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 3.10.3.1 may be used depending primarily on the ease of
accessibility and user friendliness. If the probes are changed, steps 3.10.3.5 b. (1), (2), and (3)
shall be repeated each time a change is made.
3.10.3.7 Marking and Recording of Inspection Results. Mark and record inspection results as required by paragraph 1.3.
3.10.4 Backup Method. Fluorescent Penetrant, refer to paragraph 1.4.7.
3.10.5 System Securing. The tail gearbox, if removed, requires installation in accordance with the applicable technical
manuals listed in Table 1-1.
3.11 TAIL GEARBOX MOUNT FITTING (ET).
3.11.1 Description (Figure 3-1. Index No. 11). The tail gearbox mount fitting is a structural component of the pylon. It
serves as the attaching point for the tail gearbox assembly.
3.11.2 Defects. Defects may occur anywhere on the surface of the tail gearbox mount fitting. Particular attention shall
be given to the joining area with the fitting to front spar caps in the area of high strength fasteners. No cracks are
allowed.
3.11.3 Primary Method. Eddy Current.
3.11.3.1 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
3.11.3.2 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 tail rotor gearbox shall be removed in accordance with the
applicable technical manuals listed in Table 1-1.
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