TM 1-1520-253-23
3.6.3
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
3.6.3.2
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 engine driveshaft shall be removed in accordance with the
applicable technical manuals listed in Table 1-1.
3.6.3.3
Access. Access is through the engine driveshaft hinged panels. See Figure 1-4 - CH-47: 5 and 6; MH-47:
26 and 27.
3.6.3.4
Preparation of Part. The engine driveshaft outside surface shall be thoroughly cleaned.
Refer to
Preparation of Part or Area for NDI, paragraph 1.4.4.
3.6.3.5
NDI Equipment Settings.
lI
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%
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 1-7).
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