TM 1-1520-265-23
4.27. MAIN LANDING GEAR BRAKE (MT).
4.27.1. Description (Figure 4-1. Index No. 27). The main landing gear brakes are self-adjusting, double disc, three-
cavity brake assembly, which includes a visual brake lining wear indicator.
4.27.2. Defects. Cracks can occur anywhere on the surface of the stationary disc, rotating discs, backing plate, and
torque tube. Pay particular attention to rotating and stationary disc slots. 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 and the brake
removed and disassembled in accordance with the applicable technical manuals listed in Table 1-1.
4.27.3.3. Access. Not applicable.
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. The position required for this inspection is illustrated in Figure 4-27.
a.
Select AC on the AC/DC power switch.
b.
Place probe/yoke on part in position 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.
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