TM 1-1520-253-23
FORWARD LANDING GEAR TORQUE ARM (ET).
4.19.1 Description (Figure 4-1. Index No. 19). The forward landing gear torque arm keeps the forward landing gear
aligned.
4.19.2 Defects. Defects can occur anywhere on the surface of the torque arm. No cracks are allowed.
4.19.3 Primary Method. Eddy Current.
a.
Eddy Current Inspection Unit
b.
Probe, straight, shielded surface, 100 KHz-500 KHz
c.
Probe, right angle, shielded surface, 100 KHz-500 KHz, 901/2 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
4.19.3.2
Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance. 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 forward landing gear torque arm shall be removed in
accordance with the applicable technical manuals listed in Table 1-1.
4.19.3.3
Access. Not applicable.
4.19.3.4
Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,
4.19.3.5
NDI Equipment Settings.
lI
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%
b.
Refer to Eddy Current Method, paragraph 1.4.11. Set up on test block as follows:
(1) Null probe on test block.
(2) Adjust phase as required to obtain horizontal lift-off.
(3) Move probe over all three notches in test block. Adjust gain to obtain a three block vertical
signal when probe is passed over 0.040 inch notch in test block. (Refer to standard instrument
display shown in Figure 1-7.)
