TM 1-1520-265-23
4.23.3.2. 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 drag beam shall be removed in accordance
with the applicable technical manuals listed in Table 1-1.
4.23.3.3. Access. Not applicable.
4.23.3.4. Preparation of Part. The part shall be thoroughly cleaned. Refer to Preparation of Part or Area for NDI,
paragraph 1.4.4.
4.23.3.5. NDI Equipment Settings. Refer to Magnetic Particle Method, paragraph 1.4.8.
4.23.3.6. 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 4-23.
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 4.23.3.8.
f.
Repeat steps a. through e. for positions 2, 3, 4, and 5.
4.23.3.7. Marking and Recording of Inspection Results. Mark and record inspection results as required by paragraph
1.3.
4.23.3.8. 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.
4.23.4. Backup Method. Fluorescent Penetrant, refer to paragraph 1.4.7.
4.23.5. System Securing. Clean the drag beam thoroughly to remove all residual magnetic particle media. Refer to
Post Cleaning and Restoration of Part or Area After NDI, paragraph 1.4.16. The drag beam, if removed, requires
installation in accordance with the applicable technical manuals listed in Table 1-1.
4.24. MAIN LANDING GEAR SHOCK STRUT UPPER CYLINDER (ET).
4.24.1. Description (Figure 4-1, Index No. 24). The shock strut supports the helicopter during ground operations and
absorbs impact loads when landing.
4.24.2. Defects. This inspection is used to verify crack indications found visually on the main landing gear shock strut
upper cylinder. No cracks are allowed.
4-55
