72-08-01 BOEING: Amdt. 39-1428. Applies to Boeing Model 747 airplanes, listed in Boeing Service Bulletin 747-32-2118, dated December 20, 1971, or later FAA-approved revisions except the Model 747-131. \n\tCompliance required within the next 100 hours' time in service after the effective date of this AD, unless already accomplished within the last 400 hours' time in service, and thereafter at intervals not to exceed 500 hours' time in service from the last inspection, until modified per Boeing Service Bulletin 747-32-2118, dated December 20, 1971, or later FAA-approved revisions. \n\tTo detect failed landing gear alternate extension actuators, accomplish the following: \n\tInspect landing gear alternate extension actuators in accordance with Boeing Service Bulletin 747-32-2118, dated December 20, 1971, or later FAA-approved revisions, until modified in accordance with Boeing Service Bulletin 747-32-2118, dated December 20, 1971, or later FAA-approved revision, or an equivalent inspection approved by the Chief, Aircraft Engineering Division, FAA Western Region. \n\tThis amendment becomes effective April 7, 1972.