TM 1-1520-253-23
5.2.1 Description (Figure 5-1. Index No. 2). This inspection is to verify cracks found visually during an excessive G-force
load inspection. Items to be inspected are: (1) accessory gearbox flanges; (2) oil pump flanges; and (3) fuel control
flanges.
5.2.2 Defects. Inspect all above flanges for cracks. No cracks are allowed.
5.2.3 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
5.2.3.2 Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance. If required, the
components shall be removed in accordance with the applicable technical manuals listed in Table 1-1.
5.2.3.3 Access. Access is through the engine upper and lower doors from the engine work platform.
See Figure 1-4 CH-47: 20, 21, and 22; MH-47: 18, 20, and 21.
5.2.3.4 Preparation of Part. The areas to be inspected shall be thoroughly cleaned. Refer to Preparation of Part or
Area for NDI, paragraph 1. 4. 4.
5.2.3.5
NDI Equipment Settings.
II
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
-56
Rot
Probe drive
-mid
LPF
-100
HPF
-0
H Pos
-80%
V Pos
-20%
5-3
