AD 94-10-06 ACTIVE

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 707/720 series airplanes, that requires certain structural inspections of older airplanes. This amendment is prompted by reports of incidents involving fatigue cracking and corrosion in transport category airplanes that are approaching or have exceeded their economic design service goal. The actions specified by this AD are intended to prevent degradation of the structural capabilities of the affected airplanes. This amendment relates to the recommendations of the Airworthiness Assurance Task Force assigned to review Model 707/720 series airplanes, which indicate that, to assure long term continued operational safety, various structural inspections should be accomplished.

Final rule

94-10-06 BOEING: Amendment 39-8913. Docket 93-NM-80-AD. \n\n\tApplicability: Model 707/720 series airplanes, as listed in Section 4 and Appendix A.4 of Boeing Document D6-54996, "Aging Airplane Service Bulletin Structural Modification and Inspection Program - Model 707/720," Revision E, dated March 8, 1994; certificated in any category. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent degradation of the structural capability of the airplane, accomplish the following: \n\n\t(a)\tAccomplish the inspections specified in Section 4 and Appendix A.4 of Boeing Document Number D6-54996, "Aging Airplane Service Bulletin Structural Modification and Inspection Program - Model 707/720," Revision E, dated March 8, 1994, in accordance with the schedule specified in paragraph (b) of this AD. Repeat these inspections thereafter at intervals not to exceed those specified in the Boeing Document for each inspection. \n\n\t(b)\tThe maximum initial inspection timefor the inspections required by paragraph (a) of this AD shall be the later of the times specified in either paragraph (b)(1) or (b)(2) of this AD: \n\n\t\t(1)\tThe threshold for inspection time for the inspection specified in the Boeing Document, measured as an accumulated total of flight cycles or time-in-service, as appropriate; or \n\n\t\t(2)\tThe "phase-in" period for the inspection specified in the Boeing Document, measured from a date 18 months after the effective date of this AD. \n\nNOTE 1: For the purposes of this AD, the "phase-in period" is defined as the allowable period to accomplish the initial inspection when the "threshold" specified in paragraph (b)(1) of this AD is imminent or has elapsed. \n\n\t(c)\tIf any discrepant condition identified in the service bulletins (that are specified in the Boeing Document) is found as a result of the inspections required by this AD, prior to further flight, accomplish the corresponding corrective action specified in the service bulletins.(d)\tThe terminating action for each inspection required by paragraph (a) of this AD consists of the accomplishment of the modification specified in the corresponding service bulletin. \n\n\t(e)\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 ACO.\n \nNOTE 2: 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(f)\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(g)\tThe inspections and corrective actions shall be done in accordance with Boeing Document Number D6-54996, "Aging Airplane Service Bulletin Structural Modification and Inspection Program - Model 707/720," Revision E, dated March 8, 1994, which includes the following list of effective pages: \t\t\t\t\t\t\n\n\nPage Number\nRevision Level \nShown on Page \nList of Active Pages \nPages c.1 and c.2\nE \n\n(NOTE: The issue date of Revision E is indicated only on the title page; no other page of the document is dated.) 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(h)\tThis amendment becomes effective on June 20, 1994.

A proposal to amend part 39 of the Federal Aviation Regulations to include an airworthiness directive (AD) that is applicable to certain Boeing Model 707/720 series airplanes was published in the Federal Register on October 18, 1993 (58 FR 53678). That action proposed to require inspections of certain structural components on older airplanes for cracks, corrosion, and other discrepancies, and repair or correction of discrepancies, if necessary. \n\n\tInterested persons have been afforded an opportunity to participate in the making of this amendment. Due consideration has been given to the comments received. \n\n\tOne commenter supports the proposed rule. \n\n\tOne commenter requests that the structural inspections and modifications referenced in Section A.3 and Section A.4 of Appendix A of Boeing Document Number D6-54996, "Aging Airplane Service Bulletin Structural Modification and Inspection Program - Model 707/720," Revision D, dated January 23, 1992, becombined and addressed as a single AD action, rather than in two separate actions, as proposed by the FAA in this notice. This commenter points out that the FAA previously issued AD 94-06-08, Amendment 39-8856 (59 FR 13446, March 22, 1994), which requires the accomplishment of a certain structural modification of the wing front spar lower chord in accordance with Section A.3 of Appendix A of the Boeing Document. This commenter contends that by issuing a single AD to cover both sections of the Boeing Document, the FAA will contribute to reducing the cost and complexity of publishing and tracking multiple AD's, while maintaining the same level of safety. \n\n\tThe FAA does not concur with this commenter's request, specifically because of the nature of the requirements of the rules. The requirements contained in AD 94-06-08 address a single structural modification applicable to Model 707 series airplanes listed in Appendix A.3 of the Boeing Document. The compliance time for accomplishing that modification is based on either the number of flight cycles on the airplane or a specific calendar time. The requirements of this AD, however, address structural inspections for both Model 707 and Model 720 series airplanes listed in Section 4 and Appendix A.4 of the Boeing Document. The compliance times for implementation of these various inspections vary, as do- the repetitive inspection intervals. The FAA considers that combining the requirements for these dissimilar actions into one complex AD would create unnecessary confusion for affected operators. Therefore, the FAA finds it appropriate to issue one AD addressing the modification and another AD addressing "inspections only." This method of issuance will ease tracking of and facilitate compliance with the requirements of these two separate AD's. \n\n\tSince the issuance of the proposal, the FAA has reviewed and approved Revision E of Boeing Document Number D6-54996, "Aging Airplane Service Bulletin Structural Modification and Inspection Program - Model 707/720," dated March 8, 1994. The inspections described in this revision are identical to those described in Revision D, which was referenced in the proposal as the appropriate source of service information. The only change effected by Revision E is that it excludes the inspections of the upper skin on the wing center section described in Boeing Service Bulletin 2590. The actions specified in Boeing Service Bulletin 2590 currently are the subject of AD 68-18-03, Amendment 39-2056. In light of this, the final rule has been revised to reference Revision E of the Boeing Document as the appropriate source of service information in order to eliminate these redundant inspection requirements. The applicability of the final rule has also been revised to reference those airplanes listed in Revision E of the Boeing Document in order to exclude those airplanes that are subject to the requirements of Boeing Service Bulletin 2590. Additionally, the economic impact information, below, has been revised to reflect the deletion of these inspections from the required number of work hours for accomplishment of the actions required by this final rule. \n\n\tUpon further review of the inspection actions required by this AD, the FAA has revised the final rule to extend the proposed 15-month compliance time to 18 months (for airplanes that have surpassed the specified compliance threshold in terms of accumulated flight cycles or time-in- service). The FAA has determined that increasing the compliance time by an additional three months will not adversely affect safety, and will allow the inspections to be performed during regularly scheduled maintenance at a main base where special equipment and trained maintenance personnel will be available if necessary. Moreover, this is the compliance time currently recommended by the manufacturer in the latest revision to the Boeing Document, which is referenced in the final rule. \n\n\tAfter careful review of the available data, including the comments noted above, the FAA has determined that air safety and the public interest require the adoption of the rule with the changes previously described. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD. \n\n\tThere are approximately 416 Model 707/720 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 82 airplanes of U.S. registry will be affected by this AD, that it will take approximately 691 work hours per airplane to accomplish the required actions, and that the average labor rate is $55 per work hour. Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $3,116,410, or $38,005 per airplane. \n\n\tThe total cost impact figure discussed above is based on assumptions that no operator has yet accomplished any of the requirements of this AD action, and that no operator would accomplish those actions in the future if this AD were not adopted. \n\n\tThe FAA recognizes that the obligation to maintain aircraft in an airworthy condition is vital, but sometimes expensive. Because AD's require specific actions to address specific unsafe conditions, they appear to impose costs that would not otherwise be borne by operators. However, because of the general obligation of operators to maintain aircraft in an airworthy condition, this appearance is deceptive. Attributing those costs solely to the issuance of this AD is unrealistic because, in the interest of maintaining safe aircraft, most prudent operators would accomplish the required actions even if they were not required to do so by the AD. \n\n\tA full cost-benefit analysis has not been accomplished for this AD. As a matter of law, in order to be airworthy, an aircraft must conform to its type design and be in a condition for safe operation. The type design is approved only after the FAA makes a determination that it complies with all applicable airworthiness requirements. In adopting and maintaining those requirements, the FAA has already made the determination that they establish a level of safety that is cost- beneficial. When the FAA, as in this AD, makes a finding of an unsafe condition, this means that this cost-beneficial level of safety is no longer being achieved and that the required actions are necessary to restore that level of safety. Because this level of safety has already been determined to be cost-beneficial, a full cost-benefit analysis for this AD would be redundant and unnecessary. \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 thepreparation of a Federalism Assessment. \n\n\tFor the reasons discussed above, I certify that this action (1) is not a "significant regulatory action" under Executive Order 12866; (2) is not a "significant rule" under DOT Regulatory Policies and Procedures (44 FR 11034, February 26, 1979); and (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. A final evaluation has been prepared for this action and it is contained in the Rules Docket. A copy of it 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\nAir transportation, Aircraft, Aviation safety, Incorporation by reference, Safety. \n\nAdoption of the Amendment \n\nAccordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration amends 14 CFR part 39 of the Federal Aviation Regulations as follows: \n\nPART 39 - AIRWORTHINESS DIRECTIVES \n\n1.\tThe authority citation for part 39 continues to read as follows: Authority: 49 U.S.C. App. 1354(a), 1421 and 1423; 49 U.S.C. 106(g); and 14 CFR 11.89. § 39.13 - (Amended) \n\n2.\tSection 39.13 is amended by adding the following new airworthiness directive:

The service information referenced in this AD may be obtained from Boeing\nCommercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124-2207. This information may be examined at the Federal Aviation Administration (FAA), Transport Airplane Directorate, Rules Docket, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC.

Phil Forde, Aerospace Engineer, Airframe Branch, ANM-120S, FAA, Transport Airplane Directorate, Seattle Aircraft Certification Office, 1601 Lind Avenue, SW., Renton, Washington 98055-4056; telephone (206) 227-2771; fax (206) 227-1181.