AD 96-19-09

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-9-80 series airplanes and Model MD-88 airplanes was published in the Federal Register on April 15, 1996 (61 FR 16413). That action proposed to require a one-time dye penetrant and magnetic particle inspection to detect cracking of the main landing gear (MLG) pistons, and repair or replacement of the pistons with new or serviceable parts, if necessary.

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

One commenter supports the proposed rule.

Request to Review Availability of Spare Parts

Several commenters request that, prior to the issuance of a final rule, the FAA consider the availability of spare MLG pistons. The commenters are concerned that ample replacement parts may not be available to the fleet in a timely manner.

The FAA has contacted the McDonnell Douglas Corporation, who advises that it has anticipated the need for additional spares and is addressing that issue with the gear manufacturer. Additionally, the FAA has approved procedures for removal of cracks from MLG pistons. Cracked pistons have been found on several aircraft so far, and the approved repairs (rather than replacement) have been applicable to most of those pistons.

Request to Extend Compliance Time for Inspection

Two commenters request that the proposed compliance time be extended. One commenter indicates that the proposed compliance time of 12 months or 1,500 landings (whichever occurs first) is not acceptable due to a lack of spare parts. The commenter suggests that a compliance time of 18 months or 3,000 landings (whichever occurs first) will provide an acceptable level of safety.

The FAA does not concurwith the commenters' request. In developing an appropriate compliance time for this AD, the FAA considered not only the safety implications, but parts availability and normal maintenance schedules for timely accomplishment of the inspection of the affected fleet. In consideration of these factors, the FAA determined that the compliance time, as proposed, represents an appropriate interval in which the inspection can be accomplished in a timely manner within the fleet and an adequate level of safety can still be maintained. Additionally, as discussed above, parts availability should not pose a problem for affected operators. However, the provisions of paragraph (f) of this AD afford operators the opportunity to request an adjustment of the compliance time, provided that adequate justification is presented to support such a request.

Request to Revise Applicability of the Rule

One commenter requests that the FAA revise the applicability of the proposed AD to exempt from the AD requirements all Model MD-88 airplanes that have an improved or reworked/reidentified MLG piston.

The FAA concurs with the commenter's request. The FAA finds that the only Model MD-88 airplanes that are subject to the addressed unsafe condition are those airplanes equipped with MLG pistons having part numbers 5935347-1 through 5935347-509, inclusive. The FAA has revised the applicability of the final rule accordingly.

Request to Cite Additional Service Information

One commenter requests that the FAA revise the proposal to cite the original issue of McDonnell Douglas Service Bulletin MD80-32-277 as an additional source of service information for accomplishment of the proposed inspection.

The FAA concurs. The FAA has determined that the original issue of the service bulletin contains the same inspection criteria outlined in Revision 1 of the service bulletin, which was referenced in the proposal as the appropriate source for service information. The FAA considersaccomplishment of the inspection in accordance with the original issue of the service bulletin to be acceptable for compliance with this AD. Paragraph (a) of the final rule has been revised accordingly.

Request to Revise Work Hour Estimate

One commenter considers that the cost estimate presented in the preamble to the proposal was too low. The commenter indicates that the cost estimate should be revised to specify that the proposed inspection necessitates 8 work hours to accomplish.

The FAA does not concur that the number of work hours required is higher than approximated previously. The airplane manufacturer advises that it has worked extensively with operators of the affected airplanes to determine the length of time necessary for accomplishment of the required inspection. Several airplanes have already been inspected, and 2 work hours, as specified in the proposal, has been shown to be a reasonable estimate for accomplishment of the inspection.

ConclusionAfter 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 1,119 Model DC-9-80 series airplanes and Model MD-88 airplanes of the affected design in the worldwide fleet. The FAA estimates that 609 airplanes of U.S. registry will be affected by this AD, that it will take approximately 2 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 $73,080, or $120 per airplane.

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 U.S.C. 106(g), 40113, 44701.

§ 39.13 - (Amended)

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