NORMAL BRAKING - DESCRIPTION AND OPERATION

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1. General

Normal Braking Schematic ** ON A/C NOT FOR ALL

The braking is normal:

when the Green high pressure is available,
when the A/SKID & NOSE WHEEL control switch is in the ON position,
and when the PARK BRK control switch is in the OFF position or the PARK BRK control is in the ON position and the parking brake pressure really applied is less than 35 bar (507 psi).

The control is electrical and the Normal braking uses the first set of brake pistons.

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2. Component Location

XMTR UNIT-BRK PEDAL - Component Location ** ON A/C NOT FOR ALL

BSCU- Component Location ** ON A/C NOT FOR ALL

PRESS XDCR NORM BRK- Component Location ** ON A/C NOT FOR ALL

SERVOVALVE- NORM BRK - Component Location ** ON A/C NOT FOR ALL

Axle Sleeve / Drive Assy / Tachometer - Component Location ** ON A/C NOT FOR ALL

Brake Selector Valve 23GG- Component Location ** ON A/C NOT FOR ALL

Pressure Transducer NORM BRK SUPPLY- Component Location ** ON A/C NOT FOR ALL

Manifold NORM BRK SERVOVALVE / Safety Valve NORM BRK - Component Location ** ON A/C NOT FOR ALL

Brake - Component Location ** ON A/C NOT FOR ALL

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FIN ! FUNCTIONAL DESIGNATION ! PANEL ! ZONE! ACCESS! ATA

! ! ! ! DOOR ! REF.

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9GG XMTR UNIT-BRK PEDAL 121 811 32-42-47

10GG BSCU 94VU 122 811 32-42-34

11GG PRESS XDCR-NORM BRK WHEEL 1 731 32-42-21

12GG PRESS XDCR-NORM BRK WHEEL 3 741 32-42-21

13GG PRESS XDCR-NORM BRK WHEEL 2 731 32-42-21

14GG PRESS XDCR-NORM BRK WHEEL 4 741 32-42-21

15GG SERVO VALVE-NORM BRK WHEEL 1 731 32-42-48

16GG SERVO VALVE-NORM BRK WHEEL 3 741 32-42-48

17GG SERVO VALVE-NORM BRK WHEEL 2 731 32-42-48

18GG SERVO VALVE-NORM BRK WHEEL 4 741 32-42-48

19GG TACHOMETER-WHEEL 1 731 32-42-57

20GG TACHOMETER-WHEEL 3 741 32-42-57

21GG TACHOMETER-WHEEL 2 731 32-42-57

22GG TACHOMETER-WHEEL 4 741 32-42-57

23GG SEL VALVE-BRK 146 734 32-42-11

96GG PRESSURE TRANSDUCER NORM BRK SUPPLY 32-42-22

2584GM FILTER-HYDRAULIC, BRK 146 734 32-42-12

2612GM MANIFOLD-NORM BRK SERVOVALVE, R 741 32-42-16

2613GM MANIFOLD-NORM BRK SERVOVALVE, L 731 32-42-16

2616GM SAFETY VALVE-NORM BRK WHEEL 2 731 32-42-36

2617GM SAFETY VALVE-NORM BRK WHEEL 3 741 32-42-36

2618GM SAFETY VALVE-NORM BRK WHEEL 1 731 32-42-36

2619GM SAFETY VALVE-NORM BRK WHEEL 4 741 32-42-36

2631GM AXLE SLEEVE-ADAPTER, WHEEL 4 741 32-42-71

2632GM AXLE SLEEVE-ADAPTER, WHEEL 3 741 32-42-71

2633GM AXLE SLEEVE-ADAPTER, WHEEL 2 731 32-42-71

2634GM AXLE SLEEVE-ADAPTER, WHEEL 1 731 32-42-71

2641GM BRAKE-WHEEL 2 731 32-42-27

2642GM BRAKE-WHEEL 4 741 32-42-27

2643GM BRAKE-WHEEL 1 731 32-42-27

2644GM BRAKE-WHEEL 3 741 32-42-27

2678GM DRIVE ASSY-TACHOMETER, WHEEL 4 741 32-42-68

2679GM DRIVE ASSY-TACHOMETER, WHEEL 3 741 32-42-68

2680GM DRIVE ASSY-TACHOMETER, WHEEL 2 731 32-42-68

2681GM DRIVE ASSY-TACHOMETER, WHEEL 1 731 32-42-68

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3. System Description

A. General

The normal braking system is electrically controlled and hydraulically operated. The system has:

a manual mode of operation, (the necessary rate of decrease in speed set at the brake pedals)
an automatic mode of operation, (the necessary rate of decrease in speed set at the AUTO/BRK control panel).

Each of the two modes of operation gives automatic anti-skid protection at each wheel when the aircraft moves at more than ten meters a second.

The system includes electrical components that control hydraulic components. The hydraulic components control the quantity of hydraulic pressure that goes to the brakes.

B. Electrical System Components

The electrical control system has two independent sub-systems that are isolated from each other. The two sub-systems connect to these components in the brake system:

an anti-skid (A/SKID & N/W STRG) switch
three autobrake pushbutton switches (LO, MED and MAX)
a normal brake pedal transmitter unit mechanically connected to the brake pedals
a control channel of the BSCU
a tachometer on each axle.

The A/SKID & N/W STRG switch has two positions, in the ON position it sets the BSCU to make the normal braking system available. In the OFF position, normal braking is not available . In this condition the Alternate Brake Control Unit (ABCU) gives the control to the Alternate Braking without anti-skid (Ref. 32-44-00).

When an autobrake mode (LO, MED or MAX) is selected, the BSCU sends a controlled pressure to the brakes until the deceleration measured by the IRU(s) matches the programmed deceleration.
Before takeoff, the pilot select the MAX mode.
The brake pedals apply the related brakes of the left or right MLG. The brake pedals are installed in pairs and are mechanically connected together. The two left pedals are connected together and the two right pedals are connected together. Each pedal is connected to a spring operated unit that:

supplies an artificial feel when the brake pedals are operated.
puts the pedals back to their initial position when released.

The brake pedals operate the brake pedal transmitter unit which is installed below the pedals at the first officers position. The transmitter unit contains two potentiometers each with four tracks. One potentiometer is for the left MLG.The other potentiometer is for the right MLG. The BSCU sends an electrical supply to the potentiometers. When a brake pedal is operated, the related potentiometer sends an output to the BSCU. This output is in proportion to the angle through which the brake pedal moves.

The BSCU controls the operation of the electrohydraulic valves in the system to supply these primary functions:

the quantity of braking
the anti-skid function (to give maximum braking efficiency)
the automatic braking of the main gear wheels during the L/G retraction
the test of the brake system and nose wheel steering system before a landing
the nose wheel steering (Ref. AMM D/O 32-51-00-00).

The BSCU also has these secondary functions, it:

monitors the temperature of each brake
calculates the wheel speed
uses Built-In Test Equipment (BITE) to do software controlled tests when the aircraft is on the ground
supplies data to other systems in the aircraft.

The BSCU has two systems, System 1 and System 2. These systems are isolated from each other and each connects to its related electrical sub-system. Only one system (the active system), controls the operation of the braking system. The other system (the standby system) is available if the active system becomes unserviceable. If available, the two systems monitor the operation of the braking system.

When the BSCU is supplied with power system 1 becomes active. After each pre-land test, the BSCU makes a record in an Electrically Erasable Programmable Read-Only Memory (EEPROM) that identifies which system was active during the landing. Before the next landing, the BSCU reads the EEPROM and makes active the system that was in standby mode during the last landing.

A tachometer is installed in the end of each MLG axle. A drive assembly connects the tachometer to the related wheel. The tachometer measures the speed of the wheel and sends this data to the BSCU. The BSCU uses this data to control the hydraulic pressure supply to the related brake for anti-skid and autobrake functions.

C. Hydraulic System Components

The components that control the supply of hydraulic power to the system are installed on a manifold that is located in the hydraulics compartment. These components are:

selector valve 23GG
high pressure filter 2584GM
pressure transducer 96GG.

A manifold installed on each MLG includes the necessary components to control the hydraulic pressure at its related brakes.

The selector valve 23GG is attached to the GREEN PTU manifold 1113GM (Ref. 29-11-00). The selector valve is solenoid operated and controls the supply and release of the Green hydraulic pressure in the brake system. When the valve is de-energized it connects the system to the Green LP manifold 1003GM to release the pressure in the system.

The BSCU energizes the selector valve 23GG to connect the Green hydraulic pressure to the system when:

the brake pedals move more than a specified limit
the conditions necessary for an automatic braking program are available
the landing gear is set to UP (retraction braking). The selector valve 23GG stays energized for 3 seconds or until the NLG is not down-locked.
it does a test of the normal braking system (this occurs before each landing or when a specified BITE test (Ref. AMM D/O 32-46-00-00) is set).

The high pressure filter 2584GM and pressure transducer 96GG are installed downstream of the selector valve 23GG. The filter prevents contamination of the braking system components. The transducer measures the hydraulic pressure in the system and supplies the data to the BSCU and to the ABCU (to give the condition of the selector valve).

The hydraulic line divides to supply the two Normal Brake Servovalve Manifold assemblies 2612GM and 2613GM installed on the MLG.

The manifold assemblies are the same. They have an inlet port that includes a filter, a return port and two outlet ports that each supply a related brake. At the filter outlet, the hydraulic supply divides equally to supply two sets of components that are attached to the manifold (one set for each brake). Each set of components includes a servovalve, a safety valve and a pressure transducer.

Each servovalve has an electrically operated solenoid. The active channel of the BSCU supplies the servovalve control current to the related coil to:

get the correct quantity of pressure in the brake line
connect the brake line to return to release the pressure.

If a leak of hydraulic fluid occurs downstream of the safety valve, the valve automatically closes to prevent loss of fluid in the related brake line. The pressure transducer measures the hydraulic pressure in the related brake line and supplies an input to the BSCU. The input is in proportion to the pressure.

Each manifold assembly has a return line with a check valve. The return line from each MLG manifold connects the related manifold to the Green LP Manifold 1003GM. The check valves isolate the related manifold from the other return pressures.

Half couplings connect the brake line to half couplings in the brake. The two half couplings seal automatically if disconnected from each other to prevent a decrease of system fluid and fluid contamination.

Each MLG axle has a multi-disc brake. The brake has two sets of hydraulic pistons. One set of pistons connects to the normal braking system and the other connects to the alternate braking system (Ref. AMM D/O 32-43-00-00). A temperature sensor is also installed on each brake (Ref. AMM D/O 32-47-00-00) to send data to the BSCU which is then shown on the SD WHEEL page.

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4. Power Supply

A. Electrical Power Supply

Normal Braking- Power Supplies Schematic ** ON A/C NOT FOR ALL

B. Hydraulic Power Supply
The hydraulic pressure is supplied from the Green Main Hydraulic Power system (Ref. AMM D/O 29-11-00-00).

** ON A/C NOT FOR ALL

5. Interface

Normal Braking System _ Interface ** ON A/C NOT FOR ALL

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6. Component Description

A. Brake Pedal Assembly

Brake Pedal Assembly ** ON A/C NOT FOR ALL

There are two brake pedal assemblies (one at the captains position and one at the first officers position) with two pedals in each assembly. They transmit the manual braking inputs through a brake pedal transmitter unit (located at the first officers pedals) to the BSCU. They also transmit the manual braking inputs through a brake pedal transmitter unit (located at the captains pedals) to the ABCU (Ref. 32-43-00-00).

Each pedal in each assembly is installed at one side of a vertical column and they are free to turn independently. Levers and rods connect the left pedals of each assembly to each other. Levers and rods connect the right pedals of each assembly to each other. The pedals in each assembly are also connected to:

a spring operated actuator (spring rods)
the input shaft of their related transmitter units.

The spring rods:

gives a resistance (artificial feel) when a force is put on the related pedal
put the pedal back to its initial position when the force is removed.

B. Brake Pedal Transmitter Unit FIN: 9-GG

Brake Pedal Transmitter Unit ** ON A/C NOT FOR ALL

Brake Pedal Transmitter Unit _ Characteristics ** ON A/C NOT FOR ALL

The transmitter unit is an electro-mechanical device connected to the brake pedals at the first officers position. It changes an electrical input (that the BSCU supplies) to give an electrical output in proportion to the movement of the brake pedals. The unit has two mechanical assemblies (left and right) and a case with two electrical connectors.

The mechanical assemblies each include an end plate attached to the casing. The end plate contains a number of ball bearings and a bush in which a shaft turns. A lever is attached to the outer end of the shaft. A pin and a drive plate at the other end of the shaft engage a potentiometer drive shaft. A stop installed in the end plate prevents angular movement of the shaft more than a specified value.

The case contains two potentiometers that are attached to their related end plate. Each potentiometer has four electrical tracks. One potentiometer gets the mechanical movement from the left lever, the other potentiometer gets the mechanical movement from the right lever. A cable assembly connects the tracks of each potentiometer to the electrical connectors.

When a lever turns the shaft of the related potentiometer, it gives four electrical output voltages that are the same. The voltage is in proportion to the angle through which the lever turns.

Two outputs go through each connector to the BSCU. Two go to system 1, the others go to system 2.

C. Brake Selector Valve FIN: 23-GG

Brake Selector Valve 23GG ** ON A/C NOT FOR ALL

The brake selector valve 23GG is a solenoid operated valve (installed on the Green PTU manifold 1113GM (Ref. AMM D/O 29-11-00-00)) that isolates the Green hydraulic supply from the normal brake system.

The brake selector valve has:

a body with holes drilled in it to connect a bore and three ports
two plugs, attached by three bolts which close the bore of the body
a valve held on its seat by a spring
a piston
a solenoid with a plug type electrical adaptor.

Normal Brake Selector Valve - Schematic ** ON A/C NOT FOR ALL

The solenoid is electrically operated which controls a plunger which has a ball. The ball and plunger control a valve and piston in the valve body that controls the flow of hydraulic fluid through the valve body to the three ports.

The three ports are identified as:
the supply port (A)
the return port (B)
the service port (C).

With the solenoid de-energized and hydraulic pressure available in the supply port the ball of the solenoid is held on its seat by the spring and the core of the solenoid valve. The pressure in chamber (a) and the effect of the spring holds the valve on its seat.

When the solenoid valve is energized the hydraulic pressure applied to port A (the supply) pushes away the ball which is held against its upper seat. The pressurized fluid flows to chamber (b). The pressure in chamber (b) increases and pushes the piston. When the pressure in chamber (b) becomes more than the pressure in chamber (a) the piston pushes the valve and compresses the spring.

The pressure in chamber (b) holds the piston on its seat and closes port B (the return). Port A (the supply) is then connected to port C (the service).

When the electrical power is removed from the solenoid valve:
the core of the solenoid valve moves because of the effect of the spring and the core pushes the ball on its lower seat.
the pressure in chamber (a) increases and pushes the valve against the seat.
the pressure in chamber (b) decreases and the valve pushes back the piston. The pressure at port C (the service) then fully pushes back the piston against the plug (mechanical stop).
the pressure in chamber (a) and the effect of the spring hold the valve on its seat, which closes port A (the supply).
Port C (the service) is then connected to port B (the return).

D. High Pressure (HP) Filter

High Pressure Filter ** ON A/C NOT FOR ALL

The HP filter is installed near the manifold (1113GM) (Ref. AMM D/O 29-11-00-00). The filter head is machined to make an inlet port, an outlet port and a port for a filter bowl. The filter bowl contains a filter element. An indicator unit is installed in the head. The unit includes a red indicator piston which shows when the filter element is blocked. The piston has a transparent cap on it for protection.

The filter bowl is a cylinder closed at one end. The open end has internal threads which engage threads in the head. A square boss at the closed end of the bowl is used to remove the bowl to get access to the filter.

Hydraulic fluid at system pressure goes through the inlet port and into the filter bowl. It goes through the filter element, and through the outlet port. When the pressure at the inlet port is 6 bar (87 psi) more than the outlet port, the indicator piston comes out. It keeps this position to show that the filter element is blocked and it must be manually pushed in after the element has been replaced.

E. Pressure Transducer Normal Braking Supply FIN: 96-GG

Normal Brake Pressure Transmitter 96GG ** ON A/C NOT FOR ALL

The pressure transducer is located in the hydraulic compartment
The pressure transducer measures the hydraulic pressure in the related brake service line. It contains an electronic bridge-type circuit which is installed on a number of circuit boards.
Hydraulic pressure sent to the transducer causes a change in the electrical resistance of the bridge circuit.This changes the electrical input voltage to give an output voltage in proportion to the hydraulic pressure.
The integrated-logic transducer supplies a DC voltage between 1 and 5V for a pressure signal between 0 and 200 bars.The zero has been shifted to enable BITE testing.

F. Normal Brake Servovalve Manifolds and Pressure Transducers FIN: 2612-GM FIN: 2613-GM FIN: 11-GG FIN: 12-GG FIN: 13-GG FIN: 14-GG

Normal Brake Manifold ** ON A/C NOT FOR ALL

The manifold includes:

a manifold assembly
a filter
two servovalves
two safety valves
two pressure transducers

The body of the manifold assembly is machined externally to give faces for the servovalves, the safety valves and the pressure transducers.Holes are machined internally to connect these faces.The body includes four unions which are the connections for the fluid supply, the fluid return and the two service line connections.

A filter is installed near the supply connection to keep the holes through the body (and the components attached) free from contamination.A sealed plug keeps the filter in position.

The machined faces for the externally installed components have holes to make the hydraulic connections.The faces for the safety valves have two bobbins and a filter installed.The bobbins align and seal the faces of the safety valves.

G. Normal-Brake Pressure Transducers FIN: 11-GG FIN: 12-GG FIN: 13-GG FIN: 14-GG

Normal- Brake Pressure Transducer ** ON A/C NOT FOR ALL

The brake pressure transducers are installed on the manifold of the Normal brake servovalve, one downstream of each servovalve.
The pressure transducer measures the hydraulic pressure in the related brake service line. It contains an electronic bridge-type circuit which is installed on a number of circuit boards.
Hydraulic pressure sent to the transducer causes a change in the electrical resistance of the bridge circuit.This changes the electrical input voltage to give an output voltage in proportion to the hydraulic pressure.
The integrated-logic transducer supplies a DC voltage between 1 and 5V for a pressure signal between 0 and 200 bars.The zero has been shifted to enable BITE testing.

H. Normal Brake Servovalve FIN: 15-GG FIN: 16-GG FIN: 17-GG FIN: 18-GG

Normal Brake Servovalve ** ON A/C NOT FOR ALL

Normal Brake Servovalve - Static Characteristics ** ON A/C NOT FOR ALL

Normal Brake Servovalve - Flow Characteristics ** ON A/C NOT FOR ALL

Normal Brake Servovalve - Schematic ** ON A/C NOT FOR ALL

The servovalve supplies a pressure proportional to the current which passes through the control coil used.
The servovalve is an electro-hydraulic valve that includes a hydraulic assembly with an electrical assembly attached. The valve has three primary positions of operation, with more positions of operation between the primary positions. The valve is electrically controlled to keep the pressure in its related brake service line at the necessary value, or release the pressure.

The hydraulic assembly has a body with a control bore and a distribution bore. The body is drilled to connect these two bores and to make a supply port A, a service port B and a return port C. The control bore contains two nozzles that are the same. The nozzles are held stable in the bore and each is connected to its related end of the distribution bore. The distribution bore contains a slide valve which can move in the bore to connect two ports together.

The electrical assembly has a body with an electrical plug-in type connector. The assembly includes a top and bottom pole piece. Two permanent magnets keep the pole pieces stable and apart. Two coils are installed between the pole pieces. The coils connect to the electrical connector and this connects each coil to its related channel of the BSCU.

The electrical assembly has a flapper assembly that includes an armature. The armature is installed between the pole pieces. The flapper is installed in the armature. The flapper goes between the nozzles in the control bore then through to the slide valve.

When the coil is de-energized, the slide valve connects port B to port C (brakes released).

When the coil is energized:

the flapper moves nearer the nozzle 1
the flow through the nozzle 2 is more than the flow through the nozzle 1
a larger pressure decrease occurs across jet 2 than jet 1
the pressure at one end of the slide valve is more than the pressure at the opposite end
the slide valve moves to connect port A to port B, it controls the pressure (that goes to the brakes) to a specified value.

When the pressure at port B is at the necessary pressure:

the pressure of the slide valve on the flapper becomes the same as the magnetic force on the flapper
the flapper moves away from the nozzle 1 and goes back to its initial position
the slide valve stays at the set position.

When the control current to the coil is decreased to the minimum (anti-skid control):

the flapper moves nearer the nozzle 1
a larger pressure decrease occurs across jet 2 than jet 1
the pressure at the one end of the slide valve is more than the pressure at the opposite end
the slide valve moves to connect port B to port C.

I. Safety valve FIN: 2616-GM FIN: 2617-GM FIN: 2618-GM FIN: 2619-GM

Safety Valve ** ON A/C NOT FOR ALL

Safety Valve - Schematic ** ON A/C NOT FOR ALL

The safety valve is a hydraulic valve that automatically closes when the flow of fluid through it is more than a specified limit.

The valve has a body that has a bore through the center. Two other bores, the inlet and outlet ports, connect to the center bore. The center bore has different diameters:

the large end holds a valve and a spring
the small end supplies a seat for the valve.

A threaded plug keeps the valve and spring in position and seals the open end of the center bore. The spring keeps the valve away from the seat. The valve has an external flange and an internal bore. Holes go through the flange and another hole goes through to the bore.

With the unit pressurized and no flow from the outlet port, the pressures in chambers X and Y are equal. The spring holds the valve in the open position. When fluid flows through the holes in the valve flange to the outlet port, the pressure in chamber Y decreases. The pressure in chamber X moves the valve nearer to the valve seat. The flow of fluid around the valve to chamber Y controls the rate of travel of the valve. When the flow from the outlet port stops, the pressures in chambers X and Y become equal and the valve stays opens.

If the fluid flow from the outlet port is more than the specified limit, the pressure in chamber X becomes more than the pressure in chamber Y. This causes the valve to move against the valve seat and prevents fluid flow from the outlet port. The pressure in chamber X keeps the valve closed.

If the threaded plug is manually operated, the pressure in chamber X is released and the spring moves the valve back to the open position.

J. Tachometer FIN: 19-GG FIN: 20-GG FIN: 21-GG FIN: 22-GG FIN: 2678-GM FIN: 2679-GM FIN: 2680-GM FIN: 2681-GM

Tachometer ** ON A/C NOT FOR ALL

A tachometer, held in a carrier, is installed in each axle of the MLG. A drive shaft connects the tachometer to the related wheel.

The tachometer has a casing with a front end plate. A drive shaft comes out of the end plate. The casing has an electrical connector and contains a stator assembly and a rotor assembly. The stator assembly includes a toothed ring, a coil assembly and four permanent magnets. The coil assembly connects to the pins of the electrical connector. The rotor assembly includes a rotor and its drive shaft. A drive coupling is attached to the end of the shaft.

When the related wheel turns, the rotor causes an alternating current to flow in the coil assembly. The frequency and the amplitude of the current is in proportion to the wheel speed.

K. Brakes FIN: 2641-GM FIN: 2642-GM FIN: 2643-GM FIN: 2644-GM

Wheel Brake Assembly ** ON A/C NOT FOR ALL

Brake Assembly ** ON A/C NOT FOR ALL

The brakes are of the multidisc type. Each brake includes:

a piston housing,
a torque tube,
a carbon heat pack.

(1) Piston housing
The piston housing is a forged aluminum-alloy part which changes the hydraulic pressure into a load by the use of pistons.
The piston housing has:

two hydraulically independent sets of pistons,
a bleeder for each of the two systems,
a half self-sealing coupling for each system,
a torque tube,
two wear indicators for the heat pack,
a brake temperature sensor.

Two 1/4 in. hoses supply the hydraulic pressure to the brake.

(a) Self-sealing couplings

Self - Sealing Coupling ** ON A/C NOT FOR ALL

These are two half couplings attached together:

one installed on the piston housing,
the other one installed on the 1/4 in. hose and thus included in the landing gear plumbing.
The couplings seal off the brake and supply lines and thus prevent the need to bleed the brakes.

(b) Pistons

Piston/Adjuster Assembly ** ON A/C NOT FOR ALL

There are seven pistons for each system.
The pistons have a return spring and a spiral friction spring which:

cause the automatic return of the piston,
take-up the play in the heat pack caused by the wear of the carbon discs.

Insulators give a protection to the pistons against the heat.
They are installed on a steel plate.
The pistons act on a pressure plate which applies the braking loads evenly to the brake discs.

(2) Torque tube
The torque tube is a forged steel part with a bolted back plate.
The braking reaction is transmitted:

from the stators to the torque tube by splines,
to the landing gear axle by three attachment bolts and nine pins.

Three tie bolts of high-tensile steel attach the torque tube to the piston housing.
Three bolts and nine pins attach the brake to the axle flange of the landing gear.
They also transmit the torque from the torque tube to the axle.

(3) Heat pack
The heat pack has several structural carbon rotors and stators.
There are four rotors. Steel drive keys which are riveted to the discs give a protection to the two rotors and stators.

(a) Wear pin indicator

Wear Pin Indicator ** ON A/C NOT FOR ALL

Two wear pins are attached to the pressure plate. They give a visual indication of the overall wear of the heat pack without removal (Parking brake applied).

(b) Temperature sensor (Ref. 32-47)

Temperature Sensor ** ON A/C NOT FOR ALL

The temperature sensor gives the temperature of the heat pack.
The body of the temperature sensor is attached to the piston housing.

(4) Cooling fans (Ref. 32-48)
The fans increase the cooling of the heat packs.

L. Braking/Steering Control Unit (BSCU) FIN: 10-GG
The BSCU is installed in a 6MCU-size case in rack 90VU (Shelf 94VU). Its functions are:

Braking control through the servovalves and the pressure transducers,
Braking regulation through the check of the speed of each braked wheel,
Integrated monitoring with memorization of the failures which come from the different LRUs of the system. It permits to locate the failures during maintenance operations, from the CFDS.
Automatic braking control via a braking order.
The braking order is servoed to control the A/C acceleration rate according to a predetermined deceleration rate.
Nosewheel steering control through a hydraulic block and an actuating cylinder (Ref. 32-50),
Conversion into ARINC 429 data of the brake temperatures which come from the Brake Temperature Monitoring Units (BTMU) attached to the main landing gear.

All the functions use the digital technology.

(1) Description of the BSCU

BSCU ** ON A/C NOT FOR ALL

The BSCU has:

Two power supply units (one for each system)
An ARINC 600 connector at the back (Size 2, 400 contacts).
A rear interface with a specific cover to protect the unit against EMI.
Six electronic boards
The dimensions of these boards are 225 x 175 mm. They are installed vertically and lengthwise in the case.
They are connected together and to the rear interface by means of two connectors that occupy the totality of their backplanes.
There are two identical sets of three boards that form the systems 1 and 2: two Input/Output boards and one CPU board.
Each board with a CPU is connected to an On-Board Reprogrammable Module (OBRM) that includes PROMs.

The layout of the boards in the BSCU is shown in the referenced figure.

BSCU - Internal Architecture ** ON A/C NOT FOR ALL

(2) Description of the systems 1 and 2
Each system is supplied independently with 115V 400 Hz power and has two channels.
Each channel has its own power supply (+ 5V, plus or minus 15V) and acquisition modules.
A control channel ensures the slaving functions and produces the currents which are sent to the electro-hydraulic components.
A monitoring channel dialogues with the control channel through a serial link and monitors the control channel.

(a) Control channel
This channel uses two boards: the CPU board and the I/O1 board

1 CPU board

BSCU - Control Channel - CPU card ** ON A/C NOT FOR ALL

This board executes all the functional programs.
It is built around an INTEL 80486 microprocessor that operates at 32Mhz.
This board has:

a 4 Mbyte flash memory (OBRM)
a 256 Kbyte RAM
a 64 Kbyte EEPROM (dedicated to the BITE)

The CPU board ensures:

DSI (discrete inputs) acquisitions,
DSO (discrete outputs) generations,
DGO (digital outputs) generations,
Relays controls,
RS232 link with Automatic Test Equipment (ATE),
Link with I/O1 and I/O2 boards
BITE functions

2 I/O1 board

BSCU - Control Channel - I/01 card ** ON A/C NOT FOR ALL

This board perform the analog and digital (ARINC) acquisition.
It generates analog output and dialogs with the CPU board via a common RAM located on the CPU board.
This board is built around a DSP TMS 320C31 microprocessor that Operates at 40Mhz.
This board has:

a 1 Mbyte flash EPROM
a 512 Kbyte RAM

The I/O1 board ensures:

ANI (analog inputs) acquisitions,
DGI (digital inputs) acquisitions,
ANO (analog outputs) generations,
Power supply (5V plus or minus 15V) monitoring
Switching controls.

(b) Monitoring channel

BSCU - Monitoring Channel - I/02 card ** ON A/C NOT FOR ALL

This channel uses a single board: the I/O2 board.
This board is built around a DSP TMS320C31 that operates at 40Mhz.
It performs all the acquisitions and computations which enables to monitor the control channel.
The monitoring function is ensured by the comparison of the computation results with wraparound of the orders sent by the control channel.
The monitoring board is connected to the control boards by an interface bus.
This board has:

a 1 Mbyte flash EPROM
a 512 Kbyte RAM

The I/O2 board ensures:

DSI (discrete inputs) acquisitions,
ANI (analog inputs) acquisitions,
DGI (digital inputs) acquisitions,
DSO (discrete outputs) generations,
ANO (analog outputs) generations,
Power supply (5V plus or minus 15V) monitoring
Switching controls.

(c) Connection between the two systems
The dialogue is through 4 validity discretes (1 for each channel).
During the functional test upon the landing gear extension an exchange of the codes sent over 8 discretes enables to test the two systems.

(d) Operation
At each energization the first system supplied takes control.
The exclusion between the two systems is ensured by the software. If the two systems are supplied simultaneously the SYS1 has priority.
If there is a disagreement between the control and monitoring channels of the system engaged:

the system is disconnected, it cancels its validity bits and isolates its commands,
the system in standby takes over. It validates its commands and ensures again all the functions of the unit with the same level of performance.

(3) Software organization of the BSCU
The BSCU is made of two systems physically distinct but functionally identical:

System 1,
System 2.

The unit has two identical software programs (one for each system).
Each system itself has two channels:

Control,
Monitoring.

(a) Software architecture
The software is divided into two parts:

operational software,
workshop maintenance software.

Operational software
The operational software includes:

the functional software,
the test software,
the monitoring and test software.

The functional software (braking control, anti-skid, ARINC 429 management...) and the test software are integrated in the control channel.
The monitoring software is integrated in the monitoring channel.
The operational software is divided into modules as per the IDEFO method (ICAM Definition Method). The corresponding diagrams are given in the figures below:

BSCU Operational Software ** ON A/C NOT FOR ALL

** ON A/C NOT FOR ALL

7. Parameter List
This table contains all the output parameters in the digital form. They are put in the numerical order after their output label.
The following table gives:

EQ. SYS. LABEL. SDI: (SDAC,FWC,DMC,...) output label for which the parameter is available.
PARAMETER DEFINITION: Parameter name
WORD RANGE/OPER RANGE/RESOLUTION ACCURACY: Measurement range. Maximum value transmitted. When the digital value changes, the change step is equal to the accuracy.
UNIT: Unit in which the digital value is transmitted.
SIG BIT: Indicates if a sign bit is available.
ITS: Number of bits used by the parameter in the label
XMSN/INTV: Output transmission interval. The refresh rate is given in milliseconds.
CODE:
BNR: binary data word
BCD: binary coded decimal data word
ISO: data word coded in ISO5 code
DIS: discrete data word
HEX: hexadecimal code
HYB: mixed code
ALPHA CODE: Indicates the parameter mnemonic code.
Note: The alpha codes can be different because of the DMU/FDIMU software versions. To get the list of alpha codes applicable to your configuration, you must refer to the alpha call-up list of the AIDS input interface (Ref. AMM D/O 31-37-00-00). It is also possible to use the label call-up menus (REF. AMM 31-36-00-740-008).

SOURCE ORIGIN: Parameter source computer or system.

NOTE: The equipment identification for the BSCU is 06E.

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| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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! 1 . 026 . 01 !DSCRT DATA! ! ! ! 15!250 !DIS !DSW2 ! !

! 2 . 026 . 10 !WORD ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !OVERHEAT !Bit status 1! ! ! 11! ! ! ! !

! !BRAKE 1 ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !OVERHEAT !Bit status 1! ! ! 12! ! ! ! !

! !BRAKE 2 ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !OVERHEAT !Bit status 1! ! ! 13! ! ! ! !

! !BRAKE 3 ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !OVERHEAT !Bit status 1! ! ! 14! ! ! ! !

! !BRAKE 4 ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 15! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 16! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 17! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 18! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !AUTOBRAKE !Bit status 1! ! ! 19! ! ! ! !

! !OFF ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !AUTOBRAKE !Bit status 1! ! ! 20! ! ! ! !

! !INOP ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !BRAKING !Bit status 0! ! ! 21! ! ! ! !

! !MODE !: Normal ! ! ! ! ! ! ! !

! ! !Bit status 1! ! ! ! ! ! ! !

! ! !: Alternate ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !NWS INOP !Bit status 1! ! ! 22! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !TOWING KEY!Bit status 0! ! ! 23! ! ! ! !

! ! !: OFF ! ! ! ! ! ! ! !

! ! !Bit status 1! ! ! ! ! ! ! !

! ! !: ON ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !VALIDITY !Bit status 1! ! ! 24! ! ! ! !

! !BIT COM ! ! ! ! ! ! ! ! !

! !SYS 1 ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !VALIDITY !Bit status 1! ! ! 25! ! ! ! !

! !BIT COM ! ! ! ! ! ! ! ! !

! !SYS 2 ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !TYPE OF !PIN PROG. ! ! ! 26! ! ! ! !

! !BRAKE ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !TYPE OF !PIN PROG. ! ! ! 27! ! ! ! !

! !BRAKE ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !TYPE OF !PIN PROG. ! ! ! 28! ! ! ! !

! !BRAKE ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !BRAKE FAN !Bit status 1! ! ! 29! ! ! ! !

! ! !: Installed ! ! ! ! ! ! ! !

!-----------------------------------------------------------------------------!

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| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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! 1 . 027 . 01 !DSCRT DATA! ! ! ! 15!250 !DIS !DSW3 ! !

! !WORD ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !RELEASE !Bit status 1! ! ! 11! ! ! ! !

! !WHEEL 1 ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !RELEASE !Bit status 1! ! ! 12! ! ! ! !

! !WHEEL 2 ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !RELEASE !Bit status 1! ! ! 13! ! ! ! !

! !WHEEL 3 ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !RELEASE !Bit status 1! ! ! 14! ! ! ! !

! !WHEEL 4 ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 15! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 16! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 17! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 18! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !BRAKE !Bit status 0! ! ! 19! ! ! ! !

! !FAN CTL !:OFF ! ! ! ! ! ! ! !

! ! !Bit status 1! ! ! ! ! ! ! !

! ! !:ON ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !LO ON !Bit status 1! ! ! 20! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !MED ON !Bit status 1! ! ! 21! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !MAX ON !Bit status 1! ! ! 22! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !WHEEL !Bit status 1! ! ! 23! ! ! ! !

! !SPEED 1 ! ! ! ! ! ! ! ! !

! !>70KTS ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !WHEEL !Bit status 1! ! ! 24! ! ! ! !

! !SPEED 3 ! ! ! ! ! ! ! ! !

! !>70KTS ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !NWS !Bit status 1! ! ! 25! ! ! ! !

! !SELECTOR ! ! ! ! ! ! ! ! !

! !FAULT ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !BRAKE !Bit status 1! ! ! 26! ! ! ! !

! !SELECTOR ! ! ! ! ! ! ! ! !

! !VALVE ! ! ! ! ! ! ! ! !

! !FAULT ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !MAX DECEL !Bit status 1! ! ! 27! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !ENG SYS !Bit status 1! ! ! 28! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !BOGIE ! ! ! ! 29! ! ! ! !

! !OPTION ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 2 . 027 . 10 !DSCRT DATA! ! ! ! 15!250 !DIS !DSW3 ! !

! !WORD ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !RELEASE !Bit status 1! ! ! 11! ! ! ! !

! !WHEEL 1 ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !RELEASE !Bit status 1! ! ! 12! ! ! ! !

! !WHEEL 2 ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !RELEASE !Bit status 1! ! ! 13! ! ! ! !

! !WHEEL 3 ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !RELEASE !Bit status 1! ! ! 14! ! ! ! !

! !WHEEL 4 ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 15! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 16! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 17! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 18! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !BRAKE !Bit status 0! ! ! 19! ! ! ! !

! !FAN CTL !:OFF ! ! ! ! ! ! ! !

! ! !Bit status 1! ! ! ! ! ! ! !

! ! !:ON ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !LO ON !Bit status 1! ! ! 20! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !MED ON !Bit status 1! ! ! 21! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !MAX ON !Bit status 1! ! ! 22! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !WHEEL !Bit status 1! ! ! 23! ! ! ! !

! !SPEED 1 ! ! ! ! ! ! ! ! !

! !>70KTS ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !WHEEL !Bit status 1! ! ! 24! ! ! ! !

! !SPEED 3 ! ! ! ! ! ! ! ! !

! !>70KTS ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !LO DECEL !Bit status 1! ! ! 25! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !MED DECEL !Bit status 1! ! ! 26! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !MAX DECEL !Bit status 1! ! ! 27! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !ENG SYS !Bit status 1! ! ! 28! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !BOGIE ! ! ! ! 29! ! ! ! !

! !OPTION ! ! ! ! ! ! ! ! !

!-----------------------------------------------------------------------------!

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| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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! 1 . 114 . 01 !BRAKE 1 ! W 2048 !DegC! ! 28 !500 !BNR !BT1 ! !

! 2 . 114 . 10 !TEMP. ! R 1 ! ! ! to ! ! ! ! !

! ! ! ! ! ! 18 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 115 . 01 !BRAKE 2 ! W 2048 !DegC! ! 28 !500 !BNR !BT2 ! !

! 2 . 115 . 10 !TEMP. ! R 1 ! ! ! to ! ! ! ! !

! ! ! ! ! ! 18 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 116 . 01 !BRAKE 3 ! W 2048 !DegC! ! 28 !500 !BNR !BT3 ! !

! 2 . 116 . 10 !TEMP. ! R 1 ! ! ! to ! ! ! ! !

