AD 94-04-08

A proposal to amend part 39 of the Federal Aviation Regulations to include an airworthiness directive (AD) that is applicable to certain McDonnell Douglas Model DC-10 series airplanes and Model KC-10A (military) airplanes was published in the Federal Register on October 26, 1993 (58 FR 57568). That action proposed to require inspections to detect cracking in the No. 2 engine pylon lower spar forward mount and thrust link fitting attach bolts, replacement of cracked bolts, and the eventual replacement of all bolts made of H-11 material with bolts made of Inconel.

Interested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received.

One commenter supports the proposal.

Two commenters request that the proposed compliance time for the inspections be extended to coincide with normally scheduled maintenance intervals. These commenters suggest that if the compliance times were extended to 24 months, the confusion and expense of special scheduling could be avoided. The FAA does not concur. In developing the proposed compliance time, the FAA primarily considered analyses of the mode of failure of the subject bolts due to stress corrosion, as well as the service history of the fleet. Based on this data and the safety implications presented by loss of fail-safe capability of the attachment assembly should the bolts fail, the FAA has determined that the proposed compliance times of 12 months for the initial inspection and 18 months for the repetitive inspection interval are both appropriate and warranted. Further, the FAA took into account the average utilization rate of the affected fleet, the practical aspects of an orderly inspection of the fleet during regular maintenance periods, and the availability of required replacement parts. The compliance times as proposed should allow ample time for the inspections to be conducted concurrently with scheduled maintenance, thereby minimizing the costs associated with special airplane scheduling. In light of all of these factors, the FAA considers that any extension of the compliance intervals to be unacceptable.

After careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule as proposed.

There are approximately 354 Model DC-10 series airplanes and Model KC-10A airplanes of the affected design in the worldwide fleet. The FAA estimates that 206 airplanes of U.S. registry will be affected by this AD.

The inspections required by this AD will take approximately 8 work hours per airplane to accomplish, at an average labor rate of $55 per work hour. Based on these figures, the total cost impact of the inspections requirements of this AD on U.S. operators is estimated to be $90,640, or $440 per airplane, per inspection cycle.

The replacement actions requiredby this AD will take approximately 8 work hours per airplane to accomplish, at an average labor rate of $55 per work hour. Required parts will cost approximately $2,700 per airplane. Based on these figures, the total cost impact of the replacement actions of this AD on U.S. operators is estimated to be $646,840, or $3,140 per airplane.

The total cost impact figures discussed above are based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted.

The regulations adopted herein will not have substantial direct effects 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. Therefore, in accordance with Executive Order 12612, it is determined that this final rule does not have sufficient federalism implications to warrant thepreparation of a Federalism Assessment.

For the reasons discussed above, I certify that this action (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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it may be obtained from the Rules Docket at the location provided under the caption "ADDRESSES."

List of Subjects in 14 CFR Part 39

Air transportation, Aircraft, Aviation safety, Incorporation by reference, Safety.

Adoption of the Amendment

Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 14 CFR part 39 of the Federal Aviation Regulations as follows:

PART 39 - AIRWORTHINESS DIRECTIVES

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

Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89.

§ 39.13 - (Amended)

2. Section 39.13 is amended by adding the following new airworthiness directive: