TM 1-1520-265-23
3.2 MAIN TRANSMISSION (ET).
3.2.1 Description (Figure 3-1. Index No. 2). The main transmission is mounted on the main fuselage. It mounts and
drives the main rotor head, changes the angle of drive from the engines, reduces engine rpm, and drives the tail rotor
drive shaft along with the accessory modules.
3.2.2 Defects. Defects may occur anywhere on the surface of the main transmission. All areas where rework has been
performed shall be inspected for cracks. No cracks are allowed.
3.2.3 Primary Method. Eddy Current.
3.2.3.1 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, 100KHz-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
3.2.3.2 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 transmission shall be removed in accordance with the
applicable technical manuals listed in Table 1-1.
3.2.3.3 Access. Not applicable.
3.2.3.4 Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,
paragraph 1.4.4.
3.2.3.5 NDI Equipment Settings.
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
Rot
- 56°
Probe drive
- mid
LPF
- 100
HPF
- 0
H Pos
- 80%
V Pos
-20%
3-3