! ! ! ! ! ! 18 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 117 . 01 !BRAKE 4 ! W 2048 !DegC! ! 28 !500 !BNR !BT4 ! !

! 2 . 117 . 10 !TEMP. ! R 1 ! ! ! to ! ! ! ! !

! ! ! ! ! ! 18 ! ! ! ! !

!-----------------------------------------------------------------------------!

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| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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! 1 . 270 . 01 !DSCRT DATA! ! ! ! 3!200 !DIS !DSW1 ! !

! 2 . 270 . 10 !WORD ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !BRAKE !Bit status 0! ! ! 11! ! ! ! !

! !SELECTOR !: Closed ! ! ! ! ! ! ! !

! !VALVE !Bit status 1! ! ! ! ! ! ! !

! ! !: Open ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !STEERING !Bit status 0! ! ! 12! ! ! ! !

! !SELECTOR !: Closed ! ! ! ! ! ! ! !

! !VALVE !Bit status 1! ! ! ! ! ! ! !

! ! !: Open ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !FUNCT. !Bit status 0! ! ! 13! ! ! ! !

! !TEST ORDER! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 14! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 15! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 16! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 17! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 18! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 19! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 20! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 21! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 22! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! !SPARE ! ! ! ! 23! ! ! ! !

!-----------------------------------------------------------------------------!

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| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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! 1 . 300 . 01 !NORMAL ! W 4096 !PSI ! ! 28 !100 !BNR !BP1 ! !

! 2 . 300 . 10 !BRAKE ! R 1 ! ! ! to ! ! ! ! !

! !PRES. 1 ! ! ! ! 17 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 301 . 01 !NORMAL ! W 4096 !PSI ! ! 28 !100 !BNR !BP2 ! !

! 2 . 301 . 10 !BRAKE ! R 1 ! ! ! to ! ! ! ! !

! !PRES. 2 ! ! ! ! 17 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 302 . 01 !NORMAL ! W 4096 !PSI ! ! 28 !100 !BNR !BP3 ! !

! 2 . 302 . 10 !BRAKE ! R 1 ! ! ! to ! ! ! ! !

! !PRES. 3 ! ! ! ! 17 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 303 . 01 !NORMAL ! W 4096 !PSI ! ! 28 !100 !BNR !BP4 ! !

! 2 . 303 . 10 !BRAKE ! R 1 ! ! ! to ! ! ! ! !

! !PRES. 4 ! ! ! ! 17 ! ! ! ! !

!-----------------------------------------------------------------------------!

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| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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! 1 . 310 . 01 !NORMAL SV1! W 64 ! mA ! ! 28 !100 !BNR !CSV1 ! !

! 2 . 310 . 10 !CURRENT ! R 1 ! ! ! to ! ! ! ! !

! ! ! ! ! ! 23 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 311 . 01 !NORMAL SV2! W 64 ! mA ! ! 28 !100 !BNR !CSV2 ! !

! 2 . 311 . 10 !CURRENT ! R 1 ! ! ! to ! ! ! ! !

! ! ! ! ! ! 23 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 312 . 01 !NORMAL SV3! W 64 ! mA ! ! 28 !100 !BNR !CSV3 ! !

! 2 . 312 . 10 !CURRENT ! R 1 ! ! ! to ! ! ! ! !

! ! ! ! ! ! 23 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 313 . 01 !NORMAL SV4! W 64 ! mA ! ! 28 !100 !BNR !CSV4 ! !

! 2 . 313 . 10 !CURRENT ! R 1 ! ! ! to ! ! ! ! !

! ! ! ! ! ! 23 ! ! ! ! !

!-----------------------------------------------------------------------------!

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| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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! 1 . 320 . 01 !WHEEL ! W 256 !KTS ! ! 28 !100 !BNR !WS1 ! !

! 2 . 320 . 10 !SPEED 1 ! R 1 ! ! ! to ! ! ! ! !

! ! ! ! ! ! 21 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 321 . 01 !WHEEL ! W 256 !KTS ! ! 28 !100 !BNR !WS2 ! !

! 2 . 321 . 10 !SPEED 2 ! R 1 ! ! ! to ! ! ! ! !

! ! ! ! ! ! 21 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 322 . 01 !WHEEL ! W 256 !KTS ! ! 28 !100 !BNR !WS3 ! !

! 2 . 322 . 10 !SPEED 3 ! R 1 ! ! ! to ! ! ! ! !

! ! ! ! ! ! 21 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 323 . 01 !WHEEL ! W 256 !KTS ! ! 28 !100 !BNR !WS4 ! !

! 2 . 323 . 10 !SPEED 4 ! R 1 ! ! ! to ! ! ! ! !

! ! ! ! ! ! 21 ! ! ! ! !

!-----------------------------------------------------------------------------!

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| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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! 1 . 330 . 01 !RIGHT ! W 128 !Deg ! ! 28 !200 !BNR !ROPP ! !

! 2 . 330 . 10 !BRAKE ! R 1 ! ! ! to ! ! ! ! !

! !PEDAL ! ! ! ! 22 ! ! ! ! !

! !ANGLE ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 331 . 01 !LEFT BRAKE! W 128 !Deg ! ! 28 !200 !BNR !LOPP ! !

! 2 . 331 . 10 !PEDAL ! R 1 ! ! ! to ! ! ! ! !

! !ANGLE ! ! ! ! 22 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 332 . 01 !REF SPEED ! W 256 !Kts ! ! 28 !100 !BNR !RSCC ! !

! 2 . 332 . 10 ! ! R 1 ! ! ! to ! ! ! ! !

! ! ! ! ! ! 21 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 334 . 01 !NWS ANGLE ! W +/-128 !Deg ! 29 ! 28 !100 !BNR !NWSA ! !

! ! ! Positive ! ! ! to ! ! ! ! !

! ! ! direction ! ! ! 19 ! ! ! ! !

! ! ! left ! ! ! ! ! ! ! !

! ! ! R 1/8 ! ! ! ! ! ! ! !

! 2 . 334 . 10 !NWS ANGLE ! W+/-128 !Deg ! 29 ! 28 !100 !BNR !NWSA ! !

! ! ! Positive ! ! ! to ! ! ! ! !

! ! ! direction ! ! ! 19 ! ! ! ! !

! ! ! left ! ! ! ! ! ! ! !

! ! ! R 1/8 ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 335 . 01 !STEERING ! W +/-8 ! mA ! 29 ! 28 !100 !BNR !NSVC ! !

! 2 . 335 . 10 !SV CURRENT! R 1/16 ! ! ! to ! ! ! ! !

! ! ! ! ! ! 22 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 336 . 01 !NWS REF ! W +/-128 !Deg ! 29 ! 28 !100 !BNR !NRA ! !

! 2 . 336 . 10 !ORDER ! Positive ! ! ! to ! ! ! ! !

! ! ! direction ! ! ! 19 ! ! ! ! !

! ! ! left ! ! ! ! ! ! ! !

! ! ! R 1/8 ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 340 . 01 !CAPT NWS ! W +/-128 !Deg ! 29 ! 28 !200 !BNR !SCC ! !

! 2 . 340 . 10 !HANDWHEEL ! Positive ! ! ! to ! ! ! ! !

! !ORDER ! direction ! ! ! 22 ! ! ! ! !

! ! ! left ! ! ! ! ! ! ! !

! ! ! R 1 ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 341 . 01 !F/O NWS ! W +/-128 !Deg ! 29 ! 28 !200 !BNR !SCFD ! !

! 2 . 341 . 10 !HANDWHEEL ! Positive ! ! ! to ! ! ! ! !

! !ORDER ! direction ! ! ! 22 ! ! ! ! !

! ! ! left ! ! ! ! ! ! ! !

! ! ! R 1 ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 356 . 01 !MAINT WORD! ! ! ! !100 !ISO ! ! !

! 2 . 356 . 10 ! ! ! ! ! ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

! 1 . 377 . 01 !IDENT. ! ! ! ! !200 !BNR ! ! !

