47-21-22 REPUBLIC: (Was Service Note 2 of AD-769-2.) Applies to Model RC-3 Aircraft.
Inspection required before next flight and at each subsequent 25 hours of operation.
If no tab type lockwashers are installed, check tightness of engine mounting bolts to torque of 25 foot-pounds on 3/8-inch bolts and 30 foot-pounds on 7/16-inch bolts. If it is found that loosening has occurred it will be necessary to install tab type lockwashers under all engine mounting bolts. (AMI P/N 15175 for 3/8-inch bolts, AMI P/N 15176 for 7/16-inch bolts.)
If tab type lockwashers have been installed previously and tabs are in place, inspection is required only at the regular 100-hour periods.
(Aircooled Motors Service Bulletin No. 47 pertains to this subject.)