The main wheels are equipped with carbon multi-disc brakes, which can be actuated by either of two independent brake systems.
Normal system uses green hydraulic pressure
Alternate system uses the yellow hydraulic system backed up by the hydraulic accumulator.
Anti-skid and auto brake system is also provided.
Braking commands come from either the brake pedals (pilot action), or the autobrake system (deceleration rate selected by the crew).
In normal operation, a dual channel Brake and Steering Control Unit (BSCU) controls normal braking and antiskid.
Depending on the failure, braking may revert to:
‐ Alternate braking with antiskid. This braking mode is controlled by the Alternate Braking Control Unit (ABCU ), and the antiskid is controlled by the BSCU
‐ Alternate braking without antiskid. This braking mode is fully-controlled by the ABCU
‐ Alternate braking without antiskid on accumulator. This braking mode is fully-controlled by the ABCU.
All the normal and alternate braking components are fully-monitored. Any detected failure is signaled to the crew via ECAM warnings.
The BSCU performs the following secondary functions:
‐ Checks the residual pressure in the brakes
‐ Monitors the brake temperature
‐ Provides discrete wheel speed information to other aircraft systems.
A changeover between the two BSCU channels takes place at each DOWN landing gear lever selection, or in case one channel fails.
The main gear wheels are fitted with fusible plugs which protect against tire burst, in the event of overheat.
LOSS OF BRAKING MEMORY ITEMS
If the flight crew does not perceive deceleration when required, the flight crew will apply the LOSS OF BRAKING procedure from memory because of the urgency of the situation.
If no braking available…….
PF Announces………….. “LOSS OF BRAKING”
(PF) REVERSE THRUST………………. MAX
If needed, full reverse thrust may be used until coming to a complete stop. Below 70 kt, when the flight crew considers that the aircraft can stop on the runway, the flight crew should set idle reverse thrust.
Unless required due to an emergency, it is recommended to avoid the use of high level of reverse thrust at low speed, in order to avoid engine stall and excessive EGT.
(PF) BRAKE PEDALS……………… RELEASE
Brake pedals should be released when the A/SKID & N/W STRG sw is switched OFF, since the pedal force or displacement produces more braking action in alternate mode than in normal mode.
(PF) A/SKID OFF……………… ORDER OFF
The PF orders the PM to set the A/SKID & N/W STRG sw to OFF
(PM) A/SKID & N/W STRG……….. OFF
In order to successfully revert to alternate braking, it is important to sequence the actions in three steps.
1. Release the brake pedals
2. Request the PM to set the A/SKID & N/W STRG switch to OFF
3. Press the brake pedals, only after the PM has set the A/SKID & N/W STRG switch to OFF.
(PF) BRAKE PEDALS…………….PRESS
Apply brake with care, since initial pedal force or displacement produces more braking action in alternate mode than in normal mode.
(PF) MAX BRK PR……………1000 PSI
Monitor brake pressure or BRAKES PRESS indicator. Limit brake pressure to approximately 1 000 PSI and, at low ground speed, adjust brake pressure as required.
If still no braking…
(PF) PARK BRAKE…….SHORT AND SUCCESSIVE APPLICATIONS
Use short successive parking brake applications to stop the aircraft. Brake onset asymmetry may be felt at each parking brake application. If possible, delay the use of the parking brake until low speed, to reduce the risk of tire burst and lateral control difficulties.