! 2 . 377 . 10 ! ! ! ! ! ! ! ! ! !

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A. Manual Braking

Normal Braking - Electrical Control Schematic ** ON A/C NOT FOR ALL

Normal Braking Control (Principle) ** ON A/C NOT FOR ALL

Manual braking is available when the Green hydraulic pressure is more than 150 bar (2176 psi) and one of these conditions occur:

the left MLG or the right MLG is on the ground
the average computed wheel speed is more than a specified value
the ground speed (from the ADIRS) is less than a specified value.

The operation of the brake pedal(s) causes the control lever(s) of the brake pedal transmitter unit (at the first officers position) to turn. The control lever(s) turns its related potentiometer which gives an electrical output to the BSCU. This output is in proportion to the angle through which the pedal(s) turn.

Differential braking is available when the travel of the left and right brake pedals is different. The left pedal gives the quantity of braking at the left MLG. The right pedal gives the quantity of braking at the right MLG.

When the output from the transmitter unit is more than a specified value, the BSCU:

energizes the brake selector valve to open the valve
sends a control current to the related servovalves in proportion to the pedal movement to give the specified pressure at the brakes (max 175 bar (2538 psi)).

The brake selector valve opens to connect the Green hydraulic pressure to the normal braking system. The fluid goes through the HP filter and goes freely to the individual manifolds on the landing gear. The pressure transducer at the filter outlet sends data to the BSCU. This lets the BSCU make sure that the system is pressurized.

At each manifold and valve assembly the hydraulic pressure divides equally to supply the servovalves. The servovalves are energized with the necessary control current to supply the correct hydraulic pressure to the individual brakes.

The pressure transducers continuously monitor the pressure in their related brake service line. A signal that agrees with the pressure is sent to the BSCU. If the fluid pressure changes, the control current sent to the related servovalve is changed to adjust the pressure.

When the brake pedals go back to their initial position, the output from the transmitter unit returns to a set value (set for the initial pedal position). When the output is less than a specified value this causes the BSCU to de-energize the brake selector valve. At the same time it decreases the control current it sends to the servovalves which releases the brakes.

When the brake selector valve is de-energized, it connects the HP filter to the LP manifold (Port A) of the Green hydraulic system.

When the servovalves are de-energized, they operate to connect their related brake service line to the LP manifold of the Green hydraulic system.

B. Automatic Braking

(1) Principle

(a) Operation

Auto Brake Control ** ON A/C NOT FOR ALL

The automatic braking system has these functions:

generation of the arming or disarming orders to the system,
servoing of the aircraft deceleration to a programmed deceleration rate,
braking control when the spoiler signals are present, depending on the requested deceleration.

When an autobrake mode (LO, MED or MAX) is selected, the BSCU sends a controlled pressure to the brakes until the deceleration measured by the IRUs matches the programmed deceleration.
The anti skid system operates to avoid wheel lock-up.
The auto brake system advantages are:

get the optimum deceleration rate compatible with the length of the runway,
decrease the pilot workload during landing,
decrease the number of pilot actions in case of rejected take-off (one action on throttle instead of two actions: braking + throttle)
improve passenger comfort.

Before landing, the pilot sets the deceleration rate he thinks to be adapted to the runway. For this purpose, he uses the AUTO BRK LO and MED on the center instrument panel. The pilot can disengage the autobrake when he depresses the pedals or when he pushes again the AUTO BRK LO and MED.
Before takeoff, the pilot selects the MAX mode.

(b) Indicating
Each lighted pushbutton switch is divided into two parts:

the lower part (ON legend) comes on blue to show that the pushbutton switch has been selected and the system armed,
the upper part (DECEL legend) comes on green: when 80% of the corresponding deceleration rate has been reached, (LO and MED pushbutton switches) or when you have a deceleration rate higher than 0.27 g (MAX pushbutton switch).

(2) Auto brake logic

Auto Brake Control Modes ** ON A/C NOT FOR ALL

The auto brake logic is located in the BSCU on the control and monitoring boards of the SYS 1 and SYS 2.
The signals below are sent to the logic circuits of the auto brake:

3 signals that the AUTO BRK LO/MED and MAX on the center instrument panel supply:
2 deceleration rates, LOW = 1.7 m/square second (LOW type 1) and MED = 3 m/ square second (2 m/square second in MED limited) , and a MAX = 10 m/square second (higher than the maximum possible deceleration of the aircraft)
there is a LOW type 2 mode = 2m/square second depending of the aircraft pin programming.
3 signals which tell that the ground spoilers are commanded.
Two of them must be present to permit the automatic braking.
a signal which gives the pedal position,
a signal which tells that the pressure in the Green system is low,
a signal which gives the longitudinal deceleration of the aircraft ADIRs.
no tachometer failure.
GROUND/FLIGHT information.

The auto brake logic supplies:

the command for the energization of the selector valve,
the braking command to the four servovalves,
the information below to the lighted pushbutton switches:
the system is armed or the deceleration rate that you get
to the ECAM system:
the deceleration rate that you select or the AUTOBRK disarm signal or the AUTO BRK FAULT signal if arming is not possible.

(3) Operation

(a) LOW mode

1 This mode is used at landing.

2 The selector valve is energized by the extension command of the ground spoilers.

3 Braking is applied when the ground-spoilers extension signals are present (speed of the main gear wheel > 80 kts).
The braking has a delay of 4 seconds (type1) or 2 seconds (type 2). It is then progressively applied.

4 The pressure supplied by the 4 servovalves gradually increases, t = 3 s approx.
The programmed deceleration is reached progressively.

5 The control circuit sends identical commands to the 4 servovalves.

6 The BSCU uses the deceleration from the ADIRs and limits or increases the braking order to make it reach the selected deceleration rate.

(b) MED mode

1 This mode is used at landing.

2 The selector valve is energized by the extension command of the ground spoilers.

3 Braking is applied when the ground-spoilers extension signals are present (speed of the main gear wheel > 80 kts).
The braking has two phases:

phase 1: the MED limited deceleration is progressively applied without delay until the A/C attitude is less than 1 degree or T= 5 seconds.
The pressure supplied by the 4 servovalves gradually increases,
The programmed deceleration (2 m/square second) is reached progressively.
phase 2: when the A/C attitude is less than 1 degree or T= 5 seconds, the MED deceleration is then progressively applied.
The pressure supplied by the 4 servovalves gradually increases,
The programmed deceleration (3 m/square second) is reached progressively.

4 The control circuit sends identical commands to the 4 servovalves.

5 The BSCU uses the deceleration from the ADIRs and limits or increases the braking order to make it reach the selected deceleration rate.

1 This mode is selected before take-off in case of rejected take-off (at least 2 out 3 spoilers must be out).

2 The command for the ground spoiler extension controls:

the energization of the selector valve,
the immediate delivery of a maximum pressure to the four brakes (with antiskid protection).

3 The programmed deceleration rate is such as the full pressure is applied on the four brakes.
A small differential braking is not permitted.
The auto brake system is disengaged:

when you put the landing-gear control lever in the UP position
or when you push again the mode-selection pushbutton switch already selected.
There is no AUTO BRK indication on the ECAM.

The automatic braking is only re-initiated after the selection of a new deceleration rate. This occurs if the signal for the extension of the ground spoilers is still generated.
The automatic braking is totally and immediately cut off as soon as a ground spoilers-retraction signal is applied (this signal possibly results from a go-around command).
The automatic braking is re-initiated as soon as there is a new mode selection (LO or MED mode).

(d) In the MAX mode, the load required at the pedal to cut off the automatic braking is greater than that in the LO or MED mode.
Travel of the two brake pedals: 7.5 degrees in LO and MED mode.
Travel of one brake pedal: 10.8 degrees in LO and MED mode.

NOTE: 53 per cent of the travel of the pedal is equal to 7.5 degrees. 76 per cent of the travel of the pedal is equal to 10.8 degrees.

