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APPLYING HYDRAULIC POWER.
Before connecting the hydraulic test stand to the aircraft, set the test stand controls to the positions and
values required to accomplish the aircraft tests. Operate the test stand to confirm the settings. Reduce
the volume adjustment to minimum flow and shut down the stand. Connect the test service hoses to the
aircraft ground power quick-disconnects, making sure that all connectors are clean before connection. Mate
all the attached dust caps and plugs to protect against their contamination during test stand operation.
Do not kink or damage test stand hoses when connecting them to aircraft systems. Keep the hoses
uniformly bent while bending around structures or equipment. Maintain and follow the recommended
minimum inside bend radii. A 1/2-inch pressure hose should have a 2.30-inch radius, a 5/8-inch pressure
hose a 5.37-inch radius, and a 1-inch hose a 5.90-inch radius.
NOTE: Refer to the applicable maintenance manual for the specific procedures to follow when applying external electric and hydraulic power. Before you can apply hydraulic power, you need to check the aircraft reservoir level. Fill it to the level specified in the applicable MIM or MRC. If necessary, service the reservoir using an approved fluid service unit. Then, set up the test stand for either aircraft or test stand reservoir operation, as specified in the applicable MIM. You can set the required mode of operation by using the reservoir selector valve on stands that have this equipment, or use the reservoir fluid supply valve. When the test stand reservoir supply valve is closed, the aircraft reservoir will operate. The test stand reservoir is preferred because the vented reservoir allows aircraft fluid deaeration during system operation (fig. 4-15). Use this mode whenever practical. When a test stand is equipped with return line, back pressure reducing valves, test stand reservoir operation can be used even in situations where the aircraft reservoir is normally used. Adjust the back pressure reducing valve by presetting the value equivalent to normal aircraft reservoir pressure. Make sure that the aircraft controls are in the specified ground check positions required for obtaining normal reservoir fluid level. Apply external hydraulic power and trim the back pressure reducing valve until a stable, proper fluid level is obtained in the aircraft reservoir. Periodically check the fluid level. Ensure back pressure reducing valve is set properly or the aircraft may be damaged by overpressurization. After you have adjusted the back pressure reducing valve, you can start the test stand, and allow
it to warm up with the controls set for bypass fluid flow. Adjust the flow rate and operating pressures to the required values using the volume and pump compensator controls. Set the emergency relief valve (if so equipped) to the operating pressure, plus 10 percent. The bypass control should be fully closed during aircraft operation. Adjust the operating pressure using the pump compensator control only. The test stand is now ready to power the aircraft hydraulic system. NOTE: Use the procedures found in the applicable MIM to actually power the aircraft hydraulic system. |
 
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