TM 1-1520-264-23
3.17.3.7 Marking and Recording of Inspection Results. Mark and record the inspection results as required by paragraph
1.3.
3.17.3.8 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.
3.17.4
Backup Method. None required.
3.17.5
System Securing. Clean the main rotor gearshaft 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 gearshaft requires
installation in accordance with the applicable technical manuals listed in Table 1-1.
3.18
MAIN ROTOR MAST SUPPORT BASE (ET).
3.18.1
Description (Figure 3-1. Index No. 18). The main rotor mast support base is located in the center fuselage
area, underneath the main rotor components. It is attached to four transmission rotor support assemblies.
3.18.2
Defects. This inspection is used to verify crack indications found visually on the rotor support mast support
base. No cracks are allowed.
3.18.3
Primary Method. Eddy Current.
3.18.3.1 NDI Equipment and Materials. (Refer to Appendix B.)
a.
Eddy Current Inspection Unit
b.
Probe, straight, shielded surface, 100 KHz-500 KHz
c.
Probe, right angle, shielded surface, 100 KHz-500 KHz, 90 1/2 inch drop
d.
Cable Assembly
e.
Reference Block, three-notched aluminum (0.008, 0.020, and 0.040 EDM notches)
f.
Teflon Tape, refer to Table 1-8
g.
Aircraft Marking Pencil, refer to Table 1-8
3.18.3.2 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 main rotor station mast shall be removed in accordance with the
applicable technical manuals listed in Table 1-1.
3.18.3.3 Access. Access is through panels (Figure 1-4, Items L200 and R200).
3.18.3.4 Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,
paragraph 1.4.4.
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