TM 1-1520-253-23
6.5.4 Backup Method. Refer to paragraph 1.4.7.
6.5.5 System Securing. The bellcrank, if removed, requires installation in accordance with the applicable technical
manual listed in Table 1-1.
6.6.1 Description (Figure 6-1, Index No. 6). The first and second stage controls consist of bellcranks and linkage which
mix inputs from the thrust, pitch, roll, and yaw closet control motions into two motions which are transmitted directly to
the forward and aft controls.
6.6.2 Defects. Inspect for damage after removal of bent or sheared pin. Pay particular attention to rigging pin holes and
lug areas. No cracks are allowed.
6.6.3 Primary Method. Eddy Current.
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
6.6.3.2 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 bellcrank shall be removed in accordance with the applicable
technical manuals listed in Table 1-1.
6.6.3.3 Access. Access is through the flight controls closet to inspect the supports. See Figure 1-4 CH-47: 47; MH-47:
32.
6.6.3.4 Preparation of Part. The bellcranks and supports shall be thoroughly cleaned. Refer to Preparation of Part or
Area for NDI, paragraph 1.4.4.
6.6.3.5 NDI Equipment Settings.
II
a. Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-19e .
Frequency F1
- 200 KHz
F2
- off
HdB
- 57.0
VdB
- 69.0
Rot
- 56
Probe drive
- mid
LPF
- 100
HPF
-0
H Pos
- 80%
V Pos
- 20%
