DOC AIRBUS | AMM A320FPARKING/ULTIMATE EMERGENCY BRAKING - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The parking/ultimate emergency braking system is an electrohydraulic system. Its primary function is to prevent movement of the aircraft when it is parked. It can also be used in an emergency mode to stop the aircraft if control in all the other braking modes (Ref. 32-42-00), (Ref. 32-43-00) and (Ref. 32-44-00) is not available. Use of the parking brake overrides all other braking systems when the parking brake pressure is available.
The system gets its hydraulic power supply from the accumulator of the Alternate Braking Without Anti Skid system (Ref. AMM D/O 32-44-00-00) or the Yellow Main Hydraulic Power system (Ref. AMM D/O 29-13-00-00). The accumulator has sufficient capacity to hold the brakes on for a minimum time of twelve hours.
When the selector switch PARK BRK in the cockpit is set to ON, it sends an electrical supply to the electrohydraulic park brake control valve 102GG. This valve controls the supply of hydraulic pressure to the MLG brake pistons of the Alternate Braking with Anti Skid system (Ref. AMM D/O 32-43-00-00). The hydraulic pressure available to the system (accumulator or Yellow system) and the brake pressure supplied to the MLG is shown on a triple pressure indicator (Ref. AMM D/O 32-44-00-00) in the cockpit.
If the Normal braking system is available and, if the pedals are depressed when the PARK BRK is ON and the pressure commanded by the pedal deflection exceeds the pressure delivered by the Park brake system, the Normal system will send a complement of pressure to the Normal set of pistons to reach the commanded value.
** ON A/C NOT FOR ALL 
Parking/Ultimate Emergency BrakingThe parking/ultimate emergency braking system is an electrohydraulic system. Its primary function is to prevent movement of the aircraft when it is parked. It can also be used in an emergency mode to stop the aircraft if control in all the other braking modes (Ref. 32-42-00), (Ref. 32-43-00) and (Ref. 32-44-00) is not available. Use of the parking brake overrides all other braking systems when the parking brake pressure is available.
The system gets its hydraulic power supply from the accumulator of the Alternate Braking Without Anti Skid system (Ref. AMM D/O 32-44-00-00) or the Yellow Main Hydraulic Power system (Ref. AMM D/O 29-13-00-00). The accumulator has sufficient capacity to hold the brakes on for a minimum time of twelve hours.
When the selector switch PARK BRK in the cockpit is set to ON, it sends an electrical supply to the electrohydraulic park brake control valve 102GG. This valve controls the supply of hydraulic pressure to the MLG brake pistons of the Alternate Braking with Anti Skid system (Ref. AMM D/O 32-43-00-00). The hydraulic pressure available to the system (accumulator or Yellow system) and the brake pressure supplied to the MLG is shown on a triple pressure indicator (Ref. AMM D/O 32-44-00-00) in the cockpit.
If the Normal braking system is available and, if the pedals are depressed when the PARK BRK is ON and the pressure commanded by the pedal deflection exceeds the pressure delivered by the Park brake system, the Normal system will send a complement of pressure to the Normal set of pistons to reach the commanded value.
2. Component Location
** ON A/C NOT FOR ALL | FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C NOT FOR ALL | |||||
| 73GG | CTL SW-PARK BRK | 110VU | 210 | 32-45-52 | |
| 102GG | CTL VALVE-PARK BRK, ELEC | 145 | 32-45-53 | ||
3. System Description
The parking/ultimate emergency brake system has these components:
The selector switch is a four-pole, two position (OFF/ON) switch that sends the power supplies to the two electrohydraulic control valves in the system.
The system has two independent electrical circuits each with a different power supply (service bus and hot bus). Usually the circuits are energized at the same time. Each circuit can operate the park brake control valve 102GG the other is not available.
The HP alternate brake manifold assembly 3016GM connects the hydraulic power supply lines from the Yellow system and the accumulator (Ref. AMM D/O 32-44-00-00) to the park brake control valve 102GG.
The HP alternate brake manifold assembly 3016GM includes a pressure relief valve. If the pressure in the system increases to more than a specified quantity (because of changes in temperature), the pressure relief valve connects the supply to the return. A manual depressurization switch lets maintenance personnel open the relief valve to release the accumulator pressure (for system servicing).
