NORMAL BRAKING - DESCRIPTION AND OPERATION

** ON A/C NOT FOR ALL

1. General

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

Brake Pedal Control ** 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.

** ON A/C NOT FOR ALL

2. Component Location

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

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

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

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

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

Selector Valve / Hydraulic Filter - Component Location ** ON A/C NOT FOR ALL

Automatic Selector/ Throttle Valve - Component Location ** ON A/C NOT FOR ALL

Check Valve - Component Location ** ON A/C NOT FOR ALL

Safety Valve / Servovalve Manifold - Component Location ** ON A/C NOT FOR ALL

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

FIN	FUNCTIONAL DESIGNATION	PANEL	ZONE	ATA REF
** ON A/C NOT FOR ALL
9GG	XMTR UNIT-BRK PEDAL		122	32-42-47
** ON A/C NOT FOR ALL
10GG	BSCU	94VU	122	32-42-34
** ON A/C NOT FOR ALL
10GG	BSCU	94VU	122	32-42-34
** ON A/C NOT FOR ALL
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	SERVOVALVE-NORM BRK WHEEL 1		731	32-42-48
16GG	SERVOVALVE-NORM BRK WHEEL 3		741	32-42-48
17GG	SERVOVALVE-NORM BRK WHEEL 2		731	32-42-48
18GG	SERVOVALVE-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		147	32-42-11
2576GM	AUTOMATIC SEL-BRK		148	32-42-13
2581GM	THROTTLE VALVE-NORM BRK		148	32-42-76
2584GM	BRAKE HYDRAULIC FILTER		146	32-42-12
2593GM	CHECK VALVE-BRK,L		571	32-42-77
2594GM	CHECK VALVE-BRK,R		671	32-42-77
** ON A/C NOT FOR ALL
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
** ON A/C NOT FOR ALL
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

** ON A/C NOT FOR ALL

3. Component Description

A. Controls in the Cockpit
The control is electrical and is achieved:

either via the pedals.
or automatically:
On the ground by the auto brake system and in flight, when the landing-gear Normal control-lever is put in the UP position.

In all the cases, the energization of a selector valve causes the supply of the system.
When you put the A/SKID & NOSE WHEEL control switch in the OFF position or when you apply the parking brake:

the selector valve is de-energized,
the Normal mode is de-activated.

Rods and bellcranks mechanically link the Captain and First Officer pedal controls.

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

The left pedals control one of the input levers of the brake pedal transmitter unit. The right pedals control the other lever.

B. Brake-Pedal Transmitter Unit FIN: 9-GG

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

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

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

The brake-pedal transmitter unit is located underfloor on the First Officer side.
It transforms the mechanical input from the left and right pedals into four identical electrical voltages per side. This is done via plastic-track potentiometers. These voltages are sent to the Braking/Steering Control Unit (BSCU).
For a given position of the pedals, the BSCU delivers a command for the energization of the selector valve.
When the pedals are depressed, any overtravel is absorbed by the spring rods which actuate the levers of the transmitter unit.

C. Selector Valve and Filter FIN: 23-GG

Selector Valve and Filter ** ON A/C NOT FOR ALL

The selector valve is located in the hydraulics compartment.
The selector valve is of the 3-way type and isolates the Normal braking system when:

the solenoid is de-energized,
the Normal braking is not selected, or
the pedals are released.

An internal valve progressively opens the supply-to-delivery passage of the selector valve.
A filter with a filtering capacity of 15 microns absolute is installed on the delivery port.
The purpose of the filter is to protect the supply to the servovalves downstream of the selector valve.

D. Automatic Selector and Throttle Valve FIN: 2576-GM FIN: 2581-GM

Automatic Selector ** ON A/C NOT FOR ALL

Automatic Selector - Schematic ** ON A/C NOT FOR ALL

Throttle Valve ** ON A/C NOT FOR ALL

The brake automatic selector is located in the hydraulics compartment.
The main function of the selector is to automatically supply during braking the Normal or Alternate braking systems depending on the hydraulic system available. The selector ensures the segregation of the two systems and preferential supply of the Normal system.
When the pedals are released, the Yellow system positions the slide valve in the automatic selector. Consequently the Yellow pressure is available for the Alternate braking (D to E).
When the brake selector valve delivers the Green pressure to A, the automatic selector:

connects the Alternate system to the return of the Yellow reservoir (I to H),
connects the Green pressure to the Normal system (A to B), as soon as P is more than or equal to 150 plus or minus 6 bars (2175 plus or minus 87 psi).

The inverse operation occurs when the Green pressure falls below 90 bars.
A throttle valve is installed on the Green supply port (A) of the automatic selector.
It decreases the speed of movement of the main slide valve of the selector when the brake selector valve is de-energized.

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

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 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 Servovalves FIN: 15-GG FIN: 16-GG FIN: 17-GG FIN: 18-GG
There are four servovalves; one for each brake.

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

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

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

There are also:

two associated safety valves, with integrated downstream filter,
two pressure transducers located downstream of the safety valve,
one filter on the supply line of the manifold.

The brake servovalve supplies a pressure inversely proportional to the current which passes through the control coil used.
The influence of the supply pressure on the pressure/current gain is negligible (unigain-type servovalve).
The current moves a flapper located between two jets. Two coils are installed around the core which is mounted in the gap of a permanent magnet.
The attraction of the core by the poles of the magnet is function of the current which passes through the coils.
The movement of the flapper modifies the sections of the fluid passage at the jets. Consequently the pressure in the control chambers of the slide valve is modified. The differential action of the pressure moves a slide valve. This fills or drains the brake depending on whether the current decreases or increases.
The slide valve is in a balanced position under the action of the pressure supplied on one of the opposite faces of the slide valve.
With zero current in the coil, the pressure supplied is equal to the pressure supplied to the servovalve.
If there is no supply pressure, the servovalve connects the brake to the reservoir return system.

G. Restrictors
Restrictor has been installed to adapt the Normal system to the hydraulic behavior during transients.
1 restrictor on the Normal system:

1 at automatic selector outlet (Dia. 2.1 mm).

H. Safety Valves FIN: 2616-GM FIN: 2617-GM FIN: 2618-GM FIN: 2619-GM

Normal Brake Safety-Valve P/N C24757000 - Location ** ON A/C NOT FOR ALL

Normal Brake Safety-Valve P/N C25243002-2 - Location ** ON A/C NOT FOR ALL

Safety Valve P/N C24757000 - Schematic ** ON A/C NOT FOR ALL

Safety Valve P/N C25243002-2 ** ON A/C NOT FOR ALL

A safety valve is installed between the brake servovalve and the brake.
It stops the flow in the line if there is a leakage.
The safety valve is made to operate only if the flow is more than or equal to 4 l/mn.
The time for valve closure is less than 5 s (with fluid temperature = 30 deg.C) for a flow rate more than or equal to 5 l/mn under a supply pressure of 206 bars (2987 psi).
Normally, the valve is in the position shown on the referenced figure.
Under the above conditions, the valve operates and the supply pressure acts on the slide valve in chamber A. As a result, the valve closes.
When the chamber A is filled, there is a time delay which prevents an untimely operation as a result of the transient high flow rates found during filling of the brakes or anti-skid regulation.
To prevent the untimely operation of the valve when the brake are bled, the bleeders are moderately open and the brake pressure must not be more than 50 bars.
The valve stays closed after operation for a supply pressure more than or equal to that of the reservoir.
The valve is reset when you depressurize the reservoir return systems or when you open the bleed screw on one end of the valve.

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

Wheel and Brake Assembly

Wheel and 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 during a removal/installation of the brake.

(b) Pistons

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

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.

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

Four identical tachometers are installed in the main-gear wheel axles (one for each wheel).
The tachometers supply wheel speed information. Each tachometer has two 200-tooth rings:

1 stationary ring associated with a coil and a permanent magnet,
1 ring driven by the wheel.

The rotation of the wheel causes variations in the induction frequency which are proportional to the angular speed (Frequency = 200 x angular speed).
The variable-frequency voltage supplied by the tachometer is sent to the Braking/Steering Control Unit.

K. 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/O1 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/O2 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.

(e) When the BSCU is supplied with power system 1 becomes active. After each landing 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.

(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

4. Operation/Control and Indicating

A. Control

(1) General

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

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

Braking Electrical Control - Schematic Part 1 ** ON A/C NOT FOR ALL

Braking Electrical Control - Schematic Part 2 ** ON A/C NOT FOR ALL

Arinc 429 Inputs/Outputs ** ON A/C NOT FOR ALL

The various inputs and outputs associated with the control are shown in the schematic.
Functions performed:

Control of the brake selector valve,
Automatic braking of the wheels upon initiation of the landing gear retraction,
Auto brake.

(2) Selector valve control
The opening of the selector valve results from the actions given below:

depression of a left or right pedal past the load threshold (approx 14%).
activation of the auto brake,
automatic braking of the wheel during the landing gear retraction.
opening order sent by the functional test at landing gear extension.

(3) Pressure slaving of the Normal servovalve
For each gear, the brake command obtained by the depression of a pedal is transformed into a pressure by the normal servovalve.
The servovalve delivers the commanded pressure to the brakes.
The BSCU uses a feedback loop with a pressure transducer to adjust the commanded pressure and prevent pressure shifts.

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

The maximum pressure supplied by the servovalve is 175 bars.

(4) Digital outputs
This table contains all the output parameters in the digital form. They are sorted per the numerical order of 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 whether a sign bit is available.
BITS: 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 coded
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.

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

| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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

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

! 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 ! ! ! ! ! ! ! !

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

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

| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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

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

! 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 ! ! ! ! ! ! ! ! !

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

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

| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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

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

! 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 ! ! ! ! !

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

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

| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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

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

! 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! ! ! ! !

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

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

| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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

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

! 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 ! ! ! ! !

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

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

| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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

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

! 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 ! ! ! ! !

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

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

| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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

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

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

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

! ! ! ! ! ! 20 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

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

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

! ! ! ! ! ! 20 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

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

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

! ! ! ! ! ! 20 ! ! ! ! !

! ! ! ! ! ! ! ! ! ! !

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

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

! ! ! ! ! ! 20 ! ! ! ! !

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

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

| PARAMETER LIST PARAMETER CHARACTERISTICS (NUMERIC) |

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

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

! 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 ! ! ! ! ! ! ! ! ! !

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

B. BSCU Configuration (PIN PROGRAMMING)

(1) Principle
At BSCU energization, the pin programming integrated in the BSCU is compared with the aircraft pin programming (strap connection).
Any disagree results in switching the Normal braking to the Alternate mode without anti-skid regulation (ALT OFF-NWS OFF).
The BSCU pin programming can be adapted by means of the BSCU menu mode, via the CFDIU.
This procedure is described in 32-46-00-00.
At the end of the menu mode, the system must be set to OFF then to ON to be correctly reset.
Moreover, the pin programming modification must also be performed on the second BSCU system.

(2) BSCU configurations
The various configurations available depend on the parameters below:

aircraft type,
brake type,
wheel type (different diameters),
deceleration rate in special automatic braking mode,
brake fan option.

C. Anti Skid Control

(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 several types of brakes.
The selection is made through the pin-programming integrated in the BSCU, 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.
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.
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.

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

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 0.25 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) - 2.5dt ; 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) - 2.5dt ; 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 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 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

Regulation Circuit ** ON A/C NOT FOR ALL

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 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).

(4) Indicating

Indicating ** ON A/C NOT FOR ALL

BSCU Failure Categories ** 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.

D. Auto Brake

(1) Principle

(a) Operation

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

The automatic braking system has these functions:

Generation of arming or disarming commands to the system.
Servoing of the aircraft deceleration to a programmed deceleration rate
Braking control when there are spoiler signals in relation to the necessary deceleration.

When an autobrake mode (LO, MED or MAX) is selected, the BSCU sends a controlled pressure to the brakes until the deceleration that the IRUs measure agree with the programmed deceleration.
The anti-skid system operates to prevent wheel lock-up.
The auto brake system:

Gets the best possible deceleration rate compatible with the length of the runway
Decreases the workload of the pilot during the landing
Decreases the worksteps of the pilot if there is a rejected take-off (one action on the throttle and not two: braking + throttle)
Increases the passenger comfort.

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

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

The lower part (ON legend) comes on blue to show that the pushbutton switch was selected and the system armed
The upper part (DECEL legend) comes on green: when 80% of the related deceleration rate is reached, (LO and MED pushbutton switches) or when the deceleration rate is more than 0.27 g (MAX pushbutton switch).

(2) Auto brake logic
The auto brake logic is in the BSCU on the control and monitoring boards of SYS 1 and SYS 2.
The signals that follow are sent to the logic circuits of the auto brake:

Three signals that the AUTO BRK LO/MED and MAX on the center instrument panel supply:

Two deceleration rates, LOW = 1.7 m/square second and MED = 3 m/square second (2 m/square second in MED limited), and a MAX = 10 m/square second (more than the maximum possible deceleration of the aircraft).
There is a LOW type 2 mode = 2 m/square second related to the aircraft pin programming.

Three signals that tell that the ground spoilers are extended.
Two of them are necessary for the automatic braking.
A signal that gives the pedal position
A signal that tells that the pressure in the Green system is low
A signal that gives the longitudinal deceleration of the aircraft ADIRs
No tachometer failure
GROUND/FLIGHT information.

The auto brake logic supplies:

The command for the power supply of the selector valve
The braking command to the four servovalves
The information that follows to the illuminated 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 with the extension command of the ground spoilers.

3 Braking is applied when there are ground-spoiler extension signals (speed of the main gear wheel more than 80 kts).
The braking has a delay of four seconds. It is then gradually applied.

4 The pressure that the four servovalves supply gradually increases, t = three seconds approximately.
The programmed deceleration is reached gradually.

5 The control circuit sends the same commands to the four servovalves.

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

(b) MED mode

1 This mode is used at the landing.

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

3 Braking is applied when there are ground-spoiler extension signals (speed of the main gear wheel more than 80 kts).
The braking has two phases:

Phase 1: the MED limited deceleration is gradually applied without delay until the A/C attitude is less than one degree or T= four seconds.
The pressure that the four servovalves supply gradually increases,
The programmed deceleration (2 m/square second) is reached gradually.
Phase 2: when the A/C attitude is less than one degree or T= four seconds, the MED deceleration is then gradually applied.
The pressure that the four servovalves supply gradually increases,
The programmed deceleration (3 m/square second) is reached gradually.

4 The control circuit sends the same commands to the four servovalves.

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

1 This mode is selected before take-off if there is a rejected take-off (a minimum of two out of three 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 anti-skid 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 push again the mode-selection pushbutton switch already selected
When you put the landing-gear control lever in the UP position.
There is no AUTO BRK indication on the ECAM.

The automatic braking is only started again 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 stopped when a ground spoiler-retraction signal is applied (this signal is possibly a result of a go-around command).
The braking is inhibited but the system stays armed.
The automatic braking is started again immediately when there is a new mode selection (LOW or MED mode).

(d) In the MAX mode, the load necessary on the pedal to stop the automatic braking is more than that in the LOW or MED mode.
In the LOW and MED modes, the autobrake is disconnected if:

The angular travel of one brake pedal is more than 42 degrees.
The angular travel of the two brake pedals is more than 9 degrees.

In the MAX mode, the autobrake is disconnected if:

The angular travel of one brake pedal is more than 61 degrees.
The angular travel of the two brake pedals is more than 42 degrees.

NOTE: The maximum angular travel of a brake pedal is 79.4 degrees.

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

(4) Disengagement if there is a failure
The system cannot be armed and is disengaged if:

The arming is not possible 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 of the arming conditions.

E. Braking during Landing Gear Retraction

(1) Principle
In order to ensure main gear wheel braking before landing gear retraction, a braking pressure command is sent to the Normal braking system when landing gear retraction is commanded.

F. Pedal Artificial Feel
The artificial feel at the pedals is identical in the Normal and Alternate braking modes.
The master cylinders of the Alternate system give the artificial feel (master cylinder spring + pressure in the master cylinder).
The pressure supplied to the brakes in the Normal mode is in relation to the pedal load/angle.

** ON A/C NOT FOR ALL

5. Test

A. Power-up Tests Initialization and Cockpit Repercussions

(1) Conditions of power-up tests initialization

de-energization time of computer: 5 s.
A/C configuration:
- whatever the A/C configuration on ground.

(2) Progress of power-up tests

Duration: < 5 s.
Cockpit repercussions directly linked to power-up test accomplishment:
BSCU ECAM warnings, audio warning, pushbutton flashing.

(3) Results of power-up tests
(cockpit repercussions, if any, in case of test passed/tests failed).

(a) Tests passed:

All warnings and indications disappear after 5 s.

(b) Tests failed:

ECAM MAINTENANCE:
- At least one BSCU ECAM warning remain displayed
NOTES:
In case of double BSCU failure: MASTER CAUT light on red and single chime.
ECAM warning:
- BRAKES A/SKID NWS FAULT.
ECAM WHEEL page:
1* STEERING and A/SKID in amber,
2* if AUTO/BRK selected: AUTO BRK in amber.

[Rev.10 from 2021] 2026.04.01 12:29:45 UTC