TM 1-1520-265-23Change 3 2-9a. Select AC on the AC/DC switch.b. Place probe/yoke on part in position 1 as shown.c. Press the test switch and apply a light coat of magnetic particle media at the same time.Remove the media momentarily before removing the current. Current should be applied forno more than five seconds.d. Inspect for cracks using the black light.e. Demagnetize before moving to the next position. Refer to paragraph 2.5.3.8.f. Repeat steps a. through e. for positions 2 and 3.2.5.3.7 Marking and Recording of Inspection Results. Mark and record inspection results asrequired by paragraph 1.3.2.5.3.8 Demagnetization. With the switch remaining in the AC position, place the probe/yoke legsin the same position used for magnetizing. Press the test switch and withdraw the probe/yoke fromthe part for a distance of two feet before releasing the switch.2.5.4 BackupMethod. None required.2.5.5 SystemSecuring. Clean the main rotor shaft nut thoroughly to remove all residual magneticparticle media. Refer to Post Cleaning and Restoration of Part or Area After NDI, paragraph 1.4.16.The main rotor shaft nut requires installation in accordance with the applicable technical manualslisted in Table 1-1.2.6 MAIN ROTOR HUB (ET).2.6.1 Description(Figure2-1,IndexNo.6). The main rotor hub is part of the main rotor headwhich transmits movements of the main transmission to the four main rotor blades.2.6.2 Defects. Defects may occur anywhere on the surface of the main rotor hub. No cracks areallowed.2.6.3 PrimaryMethod. Eddy Current.2.6.3.1 NDI Equipment and Materials. (Refer to Appendix B.)a. Eddy Current Inspection Unitb. Probe, straight, shielded surface, 2 MHzc. Probe, right angle, shielded surface, 2 MHz, 90_ 1/2 inch dropd. Cable Assemblye. Adapter, Probe f. Reference Block, three-notched Titanium (0.008, 0.020, 0.040 EDM notches)g. Teflon Tape, refer to Table 1-8h. Aircraft Marking Pencil, refer to Table 1--8
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