2.11.3.2 Preparation of Helicopter

TM 1-1520-265-23 2.11.3.2 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 spindle horn shall be removed in accordance with the applicable technical manuals listed in Table 1-1. 2.11.3.3 Access. Access to the spindle horn is from the UR engine cowl (Figure 1-4, Items 3T-7 and 4T-8). 2.11.3.4 Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI, paragraph 1.4.4. 2.11.3.5 NDI Equipment Settings. a. Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-19e^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.) 2.11.3.6 Inspection Procedure. Refer to Eddy Current Method, paragraph 1.4.11 and Figure 2-11. a. Place probe on a good area in the inspection location and null. Adjust phase as required to obtain horizontal lift- off. b. Inspect the part. c. Any signal similar to the notches in the test block are cause for rejection. NOTE Either probe identified in paragraph 2.11.3.1 may be used depending primarily on the ease of accessibility and user friendliness. If the probes are changed, steps 2.11.3.5 b. (1), (2), and (3) shall be repeated each time a change is made. 2-22