Discussion \n\n\tWe have received a report that an operator found a cracked strut number 2 upper chord on a Rolls-Royce-powered airplane while accomplishing the actions specified in Boeing Service Bulletin 747-54- 2213. The upper chord was 50 percent cracked and had to be replaced. The airplane had accumulated approximately 10,500 total flight cycles and 83,700 total flight hours. \n\tIn addition, two other operators reported finding two cracks on two Rolls-Royce RB211-powered airplanes on the strut number 1 upper chord. Both cracks were repaired and neither upper chord had to be replaced. The upper chords on these two airplanes had accumulated approximately 9,300 and 16,100 total flight cycles and 78,100 and 56,700 total flight hours respectively. \n\tThis condition, if not corrected, could result in the loss of the strut upper link load path. Continued operation without the strut upper link load path could result in the fracture of the diagonal brace, andsubsequent separation of the strut and engine from the airplane during flight. \n\nRelevant Service Information \n\n\tWe reviewed Boeing Alert Service Bulletin 747-54A2224, Revision 3, dated May 20, 2010. Revision 3 of this service bulletin was issued, among other reasons, to add Model 747-100B, 747-200B, 747-200F, 747- 300, 747-400, 747-400F, and 747SP equipped with Rolls-Royce RB211-524 series engines. This service bulletin describes procedures for repetitive detailed inspections and high frequency eddy current (HFEC) inspections of the forward and aft sides of the strut front spar chord assemblies for cracks and fractures at each strut location, and corrective actions if necessary. Corrective actions include contacting Boeing for additional instructions if any crack or fracture is found, and repairing any cracks and fractures. \n\nOther Related Rulemaking \n\n\tOn December 30, 2009, we issued AD 2010-01-10, Amendment 39-16168 (75 FR 3150, January 20, 2010), applicable to certain Model747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP series airplanes equipped with General Electric (GE) CF6-45 or -50 series engines, or equipped with Pratt & Whitney JT9D-3 or -7 (excluding -70) series engines. That AD currently requires repetitive inspections to detect cracks and fractures of the strut front spar chord assembly (including the forward side) at each strut location, and repair if necessary. That AD requires a one-time inspection for cracking of the forward side of the front spar chord assembly on the inboard and outboard struts, installation of a cap skin doubler for certain airplanes, and repair if necessary. Certain actions provided in that AD terminate the repetitive inspections of the forward side of the strut front spar chord assembly; the inspections of the aft side assembly are not terminated and continue to be required. That AD referred to Boeing Alert Service Bulletin 747-54A2224, Revision 1, dated November 16, 2006, to address the identified unsafe condition on Model 747-100, 747-100B, 747-100B SUD, 747-200B, 747-200C, 747-200F, 747-300, 747SR, and 747SP series airplanes equipped with GE CF6-45 or - 50 series engines, or equipped with Pratt & Whitney JT9D-3 or -7 (excluding -70) series engines. \n\nFAA's Determination and Requirements of This AD \n\n\tWe are issuing this AD because we evaluated all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of these same type designs. This AD requires accomplishing the actions specified in the service information described previously, except as discussed under "Differences Between the AD and the Service Information." \n\nDifferences Between the AD and the Service Information \n\n\tBoeing Alert Service Bulletin 747-54A2224, Revision 3, dated May 20, 2010, specifies to contact the manufacturer for instructions on how to repair certain conditions, but this AD would require repairing thoseconditions in one of the following ways: \n\tIn accordance with a method that we approve; or \n\tUsing data that meet the certification basis of the airplane, and that have been approved by the Boeing Commercial Airplanes Organization Designation Authorization (ODA) whom we have authorized to make those findings. \n\nInterim Action \n\n\tWe consider this AD interim action. If final action is later identified, we might consider further rulemaking then. \n\nFAA's Justification and Determination of the Effective Date \n\n\tContinued operation without the strut upper link load path could result in the fracture of the diagonal brace, and subsequent separation of the strut and engine from the airplane during flight. Because of our requirement to promote safe flight of civil aircraft and thus, the critical need to assure structural integrity of the engine support structure and the short compliance time involved with this action, this AD must be issued immediately. \n\tBecause an unsafe conditionexists that requires the immediate adoption of this AD, we find 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\tThis AD is a final rule that involves requirements affecting flight safety, and we did not provide you with notice and an opportunity to provide your comments before it becomes effective. However, we invite you to send any written data, views, or arguments about this AD. Send your comments to an address listed under the ADDRESSES section. Include "Docket No. FAA-2010-0641; Directorate Identifier 2010-NM-130-AD" at the beginning of your comments. We specifically invite comments on the overall regulatory, economic, environmental, and energy aspects of this AD. We will consider all comments received by the closing date and may amend this AD because of those comments. \n\tWe will post all comments we receive, without change, to http:// www.regulations.gov, including any personal information you provide. We will also post a report summarizing each substantive verbal contact we receive about this AD. \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\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\tThis 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\tFor the reasons discussed above, I certify that this AD: \n\t(1) Is not a "significant regulatory action" under Executive Order 12866, \n\t(2) Is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979), and \n\t(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. \n\tYou can find our regulatory evaluation and the estimated costs of compliance in the AD Docket. \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 FAA amends Sec. 39.13 by adding the following new AD: