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 747-400, - 400D, and -400F series airplanes was published in the Federal Register on August 28, 2003 (68 FR 51735). That action proposed to require reviewing airplane maintenance records; inspecting the yaw damper actuator portion of the upper and lower rudder power control modules (PCM) for cracking, and replacing the PCMs if necessary; and reporting airplane maintenance records review and inspection results to the manufacturer. \n\nComments \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\nAgreement With the Notice of Proposed Rulemaking (NPRM) \n\n\tTwo commenters state that they agree with the NPRM. \n\nRequest To Revise Paragraph (f) of the NPRM \n\n\tOne commenter requests that paragraph (f) of the NPRM be revised to permit installation of the components without continuing inspections at each installation of the components. The commenter states that it does not believe that is the intent of the applicable service bulletin. The commenter further states that, without specific relief, paragraph (f) of the NPRM will eventually require inspections on parts with fewer total flight hours or total flight cycles than the thresholds specified by the NPRM. \n\n\tThe FAA notes that the requirements of paragraph (f) of the final rule to prohibit units that have reached the thresholds specified in paragraph (f) of the final rule (15,000 total flight hours or more or 2,000 total flight cycles or more) may impose a burden to the affected operators. However, as noted in the "Interim Action" section of the NPRM, we consider the actions specified in this final rule to be interim actions, since the root cause of the fatigue cracking has not been determined. We are trying to gain better insight into the nature, cause, extent of the cracking, and to develop a final action for the unsafe condition. However, to prevent continuing inspections upon each installation, we acknowledge that some relief should be provided. Therefore, we have revised paragraph (f) of the final rule to specify that a rudder PCM with 15,000 total flight hours or more or 2,000 total flight hours or more may not be installed "unless it has been inspected within the previous 15,000 flight hours or 2,000 flight cycles" of the PCM. We have determined that the relief provided by revising paragraph (f) of the final rule will continue to provide an acceptable level of safety for the fleet. \n\nRequest To Clarify the Term Power Control Modules "PCMs" \n\n\tOne commenter, the airplane manufacturer, requests that use of the term "PCM" in the NPRM be clarified by adding the following words: "with a main manifold." The commenter notes that the 15,000 total flight hours and 2,000 total flight cycle thresholds are based on the life of the PCM main manifold. \n\n\tWe agree that clarification is necessary, and have revised the final rule accordingly. \n\nRequest To Extend the Compliance Time \n\n\tOne commenter requests that the compliance time be extended from "within 3 months after the effective date of the AD" to "within 1 year after the effective date of the AD" for the following reasons: \n\nTool Availability--The commenter notes that Boeing Alert Service Bulletin 747-27A2397, dated July 24, 2003, states that no special tools are needed to perform the proposed ultrasonic inspection. However, the commenter points out that two special tools are actually needed and that it was only recently able to obtain them. \n\nAccessibility--The commenter states that hangar availability will cause a problem, since the hangars available for inspecting airplanes affected by the NPRM are always occupied by airplanes undergoing heavy maintenance. The commenter states that it will lose valuable time for its fleet if it has to inspect within the proposed 3-month compliance time. \n\nInspection Criteria--The commenter notes that the applicable service bulletin does not specify repetitive inspections or any terminating action. The commenter thinks that the inspection is mainly to collect data and, therefore, cannot understand the urgency of the 3-month compliance time. \n\n\tWe do not agree with the commenter's request. As stated previously in this final rule, the root cause of the fatigue cracking has not been determined. Because the root cause is unknown, we do not know if the fatigue cracking that was reported is a random event or if it may indicate that the structural life of the PCMs with a main manifold is shorter than expected. We agree with the referenced service bulletin that special tools are not necessary to perform the ultrasonic inspection. However, the manufacturer has advised that other tools used as aids in performing the inspection are available to operators. Additionally, we acknowledge that the commenter may lose time for its fleet if it has to inspect within the proposed 3-month compliance time. However, because of the severe consequences of the unsafe condition existing and the fact that there were apparently no indications of a crack developing, we have determined that the 3-month compliance time is prudent and appropriate. No change is necessary to the final rule in this regard. However, under