AD 96-10-17

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain McDonnell Douglas Model DC-10-10, -15, and -30 series airplanes and KC-10A (military) airplanes series airplanes was published in the Federal Register on September 27, 1995 (60 FR 49809). That action proposed to require repetitive ultrasonic or eddy current inspections to detect cracks of the upper aft mating bolt hole of the wing pylon truss fittings, and various follow-on actions.

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

Support for the Proposal

Two commenters support the proposed rule.

Request for Extension of Compliance Time for Initial Inspection

One commenter requests that the compliance time for the initial inspection be extended from the proposed 1,000 landings to 1,200 landings for Model DC-10-30 series airplanes. The commenter states such a compliance time would follow the recommendations of McDonnell Douglas DC-10 Service Bulletin 54-108, dated February 9, 1995. The commenter also questions what data or analysis the FAA used to justify shortening the threshold to 1,000 landings.

The FAA does not agree with the commenter's request to extend the compliance time. The FAA points out that 1,000 landings is not the inspection "threshold," but a "grace period" that was established to preclude unnecessarily grounding airplanes that have exceeded the 10,000-landing threshold or will exceed it within 1,000 landings. In determining the appropriate "grace period" for this action, the FAA not only considered the degree of urgency associated with addressing the unsafe condition, but the amount of time necessary for operators to accomplish the required inspection and other factors affecting the ability of the operators to comply. In light of all these factors, the FAA finds the 1,000 landing "grace period" for initiating the required inspections to be warranted, in that it represents an appropriate interval of time allowable for affected airplanes to continue to operate without compromising safety.

Clarification of Requirements for Type of Inspection

One commenter points out that proposed paragraphs (a) and (b) indicate that operators are to perform either ultrasonic or eddy current inspections to detect the subject cracking. However, the commenter states that the initial and repetitive eddy current inspections are not an option if the upper aft and/or middle mating bolt hole(s) have bushings installed from previous rework, in accordance with McDonnell Douglas DC-10 Service Bulletin 54-108, dated February 9, 1995.

The FAA finds that clarification of this point is necessary. As paragraphs (a) and (b) of the proposed rule were worded, operators could incorrectly interpret the requirements as meaning that they have a choice between performing an ultrasonic inspection or an eddy current inspection for all configurations of the bolt holes. However, the intent of those requirements was to require operators to perform either an ultrasonic inspection or an eddy current inspection, as appropriate, depending upon the configuration of the subject area and as specified in the service bulletin. Therefore, the commenter is correct in noting that, for airplanes on which the upper aft and middle mating bolt holes have bushings installed from previous rework (Condition 2), operators must accomplish the inspection by using only the ultrasonic method. In light of this, the FAA has revised the wording of paragraphs (a) and (b) of the final rule to clarify this.

Clarification of Requirements for Repetitive Inspections

The same commenter asks if the repetitive ultrasonic inspection intervals are the same for bolt hole(s) that have bushings installed from previous rework as well as for bolt hole(s) that do not have bushings installed.

The FAA finds that clarification of this point is necessary. The FAA points out that, for certain Model DC-10-15, and -30 series airplanes, and KC-10A (military) airplanes, Service Bulletin 54-108 recommends that the compliance time for the repetitive ultrasonic inspections be accomplished at intervals of 4,000 landings if the bolts holes have bushings installed, and at intervals of 5,000 landings if the bolt holes do not have bushings installed. However, for those airplanes, paragraph (b)(1)(i) of the final rule differs from the recommendations of the service bulletin in that it requires a compliance time interval of 5,000 landings, whether or not the bolt holes have bushings installed. In developing an appropriate compliance time for that action, the FAA, along with McDonnell Douglas, reviewed the damage tolerance analysis of the bolt hole, and determined that the compliance time of 5,000 landings will not adversely affect safety. McDonnell Douglas is planning to revise Service Bulletin 54-108 in the future to be consistent with this AD.

Conclusion

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 with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD.

Cost Impact

There are approximately 376 McDonnell Douglas Model DC-10-10, -15, and -30 series airplanes and KC-10 (military) airplanes of the affected design in the worldwide fleet. The FAA estimates that 228 airplanes of U.S. registry will be affected by this AD, that it will take approximately 5 work hours per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $68,400, or $300 per airplane, per inspection.

The cost impact figure discussed above is 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.

Regulatory Impact

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 the preparation 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 part 39 of the Federal Aviation Regulations (14 CFR part 39) as follows:

PART 39 - AIRWORTHINESS DIRECTIVES

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

Authority: 49 USC 106(g), 40113, 44701.

§ 39.13 - (Amended)

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