TM 1-1520-265-23
Change 3
2-49
2.21.3 Primary Method. Eddy Current.
2.21.3.1 NDI Equipment and Materials. (Refer to Appendix B.)
a. Eddy Current Inspection Unit
b. Probe, straight, shielded surface, 2 MHz
c. Probe, right angle, shielded surface, 2 MHz, 90_ 1/2 inch drop
d. Cable Assembly
e. Adapter, Probe, 2 MHz
f. Reference Block, three-notched titanium (0.008, 0.020, 0.040 EDM notches)
g. Teflon Tape, refer to Table 1-8
h. Aircraft Marking Pencil, refer to Table 1-8
2.21.3.2 Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance.
A 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 main
rotor blade shall be removed in accordance with the applicable technical manuals listed in Table
1-1.
2.21.3.3 Access. Access to the main rotor blade cuff assembly is from the L/R engine cowl (Figure
1-4, Items 3T-7 and 4T-8).
2.21.3.4 Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part
or Area for NDI, paragraph 1.4.4.
2.21.3.5 NDI Equipment Settings.
a. Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-19eII.
Frequency F1
- 1000 KHz
F2
- off
HdB
- 57.0
VdB
- 69.0
Rot
- 30_
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. (See the standard
instrument display shown in Figure 1-7.)
