AD 94-20-11

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747-400 series airplanes, that requires replacement of the thrust reverser flow restrictor devices with one-way (check) valve restrictors. This amendment is prompted by reports of actuator piston seal leakage found during actuator overhaul on certain Model 747-400 series airplanes. The actions specified by this AD are intended to prevent possible deployment of a thrust reverser in flight and subsequent reduced controllability of the airplane.

Final rule

94-20-11 BOEING: Amendment 39-9040. Docket 94-NM-37-AD. \n\n\tApplicability: Model 747-400 series airplanes up to and including line position 1022, equipped with Pratt & Whitney PW4000 series engines, certificated in any category. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent possible deployment of a thrust reverser in flight and subsequent reduced controllability of the airplane, accomplish the following: \n\n\t(a)\tWithin 18 months after the effective date of this AD, replace the thrust reverser flow restrictor devices with one-way (check) valve restrictors in accordance with Boeing Alert Service Bulletin 747-78A2128, dated March 10, 1994; or Revision 1, dated May 26, 1994. \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: 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 replacement shall be done in accordance with Boeing Alert Service Bulletin 747- 78A2128, dated March 10, 1994; or Boeing Alert Service Bulletin 747-78A2128, Revision 1, dated May 26, 1994. 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 November 25, 1994.

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 22, 1994 (59 FR 19151). That action proposed to require replacement of the thrust reverser flow restrictor devices with one-way (check) valve restrictors. \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\tThe Air Transport Association (ATA) of America, on behalf of one of its members, requests that the proposed rule be revised to cite the latest revision of Boeing Alert Service Bulletin 747- 78A2128. The FAA concurs. Since the issuance of the proposed rule, the FAA has reviewed and approved Revision 1, dated May 26, 1994, of the Boeing alert service bulletin. Revision 1 corrects certain discrepancies contained in the original issue of the alert service bulletin. The FAA has revised paragraph (a) of the final rule to reflect the latest revision to the alert service bulletin as an additional source of service information. \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 change previously described. The FAA has determined that this change will neither increase the economic burden on any operator nor increase the scope of the AD. \n\n\tThere are approximately 94 Model 747-400 series airplanes of the affected design in the worldwide fleet. The FAA estimates that 32 airplanes of U.S. registry will be affected by this AD, that it will take approximately 24 work hours per airplane to accomplish the required actions, and that the average labor rate is $55 per work hour. Required parts will be supplied by the manufacturer at no cost to operators.Based on these figures, the total cost impact of the AD on U.S. operators is estimated to be $42,240, or $1,320 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 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\n List 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.\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\n\t2.\tSection 39.13 is amended by adding the following new airworthiness directive: