80-18-07: Main Transmission Assembly

80-18-07 HUGHES HELICOPTERS: Amendment 39-3965. Applies to Model 269A, and TH-55A, 269A-1, 269B and Model 269C Helicopters with main transmission P/N 269A5175-7 or 269A5175-9, Serial Numbers: 5743 through 5804 5903 through 5908 5806 through 5811 5911 5813 through 5827 5914 5829 through 5855 5915 5857 through 5863 5918 5867 5919 5868 5922 5870 through 5882 5930 5884 5935 5886 through 5890 5938 5893 5966 5894 5972 5895 through 5901 5986 Compliance is required within 50 hours' time in service from the effective date of this AD, unless already accomplished. To prevent loss of power into main transmission, due to fracture of main transmission pinion shaft, accomplish the following: (a) Remove main transmission assembly, per Basic Hughes Maintenance Instruction (HMI). Disassemble main transmission assembly, and pinion and bearing retainer assemblies, per HMI Appendix C. (b) Clean pinion assembly. Using 10X glass, visually inspect pinion for scratches, tooling marks, corrosion or other surface defects. Pay particular attention to area of fillet radii and threaded area forward of bearing journal. If scratches, tooling marks, corrosion or other surface defect is noted, perform the following: 1. Position pinion on lathe or equivalent rotating fixture. 2. Polish out defect(s) on pinion as it is rotated on lathe or fixture. Use fine emery cloth wrapped around tongue depressor or equivalent for polishing. Extra fine arkansas or carborundum stone may be used, provided diameter of stone matches radius. Emery cloth and hand stone are the only polishing methods approved. (c) Clean pinion assembly and perform magnetic particle inspection of entire pinion in accordance with MIL-I-6868. Pay particular attention to forward end of bearing journal and fillet radii, pinion gear teeth, and threaded area just forward of H-frame bearing journal. If no defects are found, treat polished area with wet zinc chromate, as applicable. (d) If magnetic particle inspection indication is noted in area polished per step (B) 2 above, repolish and repeat magnetic particle inspection of the area. If indication cannot be removed by repolishing, or the minimum diameter at the bottom of the fillet radius after polishing is less than 1.472 inches, mark and tag the pinion as unserviceable. (e) If evidence of cracking is noted, mark and tag pinion as unserviceable. (f) If inspection pinion is found serviceable and reinstalled in helicopter transmission, treat polished area with zinc chromate primer, as applicable. Paint white dot on gear box ID plate next to Serial Number to denote compliance with this Notice. (g) As applicable, reassemble pinion and bearing retainer assemblies, and main transmission assembly, per HMI Appendix C. (h) As applicable, reinstall main transmission assembly, per Basic HMI. (i) Special flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base for the accomplishment of inspection required by this AD. (j) Alternative inspections, modifications or other actions which provide an equivalent level of safety may be used when approved by the Chief, Aircraft Engineering Division, FAA Western Region. This amendment becomes effective November 11, 1980 to all persons, except those to whom it was made immediately effective by letter dated August 26, 1980.