TM 1-1520-253-23
CENTER CARGO HOOK (MT).
4.22.1 Description (Figure 4-1. Index No. 22). The center cargo hook is located in the cabin fuselage at the rescue
hatch door.
4.22.2 Defects. Defects may occur anywhere on the surface of the center cargo hook. No cracks are allowed.
4.22.3 Primary Method. Magnetic Particle.
4.22.3.1 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
4.22.3.2
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 center cargo hook shall be removed in accordance
with the technical manuals listed in Table 1-1.
4.22.3.3
Access. Access is through the rescue hatch door. See Figure 1-4 - CH-47: 29; MH-47: 35.\par4.22.3.4
Preparation of Part. The center cargo hook shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,
4.22.3.5
NDI Equipment Settings. Refer to Magnetic Particle Method, paragraph 1.4.8.
4.22.3.6
Inspection Procedure. A magnetic field shall be applied to the part perpendicular to the orientation of
possible cracks. Positions required for this inspection are illustrated in Figure 4-22.
a.
Select AC on the AC/DC power switch.
b.
Place probe/yoke on part in 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.
e.
Demagnetize before moving to the next position. Refer to paragraph 4.22.3.8.
f.
Repeat steps a. through e. for Position 2.
4.22.3.7
Marking and Recording of Inspection Results. Mark and record the inspection results as required by
