TM 1-1520-253-23
4.4.3.7
Marking and Recording of Inspection Results. Mark and record as required by paragraph 1.3.
4.4.4
Backup Method, None required.
4.4.5 System Securing. If removed, the forward transmission requires installation in accordance with the applicable
technical manuals listed in Table 1-1. Secure the forward transmission work platform.
4.5.1 Description (Figure 4-1. Index No. 5). The forward dynamic absorber support structure is located in the nose of
the cockpit section. The dynamic absorber lowers vibration in the helicopter throughout its operating range.
4.5.2 Defects. Defects may occur anywhere on the surface of the dynamic absorber support structure. The primary
purpose of this inspection is to verify crack indications found visually. No cracks are allowed.
4.5.3
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
4.5.3.2
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 dynamic absorber shall be removed in accordance with the
applicable technical manuals listed in Table 1-1.
4.5.3.3
Access. Access is through the nose compartment door. See Figure 1-4 - CH-47: 10; MH-47:1.
4.5.3.4
Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,
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