TM 1-1520-265-233.2 MAIN TRANSMISSION (ET).3.2.1 Description(Figure3-1.IndexNo.2). The main transmission is mounted on the main fuselage. It mounts anddrives the main rotor head, changes the angle of drive from the engines, reduces engine rpm, and drives the tail rotordrive shaft along with the accessory modules.3.2.2 Defects. Defects may occur anywhere on the surface of the main transmission. All areas where rework has beenperformed shall be inspected for cracks. No cracks are allowed.3.2.3 PrimaryMethod. Eddy Current.3.2.3.1 NDI Equipment and Materials. (Refer to Appendix B.)a.Eddy Current Inspection Unitb.Probe, straight, shielded surface, 100 KHz-500 KHzc.Probe, right angle, shielded surface, 100KHz-500 KHz, 900 1/2 inch dropd.Cable Assemblye.Reference Block, three-notched aluminum (0.008, 0.020, 0.040 EDM notches)f.Teflon Tape, refer to Table 1-8g.Aircraft Marking Pencil, refer to Table 1-83.2.3.2 Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance. A partial inspectionfor cause (visual indications, sites of mechanical damage, corrosion, etc.) may be performed on all exposed surfaces ofthe installed part using this procedure. If required, the main transmission shall be removed in accordance with theapplicable technical manuals listed in Table 1-1.3.2.3.3 Access. Not applicable.3.2.3.4 Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,paragraph 1.4.4.3.2.3.5 NDI Equipment Settings.a. Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-19e”.Frequency F1- 200 KHzF2- offHdB- 57.0VdB- 69.0Rot- 56°Probe drive- midLPF- 100HPF- 0H Pos- 80%V Pos-20%3-3
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