TM 1-1520-253-23
3.5.3.2
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 aft driveshafting tubes shall be removed in accordance with the
applicable technical manuals listed in Table 1-1.
3.5.3.3
Access. Access is through the aft driveshafting baffle. See Figure 1-4 - CH-47: 45; MH-47: 33.
WARNING
Maintenance Platforms/Workstands
Use only appropriate platforrms, workstands, or other approved locally procured
stands and restraint equipment when working above 10 feet on helicopters in a
nontactical environment. Otherwise, personnel injury could result from accidental
falls.
3.5.3.4
Preparation of Part. The aft driveshafting tubes shall be thoroughly cleaned. Refer to
Preparation of Part or Area for NDI, paragraph 1.4.4.
3.5.3.5
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).
3.5.3.6
Inspection Procedure. Refer to Eddy Current Method, paragraph 1.4.11 and Figure 3-5.
a.
Place probe on part in the required 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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