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-9-10, -20, -30, and -40 series airplanes and C-9 airplanes was published in the Federal Register on July 23, 2001 (66 FR 38198). That action proposed to require modification of the spoiler control system, and installation of protective interlock box assemblies in the spoiler circuit. That action was proposed to prevent smoke/fire in the flight compartment in the event that the automatic spoiler actuator overheats, and/or loss of the spoiler control system, which could significantly reduce the braking effectiveness of the airplane. \n\nSince the Issuance of the NPRM \n\n\tThe FAA has been advised by the manufacturer that there may be a problem in supplying an adequate number of parts to modify the spoiler control system and to install protective interlock box assemblies in the spoiler circuit within the 1-year compliance time proposed in the NPRM. Consequently, we have extended the compliance times of paragraphs (a) and (b) of this AD to within 18 months after the effective date of this AD. We have determined that such an extension of the compliance times will accommodate the time necessary for affected operators to order, obtain, modify, and install certain parts necessary to accomplish the requirements of paragraph (a) and (b) of the AD, without adversely affecting safety. \n\nPublic Comments \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. \n\nRequest To Clarify Requirements \n\n\tThe commenter states that the service bulletin (Boeing Alert Service Bulletin DC9-27A-147, Revision 03, dated May 8, 2001) referenced in the proposed rule specifies that Service Bulletin DC9-27-103 should be incorporated as a prerequisite. However, the commenter statesthat Service Bulletin DC9-27-103 is not mentioned in the proposed rule. The commenter concludes that compliance with the other service bulletin is implied, but not mandated by the proposed rule. The FAA infers that the commenter is requesting clarification.\n \n\tThe FAA acknowledges the request for clarification. Paragraph (a) of the final rule requires modification of the spoiler control system per Boeing Alert Service Bulletin DC9-27A147, which references Boeing Service Bulletin DC9-27-103. Specifically, however, paragraph (b) of the final rule does require installation of protective interlock box assemblies in the spoiler circuit per McDonnell Douglas DC-9 Service Bulletin 27-103, dated March 19, 1968. The compliance time for accomplishing that installation is clearly stated in paragraph (b) of the final rule as: "Prior to or in conjunction with the requirements of paragraph (a) of this AD." No change to the final rule is necessary. \n\nRequest To Revise Reference to Service Information \n\n\tThe commenter requests that the FAA revise the proposed rule to require the procedures described in Boeing Service Bulletin DC9-27-283, which further modifies the spoiler interlock box by replacing the relay with an improved 6-pole double throw relay. Additionally, the commenter suggests that a "proposed" service bulletin that modifies the interlock box with the 6-pole relay and an "as-yet-undefined" service bulletin that describes procedures for modifying interlock boxes without the 6-pole relay be considered by the FAA. The commenter states that these service bulletins have been issued or soon will be issued.\n\n\tThe FAA does not concur with the request to add additional service information to the final rule. Installation of the time-delay relay (as part of the actions required by this AD) will terminate power to the actuator in 10 seconds after energizing the spoiler automatic actuator, and provides adequate protection against overheating of the actuator. To add further requirements to this rule as the commenter proposed, we would have to reissue the Notice of Proposed Rulemaking (NPRM) as a Supplemental NPRM in order to provide an appropriate time for public comment. Furthermore, we cannot require implementation of actions of service bulletins not yet developed and approved by the FAA. Therefore, we find that, in order to adequately address the unsafe condition in a timely manner, implementation of the required actions as proposed are warranted. \n\nRequest To Revise the Cost Estimate \n\n\tThis same commenter also requests that the 3 work hours estimated in the proposed rule for the installation of the protective interlock box assemblies in the spoiler circuit be revised to 24 work hours. The commenter also requests that the estimated cost of replacement parts specified as $20 in the proposed rule be revised to $2,750. The commenter provides this justification based on information retrieved from its SCEPTRE database. \n\n\tThe FAA does not concur that the cost estimates should be revised. We used the work hours specified in McDonnell Douglas DC-9 Service Bulletin 27-103(which is referenced in the AD as the appropriate source of service information for accomplishment of the required installation). We note that the economic analysis of this AD represents the time necessary to perform only the actions actually required by this AD. We recognize that, in accomplishing the requirements of any AD, operators may incur "incidental" costs in addition to the "direct" costs. As indicated in the preamble of the NPRM, the cost analysis in AD rulemaking actions typically does not include incidental costs, such as the time required to gain access and close up; planning time; or time necessitated by other administrative actions. Because incidental costs may vary significantly from operator to operator, they are almost impossible to calculate. Therefore, no change to the final rule is necessary. \n\nConclusion \n\n\tAfter 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. \n\nCost Impact \n\n\tThere are approximately 504 Model DC-9-10, -20, -30, and -40 series airplanes and C-9 airplanes of the affected design in the worldwide fleet. The FAA estimates that 272 airplanes of U.S. registry will be affected by this AD. \n\n\tIt will take approximately 5 work hours per airplane to accomplish the required modification, and that the average labor rate is $60 per work hour. Required parts will cost approximately $937 per airplane. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $336,464, or $1,237 per airplane. \n\n\tIt will take approximately 3 work hours per airplane to accomplish the proposed installation, and the average labor rate is $60 per work hour. Required parts would cost approximately $20 per airplane. Based on these figures, the cost impact of the installation proposed by this AD on U.S. operators is estimated to be $54,400, or $1,237 per airplane.\n \n\tThe 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. The cost impact figures discussed in AD rulemaking actions represent only the time necessary to perform the specific actions actually required by the AD. These figures typically do not include incidental costs, such as the time required to gain access and close up, planning time, or time necessitated by other administrative actions. \n\nRegulatory Impact \n\n\tThe regulations adopted herein will not have a substantial direct effect on the States, on the relationship between the national Government andthe States, or on the distribution of power and responsibilities among the various levels of government. Therefore, it is determined that this final rule does not have federalism implications under Executive Order 13132.\n \n\tFor 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. \n\nList of Subjects in 14 CFR Part 39 \n\n\tAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \nAdoption of the AmendmentAccordingly, 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: \n\nPART 39--AIRWORTHINESS DIRECTIVES \n\n\t1. The authority citation for part 39 continues to read as follows: \n\n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\nSec. 39.13 (Amended) \n\n\t2. Section 39.13 is amended by adding the following new airworthiness directive: