TM 1-1520-265-234.24.3. PrimaryMethod. Eddy Current.4.24.3.1. 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, 100 KHz-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 1-84.24.3.2. 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 landing gear shock strut upper cylinder shall be removed inaccordance with the applicable technical manuals listed in Table 1-1.4.24.3.3. Access. Access to the MLG shock strut upper cylinder is through the shock strut hinged panel (Figure 1-4,Items 3T-3 and 4T-4).4.24.3.4. Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,paragraph 1.4.4.4.24.3.5. NDI Equipment Settings.a.Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-1 9e'.Frequency F1- 200 KHzF2- offHdB- 57.0VdB- 69.0Rot- 560Probe drive- midLPF- 100HPF- 0H Pos-80%V Pos- 20%b.Refer to Eddy Current Method, paragraph 1.4.11. Set up on test block as follows:(1)Null probe on test block.(2)Adjust phase as required to obtain horizontal lift-off.(3)Move probe over all three notches in test block. Adjust gain to obtain a three block vertical signal whenprobe is passed over 0.040-inch notch in test block. (See the standard instrument display shown in Figure1-7.)4-57
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