DOC AIRBUS | AMM A320FPARKING/ULTIMATE EMERGENCY BRAKING - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
1. General
When you set the PARK BRK control switch to the ON position, this deactivates the other modes and supplies the brakes with Yellow high pressure. If Yellow high pressure is not available the brake Yellow pressure accumulator supplies power limited at 145 bar (2103.0467 psi) to the brakes.
If the parking brake pressure decreases to less than 35 bar (507.6320 psi) when the PARK BRK is in ON position, the system reactivates the Normal Braking mode automatically.
The accumulator has sufficient capacity to hold the brakes on for a minimum time of twelve hours. The TO CONFIG warning light (on the ECAM control panel) reminds the crew to release the parking brake when the engine is at full throttle.
** ON A/C NOT FOR ALL When you set the PARK BRK control switch to the ON position, this deactivates the other modes and supplies the brakes with Yellow high pressure. If Yellow high pressure is not available the brake Yellow pressure accumulator supplies power limited at 145 bar (2103.0467 psi) to the brakes.
Parking/Ultimate Emergency Braking - SchematicIf the parking brake pressure decreases to less than 35 bar (507.6320 psi) when the PARK BRK is in ON position, the system reactivates the Normal Braking mode automatically.
The accumulator has sufficient capacity to hold the brakes on for a minimum time of twelve hours. The TO CONFIG warning light (on the ECAM control panel) reminds the crew to release the parking brake when the engine is at full throttle.
2. Component Location
** ON A/C NOT FOR ALL | FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C NOT FOR ALL | |||||
| 72GG | CTL VALVE-PARK BRK,ELEC. | 148 | 32-45-51 | ||
| 73GG | CTL SW-PARK BRK | 110VU | 210 | 32-45-52 | |
| 2578GM | DUAL SHUTTLE VALVE-BRK YELLOW PRESS | 148 | 32-45-16 | ||
| 2579GM | VALVE-PARK BRK OPERATED | 148 | 32-45-14 | ||
| ** ON A/C NOT FOR ALL | |||||
| 86GG | PRESS SW-PARK BRK | 145 | 32-45-17 | ||
| ** ON A/C NOT FOR ALL | |||||
| 86GG | PRESS SW-PARK BRK | 148 | 32-45-17 | ||
3. Component Description
A. PARK BRK Control FIN: 73-GG
A two-position control switch identified PARK BRK installed on the center pedestal controls the parking/ultimate emergency braking system.
A two-position control switch identified PARK BRK installed on the center pedestal controls the parking/ultimate emergency braking system.
B. Parking-Brake Electrical Control-Valve FIN: 72-GG
The parking-brake electrical control-valve is located in the hydraulics compartment. It receives signals from the ON position of the PARK BRK control switch through an electrical linear transmitter.
The electrical control is duplicated (2 channels).
The figures below show the principle of operation of one linear transmitter channel.
When you put the PARK BRK control switch in the ON (Park) position, this energizes the linear transmitter coil. The transmitter then reaches the stop in almost 2 seconds. The limit switch de-energizes the coil.
The limit position is indicated in the cockpit through a switch connected in parallel.
When you set the PARK BRK control switch to the OFF (Normal) position, this energizes the opposite contact. The transmitter then reaches the opposite stop in almost 2 seconds. Then, another limit switch de-energizes the coil.
The linear transmitter operates a hydromechanical valve which connects the accumulator pressure from port A to service ports C and D.
The valve limits the parking brake pressure at port C up to 145 bar (2103.0467 psi). The pressure at port C pushes back the control piston which causes the valve to close.
This shuts off port B from port C and expels any excess fluid from port C to reservoir return B.
Full pressure is delivered at port D. This causes:
A thermal fuse installed in the case prevents overheating of the linear transmitter coil. The fuse is visible through a transparent cover. This cover is attached by screws. It is possible to remove this cover to reset the fuse.
The parking-brake electrical control-valve is located in the hydraulics compartment. It receives signals from the ON position of the PARK BRK control switch through an electrical linear transmitter.
The electrical control is duplicated (2 channels).
The figures below show the principle of operation of one linear transmitter channel.
When you put the PARK BRK control switch in the ON (Park) position, this energizes the linear transmitter coil. The transmitter then reaches the stop in almost 2 seconds. The limit switch de-energizes the coil.
The limit position is indicated in the cockpit through a switch connected in parallel.
When you set the PARK BRK control switch to the OFF (Normal) position, this energizes the opposite contact. The transmitter then reaches the opposite stop in almost 2 seconds. Then, another limit switch de-energizes the coil.
The linear transmitter operates a hydromechanical valve which connects the accumulator pressure from port A to service ports C and D.
The valve limits the parking brake pressure at port C up to 145 bar (2103.0467 psi). The pressure at port C pushes back the control piston which causes the valve to close.
This shuts off port B from port C and expels any excess fluid from port C to reservoir return B.
Full pressure is delivered at port D. This causes:
- operation of the secondary slide valve of the brake automatic selector to isolate the return line of the alternate brake servovalve. This prevents leakage of fluid to the Yellow reservoir.
- operation of the parking-brake operated valve.
A thermal fuse installed in the case prevents overheating of the linear transmitter coil. The fuse is visible through a transparent cover. This cover is attached by screws. It is possible to remove this cover to reset the fuse.
C. Parking-Brake Operated Valve FIN: 2579-GM
The parking-brake operated valve is installed between the brake automatic selector and the dual valve of the Alternate brake distribution. It shuts off supply to the Alternate brake system to prevent leakage through the distribution dual valve.
Parking brake pressure is delivered through port C.
The parking-brake operated valve is installed between the brake automatic selector and the dual valve of the Alternate brake distribution. It shuts off supply to the Alternate brake system to prevent leakage through the distribution dual valve.
Parking brake pressure is delivered through port C.
D. Parking Brake Pressure Switch (86GG) FIN: 86-GG
This pressure switch is installed at port B of the Dual Shutle Valve in the high pressure line.
The pressure switch indicates to the braking control system (BSCU) that the parking brake pressure is available.
With the PARK BRK control switch in the ON position, if the parking brake pressure decreases to less than 35 bar (507.6320 psi), the system gives back Normal Braking control via the brake pedals.
This pressure switch is installed at port B of the Dual Shutle Valve in the high pressure line.
The pressure switch indicates to the braking control system (BSCU) that the parking brake pressure is available.
With the PARK BRK control switch in the ON position, if the parking brake pressure decreases to less than 35 bar (507.6320 psi), the system gives back Normal Braking control via the brake pedals.