-
a 40 micron filter,
-
a servovalve of the deflection-jet type, equipped with a LVDT sensor which detects the position of the slide valve,
-an adjustable diaphragm located on each output line of the servovalve, this diaphragm is used to adjust the flow to each actuating cylinder chamber and consequently the wheel steering speed,
-a by-pass valve which interconnects the two chambers of the steering cylinder in the event of hydraulic system depressurization which may be due to: the loss of hydraulic power or the de-energization of the selector valve by the monitoring channel or the de-energization of the selector valve by the towing control lever on the electrical box,
-when the hydraulic system is pressurized, the bypass valve can open for a pressure exceeding 273 bars. Any overpressure is then limited in the steering cylinder,
-an anti-shimmy accumulator with a built-in pressure-relief valve, It can supply fluid pressurized to 15 bars in case of cavitation in one chamber of the cylinder, initiated by the shimmy.
-two check valves which ensure the distribution of fluid from the
accumulator to the chamber of the steering cylinder,
-
a screw for the bleeding and/or depressurization of the hydraulic block,
-
a non return valve allows pressurized fluid to flow in one direction.
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Hydraulic BlocK
Figure 015
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G. Sensors 3GC (4GC)
(Ref. Fig. 016)
Two identical sensor boxes give the position of the rotating tube.
The sensor box has a gear assembly with a sensor housing attached at the
top by a clamping flange and four screws.
The sensor box is shock-mounted to the landing gear strut.
The sensor housing assembly contains an RVDT sensor.
One sensor is part of the electrical channel of the steering control, the
other sensor is part of the monitoring channel. These two sensors are
supplied with 115 V from AC BUS 1 through the BSCU system 1.
The gear assembly contains:
-a reduction gear train
-for maintenance only: a knob with a lockpin to lock the reduction gear in the neutral position (0 degree) before installation of the sensor box on the landing gear a worm screw to adjust the electrical 0 degree position with the sensor box installed on the landing gear.
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Sensors
Figure 016
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H. Electrical Deactivation Box 5GC
(Ref. Fig. 017)
The electrical deactivation box permits isolation of the NWS system from
the BSCU control.
The box has two electrical connectors, a lever, an indicator (parking
brake) and a P/BSW (light test) that are installed externally.
When the lever is set to the TOWING, the NWS system is deactivated from
the BSCU control. A safety pin locks the lever in the TOWING position.
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Electrical Deactivation Box 5GC
Figure 017
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J. Swivel Selector Valve
(Ref. Fig. 018)
A swivel selector valve is installed co-axially with respect to the landing gear retraction axis. It provides the hydraulic interface between the aircraft and the landing gear. When the landing gear starts to retract, the swivel selector valve cuts the hydraulic power supply and connects the hydraulic block to the reservoir return line.
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Swivel Selector Valve
Figure 018
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7. Operation/Control and Indicating
________________________________
A. The hydraulic pressure is sent to the hydraulic block when the nose gear is extended.
B. On the ground, when you open the NLG doors with the Ground Door-Opening Handle the steering is still operational. On the ground the energization of the selector valve causes the pressurization of the hydraulic block. This is done under the conditions below :
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