TM 1-1520-265-23
Change 2
4-69
4.29 PARKING BRAKE VALVE COMPONENTS (PT).
4.29.1 Description (Figure 4-1, Index No. 29) . The parking brake valve traps fluid pressure to the
brakes to prevent helicopter movement. This inspection pertains to the components contained
within the parking valve body.
4.29.2 Defects. This inspection is used to verify crack indications found visually on the parking
brake valve components. No cracks are allowed.
4.29.3 Primary Method . Fluorescent Penetrant.
4.29.3.1 NDI Equipment and Materials. (Refer to Appendix B.) Inspection equipment is listed in
Table 1-7. AMS 2644 level 3 penetrant materials shall be selected from the approved list in Table
1-8. Parts requiring flourescent penetrant inspection shall be cleaned prior to inspection with
n--Propyl Bromide (vapor degreasing only)(Table 1--8), DS--108 (Table 1--8), Electron (Table 1--8),
Positron (Table 1--8). DS--108, Electron, Positron must be followed by an acetone (Table 1--8) rinse
or wipe: or drying until there is no visible solvent residue left on parts.
4.29.3.2 Preparation of Helicopter. The helicopter shall be prepared for safe ground maintenance
and the parking valve removed and disassembled in accordance with the applicable technical
manuals listed in Table 1-1.
4.29.3.3 Access. Not applicable.
4.29.3.4 Preparation of Part. Refer to Preparation of Part or Area for NDI, paragraph 1.4.4.
4.29.3.5 Inspection Procedure. Perform fluorescent penetrant inspection. Refer to Fluorescent
Penetrant Method, paragraph 1.4.7 and Table 1-5. Inspect area of concern. See Figure 4-29.
Figure 4-29. Parking Brake Valve Components
