TM 1-1520-253-23
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.
3.14.4 Backup Method. None required.
3.14.5 System Securing. Clean the aft rotor shaft 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 aft rotor shaft requires installation in
accordance with the applicable technical manuals listed in Table 1-1. Secure the aft transmission work platform.
AFT ROTOR SHAFT SUPPORT (ET).
3.15.1 Description (Figure 3-1. Index No. 15). The aft rotor shaft support is an aluminum part that provides the thrust
bearing support for the aft rotor shaft assembly.
3.15.2 Defects. Defects may occur anywhere on the surface of the support. Any damaged area shall be inspected both
before and after rework. No cracks are allowed.
3.15.3 Primary Method. Eddy Current.
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, 901/2 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
3.15.3.2
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 aft rotor shaft support shall be removed in accordance with the
applicable technical manuals listed in Table 1-1.
3.15.3.3
Access. Access is from the aft transmission work platform. See Figure 1-4 - CH-47: 27 and/or 34; MH-47:
17.
3.15.3.4
Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,
