TM 1-1520-264-23
3.19.3.2 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 intermediate gearbox shall be removed in accordance with the
applicable technical manuals listed in Table 1-1.
3.19.3.3 Access. Access to the intermediate gearbox is through the vertical stabilizer fairing (Figure 1-4, Items L510
and R510).
3.19.3.4 Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,
paragraph 1.4.4.
3.19.3.5 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.)
3.19.3.6 Inspection Procedure. Refer to Eddy Current Method, paragraph 1.4.11 and Figure 3-19.
NOTE
The intermediate gearbox contains a higher conductivity magnesium which will require the use of the
aluminum test block when performing inspections in these areas, refer to paragraph 1.4.11.4, Sorting
Metal Using Eddy Current, to determine what test block is best suited for this inspection.
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 is cause for rejection.
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