TM 1-1520-265-23
4.6
VIBRATION ABSORBER STRUCTURAL FITTINGS (ET).
4.6.1 Description (Figure 4-1. Index No. 6). The vibration absorber structural fittings attach the vibration absorbers to
the helicopter structure. Due to similarity, this procedure is applicable to cabin and nose fittings.
4.6.2 Defects. This inspection is used to verify crack indications found visually on the vibration absorber fittings. No
cracks are allowed.
4.6.3 Primary Method. Eddy Current.
4.6.3.1
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, 900 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
4.6.3.2
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 fittings using this procedure. If required, the fittings shall be removed in accordance with the applicable
technical manuals listed in Table 1-1.
4.6.3.3
Access. Remove cabin ceiling soundproofing for access to cabin fitting. Access nose fitting through fairing
(Figure 1-4, Item 1 B-GS-A-1).
4.6.3.4
Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,
paragraph 1.4.4.
4.6.3.5
NDI Equipment Settings.
a.
Make the following initial settings on the Eddy Current Inspection Unit, NORTEC-1 9e".
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%
4-16
