TM 1-1520-265-23
5-34
Change 2
5.21.3.1 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, 90_ 1/2 inch drop
d. Cable Assembly
e. Reference Block, three-notched aluminum (0.008, 0.020, 0.040 EDM notches)
f. Teflon Tape, refer to Table 1-8
g. Aircraft Marking Pencil, refer to Table 1-8
5.21.3.2 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
support shall be removed in accordance with the applicable technical manuals listed in Table 1-1.
5.21.3.3 Access. Access is through engine cowl (Figure 1-4, items 3T-7 and 4T-8).
5.21.3.4 Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or
Area for NDI, paragraph 1.4.4.
5.21.3.5 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. (See the standard
instrument display shown in Figure 1-7.)
5.21.3.6 Inspection Procedure. Refer to Eddy Current Method, paragraph 1.4.11 and Figure 5-21.
a. Place probe on a good area in the inspection location 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 are cause for rejection.