the provisions of paragraph (g) of the final rule, we 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. \n\nRequest To Revise Criterion for Applicable Airplanes \n\n\tOne commenter requests that the criterion for airplanes specified to perform the proposed inspections be revised from 15,000 total flight hours or more or 2,000 total flight cycles or more to 55,000 total flight cycles or 7,500 total flight cycles, as specified by Boeing AlertService Bulletin 747-27A2397, dated July 24, 2003. The commenter states that its service experience supports the criterion specified in the applicable service bulletin. \n\n\tWe do not agree with the commenter's request. We acknowledge that the applicable service bulletin does specify that the reported incident occurred on a rudder PCM with approximately 55,000 flight hours and 7,500 flight cycles, and that the airplanes that were chosen for the investigation had accumulated at least 55,000 flight hours and 7,500 flight cycles. However, the Accomplishment Instructions (paragraph 3.B.1 of the applicable service bulletin) clearly states that, "If your records show that the upper and lower rudder PCMs each have a main manifold with less than 15,000 flight hours or 2,000 flight cycles: It is not necessary to do the inspections* * *" We have evaluated these criteria and conclude that the appropriate criterion for applicable airplanes to be inspected is those airplanes with PCMs that have accumulated 15,000 total flight hours or 2,000 total flight hours. No change to the final rule is necessary in this regard. \n\nRequest To Revise Sensitivity Level of Dye Penetrant Inspection \n\n\tOne commenter, the PCM manufacturer, requests that the sensitivity level of the dye penetrant inspection for PCMs that are cracked and returned to the manufacturer be revised. The commenter notes that, after the issuance of Boeing Alert Service Bulletin 747-27A2397, it increased the inspection sensitivity level from Level 3 to Level 4 for those PCMs that were returned. \n\n\tWe recognize the commenter's expertise and appreciate the information it has provided. This final rule requires PCMs with any cracking to be returned to the PCM manufacturer, but does not specify the inspection process to be used by the PCM manufacturer. Therefore, the change in sensitivity level of the dye penetrant inspection on PCMs returned to the PCM manufacturer does not directly affect the requirements of this AD. Nochange to this final rule is necessary in this regard. \n\nRequest for Industry To Provide Operational Procedures \n\n\tOne commenter states that industry must develop a set of operational procedures to allow flight crews to deal with a flight situation such as the one described in the NPRM. The commenter agrees with the actions proposed in the NPRM, but specifies that additional procedures for flight crews are necessary. \n\n\tWe acknowledge the commenter's concern. As previously explained, we consider this final rule to be interim action. Based on the findings of the reports to be submitted and any other pertinent information, we may consider further rulemaking actions. However, until such findings are made known and further actions developed, we consider the actions specified in the final rule to provide an acceptable level of safety. Therefore, no change to the final rule is necessary in this regard. \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 previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the final rule. \n\nInterim Action \n\n\tWe consider this final rule interim action. The inspection reports that are required by this final rule will enable the manufacturer and the FAA to obtain better insight into the nature, cause, and extent of the cracking, and eventually to develop final action to address the unsafe condition. Once final action has been identified, we may consider further rulemaking. \n\nCost Impact \n\n\tThere are approximately 180 airplanes of the affected design in the worldwide fleet. The FAA estimates that 13 airplanes of U.S. registry will be affected by this AD, that it will take approximately 1 work hour per airplane to accomplish the airplane maintenance records review, and that the average labor rate is $65 per work hour. Based on these figures, the cost impact of the AD on U.S. operators is estimated to be $845, or $65 per airplane.\n \n\tShould an operator be required to accomplish the inspection, it will take approximately 4 work hours per airplane, at an average labor rate of $65 per work hour. Based on these figures, the cost impact of the inspection is estimated to be $260 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.Regulatory Impact \n\n\tThe regulations adopted herein will not have a substantial direct effect 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, 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. \n\nAdoption of the Amendment \n\nAccordingly, 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\n1. The authority citation for part 39 continues to read as follows: \n\n\tAuthority: 49 U.S.C. 106(g), 40113, 44701. \n\n§ 39.13 (Amended) \n\n2. Section 39.13 is amended by adding the following new airworthiness directive: