Steering Control - Component Location
Figure 007A
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(2)
A First Officer handwheel, designed in a similar way.
(3)
Rudder pedals Steering by pedals is limited to 6 deg. depending on A/C speed.
(4)
On the nose gear: (Ref. Fig. 008)
(a)
A steering actuating cylinder which is part of the nose gear structure. The cylinder drives the rotating tube via a rack-and-pinion assembly.
(b)
A hydraulic block attached to the rear of the nose gear strut includes: (Ref. Fig. 009)
-
a check valve which keeps the anti-shimmy accumulator pressurized,
-
a 40 micron filter,
-an electrically-operated selector valve and its slaved valve. When the selector valve is energized, the pressure is applied to the servovalve.
-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,
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(c)
Two anti-shimmy valves (one per chamber) are installed on the steering cylinder.
(d)
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. (Ref. Fig. 010)
(e)
Two identical RVDT sensors give the position of the rotating tube. The RVDT sensor is driven by a reduction gearbox attached to the landing gear strut. 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. (Ref. Fig. 011, 012)
(f)
An electrical box with a towing control lever.
(g)
A pointer attached at the rear of the nose gear permits to put the nose wheels in the zero position. (Ref. Fig. 004)
(5) in the avionics compartment:
-a Braking and Steering Control Unit (BSCU) which groups the braking and steering computers.
**ON A/C 005-049, 055-099, 101-149, 151-199, 201-299, 301-399,
B. Control Components
(1)
A Captain handwheel which actuates a transmitter unit with 4 potentiometers. In addition, it includes a pushbutton switch for the disconnection of the steering control through the rudder pedals. (Ref. Fig. 006)
(2)
A First Officer handwheel, designed in a similar way.
(3)
Rudder pedals Steering by pedals is limited to 6 deg. depending on A/C speed.
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Steering System - Schematic
Figure 008
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Steering System - Hydraulic Block
Figure 009
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Swivel Selector Valve
Figure 010
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Steering - Wiring
Figure 011
