Discussion \n\n\tWe have received a report indicating that fatigue cracks were found in the skin in section 41 of the fuselage, on an in-service Model 747 airplane. A 10-inch skin crack and numerous smaller skin cracks in multiple adjacent fastener rows were found immediately aft of the left number 1 main entry door. The cracks occurred less than 7,000 flight cycles after the terminating action required by AD 2006-20-02, (described below), had been done. The fatigue cracks are the result of cyclic loading during cabin pressurization and de-pressurization. Skin cracks at the fastener rows in section 41 of the fuselage, if not detected and corrected in a timely manner, could join together and result in a loss of structural integrity and rapid decompression of the airplane. \n\nRelated AD \n\n\tOn September 14, 2006, we issued AD 2006-20-02, amendment 39-14771 (71 FR 56861, September 28, 2006) (which superseded AD 96-23-02, amendment 39-9807 (61 FR 57991, November 12, 1996)), for certain Boeing Model 747 airplanes. That AD requires inspections to detect disbonding, corrosion, and cracking at the longitudinal rows of fasteners in the bonded skin panels in section 41 of the fuselage, and repair, if necessary. That AD also requires inspections of airplanes that may have Alodine-coated rivets installed. That AD resulted from a report of cracking discovered in a skin lap joint that was previously inspected using the eddy current method. We issued that AD to prevent rapid decompression of the airplane due to disbonding and subsequent cracking of the skin panels. \n\nRelevant Service Information \n\n\tWe have reviewed Boeing Alert Service Bulletin 747-53A2675, dated October 12, 2006. The alert service bulletin describes procedures for repetitive inspections for any cracking of the fuselage skin in section 41 of the airplane, reports of inspection findings to Boeing, and related investigative and corrective actions if necessary. Repetitive inspections for any cracking of the fuselage skin includes using surface high-frequency eddy current (HFEC) inspections or, as a short- term alternative to surface HFEC inspections, external detailed inspections of the skin panel around fastener heads; and open-hole HFEC inspections or, as a short-term alternative to open-hole HFEC inspections, external surface low-frequency eddy current (LFEC) inspections of the skin at the edge row fasteners common to an external doubler and a bonded internal doubler. Related investigative and corrective actions may involve using a surface HFEC, or an open-hole HFEC inspection, as applicable, on all the affected fuselage skin in section 41; and repairing any crack damage as given in the applicable Boeing 747 Structural Repair Manual, or by contacting Boeing for repair data. \n\n\tThe alert service bulletin also specifies the following initial compliance times for the inspections: Within 150 flight cycles after the date on the alert service bulletin; before theaccumulation of 8,000 total flight cycles; or within 2,000 flight cycles after the last HFEC inspection, Method 1 (external Ultrasonic) or Method 2 (internal detailed) disbond inspection as given in Boeing Alert Service Bulletin 747-53A2409 (which is referenced in AD 2006-20-02 as the appropriate source of service information for doing the actions for that AD); whichever occurs last. The inspections must be repeated at intervals not to exceed 2,000 flight cycles for the HFEC inspections, and not to exceed 150 flight cycles for the alternative detailed and LFEC inspections that are also not to be repeated more than nine times before the applicable HFEC inspection is started. \n\nFAA's Determination and Requirements of this AD \n\n\tThe unsafe condition described previously is likely to exist or develop on other airplanes of the same type design. For this reason, we are issuing this AD to detect and correct fatigue cracks at fastener rows, which could join together and cause a loss of structural integrity and rapid decompression of the airplane. This AD requires accomplishing the actions specified in the service information described previously, except as discussed under ''Difference Between the AD and the Alert Service Bulletin.'' The AD also requires sending the inspection results of each inspection to the manufacturer. \n\nDifference Between the AD and the Alert Service Bulletin \n\n\tThe alert service bulletin specifies that you may contact the manufacturer for instructions on how to repair certain conditions, but this AD requires you to repair those conditions in one of the following ways: \n\n\tUsing a method that we approve; or \n\n\tUsing data that meet the certification basis of the airplane, and that have been approved by an Authorized Representative for the Boeing Delegation Option Authorization Organization who has been authorized by the FAA to make those findings. \n\nInterim Action \n\n\tThis is considered to be interim action. The manufacturer has advised that it currently is developing a new inspection program that will expand the size of the inspection area and add repetitive inspections that will address the unsafe condition addressed by this AD and AD 2006-20-02. Once this new inspection program is developed, approved, and available, we may consider additional rulemaking. \n\nFAA's Determination of the Effective Date \n\n\tSince an unsafe condition exists that requires the immediate adoption of this AD, we have found that notice and opportunity for public comment before issuing this AD are impracticable, and that good cause exists to make this AD effective in less than 30 days. \n\nComments Invited \n\n\tThis AD is a final rule that involves requirements that affect flight safety and was not preceded by notice and an opportunity for public comment; however, we invite you to submit any relevant written data, views, or arguments regarding this AD. Send your comments to an address listed in the ADDRESSES section. Include ''Docket No. FAA-2006- 26388; Directorate Identifier 2006-NM-234-AD'' at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of the AD that might suggest a need to modify it. \n\n\tWe will post all comments we receive, without change, to http://dms.dot.gov , including any personal information you provide. We will also post a report summarizing each substantive verbal contact with FAA personnel concerning this AD. Using the search function of that Web site, anyone can find and read the comments in any of our dockets, including the name of the individual who sent the comment (or signed the comment on behalf of an association, business, labor union, etc.). You may review the DOT's complete Privacy Act Statement in the Federal Register published on April 11, 2000 (65 FR 19477-78), or you may visit http://dms.dot.gov. \n\nExamining the Docket \n\n\tYou may examine the AD docket on the Internet at http://dms.dot.gov , or in person at the Docket Management Facility office between 9 a.m. and 5 p.m., Monday through Friday, except Federal holidays. The Docket Management Facility office (telephone (800) 647- 5227) is located on the plaza level of the Nassif Building at the DOT street address stated in the ADDRESSES section. Comments will be available in the AD docket shortly after the Docket Management System receives them. \n\nAuthority for This Rulemaking \n\n\tTitle 49 of the United States Code specifies the FAA's authority to issue rules on aviation safety. Subtitle I, Section 106, describes the authority of the FAA Administrator. Subtitle VII, Aviation Programs, describes in more detail the scope of the Agency's authority. \n\n\tWe are issuing this rulemaking under the authority described in Subtitle VII, Part A, Subpart III, Section 44701, ''General requirements.'' Under that section, Congress charges the FAA with promoting safe flight of civil aircraft in air commerce by prescribing regulations for practices,methods, and procedures the Administrator finds necessary for safety in air commerce. This regulation is within the scope of that authority because it addresses an unsafe condition that is likely to exist or develop on products identified in this rulemaking action. \n\nRegulatory Findings \n\n\tWe have determined that this AD will not have federalism implications under Executive Order 13132. This AD 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. \n\n\tFor the reasons discussed above, I certify that the regulation: \n\n\t1. Is not a ''significant regulatory action'' under Executive Order 12866; \n\n\t2. Is not a ''significant rule'' under the DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and \n\n\t3. 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. \n\n\tWe prepared a regulatory evaluation of the estimated costs to comply with this AD and placed it in the AD docket. See the ADDRESSES section for a location to examine the regulatory evaluation. \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, under the authority delegated to me by the Administrator, the FAA amends 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\nSec. 39.13 (Amended) \n\n2. The Federal Aviation Administration (FAA) amends Sec. 39.13 by adding the following new airworthiness directive (AD):