TM 1-1520-253-23
2.10.1 Description (Figure 2-1. Index No. 10). The centrifugal droop stop bolts connect the balancing arms to the lugs
in the hub oil tank. This inspection is to verify any cracks found visually.
2.10.2 Defects. Defects may occur anywhere on the surface of the bolt. No cracks are allowed.
2.10.3 Primary Method. Magnetic Particle.
2.10.3.1 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.
2.10.3.2 Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance and the centrifugal
droop stop bolts removed in accordance with the applicable technical manuals listed in Table 1-1.
2.10.3.3 Access. Not applicable.
2.10.3.4 Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or
Area for NDI, paragraph 1.4.4.
2.10.3.5 NDI Equipment Settings. Refer to Magnetic Particle Method, paragraph 1.4.8.
2.10.3.6 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 2-10.
a. Select AC on the AC/DC power switch.
b. Place probe/yoke legs on part 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.
