AD 97-26-21 SUPERSEDED

This amendment adopts a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-100, 747-200, 747-300, 747SR, and 747SP series airplanes. This action requires a one-time inspection to detect cracking of the longeron splice fittings at stringer 11, on the left and right sides at body station 2598, and replacement of any cracked fitting with a new fitting. This amendment is prompted by reports that fatigue cracking was found on longeron splice fittings. The actions specified in this AD are intended to detect and correct such fatigue cracking, which could result in reduced controllability of the horizontal stabilizer.

Final rule; request for comments

97-26-21 BOEING: Amendment 39-10264. Docket 97-NM-294-AD. \n\n\tApplicability: Model 747-100, 747-200, 747-300, 747SR, and 747SP series airplanes having line positions 201 through 886 inclusive; certificated in any category. \n\n\tNOTE 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (b) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo detect and correct fatigue cracking of the longeron splice fittings at stringer 11, which could result in reduced controllability of the horizontal stabilizer, accomplish the following: \n\n\t(a)\tPerform a one-time detailed visual inspection to detect cracking of the longeron fittings at stringer 11, on the left and right sides at body station 2598, at the later of the times specified in paragraphs (a)(1) and (a)(2) of this AD, in accordance with the Accomplishment Instructions of Boeing Alert Service Bulletin 747-53A2410, Revision 2, dated October 30, 1997, including Addendum. If any crack is detected, prior to further flight, replace the cracked fitting with a new fitting, in accordance with the alert service bulletin. \n\n\t\t(1)\tInspect prior to the accumulation of 22,000 total flight cycles or 78,000 total flight hours, whichever occurs first; or \n\n\t\t(2)\tInspect within 90 days after the effective date of this AD. \n\tNOTE2: Where there are differences between the AD and the alert service bulletin, the AD prevails. \n\n\t(b)\tAn alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle \n. \n\tNOTE 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. \n\n\t(c)\tSpecial flight permits may be issued in accordance with sections 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished. \n\n\t(d)\tThe actions shall be done in accordance with Boeing Alert Service Bulletin 747-53A2410, Revision 2, dated October 30, 1997, including Addendum. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. \n\n\t(e)\tThis amendment becomes effective on January 13, 1998.

The FAA has received three reports indicating that fatigue cracking was found on the longeron splice fittings at stringer 11 on Boeing Model 747SR and 747-200 series airplanes. The most recent cracking was detected on an airplane that had accumulated 62,783 total flight hours and 16,867 total flight cycles. Such fatigue cracking, if not detected and corrected in a timely manner, could result in reduced controllability of the horizontal stabilizer.\n \nExplanation of Relevant Service Information \n\n\tThe FAA has reviewed and approved Boeing Alert Service Bulletin 747-53A2410, Revision 2, dated October 30, 1997, including Addendum, which describes procedures for repetitive detailed inspections to detect cracking of the longeron splice fittings at stringer 11, on the left and right sides at body station 2598, and replacement of any cracked fitting with a new fitting. The alert service bulletin specifies various compliance times for groups of airplanes having different flight hour and flight cycle thresholds.\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 Boeing Model 747-100, 747-200, 747-300, 747SR, and 747SP series airplanes of the same type design, this AD requires a one-time detailed inspection to detect cracking of the longeron splice fittings at stringer 11, on the left and right sides at body station 2598, and replacement of any cracked fitting with a new fitting. The actions are required to be accomplished in accordance with the alert service bulletin described previously. \n\nDifferences between the AD and the Alert Service Bulletin \n\n\tThe AD differs from the previously described alert service bulletin in that the AD requires a one-time inspection and shortened compliance time, rather than the repetitive inspections and multiple compliance times specified in the referenced alert service bulletin. The recent report of cracking detected on a Boeing Model 747-200 series airplane at a relatively low threshold has indicated the need for interim action requiring inspection at an early date, directed to those airplanes that have accumulated the highest number of flight hours or flight cycles (i.e., 78,000 total flight hours or 22,000 total flight cycles). \n\n\tIn addition, the AD differs from the alert service bulletin by providing a compliance period in terms of calendar time, rather than flight cycles/hours, for those airplanes that have exceeded the threshold. Due to the limited availability of replacement fittings, a 90-day compliance period is provided by this AD. This compliance period will allow the operators of affected airplanes an opportunity to schedule the inspection and have necessary replacement fittings available if cracks are found during the inspection. \n\nInterim Action \n\n\tThis AD is considered to be interim action. The FAA is considering separate rulemaking action that would propose similar inspections at repetitive intervals for all airplanes affected by the previously described alert service bulletin. \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 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 97-NM-294-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." \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:

Submit comments in triplicate to the Federal Aviation Administration (FAA),\nTransport Airplane Directorate, ANM-114, Attention: Rules Docket No. 97-NM-294-AD, 1601 Lind Avenue, SW., Renton, Washington 98055-4056.\n\n\tThe service information referenced in this AD may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Bob Breneman, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington; telephone (425) 227-2776; fax (425) 227-1181.