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 747-100, -200, -300, and -400 series airplanes was published in the Federal Register on February 7, 1997 (62 FR 5783). That action proposed to require a one-time visual inspection to determine the part number of the fuel shutoff valve installed in the outboard engines. That action also proposed to require replacement of certain valves with new valves, or modification of the spar valve body assembly, and various follow-on actions. \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\n\tOne commenter supports the proposed rule. \n\nRequest to Revise Applicability of Proposed AD \n\n\tOne commenter, the manufacturer, requests that the FAA limit the applicability of the proposed ADto airplanes having line numbers 629 through 1006 inclusive. Another commenter requests that the proposed AD be limited to only Boeing Model 747-400 series airplanes. \n\n\tThe manufacturer states that the subject fuel shutoff valve with the faulty thermal relief assembly was delivered to them no earlier than January 1986. Therefore, the manufacturer estimates that airplanes starting with line number 629-- the first Boeing Model 747 series airplane delivered in January 1986--could be subject to the identified unsafe condition. \n\n\tThe manufacturer also states that eight in-service events have occurred on Boeing Model 747-400 series airplanes powered by General Electric or Rolls Royce engines that were installed in the outboard positions only. There have been no confirmed events on General Electric or Rolls Royce engines installed in the inboard positions, or Boeing Model 747-400 series airplanes or Boeing 747-100, -200, and -300, 747SP, and 747SR series airplanes (i.e., Classic airplanes) powered by Pratt & Whitney series engines. The manufacturer states that Boeing Alert Service Bulletin 747-28A2199, dated August 1, 1996 (referenced in the proposal as an appropriate source of service information), included line numbers 1 through 1006 inclusive because at the time the alert service bulletin was released, a comprehensive installation comparison had not been completed nor had the quantitative risk assessment been concluded. \n\n\tSince issuance of the alert service bulletin, the manufacturer has concluded that the close location of pneumatic ducts to the fuel lines for the outboard engine increases the possibility of higher pressures in the outboard engine fuel lines after the engines are shut down. The two Rolls Royce in-service events on the fuel cooled oil cooler (FCOC) can be attributed to the fact that the FCOC is a low pressure design. \n\n\tThe second commenter believes that malfunctioning spar valve thermal relief assemblies are a secondary cause of the subject problem. The commenter states that the primary cause is the unique configuration of the outboard strut on Boeing Model 747-400 series airplanes that has an excessive heat source near the fuel line. \n\n\tThe FAA concurs partially. The FAA does not agree with the commenter's request to limit the applicability of the final rule to only Boeing Model 747-400 series airplanes. The FAA points out that the incidents that prompted this AD occurred on certain Boeing Model 747 series airplanes on which the spar valves had a modified thermal relief assembly. Because these spar valves may be installed on airplanes other than Model 747-400 series airplanes, the FAA has determined that these airplanes also are subject to the addressed unsafe condition. In addition, the heat from sources close to the fuel lines do not per se create the problem. However, the FAA does agree with the manufacturer's request to limit the applicability of the final rule to airplanes having line numbers 629 through1006 inclusive since the Boeing Model 747 series airplane having line number 629 was the first airplane delivered on which the subject valve was installed. Therefore, the FAA has revised the applicability of the final rule accordingly. \n\nRequest to Extend Compliance Time of Visual Inspection \n\n\tSeveral commenters request that the compliance time for accomplishment of the visual inspection, as specified in paragraph (a) of the proposed AD, be extended from the proposed 12 months. One of these commenters states that a 24-month compliance time will allow the inspection to be accomplished during a regularly scheduled "C" check, and thereby eliminate any significant disruptions in flight schedules. Another commenter suggests a 15-month compliance time. \n\n\tThe FAA concurs that the compliance time can be extended somewhat. The FAA's intent was that the inspection be conducted during a regularly scheduled maintenance visit for the majority of the affected fleet, when the airplanes would be located at a base where special equipment and trained personnel would be readily available, if necessary. Based on the information supplied by the commenters, the FAA now recognizes that 18 months corresponds more closely to the interval representative of most of the affected operators' normal maintenance schedules. Paragraph (a) of the final rule has been revised to reflect a compliance time of 18 months. The FAA does not consider that this extension of an additional 6 months for compliance will adversely affect safety. \n\nRequest to Revise Part Numbers \n\n\tOne commenter requests that the FAA reference the suffix letter "A" or "M," as identified in Boeing Alert Service Bulletin 747-28A2199, for part numbers specified in the proposed AD. The FAA does not concur. The commenter is incorrect that these suffixes appear in the subject Boeing alert service bulletin; they appear in ITT Service Bulletin SB125334-28-01. After reviewing the ITT service bulletin, the FAA finds that these suffixes are meant for the parts after they have been modified and are not used for the identification of the appropriate part numbers, as suggested by the commenter. Therefore, the FAA finds that no change to the final rule is necessary. \n\nRequest to Perform Inspection on One Valve at a Time \n\n\tTwo commenters request that the FAA allow operators to inspect the fuel shutoff valves (required by paragraph (a) of the proposed AD) one at a time within the proposed 12-month compliance time. One commenter states that it will not be able to accomplish the proposed inspections and replacement (if required) without scheduling its airplanes out-of- service for extended