The manifold has a check valve to prevent the flow of fluid from the accumulator to the Yellow supply line when the Yellow line is not pressurized. A pressure transducer 3068GN (Ref. AMM D/O 32-44-00-00) attached to the manifold transmits the system pressure data to the triple pressure indicator 60GG (Ref. AMM D/O 32-44-00-00) and to the ABCU (Ref. AMM D/O 32-43-00-00).
The park brake selector valves is an electrohydraulic valve . The park brake control valve has two electric motors that can open or close the valve. When the valve is energized (open) it:
The park brake control valve also has an interface with the electrical de-activation box 5GC of the Nose Wheel Steering (N/WS) system (Ref. AMM D/O 32-51-00-00). The de-activation box includes a light that lets maintenance personnel see when the parking brake is set to ON.
** ON A/C NOT FOR ALL The parking/ultimate emergency brake system has these components:
- the park brake control switch 73GG
- the park brake control valve 102GG
The selector switch is a four-pole, two position (OFF/ON) switch that sends the power supplies to the two electrohydraulic control valves in the system.
The system has two independent electrical circuits each with a different power supply (service bus and hot bus). Usually the circuits are energized at the same time. Each circuit can operate the park brake control valve 102GG the other is not available.
The HP alternate brake manifold assembly 3016GM connects the hydraulic power supply lines from the Yellow system and the accumulator (Ref. AMM D/O 32-44-00-00) to the park brake control valve 102GG.
The HP alternate brake manifold assembly 3016GM includes a pressure relief valve. If the pressure in the system increases to more than a specified quantity (because of changes in temperature), the pressure relief valve connects the supply to the return. A manual depressurization switch lets maintenance personnel open the relief valve to release the accumulator pressure (for system servicing).
The manifold has a check valve to prevent the flow of fluid from the accumulator to the Yellow supply line when the Yellow line is not pressurized. A pressure transducer 3068GN (Ref. AMM D/O 32-44-00-00) attached to the manifold transmits the system pressure data to the triple pressure indicator 60GG (Ref. AMM D/O 32-44-00-00) and to the ABCU (Ref. AMM D/O 32-43-00-00).
The park brake selector valves is an electrohydraulic valve . The park brake control valve has two electric motors that can open or close the valve. When the valve is energized (open) it:
- reduces the pressure of the available hydraulic supply to 145 bar (2100 psi)
- sends this hydraulic supply to the alternate brake manifold assemblies (Ref. 32-43-00) of the MLG
The park brake control valve also has an interface with the electrical de-activation box 5GC of the Nose Wheel Steering (N/WS) system (Ref. AMM D/O 32-51-00-00). The de-activation box includes a light that lets maintenance personnel see when the parking brake is set to ON.
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
6. Component Description
A. Park Brake Selector Valve FIN: 102-GG
The park brake control valve is an electrohydraulic unit that controls the supply of hydraulic pressure to the parking brake system.
The park brake control valve has a body and an electrical actuator.
The body has:
The three ports are:
The selector valve bore has:
The decreased pressure bore has:
Each supply pad bore has:
The electrical actuator has:
The park brake control valve is an electrohydraulic unit that controls the supply of hydraulic pressure to the parking brake system.
The park brake control valve has a body and an electrical actuator.
The body has:
- a selector valve bore
- a decreased pressure bore
- two supply pad bores
- three hydraulic ports.
The three ports are:
- the supply port A
- the return port B
- the service port C.
The selector valve bore has:
- a ball seat, two balls and a needle
- a piston assembly to operate the selector valve
- an end fitting to hold the piston assembly in the bore
- an electrical actuator to operate the piston assembly.
The decreased pressure bore has:
- a slide valve
- a liner
- a spring, a cup and a retaining ring to hold the slide valve
- an end fitting to hold this assembly in the bore
- a spring with an end cup.
Each supply pad bore has:
- a supply pad
- a spring
- a liner.
The electrical actuator has:
- two motors which control the retraction or extension of the actuator rod
- two limit switches that cut off the power supply to the motors
- two electrical plug-in type connectors.
When the valve is in the OFF position, the actuator rod is retracted. Hydraulic pressure at supply port A holds the lower ball against the ball seat. Port A is isolated from chamber X. Spring pressure holds the slide valve in position to disconnect service port C from port A. Hydraulic fluid flows from port C to return port B.
