TM 1-1520-264-232.10.3.8Demagnetization. With the switch remaining in the AC position, place the probe/yoke legs in the sameposition used for magnetizing. Press the test switch and withdraw the probe/yoke from the part for a distance of two feetbefore releasing the switch.2.10.4Backup Method. None required.2.10.5System Securing. Clean the main rotor hub retention nut thoroughly to remove all residual magnetic particlemedia. Refer to Post Cleaning and Restoration of Part or Area After NDI, paragraph 1.4.16. The main rotor hub retentionnut requires installation in accordance with the applicable technical manuals listed in Table 1-1.2.11MAIN ROTOR HEAD (HUB) (ET).2.11.1Description (Figure 2-1. Index No. 11). The main rotor head assembly is a fully-articulated assembly thatprovides attachment points for the four main rotor blade assemblies.2.11.2Defects. This inspection is used to verify crack indications found visually on the main rotor head (hub). Nocracks are allowed.2.11.3Primary Method. Eddy Current.2.11.3.1NDI 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, 901/2 inch dropd.Cable Assemblye.Reference Block, three-notched aluminum (0.008, 0.020, and 0.040 EDM notches)f.Teflon Tape, refer to Table 1-8g.Aircraft Marking Pencil, refer to Table 1-82.11.3.2Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance. A partialinspection for cause (visual indications, sites of mechanical damage, corrosion, etc.) may be performed on all exposedsurfaces of the installed part using this procedure. If required, the main rotor head (hub) shall be removed in accordancewith the applicable technical manuals listed in Table 1-1.2.11.3.3Access. Not applicable.2.11.3.4Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,paragraph 1.4.4.2.11.3.5NDI Equipment Settings.2-25
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