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 Dornier Model 328-100 series airplanes was published as a supplemental notice of proposed rulemaking (NPRM) in the Federal Register on June 9, 1998 (63 FR 31382). That action proposed to require repetitive inspections to detect cracking of the support beam of the main landing gear (MLG) fairing, and a permanent repair, if necessary. That action also proposed to require installation of reinforcement parts for the longitudinal beam of the MLG fairing, which would terminate the requirements of the AD. In addition, that action proposed to limit the applicability of the original NPRM.
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.
Request to Revise Compliance TimeThe manufacturer provides an additional statement to comments submitted in response to the original NPRM regarding continued flight after detection of cracking. The manufacturer notes that inspections, repair, and reinforcement of the support beam of the MLG fairing are intended to prevent the possibility of separation of part of the fairing from the aircraft and injury to persons on the ground. Since the support beam and MLG fairing are secondary structure, the manufacturer states that if cracks of less than 50 millimeters are found, allowing temporary repairs along with follow-on repetitive inspections every 300 flight hours, as recommended in Dornier Alert Service Bulletin ASB-328-53-010, dated October 13, 1995, does not impair safe operation.
From this comment, the FAA infers that the manufacturer is again requesting that the FAA reconsider the requirement to accomplish a permanent repair prior to further flight if any crack is found during inspection, as specified in paragraph (a)(2) of the proposed AD. The FAA acknowledges that the structure for which repairs may be necessary is considered to be secondary structure, and that an acceptable temporary repair is available. After further consideration, the FAA partially concurs with the request.
The FAA does not concur with all procedures recommended in the alert service bulletin for continued flight following detection of cracking. Specifically, the FAA does not concur that inspections may be allowed to continue indefinitely until crack length exceeds 50 millimeters. The FAA has determined that although continued flight can be allowed under restricted conditions following accomplishment of a temporary repair, the permanent repair must be accomplished within a period of 6 months. Additionally, the FAA does not concur that repeated stop drilling of the crack should be performed as a continuing temporary repair where further cracking is detected. The FAA has determined that, if any subsequent inspection reveals crack growth beyond the stop drilled area, the permanent repair should be accomplished prior to further flight.
However, since the manufacturer has outlined circumstances of unusual need, the FAA concurs that the airplane can be operated safely with a known crack of less than 50 millimeters for a limited period of time under certain conditions. These conditions include accomplishment of a one-time temporary repair prior to further flight after cracking is detected; reinspection at intervals not to exceed 300 flight hours until the permanent repair is accomplished; accomplishment of the permanent repair within 6 months after cracking is detected; and, immediate accomplishment of the permanent repair if cracking beyond the stop drilling is found in subsequent inspections. Paragraph (a) of the final rule has been revised to specify these requirements following detection of cracks.
Request to Revise Applicability
The manufacturer requests that the applicability statement of the proposed AD be revised to include only airplanes on which the procedures specified in Dornier Service Bulletin SB-328-53-184, Revision 1, dated July 2, 1997 (which is referenced in the proposed AD as the appropriate source of service information for accomplishment of terminating action) have not been accomplished. The manufacturer states that some operators have already incorporated the subject service bulletin, and provides an updated list of airplane serial numbers on which the service bulletin has not yet been accomplished.
The FAA concurs with the manufacturer s request to limit the applicability to airplanes on which the terminating action described in Service Bulletin SB-328-53-184 has not been accomplished. However, since operators may be accomplishing such action on an ongoing basis, revising airplane serial numbers in the applicability of this AD would not provide an accurate effectivity in the future. Therefore, the FAA has limited the applicability of the final rule to those airplanes on which Dornier Service Bulletin SB-328-53-184, Revision 1, dated July 2, 1997, has not been accomplished.
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 described previously. 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 47 Dornier Model 328-100 series airplanes of U.S. registry will be affected by this AD.
It will take approximately 1 work hour 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 $2,820, or $60 per airplane, per inspection cycle.
It will take approximately 8 work hours per airplane to accomplish the required installation of reinforcement parts, at an average labor rate of $60 per work hour. Required parts will be supplied by the manufacturer at no cost to the operators. Based on these figures, the cost impact of the installation required by this AD on U.S. operators is estimated to be $22,560, or $480 per airplane.
The cost impact figures discussed above are 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.
Should an operator be required to accomplish the permanent repair of cracked structure, it would take approximately 3 work hours per airplane to accomplish it, at an average labor rate of $60 per work hour. Required parts would be supplied by the manufacturer at no cost to the operators. Based on these figures, the cost impact of the repair action, if accomplished, is estimated to be $180 per airplane.
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 itmay 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: