TM 1-1520-253-23
2.5.3.7 Marking and Recording of Inspection Results. Mark and record the inspection results as necessary per paragraph
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. Fluorescent Penetrant, refer to paragraph 1.4.7.
2.5.5 System Securing. Clean the rotor hub 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 rotor hub requires installation in accordance
with the applicable technical manuals listed in Table 1-1.
2.6.1 Description (Figure 2-1. Index No. 6). The vertical hinge pin flanges retain the upper and lower bearings within
the varying pitch housing lugs. This inspection is to verify any cracks found visually.
2.6.2 Defects. Defects may occur anywhere on the surface of the flanges. No cracks are allowed.
2.6.3 Primary Method. Magnetic Particle.
2.6.3.1 NDI Equipment and Materials. (Refer to Appendix B.)
a.
Magnetic Particle Inspection Probe/Yoke
b.
Magnetometer
c.
Black Light
d.
Fluorescent Magnetic Particles
e.
Consumable Materials, refer to Table 1-8
f.
Aircraft Marking Pencil, refer to Table 1-8
NOTE
Hand-held coil may be used. Refer to paragraph 1.4.8.1.2 and Figure 1-6.
2.6.3.2 Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance. 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 vertical hinge pin flanges shall be removed in accordance with the
applicable technical manuals listed in Table 1-1.
2.6.3.3 Access. Access is from the forward and aft transmission work platforms. See Figure 1-4 -CH-47: 9, 27, and/or
34; MH-47: 16 and 17.
2.6.3.4 Preparation of Part.
The part shall be thoroughly cleaned.
Refer to Preparation of Part or Area for NDI,
2-11
