52-26-01\tNAVION: Applies to All Models, Serial Numbers NAV-4-2 and Subsequent. \n\nCompliance required as indicated. \n\nInspect as soon as practical, but not later than February 1, 1953, and at 100-hour intervals thereafter the area in the vicinity of the stabilizer fuselage attachment for cracks. Particular attention should be given to the stabilizer spar web (gusset) immediately outboard of the root rib and the fuselage attaching fitting. If cracks are found in the fuselage fitting, P/N 143-31004-13, the entire part should be replaced. Cracks in the root rib may be repaired in accordance with CAM No. 18. Cracks in the spar web (gusset) require the replacement of the gusset with a new part made in accordance with Figure 2. \n\n\n\nAD 52-26-01 \n\nPeriodic inspections of stabilizer spar web only may be discontinued after installation of new gussets. \n\n(Ryan Navion Field Service Bulletin No. 17 dated September 28, 1952, covers this same subject.)