TM 1-1520-253-23
6.7.3.2 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 bellcranks shall be removed in accordance with the applicable
technical manuals listed in Table 1-1.
6.7.3.3 Access. Access from the left forward transmission work platform to inspect the supports. See Figure 1-4 CH-
47: 9; MH-47: 16.
6.7.3.4 Preparation of Part. The bellcranks and supports shall be thoroughly cleaned. Refer to Preparation of Part or
Area for NDI, paragraph 1.4.4.
6.7.3.5 NDI Equipment Settings.
a. Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-19eII.
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%
b. Refer to Eddy Current Method, paragraph 1.4.11. Set up on test block as follows:
(1) Null probe on test block.
(2) Adjust phase as required to obtain horizontal lift-off.
.
(3) Move probe over all three notches in test block. Adjust gain to obtain a three block vertical signal when
probe is passed over 0.040 inch notch in test block. (Refer to standard instrument display shown in Figure
a. Place probe on part in the inspection locations and null. Adjust phase as required to obtain horizontal lift-off.
b. Inspect the part.
c. Any signal similar to the notches in the test block is cause for rejection.
NOTE
Either probe identified in paragraph 6.7.3.1 may be used depending primarily on the ease of
accessibility and user friendliness. If the probes are changed, steps 6.7.3.5 b. (1), (2), and (3)
shall be repeated each time a change is made.
6.7.3.7 Marking and Recording of Inspection Results. Mark and record as required by paragraph 1.3.
6.7.4 Backup Method. Fluorescent Penetrant, refer to paragraph 1.4.7.
6.7.5 System Securing. The bellcranks, if removed, require installation in accordance with the applicable technical
manuals listed in Table 1-1. Secure the left forward transmission work platform.
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