The FAA has received reports indicating that cracking and broken and/or missing fasteners were found on the E-42 SATCOM equipment rack structure that attaches to the fuselage structure on several Boeing Model 747-300 and -400 series airplanes. Investigation revealed that one of the four stanchions (i.e., a supporting prop or brace) was found completely broken on two airplanes (one that had accumulated 23,693 total flight hours and the other with 24,752 total flight hours). Further investigation revealed that the rigid joints of the supporting structure of the E-42 SATCOM rack, coupled with environmental vibration of the airplane, may have caused the cracking to initiate in the area surrounding the fastener holes (located at the rigid joints) of the supporting structure of the E-42 SATCOM rack. The FAA also has received a report indicating that cracking has been detected on four freighter airplanes; one of the airplanes had accumulated less than 1,500 total flight hours. \n\n\tOn all airplanes, the E-42 SATCOM rack hangs above the main deck ceiling. On freighter airplanes and "combi" airplanes (i.e., configurations with provisions for passenger seating and cargo on the main deck), the E-42 SATCOM rack is located near rudder and elevator control cables, and the SATCOM wires run above the rudder and elevator control cables. \n\n\tOn all airplanes, failure of the rack and its supporting structure could result in loss of support for the E-42 SATCOM equipment, which could lead to chafing and arcing of the electrical wires and loss of SATCOM capabilities. Such failure also could result in the following unsafe conditions: \n\n\t On passenger-only airplanes, the E-42 SATCOM equipment could break through the ceiling, which could result in injury to passengers. \n\n\t On freighter and "combi" airplanes, the E-42 SATCOM equipment could fall and cause the SATCOM wires to pull and possibly break the rudder and/or elevator control cables, which could result in reduced controllability of the airplane. Failure of the SATCOM rack on "combi" airplanes carrying passengers also could result in injury to the passengers. \n\nExplanation of Relevant Service Information \n\n\tThe FAA has reviewed and approved Boeing Alert Service Bulletin 747-53A2428, dated December 17, 1998, which describes procedures for repetitive close visual inspections of the E-42 SATCOM rack and fuselage (supporting) structure to detect cracking in the area surrounding the fastener holes, and to detect broken or missing fasteners. \n\nExplanation of the Requirements of the Rule \n\n\tSince an unsafe condition has been identified that is likely to exist or develop on other airplanes of the same type design, this AD is being issued to detect and repair cracking of the E-42 SATCOM rack and its supporting structure, which could result in the SATCOM equipment falling from the rack, loss of SATCOM capabilities, injury to passengers, and reduced controllability of the airplane. This AD requires accomplishment of the actions specified in the alert service bulletin described previously, except as discussed below. This AD also requires that operators report results of initial inspection findings to the manufacturer. \n\nInterim Action \n\n\tThis is considered to be interim action. The manufacturer has advised that it currently is developing a modification that will positively address the unsafe condition addressed by this AD. Once this modification is developed, approved, and available, the FAA may consider additional rulemaking. \n\nDifferences Between AD and Alert Service Bulletin \n\n\tOperators should note that, although the Boeing alert service bulletin specifies that the manufacturer may be contacted for disposition of certain conditions, this proposal would require the repair of those conditions to be accomplished in accordance with a method approved by the FAA. \n\n\tOperators also should note that the Boeing alert service bulletin specifies thatthe manufacturer determine the repetitive inspection intervals in the event a repair and/or replacement of the fasteners is necessary. This AD would require repetitive inspections of the E-42 SATCOM rack and its supporting structure at intervals not exceeding 3,000 flight cycles, whether a repair and/or replacement of fasteners is required or not. While a manufacturer Designated Engineering Representative (DER) is authorized to determine whether a design or repair method complies with a specific requirement, at this time the FAA has not delegated the authority to a manufacturer DER to make the discretionary determination for repetitive inspection requirements. \n\nExplanation of Applicability \n\n\tOperators should note that the Boeing alert service bulletin (previously described), does not specify the line number for the effectivity of Boeing Model 747-400 series airplanes, but states that "a line number will be specified at a later date," when a design improvement can be incorporatedinto the production line. To account for this interpretative effectivity, this AD is applicable to Boeing Model 747-300 series airplanes as listed in the alert service bulletin and Boeing Model 747-400 series airplanes equipped with a Boeing-installed E-42 SATCOM rack. As discussed previously, because this AD is considered interim action, applicability may be revised accordingly in subsequent AD action. \n\nExplanation of Compliance Time \n\n\tOperators should note that the Boeing alert service bulletin (previously described) recommends that the initial inspection be performed at the applicable time, as specified below: \n\n\t For airplanes identified in the alert service as Group 1: Within 500 flight hours or within 14,000 flight hours since the E-42 SATCOM rack was installed and populated with equipment. \n\n\t For airplanes identified in the alert service as Groups 2, 3, and 4: Within 500 flight hours or 20,000 flight hours since the E-42 SATCOM rack was installed and populatedwith equipment. \n\n\tThis AD would require that the initial inspection be performed at the applicable time, as specified below: \n\n\t For airplanes identified in the alert service bulletin as Group 1: Within 30 days after the effective date of this AD. \n\n\t For airplanes identified in the alert service bulletin as Groups 2, 3, and 4: Within 90 days after the effective date of this AD. \n\n\tThe FAA finds that, in view of a recent report indicating that cracking has been detected on an airplane that had accumulated less than 1,500 total flight hours, and because of the safety implications and consequences associated with such cracking, the initial compliance time specified in this AD is appropriate. \n\nDetermination of Rule's Effective Date \n\n\tSince a situation exists that requires the immediate adoption of this regulation, it is found that notice and opportunity for prior public comment hereon are impracticable, and that good cause exists for making this amendment effective in less than 30 days. \n\nComments Invited \n\n\tAlthough this action is in the form of a final rule that involves requirements affecting flight safety and, thus, was not preceded by notice and an opportunity for public comment, comments are invited on this rule. Interested persons are invited to comment on this rule by submitting such written data, views, or arguments as they may desire. Communications shall identify the Rules Docket number and be submitted in triplicate to the address specified under the caption "ADDRESSES." All communications received on or before the closing date for comments will be considered, and this rule may be amended in light of the comments received. Factual information that supports the commenter's ideas and suggestions is extremely helpful in evaluating the effectiveness of the AD action and determining whether additional rulemaking action would be needed. \n\n\tComments are specifically invited on the overall regulatory, economic, environmental, and energyaspects of the rule that might suggest a need to modify the rule. All comments submitted will be available, both before and after the closing date for comments, in the Rules Docket for examination by interested persons. A report that summarizes each FAA-public contact concerned with the substance of this AD will be filed in the Rules Docket. \n\n\tCommenters wishing the FAA to acknowledge receipt of their comments submitted in response to this rule must submit a self-addressed, stamped postcard on which the following statement is made: "Comments to Docket Number 99-NM-45-AD." The postcard will be date stamped and returned to the commenter. \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\tThe FAA has determined that this regulation is an emergency regulation that must be issued immediately to correct an unsafe condition in aircraft, and that it is not a "significant regulatory action" under Executive Order 12866. It has been determined further that this action involves an emergency regulation under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979). If it is determined that this emergency regulation otherwise would be significant under DOT Regulatory Policies and Procedures, a final regulatory evaluation will be prepared and placed in the Rules Docket. A copy of it, if filed, 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 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: 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: