TM 1-1520-264-23
4.27 MAIN LANDING GEAR SHOCK STRUT HOUSING, PISTON, AND ROD ENDS (MT).
4.27.1
Description (Figure 4-1. Index No. 27).
The main landing gear shock strut assembly attaches to the lower
end of the landing gear trailing arm. The upper end attaches to the fuselage at the landing gear support mount.
4.27.2
Defects. This inspection is used to verify crack indications found visually on the main landing gear shock
strut housing, pistons, rod ends, and locking shear collar. No cracks are allowed.
4.27.3
Primary Method. Magnetic Particle.
4.27.3.1
NDI Equipment and Materials. (Refer to Appendix B.)
a.
Magnetic Particle Inspection Probe/Yoke
b.
Magnetometer
c.
Black Light
d.
Fluorescent Magnetic Particles, refer to Table 1-8
e.
Consumable Materials, refer to Table 1-8
f.
Aircraft Marking Pencil, refer to Table 1-8
NOTE
Hand-held magnetic coil may be used. Refer to paragraph 1.4.8.1.2 and Figure 1-6.
4.27.3.2
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 applicable positions of this procedure. If required, the main landing gear shock struts shall be
removed in accordance with the applicable technical manuals listed in Table 1-1.
4.27.3.3
Access. Access is through the main landing gear shock strut door and ammunition feed mechanism (forward)
fairing (Figure 1-4, Items L/R 135 and L/R 140).
4.27.3.4
Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,
paragraph 1.4.4.
4.27.3.5
NDI Equipment Settings. Refer to Magnetic Particle Method, paragraph 1.4.8.
4.27.3.6
Inspection Procedure. A magnetic field shall be applied to the part perpendicular to the orientation of possible
cracks. Positions required for this inspection are illustrated in Figure 4-27.
a.
Select AC on the AC/DC power switch.
b.
Place probe/yoke on part in position 1 as shown.
c.
Press the test switch and apply a light coat of magnetic particle media at the same time. Remove the media
momentarily before removing the current. Current should be applied for no more than five seconds.
d.
Inspect for cracks using the black light.
e.
Demagnetize before moving to the next position. Refer to paragraph 4.27.3.8.
f.
Repeat steps a. through e. for positions 2, 3, and 4.
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