DOC AIRBUS | AMM A320FALTERNATE BRAKING WITHOUT ANTI SKID - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The ALTN/OFF mode is different from the mode identified above in that there is no anti skid regulation. The anti skid regulation can be disconnected:
Hydraulic changes between the Yellow high-pressure system and the accumulator are automatic and reversible.
The brake Yellow-pressure triple-indicator shows the pressure of the accumulator.
The Yellow electric pump fills the accumulator.
The accumulator can supply at least seven full brake applications.
This braking mode uses the second set of pistons in the brake units.
** ON A/C NOT FOR ALL The ALTN/OFF mode is different from the mode identified above in that there is no anti skid regulation. The anti skid regulation can be disconnected:
Alternate Braking without Anti Skid - Schematic- either electrically (A/SKID NOSE WHEEL switch in the OFF position or power supply failure),
- or hydraulically if the brake Yellow-pressure accumulator only supplies.
Hydraulic changes between the Yellow high-pressure system and the accumulator are automatic and reversible.
The brake Yellow-pressure triple-indicator shows the pressure of the accumulator.
The Yellow electric pump fills the accumulator.
The accumulator can supply at least seven full brake applications.
This braking mode uses the second set of pistons in the brake units.
2. Component Location
** ON A/C NOT FOR ALL | FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C NOT FOR ALL | |||||
| 60GG | IND-BRK YELLOW PRESS TRIPLE | 400VU | 212 | 32-44-21 | |
| 62GG | PRESS XDCR-BRK,YELLOW R | 148 | 32-44-18 | ||
| 63GG | PRESS XDCR-BRK,YELLOW L | 147 | 32-44-18 | ||
| 2582GM | ACCU-BRK YELLOW PRESS | 148 | 32-44-11 | ||
| 2585GM | BRAKE ACCU PRESS GAGE | 198 | 32-44-14 | ||
| 2586GM | N2 CHARGING VALVE | 198 | 32-44-13 | ||
| 3016GM | MANIFOLD | 198 | 32-44-17 | ||
| 3067GM | BRAKE RELIEF VALVE | 198 | 32-44-15 | ||
3. Component Description
A. Triple Pressure Indicator FIN: 60-GG
The triple pressure indicator has three dials on its front face. The top gage shows the system hydraulic pressure available (Yellow hydraulic system or accumulator), and the bottom two gages show the hydraulic pressures:
The green zone on the brake gages goes from 0 to 1000 psi. When the anti-skid is not available, the brake pressure must be less than 1000 psi to prevent wheel locking and tire burst. You must only use the green band if there is an alternate braking without anti-skid.
The indicator is installed in an octagonal case and has an electrical connection at the rear. Each pressure indication is operated with a galvanometer. A printed circuit board gives a stabilized power supply and is used for the adjustment of the galvanometers.
The triple pressure indicator has three dials on its front face. The top gage shows the system hydraulic pressure available (Yellow hydraulic system or accumulator), and the bottom two gages show the hydraulic pressures:
- That go to the left MLG brakes,
- That go to the right MLG brakes.
The green zone on the brake gages goes from 0 to 1000 psi. When the anti-skid is not available, the brake pressure must be less than 1000 psi to prevent wheel locking and tire burst. You must only use the green band if there is an alternate braking without anti-skid.
The indicator is installed in an octagonal case and has an electrical connection at the rear. Each pressure indication is operated with a galvanometer. A printed circuit board gives a stabilized power supply and is used for the adjustment of the galvanometers.
B. Brake Yellow-Pressure Accumulator and Brake Yellow Pressure Relief Valve FIN: 2582-GM FIN: 3067-GM
(1) Accumulators
The accumulator is of the bladder type filled with nitrogen.
Filling pressure.:
This accumulator is used only for braking. It is pressurized by either the Yellow hydraulic system or an electrical pump.
Check valves isolate the supply lines.
A pressure transmitter is installed in the common supply line. It transmits data on the hydraulic fluid pressure to the third input of the brake Yellow-pressure triple-indicator.
The brake Yellow-pressure accumulator supplies the system that a thermal pressure-relief valve protects. This pressure relief valve limits the pressure to 237 bars (3436 psi) if a thermal expansion occurs, and is also used for manual pressure release.
The accumulator is of the bladder type filled with nitrogen.
Filling pressure.:
- 114 bars at 60 deg.C (1653 psi at 140 deg.F),
- 100 bars at 20 deg.C (1450 psi at 68 deg.F),
- 90 bars at - 10 deg.C (1305 psi at 14 deg.F),
- 86 bars at - 20 deg.C (1287 psi at -4 deg.F).
