TM 1-1520-253-23
4.17.3.2
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 strut piston tube shall be removed in accordance with
the applicable technical manuals listed in Table 1-1.
4.17.3.3
Access. Not applicable.
4.17.3.4
Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part of Area for NDI,
4.17.3.5
NDI Equipment Settings. Refer to Magnetic Particle Method, paragraph 1.4.8.
4.17.3.6
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 4-17.
a.
Select AC on the AC/DC power switch.
b.
Place probe/yoke on part at 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 4.17.3.8.
f.
Rotate the probe leg positions 180 degrees and repeat steps a. through e. for Position 2.
g.
Repeat steps a. through e. for Position 3.
4.17.3.7
Marking and Recording of Inspection Results. Mark and record the inspection results as required by
4.17.3.8 Demagnetization. With the switch remaining in the AC position, place the probe/yoke legs in the same position
used for magnetizing. Press the test switch and withdraw the probe/yoke from the part for a distance of two feet before
releasing the switch.
4.17.4 Backup Method. None required.
4.17.5 System Securing. Clean the strut piston tube thoroughly to remove all residual magnetic particle media. Refer
to Post Cleaning and Restoration of Part or Area After ND1, paragraph 1.4.17. The strut piston tube, if removed,
requires installation in accordance with the applicable technical manuals listed in Table 1-1.
AFT LANDING GEAR STRUCTURE (ET).
4.18.1 Description (Figure 4-1, Index No. 18). The aft landing gear are identical left and right. This inspection includes
the shock strut attachment fitting and the trunnion.
4.18.2 Defects. Defects may occur anywhere on the structures, shock strut attachment fitting, and the trunnion. No
cracks are allowed.