When the valve is in operation, the actuator rod is extended. The piston assembly holds the upper ball against the ball seat. Port B is isolated from chamber X. The needle moves the lower ball away from the seat to connect port A with chamber X. Increased hydraulic pressure in chamber X makes the slide valve move against spring pressure to connect ports A and C. Hydraulic fluid then flows from port A to port C.
In the decreased pressure position, the actuator rod stays extended. Hydraulic pressure in chamber Y together with spring pressure make a higher force than the pressure in chamber X. The slide valve moves until ports A and C are disconnected. Pressure at port C is then at 'decreased pressure' (service pressure).
When the valve is returned to its OFF position, the actuator rod and piston assembly retract. This causes the upper ball to move away from the seat. The chamber X and port B are connected. Hydraulic pressure holds the lower ball against the seat. Decrease of pressure in chamber X and spring pressure moves the slide valve to connect the ports B and C. Hydraulic fluid then flows from port C to port B.
B. PARK BRK Control Switch (73GG)
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.
7. Operation/Control and Indicating
A. Parking Brake set to ON
When the park brake selector-switch 73GG is set to ON, the motors in the park brake control valve 102GG are energized to open the valve. When the valve is open, an electrical contact in the valve sends a signal to the BSCU and the ABCU. This causes the BSCU and the ABCU to isolate the other braking systems (Ref. 32-42-00), (Ref. 32-43-00) and (Ref. 32-44-00). Another electrical contact in the valve completes a circuit to the NWS electrical de-activation box 5GC (this sets the NLG PARKING BRAKE indicator light to ON).
However, if the Green hydraulic pressure is available and if the brake pedals are pushed to command a higher pressure when the PARK BRK is set to ON:
The normal braking system is automatically reactivated to add a complementary pressure to the brakes.
When the valve opens it connects the accumulator pressure (or Yellow system pressure) to its service port. The valve decreases the supply pressure to 145 bars (2103 psi). The hydraulic pressure goes to the alternate brake manifolds of each MLG. At the manifolds this causes:
The related pressure transducers monitor the pressure at the forward MLG brakes and shows this pressure at the triple pressure indicator (Ref. AMM D/O 32-44-00-00).
When the park brake selector-switch 73GG is set to ON, the motors in the park brake control valve 102GG are energized to open the valve. When the valve is open, an electrical contact in the valve sends a signal to the BSCU and the ABCU. This causes the BSCU and the ABCU to isolate the other braking systems (Ref. 32-42-00), (Ref. 32-43-00) and (Ref. 32-44-00). Another electrical contact in the valve completes a circuit to the NWS electrical de-activation box 5GC (this sets the NLG PARKING BRAKE indicator light to ON).
However, if the Green hydraulic pressure is available and if the brake pedals are pushed to command a higher pressure when the PARK BRK is set to ON:
The normal braking system is automatically reactivated to add a complementary pressure to the brakes.
When the valve opens it connects the accumulator pressure (or Yellow system pressure) to its service port. The valve decreases the supply pressure to 145 bars (2103 psi). The hydraulic pressure goes to the alternate brake manifolds of each MLG. At the manifolds this causes:
- the shuttle valves to operate
- the pressure to go to the second set of pistons in the brake units (those of the alternate braking system).
The related pressure transducers monitor the pressure at the forward MLG brakes and shows this pressure at the triple pressure indicator (Ref. AMM D/O 32-44-00-00).
B. Parking Brake set to OFF
When the selector switch is set to OFF, the motors in the park brake control valve 102GG are energized again (but in the opposite direction). The selector valve closes to:
When the selector switch is set to OFF, the motors in the park brake control valve 102GG are energized again (but in the opposite direction). The selector valve closes to:
- isolate the hydraulic power supply from the MLG brakes
- connect the brakes of the MLG to return (brakes released).
C. Indication
The triple pressure indicator 60GG shows the pressure that is available from the accumulator (Ref. AMM D/O 32-44-00-00). When the parking brake is set to ON, it also shows the pressure at the forward brakes of each main landing gear.
If the pressure of the brake yellow accumulator is low, the aural warning sounds and the master caution comes ON.The failure is shown AMBER on the displays.
The triple pressure indicator 60GG shows the pressure that is available from the accumulator (Ref. AMM D/O 32-44-00-00). When the parking brake is set to ON, it also shows the pressure at the forward brakes of each main landing gear.
If the pressure of the brake yellow accumulator is low, the aural warning sounds and the master caution comes ON.The failure is shown AMBER on the displays.