The pilot can disengage the AUTO BRAKE when he pushes only one pedal.

(4) Disengagement in the event of failure
The system cannot be armed and is disengaged in the cases below:

arming is impossible when there is a Green low pressure or A/SKID failure (servovalve, pressure transducer, tachometer) or electrical supply failure.
disengagement when there is a loss of one the arming conditions.

C. Anti-skid

(1) The inputs and outputs of the anti skid system are shown in the schematic

Anti Skid - Schematic ** ON A/C NOT FOR ALL

NOTE: The Braking/Steering Control Unit is designed for use with two types of brakes.
The selection is made through shunts located at the rear of the unit, on the wiring side of the aircraft.

(2) Principle

Anti Skid - Principle ** ON A/C NOT FOR ALL

The speed of each main gear wheel is compared to the reference speed.
With braking ordered, when the speed of a braked wheel decreases to below the input control speed (Vc), the anti skid system sends a brake release order. This order keeps the wheel speed value at the input control speed. A slip law function of the reference speed is introduced.
The anti skid system has the corrective networks necessary to stabilize the feedback loop.
The servovalve is the pressure-servoed electro-hydraulic component (Ref. Para. 2. F.).
The static gain of the brake is between 300 and 450 mN/bar depending on the brake type.
The tachometer transforms the angular velocity of the braked wheel into a frequency (Ref. Para. 2. I.).
A converter transforms the input frequency into a digital signal that the microprocessor can use directly.

(3) Description

(a) Calculation of the aircraft speed

1 In flight:
The reference speed is given by a fixed value Vo = 50 m/s

VREF = Vo.

2 On impact of the main landing gears, during acceleration of the main gear wheels, a logic monitoring the acceleration of the wheels and hydroplaning determines, from the smallest of the highest wheel speeds per gear (VR) and from its derivative, the end of the wheel acceleration phase. The brakes are released as long as this phase is not over. During this phase, the reference speed is computed from a deceleration forced at 0.35 g and from VR as follows, so as to obtain the best reference speed evaluation for the following phases :

Generation of the Reference Speed - Principle ** ON A/C NOT FOR ALL

Generation of the Reference Speed - Flow Chart ** ON A/C NOT FOR ALL

Vref (t) = MAX (Vref (t-dt) - 3.5dt ; VR (t)) (in m/s)

3 During the roll, without braking control, the reference speed is obtained in the same manner as during the wheel acceleration phase, as a function of a deceleration forced at 0.25 g and of VR :

Vref (t) = MAX (Vref (t-dt) - 3.5dt ; VR (t)) (in m/s)

4 During braking, the reference speed is obtained from the speed VR and the aircraft deceleration (gamma) determined from the airframe longitudinal acceleration and pitch angle given by the ADIRUs 1, 2 and 3.

Gamma n Calculation ** ON A/C NOT FOR ALL

The reference speed is calculated as follows :

Vref (t) = MAX (Vref (t-dt) + gamma (t)dt ; VR(t)) (in m/s)

5 The logic which modifies the reference speed calculation as a function of the FLIGHT/GROUND information is obtained from LGCIU discretes (main gear shock absorbers compressed), the tachometer speed VR and the ground speed V GROUND. V GROUND is calculated from the ground speeds delivered by the ADIRUs 1, 2 and 3.

V GROUND Calculation ** ON A/C NOT FOR ALL

Generation of the Reference Speed - Flight/Ground Logic ** ON A/C NOT FOR ALL

(b) Regulation
The control speed of the speed servoing of each wheel (4 independent wheels) is calculated by decreasing the reference speed by the value of the slip ratio.

Programmed Input Control speed ** ON A/C NOT FOR ALL

Vc (t) = 0.935 VRef (t)- 0.9 (in m/s)

The regulator compares the control speed to the braked wheel speed to establish, if necessary, a brake release order so as to decrease wheel slip. The corrective networks and the static gain of the regulator of one wheel are adjusted to maintain a high level of stability and accuracy.
The regulator cannot, therefore, anticipate on the braking orders of the pilot. Below a 10 m/s reference speed, the regulator action is inhibited by forcing the control speed value at 0 m/s (enabling wheel locking).
The regulator supplies numerical values converted into current to supply the coil:

of the Normal servovalve I1 or I2,
of the Alternate servovalve (Direct Drive Valve) I'1 or I'2.
The current control is not affected by the impedance of the servovalve coil.
When sufficient brake release current is available, the voltage at the terminals of resistor R is sent to the lower ECAM DU.
It supplies the brake-release indication, REL (Release) symbolized by 5 green bars on the wheel concerned.
The regulation circuit of the Normal or Alternate servovalve supplies the REL information.
A regulation-inhibition circuit eliminates all the brake-release orders that could occur:
during an automatic in-flight wheel braking when the gear retracts,
or during application of the Parking brake (for 3 s only).

D. Braking During L/G Retraction

Braking occurs automatically during the retraction of the landing gear. This stops the rotation of the MLG wheels before the landing gears go into their related bays. This prevents damage to the aircraft components and structure if a tire has been damaged. When the landing gear selector lever is put in the UP position:

the brakes selector valve is energized to connect the Green hydraulic power supply to the normal braking system.
the servovalves are energized with a set control current to get the necessary brake pressure.

After three seconds or when the NLG moves away from the downlocked position the selector valve and the servo valves are de-energized. This connects the system to return to release the pressure at the brakes.

E. Indicating

Indicating ** ON A/C NOT FOR ALL

The A/SKID & NOSE WHEEL control switch is located on the center instrument panel.
All the indications are transmitted to the crew through the ECAM:

On the lower display unit, the WHEEL page gives the Release information, the NORMAL/ALT braking mode and the selected deceleration,

On the upper display unit the related warnings are displayed.

-------------------------------------------------------------------------------

! FAILURE WARNING ! CLASS ! LEVEL ! ASSOCIATED WARNING !

-------------------------------------------------------------------------------

! BRAKES HOT ! 1 ! 2 ! MASTER CAUTION,SINGLE CHIME !

!-----------------------------------------------------------------------------!

! BRAKES AUTO BRK FAULT ! 1 ! 2 ! MASTER CAUTION,SINGLE CHIME !

! BRAKE RELEASED ! ! ! !

!-----------------------------------------------------------------------------!

! WHEEL N/W STRG FAULT ! 1 ! 2 ! MASTER CAUTION,SINGLE CHIME !

!-----------------------------------------------------------------------------!

! CONF PARK BRK ON ! 1 ! 3 ! MASTER WARNING, CRC !

!-----------------------------------------------------------------------------!

! BRAKES A/SKID N/WS OFF ! 1 ! 2 ! MASTER CAUTION,SINGLE CHIME !

!-----------------------------------------------------------------------------!

! BRAKES A/SKID N/WS FAULT ! 1 ! 2 ! MASTER CAUTION,SINGLE CHIME !

!-----------------------------------------------------------------------------!

! WHEEL HYD SEL FAULT ! 1 ! 2 ! MASTER CAUTION,SINGLE CHIME !

!-----------------------------------------------------------------------------!

! BRAKES SYS 1(2) FAULT ! 1 ! 1 ! !

!-----------------------------------------------------------------------------!

! BRAKES NORM+ALTN FAULT ! 1 ! 2 ! MASTER CAUTION,SINGLE CHIME !

!-----------------------------------------------------------------------------!

! BRAKES NORM BRK FAULT ! 1 ! 2 ! MASTER CAUTION,SINGLE CHIME !

!-----------------------------------------------------------------------------!

! BRAKES RELEASED ! 1 ! 2 ! MASTER CAUTION,SINGLE CHIME !

!-----------------------------------------------------------------------------!

! BRAKES-N/WS MINOR FAULT ! 1 ! 1 ! !

-------------------------------------------------------------------------------

[Rev.10 from 2021] 2026.04.01 00:47:21 UTC