TM 1-1520-265-23
Change 3 2-9
a. 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 for
no 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 as
required by paragraph 1.3.
2.5.3.8 Demagnetization. With the switch remaining in the AC position, place the probe/yoke legs
in the same position used for magnetizing. Press the test switch and withdraw the probe/yoke from
the part for a distance of two feet before releasing the switch.
2.5.4 Backup Method. None required.
2.5.5 System Securing. Clean the main rotor shaft nut thoroughly to remove all residual magnetic
particle 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 manuals
listed in Table 1-1.
2.6 MAIN ROTOR HUB (ET).
2.6.1 Description (Figure 2-1, Index No. 6). The main rotor hub is part of the main rotor head
which 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 are
allowed.
2.6.3 Primary Method. Eddy Current.
2.6.3.1 NDI Equipment and Materials. (Refer to Appendix B.)
a. Eddy Current Inspection Unit
b. Probe, straight, shielded surface, 2 MHz
c. Probe, right angle, shielded surface, 2 MHz, 90_ 1/2 inch drop
d. Cable Assembly
e. Adapter, Probe
f. Reference Block, three-notched Titanium (0.008, 0.020, 0.040 EDM notches)
g. Teflon Tape, refer to Table 1-8
h. Aircraft Marking Pencil, refer to Table 1--8
