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 Fokker Model F28 Mark 1000, 2000, 3000, and 4000 series airplanes, and Model F28 Mark 0100 series airplanes was published in the Federal Register on October 16, 1996 (60 FR 53552). That action proposed to require repetitive pre-load adjustments of the main landing gear (MLG) downlock-actuator.
Comments Received
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 concurs with the proposed rule.
Request to Clarify the Description of Cause of the Unsafe Condition
One commenter, the airframe manufacturer, requests that the description of the unsafe condition be clarified. This commenter states that collapse of the MLG has only occurred under extremeinward side-load conditions, which are beyond the design ultimate load for landing conditions. The commenter asserts that the proposed wording of the unsafe condition suggests that the downlock-actuator itself removed the over-center position. The commenter further states that the investigation of the collapse of the MLG showed that the bottomed downlock-actuator was only an intermediate which transferred the relative movement between the upper and lower side stay to the lock toggle links. The commenter suggests that the wording of the unsafe condition [that appears prior to paragraph (a) of the AD] be revised as follows: "To prevent the collapse of the main landing gear (MLG) under extreme inward side-load conditions (such as touching down at large "crab" angles), due to a lock toggle-link being pulled out of its over-center position by a bottomed MLG downlock-actuator, as a result of the relative movement of the upper and lower side stay members . . ."
The FAA concurs that clarification is necessary and has revised the final rule accordingly.
Request to Extend the Compliance Time
One commenter requests that the compliance time be extended to allow the inspection within 12 months after the effective date of the AD, rather than 8 months as proposed. This will allow the inspection to be accomplished during regularly scheduled maintenance. The commenter states that the adoption of the proposed compliance time of 8 months would require operators to schedule special times for the accomplishment of this inspection at considerable expense beyond what was estimated in the cost impact of the proposed rule.
The FAA does not concur. In establishing the compliance times, the FAA considered not only the degree of urgency associated with the unsafe condition, but the manufacturer's recommended compliance time specified in the applicable service bulletins, and the foreign airworthiness authority's recommended compliance time of 8 months. In light of these factors, the FAA finds that a compliance time of 8 months is appropriate and should fall during a time of scheduled maintenance for the majority of affected operators. Paragraph (c) of the final rule, however, does provide affected operators with the opportunity to apply for an adjustment of the compliance time if data are presented to the FAA to justify such an adjustment.
Request to Delete Requirements for Repetitive Adjustments
One commenter points out that, since paragraph (a) of the proposed rule does not allow for a terminating action, the proposed rule would require operators to continue to record accomplishment of the AD requirements each time the adjustment is performed. This commenter contends that repetitive requirements in the AD are not necessary, since operators will revise their maintenance programs to include these repetitive pre-load adjustment requirements.
The FAA does not concur that the repetitive adjustment requirements should be deleted from the AD. However, the FAA has determined that incorporation of the repetitive adjustments into the FAA-approved maintenance program is an acceptable alternative method of compliance with this requirement. This alternative procedure will allow operators the option to choose either to conduct the repetitive adjustments in accordance with the AD, or to incorporate the requirement for repetitive adjustments into the their FAA-approved maintenance programs. The FAA has added a new paragraph (b) to the final rule to provide for this alternative.
Request to Revise Wording of Requirement for Repetitive Adjustments
One commenter requests that the last sentence of paragraph (a) of the proposed rule be either clarified or deleted. That sentence would require repetitive pre-load adjustment of the MLG downlock-actuator at each scheduled maintenance, installation, or replacement of the MLG downlock-actuator. The commenter states that the term "scheduled maintenance" could include maintenance (such as for lubrication only) when a pre-load adjustment is not required. Additionally, this commenter points out that use of the word "scheduled" in this context also is incorrect, since the adjustment procedure is necessary any time an actuator is installed, regardless of whether the action is scheduled or unscheduled.
The FAA concurs and has deleted the words "scheduled maintenance" from paragraph (a) of the final rule.
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
The FAA estimates that 162 airplanes of U.S. registry will be affected by this AD, that it will take approximately 8 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 $77,760, or $480 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: