TM 1-1520-264-23
2.17
MAIN ROTOR FEATHERING BEARING HOUSING (ET).
2.17.1
Description (Figure 2-1 Index No. 17). The main rotor feathering bearing housing is between the main rotor
hub and the pitch housing. The feathering bearing allows the pitch housing assembly to move up and down.
2.17.2
Defects. This inspection is used to verify crack indications found visually on the main rotor feathering bearing
housing. No cracks are allowed.
2.17.3
Primary Method. Eddy Current.
2.17.3.1
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, and 0.040 EDM notches)
f.
Teflon Tape, refer to Table 1-8
g.
Aircraft Marking Pencil, refer to Table 1-8
2.17.3.2
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 feathering bearing housing shall be removed in
accordance with the applicable technical manuals listed in Table 1-1.
2.17.3.3
Access. Not applicable.
2.17.3.4
Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,
paragraph 1.4.4.
2.17.3.5
NDI Equipment Settings.
a.
Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-19e11.
Frequency F1
- 200 KHz
F2
- off
HdB
- 57.0
VdB
- 69.0
Rot
- 56°
Probe drive - mid
LPF
- 100
HPF
-0
H Pos
- 80%
VPos
- 20%
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