TM 1-1520-265-232-10 Change 42.6.3.2 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) maybe performed on all exposed surfaces of the installed part using this procedure. If required, the mainrotor hub shall be removed in accordance with the applicable technical manuals listed in Table 1-1.2.6.3.3 Access. Access to the main rotor hub is from the L/R engine cowl (Figure 1-4, Items 3T-7and 4T-8).2.6.3.4 Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of part orArea for NDI, paragraph 1.4.4.2.6.3.5 NDI Equipment Settings.a. Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-19eII.Frequency F1 - 1000 KHz F2 - offHdB - 60.0VdB - 70.0Rot - 60_Probe drive - HighLPF - 50HPF - 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 verticalsignal when probe is passed over 0.040-inch notch in test block. (See the standardinstrument display shown in Figure 1-7.)2..6.3.6 Inspection Procedure. Refer to Eddy Current Method, paragraph 1.4.11 and Figure 2-6.a. Place probe on a good area in the inspection location and null. Adjust phase as required toobtain horizontal lift-off.b. Inspect the part.c. Any signal similar to the notches in the test block are cause for rejection.NOTEEither probe identified in paragraph 2.6.3.1 may be used depending primarily on theease of accessibility and user friendliness. If the probes are changed, steps 2.6.3.5b. (1), (2), and (3) shall be repeated each time a change is made.
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