DOC AIRBUS | AMM A320FSTEERING - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
A. Nose Wheel Steering
Nose Wheel Steering - Principle ** ON A/C NOT FOR ALL
Nose Wheel Steering - Principle ** ON A/C NOT FOR ALL
Nose wheel steering is possible from the cockpit as follows:
Nose Wheel Steering - Principle ** ON A/C NOT FOR ALL Nose Wheel Steering - Principle ** ON A/C NOT FOR ALL (1) During taxi, and more generally at low speed, through action on a handwheel.
There are two identical handwheels: one for the Captain, one for the First Officer.
In the event of simultaneous operation, the orders that the handwheels give are algebraically added.
The maximum travel of the wheels is plus or minus 74 deg.
The maximum corresponding travel of the handwheel is plus or minus 75 deg.
However, the law between these two travels is not linear.
The servoing is active with the aircraft on ground upon impact of the main landing gear. The steering angle is limited as a function of the aircraft speed.
There are two identical handwheels: one for the Captain, one for the First Officer.
In the event of simultaneous operation, the orders that the handwheels give are algebraically added.
The maximum travel of the wheels is plus or minus 74 deg.
The maximum corresponding travel of the handwheel is plus or minus 75 deg.
However, the law between these two travels is not linear.
The servoing is active with the aircraft on ground upon impact of the main landing gear. The steering angle is limited as a function of the aircraft speed.
(2) During takeoff or landing, and more generally at high speed
When the aircraft speed is above 130 knots, the steering is not available.
If the runway is icy, the pilot can disconnect the control through the pedals from the steering control.
To obtain this, the pilot presses and holds a pushbutton switch located on each handwheel.
- either through action of the Captain (or First Officer) on the rudder pedals,
- or automatically through the autopilot (yaw control).
When the aircraft speed is above 130 knots, the steering is not available.
If the runway is icy, the pilot can disconnect the control through the pedals from the steering control.
To obtain this, the pilot presses and holds a pushbutton switch located on each handwheel.
(3) After takeoff, the nose wheels are automatically centered under the action of cams in the shock absorber.
(4) Before the aircraft is towed, the hydraulic system must be depressurized through action on a lever which can be locked in its two positions.
This lever is located on an electrical box easily accessible from the ground.
The maximum towing angle is plus or minus 95 deg.
This lever is located on an electrical box easily accessible from the ground.
The maximum towing angle is plus or minus 95 deg.
2. Component Location
A. General
| FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C ALL | |||||
| 1GC | XMTR UNIT-N/W STRG HANDWHEEL,CAPT | 1VU | 211 | 32-51-11 | |
| 2GC | XMTR UNIT-N/W STRG HANDWHEEL,F/O | 7VU | 212 | 32-51-11 | |
| 3GC | SENSOR-N/W STRG FDBK,CTL CHAN | 711 | 32-51-19 | ||
| 4GC | SENSOR-N/W STRG FDBK,MONITORING CHAN | 711 | 32-51-19 | ||
| 5GC | ELEC BOX-N/W STEERING,DEACTIVATION | 711 | 32-51-12 | ||
| 6GC | SERVO CTL-N/W STEERING | 711 | 32-51-51 | ||
| ** ON A/C NOT FOR ALL | |||||
| 7GC | SEL VALVE/MANIFOLD ASSY | 140 | 32-51-23 | ||
(1) The control is electrohydraulic with position feedback of the nose wheel assembly.
(2) A monitoring channel permits:
- detection of failures,
- de-activation of the control in the event of a failure which may cause wheel runaway.
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.
In addition, it includes a pushbutton switch for the disconnection of the steering control through the rudder pedals.
(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.
Steering by pedals is limited to 6 deg. depending on A/C speed.
(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.
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:
- a check valve which keeps the anti-shimmy accumulator pressurized,
- a 40 micron filter,
- an electrically-operated selector valve and its slaved valve.
- 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,
(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.
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.
(e) 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:
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.
(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.
(5) in the avionics compartment:
- a Braking and Steering Control Unit (BSCU) which groups the braking and steering computers.
3. Interface
The corresponding figure shows the electrical interface between the BSCU, the various system components and the ECAM.
** ON A/C NOT FOR ALL The corresponding figure shows the electrical interface between the BSCU, the various system components and the ECAM.
4. Component Description
A. Steering Handwheel Transmitter Unit FIN: 1-GC FIN: 2-GC
It includes two control potentiometers and two monitoring potentiometers, driven by different gears to permit the detection of any rupture of the control.
The travel of each potentiometer is plus or minus 150 deg.
It includes two control potentiometers and two monitoring potentiometers, driven by different gears to permit the detection of any rupture of the control.
The travel of each potentiometer is plus or minus 150 deg.
B. Rudder pedals
Steering orders from the pedals are sent to the BSCU via the ELAC.
Steering orders from the pedals are sent to the BSCU via the ELAC.
C. Steering Actuating Cylinder
- Piston diameter: 79.25 mm
- Internal stop for plus or minus 95 deg. wheel travel i.e. a stroke of plus or minus 123 mm.
- Maximum flow: 7.55 l/mn which corresponds to a steering speed of 18 deg./s (at no load)
D. Selector Valve
- Power supply: 18 to 30VDC
- Max. power consumption: 0.8A at -40 deg.C
E. Servovalve
This valve is of the deflection-jet type.