periods of time. The FAA concurs partially. If an operator elects to inspect the valves one at a time within the specified compliance time, it is the operator's prerogative to do so. The FAA finds no change to the final rule is necessary. \n\nRequest for Clarification of Requirements of Proposal \n\n\tSeveral commenters question whether the requirement to perform an inspection to detect fuel leaks on all four engines is correct in paragraph (b) of the proposed AD. Other commenters question why this inspection is necessary. Two other commenters believe that paragraph (b) of the proposed AD should address only "the outboard engines" or "engines number 1 and 4," rather than "all four engines." These commenters question the reason for leak checking the inboard engines. \n\n\tThe FAA finds that clarification is necessary. Although the FAA has only received reports of the high pressure occurring in the fuel line of the outboard engines, the FAA notes that an inboard engine could have been located previously in the outboard position. Therefore, as discussed previously in the notice of proposed rulemaking (NPRM), the FAA finds that it is necessary that the subject inspection be accomplished on all four engines. However, if an operator has documentation that demonstrates that the inboard engines havenever been located in the outboard position, the FAA has determined that the operator does not have to conduct the inspection on those inboard engines. The FAA has revised the final rule to include a new paragraph (c) specifying this provision. \n\nRequest to Reference Another Source of Service Information \n\n\tOne commenter requests that the FAA allow operators to accomplish the inspection required by paragraph (b) of the proposed AD in accordance with Section 28-22-07 of the 747 Airplane Maintenance Manual, rather than Chapter 71. If not, the commenter requests that the FAA reference a specific leak check in Chapter 71. The FAA does not concur. The FAA notes that the procedures for accomplishing the subject inspection are under the heading "Fuel and Oil Leak Checks" in Chapter 71. Therefore, no change to the final rule is necessary. \n\nRequest to Revise Proposed Actions Based on Future Service Information \n\n\tThe manufacturer also states that it will revise Boeing Alert Service Bulletin 747-28A2199, dated August 1, 1996, to add a step to check the maintenance records for Model 747 series airplanes having line numbers 1 through 1006 inclusive, powered by General Electric and Roll Royce engines. If previous maintenance on the valves has been accomplished, the revised service bulletin would include procedures for inspection of the valve part number, and replacement, if necessary; if no maintenance on valves has been accomplished, the inspection would not be necessary. \n\n\tFrom this comment, the FAA infers that the commenter is requesting that the proposed AD be revised to include these procedures. The FAA does not concur. The manufacturer has not issued a revision to the referenced alert service bulletin. the FAA does not consider it appropriate to delay the issuance of this final rule. When the new service bulletin is issued, the FAA will review it and may consider future rulemaking action. \n\nRequest To Revise Cost Estimate \n\n\tOne commenter requests that the FAA revise the cost estimate of the proposed AD to reflect the latest values cited in a Notice of Status Change for the alert service bulletin. The FAA does not concur. The FAA is unaware of a Notice of Status Change for Boeing Alert Service Bulletin 747-28A2199, dated August 1, 1996. \n\nExplanation of Changes Made to Proposal \n\n\tThe NPRM indicated that the airplanes affected by the proposed AD were Boeing Model 747-100, -200, -300, and -400 series airplanes. The proposed AD was intended to apply to all Boeing Model 747 series airplanes that have the faulty fuel shutoff spar valves installed, including Model 747SP and 747SR series airplanes. The estimate of the affected fleet size that was provided in the NPRM included those airplanes, which many, including the manufacturer, consider to be part of the Model 747-100 series. Those models are listed separately on the Model 747 Type Certificate Data Sheet. Therefore, in order to clarify that this AD does apply to those models, the FAA has revised the final rule to list the affected airplanes as Boeing Model 747-100, -200, -300, -400, 747SP, and 747SR series airplanes. \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 418 Boeing Model 747-100, -200, -300, -400, 747SP, and 747SR series airplanes of the affected design in the worldwide fleet. The FAA estimates that 24 airplanes of U.S. registry will be affected by this AD. \n\n\tIt will take approximately 4 work hours per airplane to accomplish the required one-time visual inspection to determine the part number of the valve, at an average labor rate of $60 per work hour. Based on these figures,the cost impact of this visual inspection required by this AD on U.S. operators is estimated to be $5,760, or $240 per airplane. \n\n\tShould an operator be required to accomplish the necessary one-time inspection to detect leaks and cracks (after replacement of the valve or modification of the assembly), it will take approximately 16 work hours per airplane, at an average labor rate of $60 per work hour. Based on these figures, the cost impact of this one-time inspection is estimated to be $960 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. \n\n\tShould an operator elect to modify the valve body assembly of the fuel system rather than replace a discrepant valve, it would take approximately 20 work hours per airplane, at an average labor rate of $60 per work hour. Required parts would cost approximately $404 (2 kits) per airplane. Based on these figures, the cost impact of any necessary modification action is estimated to be $1,604 per airplane. \n\nRegulatory Impact \n\n\tThe 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. \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 \nunder 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\n\tAccordingly, 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\n PART 39 - AIRWORTHINESS DIRECTIVES \n\n\t1. The authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. 106(g), 40113, 44701. § 39.13 (Amended) \n\t2. Section 39.13 is amended by adding the following new airworthiness directive: