AD 72-04-01

72-04-01 BOEING: Amendment 39-1392 as amended by Amendment 39-1407. Applies to 747-100 and 747-200B Series airplanes. Compliance required as indicated. To prevent unscheduled stabilizer trim and to maintain stabilizer control capability, accomplish the following: (a) For airplanes incorporating stabilizer trim modules Boeing P/N 60B80027-2 and 60B80027-3 and/or stabilizer trim drive motors P/N 60B00250-1, within 100 hours time in service after effective date of this A.D., and, thereafter at intervals not to exceed 100 hours time in service from the last inspection, test the stabilizer trim system components per Boeing Service Bulletin 27-2054, Revision 3, dated February 15, 1972, or later FAA approved revisions or equivalent tests approved by the Chief, Aircraft Engineering Division, FAA Western Region, until modified in accordance with paragraph (c), below. (b) Replace, or modify, prior to further flight, stabilizer trim system components which are found defective bythe inspections per paragraph (a), above, in accordance with Boeing Service Bulletin 27-2054, Revision 3, dated February 15, 1972, or later FAA approved revisions or equivalent replacements or modifications approved by the Chief, Aircraft Engineering Division, FAA Western Region. (c) The inspections required per (a), above, may be discontinued after accomplishment of the following: (1) Replace stabilizer trim modules, Boeing P/N 60B80027-2 and 60B80027-3, with stabilizer trim modules modified with improved arming and control valve seals and steel retainer caps, per Boeing Service Bulletin 27-2054, Revision 3, dated February 15, 1972, or later FAA approved revisions or equivalent modifications approved by the Chief, Aircraft Engineering Division, FAA Western Region. NOTE: Boeing Service Bulletin 27-2054, Revision 3, dated February 15, 1972, incorporates LTV Electrosystems Service Bulletins 27-6, 27-8, and 27-9 in "Part II, Terminating Action." (2) Replace stabilizer trimmotor, Boeing P/N 60B00250-1, without suffix "D" identification following unit serial number identification, with stabilizer trim motors modified with solid locking pins, per Boeing Service Bulletin 27-2054, Revision 3, dated February 15, 1972, or later FAA approved revisions or equivalent modifications approved by the Chief, Aircraft Engineering Division, FAA Western Region. NOTE: Boeing Service Bulletin 27-2054, Revision 3, dated February 15, 1972, incorporates Vickers Service Bulletin 910274-4, dated February 10, 1972. (d) Within 100 hours time in service after the effective date of this A.D., unless already accomplished, incorporate in the FAA approved Airplane Flight Manual, "Emergency Procedures" (Section 2), the following procedures: "UNSCHEDULED STABILIZER TRIM Recall Stabilizer Trim Hydraulic Switches - CUTOUT Reference Autopilot - DISENGAGE Control column movement in opposition of trim will stop unscheduled trim caused by electrical fault. Moving stabilizer trim hydraulic switches to CUTOUT will stop any unscheduled trim. Allow sufficient time for valves to operate. A portion of the system may be determined to be usable by moving one stabilizer trim hydraulic switch at a time to NORM. If trim is normal that system may be used to adjust trim as required." Amendment 39-1392 became effective February 11, 1972. This amendment 39-1407 becomes effective March 14, 1972.