On July 14, 1995, the FAA issued telegraphic AD T95-15-52, which is applicable to Model 747-100 series airplanes modified in accordance with Supplemental Type Certificate (STC) SA2322SO, SA2323SO, or SA5199NM; and Model 747-200 series airplanes modified in accordance with STC SA4227NM-D or SA5759NM. \n\n\tCertain Model 747-100 and -200 series airplanes have been converted from a passenger configuration to a freighter configuration in accordance with STC's SA2322SO and SA2323SO (for Model 747-100 series airplanes) and SA4227NM-D (for Model 747-200 series airplanes). These STC's include, as part of their data packages, new Weight and Balance Supplements that specify the maximum allowable linear load per inch (commonly referred to as "running load") along the length of the fuselage. The Supplements increased this limit from 66.7 pounds per inch to 240 pounds per inch between Body Stations (BS) 1000 and 1480. The Supplements also define the maximum area load(expressed in pounds per square foot). The Supplement increased this limit from 100 pounds per square foot to 320 pounds per square foot between BS 1000 and BS 1480. \n\n\tOn January 16, 1990, the FAA issued AD 90-06-06, amendment 39-6490 (55 FR 8374, March 7, 1990), applicable to certain Boeing Model 747 series airplanes, to require structural modifications of older airplanes, including a requirement to modify the longitudinal floor beams. Recently, an operator of Model 747 airplanes applied for approval of an alternative method of compliance (AMOC) to AD 90-06-06. In reviewing the data to approve this AMOC, the FAA has found that the longitudinal floor beams between BS 1265 and BS 1480 had not been upgraded to withstand the increased running loads that would result from an airplane's conversion to freighter service. These Body Stations comprise a 215 inch-long linear portion of the fuselage over the wheel well section of the airplane. \n\n\tFurthermore, the FAA finds that this sameproblem of inadequate strength in the floor beams exists on Model 747-100 and -200 series airplanes for which the type design has been changed to allow operation in accordance with STC's SA5199NM (for Model 747-100 series airplanes) and SA5759NM (for Model 747-200 series airplanes). These two STC's modify the weight and balance limitations of STC's SA2322SO, SA2323SO, and SA4227NM-D. However, these two STC's continue to define the maximum running load at 240 pounds per inch and the maximum area load at 320 pounds per square foot without strengthening the floor beam structure between BS 1000 and BS 1480. \n\n\tThe FAA has determined that a running load of 240 pounds per inch, for the freighter configuration, is above the capability of floor beam structure between BS 1265 and BS 1480. Additionally, the FAA finds that this structure, when loaded to the STC's-allowed limits is not sufficiently strong to sustain limit loads under all of the airspeed and load factor conditions, including those defined by section 25.333, "Flight envelope," and section 25.341, "Gust loads," of the Federal Aviation Regulations (14 CFR 25.333 and 14 CFR 25.341). Failure of the longitudinal floor beams may cause the keel beam to fail, and result in the rupture of the fuselage. \n\n\tSince the unsafe condition described is likely to exist or develop on other airplanes having these STC's as part of their type design, the FAA issued Telegraphic AD T95-15-52 to require a revision to the Limitations section of the FAA-approved Airplane Flight Manual (AFM) and the Limitations section of the Airplane Weight and Balance Supplement to restrict cargo loading to a suitable level. The level established by this AD is based upon an FAA evaluation of the unmodified floor beam structure. The AD also provides for the removal of the restrictions following accomplishment of a modification of the longitudinal floor beams in accordance with a method approved by the FAA. \n\n\tAs a result of recent communications with the Air Transport Association (ATA) of America, the FAA has learned that, in general, some operators may misunderstand the legal effect of AD's on airplanes that are identified in the applicability provision of the AD, but that have been altered or repaired in the area addressed by the AD. The FAA points out that all airplanes identified in the applicability provision of an AD are legally subject to the AD. If an airplane has been altered or repaired in the affected area in such a way as to affect compliance with the AD, the owner or operator is required to obtain FAA approval for an alternative method of compliance with the AD, in accordance with the paragraph of each AD that provides for such approvals. A Note has been included in this rule to clarify this long-standing requirement. \n\n\tSince it was found that immediate corrective action was required, notice and opportunity for prior public comment thereon were impracticable and contrary to the public interest, and good cause existed to make the AD effective immediately by individual telegrams issued on July 14, 1995 to all known U.S. owners and operators of the affected Boeing Model 747-100 and -200 series airplanes. These conditions still exist, and the AD is hereby published in the Federal Register as an amendment to section 39.13 of the Federal Aviation Regulations (14 CFR 39.13) to make it effective to all persons.\n\n Comments 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 energy aspects 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 95-NM-130-AD." The postcard will be date stamped and returned to the commenter. \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, 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 USC 106(g), 40101, 40113, 44701. § 39.13 - (Amended)\n \n\t2. Section 39.13 is amended by adding the following new airworthiness directive: