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 Fokker Model F27 Mark 100, 200, 300, 400, 500, 600, and 700 series airplanes was published in the Federal Register on August 6, 1996 (61 FR 40760). That action proposed to require repetitive x-ray inspections to detect cracks of stringers 4 through 7, inclusive, at certain wing stations of the lower skin of the wings; and modification or repair, if necessary. That action also proposed to require modification of certain stringers of the lower skin of the wings, which, when accomplished, would constitute terminating action for the repetitive inspection requirements.
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 AD.
Request to Extend Proposed Compliance Time
One commenter requests that the proposal be revised to extend the compliance time for the initial x-ray inspection (Part 2 of the Fokker Service Bulletin F27/57-70)) and the terminating modification (Part 1 of the Fokker service bulletin) to the next regularly scheduled "C" check. This commenter states that the 12-month compliance time for the inspection creates unnecessary burdens both economically and operationally. However, since the downtime for accomplishing the terminating action would be a minimum of 6 days (dictated by the number of maintenance personnel who can work on this area at one time), the commenter considers that it would be more feasible to allow both the inspection and terminating action to be accomplished during that one time. A convenient time for this to take place would be during a "C" check inspection or equivalent.
The FAA acknowledges this commenter's request, but finds that clarification of the intent of the compliance time is necessary, based on the commenter's apparent misinterpretation of it.
Paragraph (a) of the AD is meant to require that the initial inspection be performed at the later of either:
- paragraph (a)(1) -- prior to the accumulation of 30,000 total flight cycles; or
- paragraph (a)(2) -- within 2,000 flight cycles or 12 months after the effective date of the AD, whichever is earlier.
The 2,000-cycle/12-month compliance time provided by paragraph (a)(2) is meant to serve as a "grace period" if an affected airplane has already accumulated nearly or more than 30,000 total flight cycles. This grace period provision eliminates the situation where an airplane having over 30,000 flight cycles would be in immediate non-compliance with the AD. For those airplanes then, the inspection must be accomplished either within 2,000 flight cycles after the effective date of the AD or within 12-months after the effective date, whichever occurs first.
As for the terminating modification, paragraph (d) requires that it be installed on all airplanes prior to the accumulation of 30,000 total flight cycles, or within 30 months after the effective date of this AD, whichever occurs later. Again, this paragraph provides a grace period of 30 months for airplanes that are nearly approaching or have exceeded 30,000 total flight cycles.
In looking at the AD as a whole, operators should note that the inspection specified in paragraph (a) actually is meant to be an "optional" interim action that can be accomplished on higher-time airplanes prior to accomplishing the terminating modification, if time and schedules dictate. For example, a higher time airplane meeting the utilization criteria relevant to paragraph (a)(2) could be initially inspected within 12 months and, if no cracking was found during any inspection, need not be modified in accordance with paragraph (d) for another 18 months (totaling 30 months after the effective date of the AD). On the other hand, thatairplane instead could be modified prior to the 12-month period and, therefore, need not be inspected in accordance with paragraph (a) at all.
For very low-time airplanes, as long as the terminating modification is accomplished prior to the accumulation of 30,000 flight cycles, the inspection specified in paragraph (a) need not be performed.
In light of this explanation, the FAA does not consider that any change to the compliance times, based on the commenters request, is necessary.
Further, the FAA does not concur with the commenter's suggestion to state compliance times in terms of maintenance checks (i.e., "C" checks), since the intervals for those checks may vary greatly from operator to operator. Based on the data available concerning fatigue cracking in the subject areas, the FAA finds that the compliance time intervals, as proposed, are appropriate. Under the provisions of paragraph (e) of this final rule, however, operators may request approval of adjustments ofthe compliance time, provided that sufficient data are presented to the FAA to justify the request.
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 as proposed.
Cost Impact
The FAA estimates that 34 Fokker Model F27 Mark 100, 200, 300, 400, 500, 600, and 700 series airplanes of U.S. registry will be affected by this AD.
It will take approximately 16 work hours per airplane to accomplish the required inspection, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of the inspection required by this AD on U.S. operators is estimated to be $32,640, or $960 per airplane, per inspection cycle.
It will take approximately 400 work hours per airplane to accomplish the required modification, at an average labor rate of $60 per work hour. Required parts will cost approximately $1,365 per airplane. Based onthese figures, the cost impact of the modification required by this AD on U.S. operators is estimated to be $862,410, or $25,365 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 nota "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: