TM 1-1520-265-23
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 are cause for rejection.
NOTE
Either probe identified in paragraph 2.16.3.1 may be used depending primarily on the ease of
accessibility and user friendliness. If the probes are changed, steps 2.16.3.5 b. (1), (2), and (3)
shall be repeated each time a change is made.
2.16.3.7 Marking and Recording of Inspection Results. Mark and record inspection results as required by paragraph 1.3.
2.16.4 Backup Method. Fluorescent Penetrant, refer to paragraph 1.4.7.
2.16.5 System Securing. The lower link, if removed, requires installation in accordance with the applicable technical
manuals listed in Table 1-1.
2.17 BIFILAR VIBRATION ABSORBER (ET).
2.17.1 Description (Figure P-1. Index No.17). The bifilar vibration absorber absorbs vibrations and stresses. It not only
contributes to longer life of all components, but to a smoother ride for the crew and passengers.
2.17.2 Defects. This inspection is used to verify crack indications found visually on the bifilar vibration absorber. 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, 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 bifilar vibration absorber shall be removed in
accordance with the applicable technical manuals listed in Table 1-1.
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