This valve is of the deflection-jet type.
- Nominal flow: 26 l/mn under 206 bars for I = 8 mA.
- Coils in parallel - Internal leakage: 0.9 l/mn
- LVDT sensor:
Power supply: 26 V -400Hz
Input current: 14.5 mA
Sensitivity: 40 mV/mm/V
Stroke: plus or minus 0.6 mm (stroke of the slide valve of the servovalve plus or minus 0.5 mm).
F. Electrcial Deactivation Box 5GC
The electrical deactivation box isolates the Nose Wheel Steering (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 on the outside of the electrical deactivation box.
When the lever is set to the TOWING position , the NWS system is deactivated from the BSCU control. A safety pin locks the lever in the TOWING position.
When the nose-wheel steering selector is in the TOWING position, the NW STRG DISC MEMO message is shown in green on the ECAM DU. The message is shown in amber if one engine is in operation.
The electrical deactivation box isolates the Nose Wheel Steering (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 on the outside of the electrical deactivation box.
When the lever is set to the TOWING position , the NWS system is deactivated from the BSCU control. A safety pin locks the lever in the TOWING position.
When the nose-wheel steering selector is in the TOWING position, the NW STRG DISC MEMO message is shown in green on the ECAM DU. The message is shown in amber if one engine is in operation.
G. Speed Adjustment Diaphragm
- Diameter: 1.3 mm for a steering speed of 18 deg./s at no load.
H. Anti-Shimmy Accumulator
- Maximum capacity: 80 cubic centimeters
- Pressure at max. capacity: 15 bars
- Pressure at zero capacity: 7.5 bars.
I. Feedback Sensor
- Reduction gearbox:
Reduction ratio: 0.46.
Automatic take-up of play by spring.
Shock-mounted on the nose gear strut. - RVDT sensor:
Inductive potentiometer with shifted windings, supplied with 26 V 400Hz obtained from transformation of 115 V from AC BUS 1 through the BSCU system 1.
Linearity range: plus or minus 35 deg.
Linearity consumption: 60 mA -0.6 W.
J. Selector-Valve Manifold Assembly (7GC) FIN: 7-GC
The selector-valve manifold assembly (7GC) supplies hydraulic fluid to the service and return lines of the hydraulic components. It includes:
The selector-valve manifold assembly (7GC) supplies hydraulic fluid to the service and return lines of the hydraulic components. It includes:
- A brake selector valve that is attached to the selector valve manifold.
- A selector valve manifold.
- Three hydraulic connections identified as:
- Supply port A
- Return port B
- Service port C.
5. Operation/Control and Indicating
A. The hydraulic pressure is sent to the hydraulic block when the nose gear is extended and when its doors are closed.
(This means that after a free-fall extension of the gear, when the doors normally remain open, the steering control is lost).
(This means that after a free-fall extension of the gear, when the doors normally remain open, the steering control is lost).
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 :
On the ground the energization of the selector valve causes the pressurization of the hydraulic block. This is done under the conditions below :
- towing control lever in the normal position,
- at least one engine in operation,
- shock absorber compressed.
C. In flight, as soon as the gear is extended for landing, the test of the steering control is made.
In this case, the energization of the selector valve occurs under the conditions below :
In this test, an electrical signal is temporarily sent to the servovalve, thus causing a slight motion of the nose wheel assembly (see 32-46-00).
The monitoring channel checks that the order has been correctly executed.
In this case, the energization of the selector valve occurs under the conditions below :
- towing control lever in the normal position,
- at least one engine in operation,
- shock absorbers of the main landing gears extended.
In this test, an electrical signal is temporarily sent to the servovalve, thus causing a slight motion of the nose wheel assembly (see 32-46-00).
The monitoring channel checks that the order has been correctly executed.
D. Operating Principle
Nose Wheel Steering Control-Principle ** ON A/C NOT FOR ALL
Nose Wheel Steering Control-Principle ** ON A/C NOT FOR ALL
The control channel acts on the servovalve as a function of the difference in position between the handwheel (in the cockpit) and the wheels.
The monitoring channel delivers in a similar manner a signal which represents the position of the slide valve in the servovalve.
If both channels disagree about the position of the slide valve in the servovalve, the steering system is depressurized.
The principle is the same when the control is either made through the pedals or in automatic mode.
Nose Wheel Steering Control-Principle ** ON A/C NOT FOR ALL Nose Wheel Steering Control-Principle ** ON A/C NOT FOR ALL The monitoring channel delivers in a similar manner a signal which represents the position of the slide valve in the servovalve.
If both channels disagree about the position of the slide valve in the servovalve, the steering system is depressurized.
The principle is the same when the control is either made through the pedals or in automatic mode.
E. Aircraft Turning Radii
Aircraft Towing Radii - A319 ** ON A/C NOT FOR ALL
Aircraft Towing Radii - A321 ** ON A/C NOT FOR ALL
Aircraft Towing Radii - A320 ** ON A/C NOT FOR ALL
Aircraft Towing Radii - A319 ** ON A/C NOT FOR ALL Aircraft Towing Radii - A321 ** ON A/C NOT FOR ALL Aircraft Towing Radii - A320 ** ON A/C NOT FOR ALL