AD 2008-13-29

This AD is effective August 12, 2008.

The Director of the Federal Register approved the incorporation by reference of a certain publication listed in this AD as of August 12, 2008.

For service information identified in this AD, contact Boeing Commercial Airplanes, Long Beach Division, 3855 Lakewood Boulevard, Long Beach, California 90846, Attention: Data and Service Management, Dept. C1-L5A (D800-0024).

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.

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 McDonnell Douglas Model DC-9-81 (MD-81), DC-9-82 (MD-82), DC-9-83 (MD-83), DC-9-87 (MD-87), and MD-88 airplanes. That NPRM was published in the Federal Register on September 28, 2007 (72 FR 55111). That NPRM proposed to require repetitive inspections for cracking of the overwing frames from stations 845 to 905 (MD-87 stations 731 to 791), left and right sides, and corrective actions if necessary.

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

Air Transport Association (ATA), on behalf of its member American Airlines, states that a 24-month compliance period for the initial inspections would be overly burdensome. The commenters request that we extend the compliance time to 48 months so operators can integrate the required actions with planned heavy maintenance visits. The commenters add that we did not consider the size of the fleet and the availability of parts when we determined the compliance period. American Airlines finds that a longer compliance time can be justified by applying statistically based risk analysis methods and accounting for the effect of flight cycles.

We do not agree to extend the compliance time. We have no data or analysis to support such an extension of the compliance period. For airplanes that have accumulated more than 20,000 total flight cycles, the extent of damage already accumulated on the affected fuselage frames cannot be predetermined, so accounting for subsequent flight cycles will provide no benefit. The 24-month compliance period is considered appropriate in light of the characteristics of crack growth, the probability of crack initiation, and the ability of operators to integrate the required actions into established maintenance practices. Currently there are insufficient statistical or other data to justify a compliance period beyond the proposed 24 months. However, paragraph (h) of this final rule provides operators the opportunity to request an extension of the compliance time if data are presented to justify such an extension. We have not changed the final rule regarding this issue.

ATA, on behalf of its member American Airlines, notes that the rate of cracking noted in early inspections suggests that the supply of available spare parts is insufficient to support completion of the proposed actions within the 24-month compliance period. Delta Air Lines also expresses concern over the availability of spare frames and reports that all its repairs done to date have been done by frame replacement with a like part.

We infer that the commenters request that we wait to issue the final rule until sufficient parts are available. We disagree with the need to delay the final rule. Boeing has arranged to have additional frames manufactured as demand builds during the 24-month compliance period. Boeing expects a sufficient supply to be available to support the AD requirements. We are proceeding with issuance of the final rule as proposed.

ATA, on behalf of its member Delta Air Lines, notes that the estimated work hours to do the required actions assume that access to the overwing frames is available during a scheduled maintenance visit. The commenters assert that the 4-hour labor estimate applies only when the inspection can be done during a scheduled heavy maintenance visit, when the airplane is already opened up. Delta states that, in reality, up to 67 percent of its fleet will not be due for the heavy maintenance visit during the proposed compliance time. That portion of the fleet will require special-schedule inspection visits, and add at least 16 work hours to gain access to the inspection areas.

We infer that the commenters are requesting that we revise the cost estimate provided in the NPRM. We do not agree. The cost information provided in AD actions describes only the direct costs of the specific requirements. Based on the best data available, the manufacturer provided the number of work hours to do the required actions for this AD. We recognize that, in doing the actions required by an AD, operators might incur incidental costs, such as the time necessary for access and close, in addition to the direct costs. These incidental costs can vary significantly among operators. We have not changed the final rule regarding this issue.

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

We consider this AD interim action. The manufacturer is currently developing a modification that will address the unsafe condition identified in this AD. Once this modification is developed, approved, and available, we may consider additional rulemaking.

There are about 1,189 airplanes of the affected design in the worldwide fleet. The following table provides the estimated costs for U.S. operators to comply with this AD.

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: