AD 98-24-26

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747-400 series airplanes, that requires replacing the cam assembly, cam bellcrank assembly, and thrust reverser control switch actuator on all four thrust levers with new components. This amendment is prompted by a report of an uncommanded automatic retraction of the leading edge flaps during takeoff. The actions specified by this AD are intended to prevent such uncommanded automatic retraction, which would seriously degrade liftoff and climb capabilities, and could result in near-stall conditions at a critical phase of the flight.

Final rule

98-24-26 BOEING: Amendment 39-10913. Docket 97-NM-13-AD. \n\n\tApplicability: Model 747-400 series airplanes, line positions 696 through 1090 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 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.To prevent uncommanded automatic retraction of the leading edge flaps during takeoff, which would seriously degrade liftoff and climb capabilities, and could result in near-stall conditions, accomplish the following: \n\n\t(a)\tWithin 18 months after the effective date of this AD, accomplish the requirements of paragraph (a)(1) or (a)(2) of this AD, as applicable, in accordance with Boeing Service Bulletin 747-27A2356, Revision 1, dated August 13, 1998. \n\n\t\t(1)\tFor Groups 1 and 2 airplanes, as listed in the service bulletin: Replace the cam assembly, cam bellcrank assembly, and thrust reverser control switch actuator on all four thrust levers with new components. \n\n\t\t(2)\tFor Groups 3 and 4 airplanes, as listed in the service bulletin: Replace the cam bellcrank assembly and thrust reverser control switch actuator on all four thrust levers with new components. \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 ACO. \n\n\tNOTE 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(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 Service Bulletin 747-27A2356, Revision 1, dated August 13, 1998. 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 BoeingCommercial 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 December 30, 1998.

A proposal to amend part 39 of the Federal Aviation Regulations (14 CFR part 39) to include an airworthiness directive (AD) that is applicable to certain Boeing Model 747-400 series airplanes was published in the Federal Register on April 14, 1997 (62 FR 18063). That action proposed to require replacing the cam assembly, cam bellcrank assembly, and thrust reverser control switch actuator on all four thrust levers with new components. \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\nRequest to Cite the Latest Service Information \n\n\tThree commenters request that the proposed rule be revised to reflect the latest revision of Boeing Alert Service Bulletin 747-27A2356; the original issue of that service bulletin was referenced in the proposal as the appropriate source of service information. \n\n\tThe FAA concurs with the commenters' request to reference the latest revision of the service bulletin. The FAA has reviewed and approved Boeing Service Bulletin 747-27A2356, Revision 1, dated August 13, 1998. That revision of the service bulletin provides a correction to certain part numbers of the cam bellcrank assemblies and clarifies certain part-marking instructions. In addition, Revision 1 of the service bulletin describes a revision of the operating position of the reverse thrust isolation valve switches in the thrust levers. The FAA has revised the final rule to reference Boeing Service Bulletin 747-27A2356, Revision 1, dated August 13, 1998, as the appropriate source of service information. The FAA has determined that requiring the replacements to be performed in accordance with Revision 1 of the service bulletin will not pose an additional burden on any operator. \n\nRequest to Revise the Cost Impact Information \n\n\tOne commenter, the manufacturer, requests that the cost impact information be corrected to reflectthat 46 airplanes of U.S. registry will be affected by this AD, rather than the 35 airplanes estimated in the proposal. The FAA concurs and has revised the cost impact information accordingly. \n\nConclusion \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 described previously. The FAA has determined that these changes will neither increase the economic burden on any operator nor increase the scope of the AD. \n\nCost Impact \n\n\tThere are approximately 394 Boeing Model 747-400 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 46 airplanes of U.S. registry will be affected by this AD, that it will take approximately 8 work hours per airplane to accomplish the required actions, and that the average labor rate is $60 per work hour. Required parts would cost between $3,412 and $4,740 per airplane. Based on these figures, the cost impact of the AD is estimated to be between $179,032 and $240,120, or between $3,892 and $5,220 per airplane. \n\n\tThe cost impact figures discussed above are 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\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\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\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\nPART 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: