TM 1-1520-253-23
4.20.3.1
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 magnetic coil may be used. Refer to paragraph 1.4.8.1.2 and Figure 1-6.
4.20.3.2
Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance and the lower
drag link removed and disassembled in accordance with the applicable technical manuals listed in Table 1-1.
4.20.3.3
Access. Not applicable.
4.20.3.4
Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,
4.20.3.5
NDI Equipment Settings. Refer to Magnetic Particle Method, paragraph 1.4.8.
4.20.3.6
Inspection Procedure. A magnetic field shall be applied to the part perpendicular to the orientation of
possible cracks. Position required for this inspection is illustrated in Figure 4-20.
a.
Select AC on the AC/DC power switch.
b.
Place probe/yoke on part at 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.
4.20.3.7
Marking and Recording of Inspection Results. Mark and record the inspection results as required by
4.20.3.8
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.
4.20.4 Backup Method. None required.
4.20.5 System Securing. Clean the parts of interest thoroughly to remove all residual magnetic par. tide media. Refer
to Post Cleaning and Restoration of Part or Area After NDI, paragraph 1.4.20. The lower drag link assembly requires
reassembly and installation in accordance with the applicable technical manuals listed in Table 1-1.
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