This accumulator is used only for braking. It is pressurized by either the Yellow hydraulic system or an electrical pump.
Check valves isolate the supply lines.
A pressure transmitter is installed in the common supply line. It transmits data on the hydraulic fluid pressure to the third input of the brake Yellow-pressure triple-indicator.
The brake Yellow-pressure accumulator supplies the system that a thermal pressure-relief valve protects. This pressure relief valve limits the pressure to 237 bars (3436 psi) if a thermal expansion occurs, and is also used for manual pressure release.
(2) Accumulators
The accumulator is of the bladder type filled with nitrogen.
Filling pressure.:
This accumulator is used only for braking. It is pressurized by either the Yellow hydraulic system or an electrical pump.
Check valves isolate the supply lines.
A pressure transmitter is installed in the common supply line. It transmits data on the hydraulic fluid pressure to the third input of the brake Yellow-pressure triple-indicator.
The brake Yellow-pressure accumulator supplies the system that a thermal pressure-relief valve protects. This pressure relief valve limits the pressure to 237 bars (3436 psi) if a thermal expansion occurs, and is also used for manual pressure release.
The accumulator is of the bladder type filled with nitrogen.
Filling pressure.:
- 80 bars at 60 deg.C (1160 psi at 140 deg.F),
- 70 bars at 20 deg.C (1015 psi at 68 deg.F),
- 63 bars at - 10 deg.C (914 psi at 14 deg.F),
- 61 bars at - 20 deg.C (885 psi at -4 deg.F).
This accumulator is used only for braking. It is pressurized by either the Yellow hydraulic system or an electrical pump.
Check valves isolate the supply lines.
A pressure transmitter is installed in the common supply line. It transmits data on the hydraulic fluid pressure to the third input of the brake Yellow-pressure triple-indicator.
The brake Yellow-pressure accumulator supplies the system that a thermal pressure-relief valve protects. This pressure relief valve limits the pressure to 237 bars (3436 psi) if a thermal expansion occurs, and is also used for manual pressure release.
C. Pressure Relief and Check Valves
Two pressure relief valves, included in the Alternate-brake servovalve manifold, connect the supply to the manifold return. This connection enables the brakes to be drained in any position of the servovalve slide valve.
Two pressure relief valves, included in the Alternate-brake servovalve manifold, connect the supply to the manifold return. This connection enables the brakes to be drained in any position of the servovalve slide valve.
4. Operation/Control and Indicating
A. Operation
The Alternate brake system without anti skid (ALTN/OFF braking) is controlled, as for the Alternate braking with anti skid (ALTN/ON), through the pedals.
Artificial feel characteristics (load on pedals/pedal angle) are identical.
When the accumulator only supplies the brakes, the maximum pressure supplied to the brakes is approximately 10 bars (145 psi) higher than in ALTN/ON mode.
The leakage, which moves lightly the balanced position of the distribution dual valve, no longer changes this pressure at the Alternate brake servovalves.
When the pedals are pushed, the pressure increases at the brakes through the Alternate brake servovalves. The servovalves can operate under brake regulation as long as the internal leakage specific to the servovalves does not pressurize the return.
You can get seven full applications of the brakes if:
The Alternate brake system without anti skid (ALTN/OFF braking) is controlled, as for the Alternate braking with anti skid (ALTN/ON), through the pedals.
Artificial feel characteristics (load on pedals/pedal angle) are identical.
When the accumulator only supplies the brakes, the maximum pressure supplied to the brakes is approximately 10 bars (145 psi) higher than in ALTN/ON mode.
The leakage, which moves lightly the balanced position of the distribution dual valve, no longer changes this pressure at the Alternate brake servovalves.
When the pedals are pushed, the pressure increases at the brakes through the Alternate brake servovalves. The servovalves can operate under brake regulation as long as the internal leakage specific to the servovalves does not pressurize the return.
You can get seven full applications of the brakes if:
- you shut off the return lines of the brake servovalves,
- you partially drain the brakes when the pedal is released.
When the pedals are released: - a spring-loaded check valve discharges the pressure of the brakes but keeps it at the demanded pressure (15bars) equal to the Zero Torque Pressure (ZTP mode) in order not to waste the limited fluid capacity of the accumulator to fill the brakes for the next brake application (the Yellow brake pistons are only kept in contact with the brake pads).