AD 97-02-16

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 Boeing Model 737-300, -400, and -500 series airplanes was published in the Federal Register on September 13, 1996 (61 FR 48435). That action proposed to require removal of the shim behind the proximity switch, if installed; and trimming of the bracket for the proximity switch.

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

Request to Extend Compliance Time

One commenter requests that the compliance time for accomplishment of the modification be extended from the proposed "3,200 flight hours or 18 months" to "4,600 flight hours or 24 months," whichever occurs first after the effective date of the AD. The commenter states that the modification is time-consuming to perform, and the requested extension of the compliance time would allow affected operators to accomplish it during regularly scheduled maintenance ("C" check).

The FAA does not concur. In developing an appropriate compliance time for this action, the FAA considered not only the degree of urgency associated with addressing the subject unsafe condition, but the availability of required parts and the practical aspect of installing the required modification within an interval of time that parallels normal scheduled maintenance for the majority of affected operators. The FAA finds that the compliance time, as proposed, represents the average "C" check maintenance interval for the majority of affected operators. Additionally, the FAA does not consider the modification to be especially time-consuming, since it takes only 7 work hours per airplane to perform, and does not entail the need for special tools or parts. In light of these items, the FAA finds the proposed compliance time to be appropriate. However, under the provisions of paragraph (b) of the final rule, the FAA may approve requests for adjustments to the compliance time if data are submitted to substantiate that such an adjustment would provide an acceptable level of safety.

Request to Clarify Description of Required Actions

One commenter requests that the description of the requirement modification of the flap control cable failure detection system be clarified. The commenter points out that the shim to be removed is located behind the proximity switch, rather than behind the bracket for the proximity switch, as was stated in the proposal. Additionally, the commenter suggests that the required action would be clearer if stated as, "trimming of the switch bracket," rather than "trimming of the bracket of the proximity switch."

The FAA concurs that the commenter's suggested changes to the description of the required actions would make the AD clearer. The FAA has made those changes throughout this final rule in the appropriate places.

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 1,619 Model 737-300, -400, and -500 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 685 airplanes of U.S. registry will be affected by this AD, that it will take approximately 7 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 $287,700, or $420 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: