16,659 total flight cycles/31,403 total flight hours and 18,128 total flight cycles/33,959 total flight hours. The cause of the cracking on the aft skin panel on the upper right side of the horizontal stabilizer is suspected to be fatigue. This condition, if not detected and corrected, could result in cracks in the fail-safe structure that may not be able to sustain limit load, which could result in the loss of overall structural integrity of the horizontal stabilizer.

Relevant Service Information

We have reviewed Boeing Alert Service Bulletin MD90-55A012, dated September 23, 2008. The service bulletin describes procedures for repetitive eddy current inspections to detect cracks on the upper aft skin panels on the left and right sides of the horizontal stabilizer, and related investigative and corrective actions. The initial compliance time is 13,500 total flight cycles or 24 months after the effective date of this AD, whichever occurs later. The related investigative actions include repetitive eddy current inspections for cracks of the rear spar upper caps of the left and right sides of the horizontal stabilizer. The repetitive interval for the inspection is within 1,600 or 2,100 flight cycles, depending on the previous inspection method used.

Corrective actions include, depending on crack findings and crack location, installing the upper aft skin panel splice of the horizontal stabilizer, and replacing the upper aft skin panel of the horizontal stabilizer. The service bulletin describes three options, depending on crack findings and crack location:

• (Option 1) The service bulletin describes procedures for a high frequency eddy current inspection of the rear spar cap of the horizontal stabilizer and installation of the upper aft skin panel splice of the horizontal stabilizer before further flight, and an eddy current inspection on the upper aft skin panel of the horizontal stabilizer within 13,500 flight cycles after the installation. If the crack is on the rear spar cap of the horizontal stabilizer, the service bulletin specifies to contact Start Printed Page 12101Boeing for repair instructions and do the repair before further flight.
• (Option 2) The service bulletin describes procedures for a high frequency eddy current inspection of the rear spar cap of the horizontal stabilizer, remove and replace the upper aft skin panel of the horizontal stabilizer before further flight, and an eddy current inspection of the upper aft skin panel of the horizontal stabilizer within 13,500 flight cycles. If the crack is on the rear spar cap of the horizontal stabilizer, the service bulletin specifies to contact Boeing for further repair instructions and do the repair before further flight.
• (Option 3) The service bulletin specifies one option is to contact Boeing for possible temporary repair of skin cracks and do the repair before further flight.

FAA's Determination and Requirements of This Proposed AD

We are proposing this AD because we evaluated all relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of the(se) same type design(s). This proposed AD would require accomplishing the actions specified in the service information described previously, except as discussed under “Difference Between the Proposed AD and Service Bulletin.”

Difference Between the Proposed AD and Service Bulletin

Boeing Alert Service Bulletin MD90-55A012, dated September 23, 2008, specifies to contact the manufacturer for instructions on how to repair certain conditions, but this proposed AD would require repairing those conditions in one of the following ways:

• Using a method that we approve; or
• Using data that meet the certification basis of the airplane, and that have been approved by an Authorized Representative for the Boeing Commercial Airplanes Delegation Option Authorization Organization whom we have authorized to make those findings.

Costs of Compliance

We estimate that this proposed AD would affect 16 airplanes of U.S. registry. The following table provides the estimated costs for U.S. operators to comply with this proposed AD.

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.

Regulatory Findings

We determined that this proposed AD would not have federalism implications under Executive Order 13132. This proposed AD would 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 proposed regulation:

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.

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

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List of Subjects in 14 CFR Part 39

• Air transportation
• Aircraft
• Aviation safety
• Incorporation by reference
• Safety

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The Proposed Amendment

Accordingly, under the authority delegated to me by the Administrator, the FAA proposes to amend 14 CFR part 39 as follows:

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PART 39—AIRWORTHINESS DIRECTIVES

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

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Authority: 49 U.S.C. 106(g), 40113, 44701.

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