Primary Method. Eddy Current.

TM 1-1520-265-23 2.9.3 Primary Method. Eddy Current. 2.9.3.1 NDI Equipment and Materials. (Refer to Appendix B.) a. Eddy Current Inspection Unit b. Probe, straight, shielded surface, 100 KHz-500 KHz c. Probe, right angle, shielded surface, 100KHz-500 KHz, 90° 1/2 inch drop d. Cable Assembly e. Reference Block, three-notched aluminum (0.008, 0.020, 0.040 EDM notches) f. Teflon Tape, refer to Table 1-8 g. Aircraft Marking Pencil, refer to Table 1-8 2.9.3.2 Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance. A partial inspection for cause (visual indications, sites of mechanical damage, corrosion, etc.) may be performed on all exposed surfaces of the installed part using this procedure. If required, the droop stop support ring nut shall be removed in accordance with the applicable technical manuals listed in Table 1-1. 2.9.3.3 Access. Access to the droop stop support ring nut is from the UR engine cowl (Figure 1-4, Items 3T-7 and 4T-8). 2.9.3.4 Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI, paragraph 1.4.4. 2.9.3.5 NDI Equipment Settings. a. Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-1 9e^ll. Frequency F1 - 200 KHz F2 - off HdB - 57.0 VdB - 69.0 Rot - 56° Probe drive - mid LPF - 100 HPF - 0 H 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 when probe is passed over 0.040-inch notch in test block. (See the standard instrument display shown in Figure 1-7.) 2-17