92-25-01 BOEING: Amendment 39-8416. Docket No. 92-NM-85-AD. Supersedes AD 90-08- 16, Amendment 39-6574. \n\n\tApplicability: Model 757 series airplanes; line numbers 1 through 411, inclusive, and 413 through 432, inclusive; certificated in any category. \n\n\tCompliance: Required as indicated, unless accomplished previously. \n\n\tTo prevent damage caused by skewed flaps resulting from excessive wear of the splines of the trailing edge flap drive torque tube coupling, accomplish the following: \n\n\t(a)\tPrior to the accumulation of 2,000 flight cycles, or within the next 200 flight cycles after April 30, 1990, (the effective date of AD 90-08-16), whichever occurs later, and thereafter at intervals not to exceed 2,000 flight cycles, perform an inspection of the torque tube coupling splines, in accordance with Boeing Service Letter 757-SL-27-52-B, dated April 30, 1990. \n\n\tNOTE: Operators who have conducted inspections of the torque tube coupling splines prior to the effective dateof this AD, in accordance with Boeing Service Letter 757-SL-27-52, dated January 31, 1990, or Boeing Service Letter 757-SL-27-52-A, dated March 21, 1990, are considered to be in compliance with paragraph (a) of this AD. \n\n\t\t(1)\tIf the measurement over the pin, as detailed in the service letter, is less than 1.8605 inches but equal to or greater than 1.8533 inches, repeat the inspection prior to the accumulation of 1,000 additional flight cycles. \n\n\t\t(2)\tIf the measurement over the pin, as detailed in the service letter, is less than 1.8533 inches, replace the coupling prior to further flight, in accordance with the service letter. \n\n\t(b)\tReplacement of the torque tube assemblies with improved torque tube assemblies, part number 251N4281-20 (one on each wing), and installation of a sealant plug in the shafts of the four gearboxes, in accordance with Boeing Service Bulletin 757-27-0099, dated March 12, 1992, constitutes terminating action for the inspections required by paragraph(a) of this AD. \n\n\t(c)\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(d)\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate the airplane to a location where the requirements of this AD can be accomplished. \n\n\t(e)\tThe inspection and replacement shall be done in accordance with Boeing Service Letter 757-SL-27-52-B, dated April 30, 1990. The replacement with improved torque tube assemblies shall be done in accordance with Boeing ServiceBulletin 757-27-0099, dated March 12, 1992. 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. 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(f)\tThis amendment becomes effective on December 23, 1992.