DOC AIRBUS | AMM A320FBLEED AND SURGE AIR - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The APU load compressor supplies the APU bleed air. The quantity changes with the different bleed air demands of the pneumatic systems. Variable Inlet Guide Vanes (IGVs) (which are installed at the load compressor inlet) control the quantity of the bleed air.
An APU bleed control valve is installed at the scroll outlet on the right lower part of the APU. The APU bleed control valve controls the air from the load compressor to the exhaust or to the pneumatic system of the aircraft.
The Electronic Control Box (ECB) 59KD controls and monitors the APU bleed air supply and the surge air flow. You start and stop the bleed air supply with the APU BLEED pushbutton switch, which is on the AIR overhead panel 30VU in the cockpit.
** ON A/C NOT FOR ALL The APU load compressor supplies the APU bleed air. The quantity changes with the different bleed air demands of the pneumatic systems. Variable Inlet Guide Vanes (IGVs) (which are installed at the load compressor inlet) control the quantity of the bleed air.
An APU bleed control valve is installed at the scroll outlet on the right lower part of the APU. The APU bleed control valve controls the air from the load compressor to the exhaust or to the pneumatic system of the aircraft.
The Electronic Control Box (ECB) 59KD controls and monitors the APU bleed air supply and the surge air flow. You start and stop the bleed air supply with the APU BLEED pushbutton switch, which is on the AIR overhead panel 30VU in the cockpit.
2. Component Location
** ON A/C NOT FOR ALL 
Bleed and Surge Air - Component Location| ------------------------------------------------------------------------------- |
| FIN | FUNCTIONAL DESIGNATION | PANEL|ZONE|ACCESS | ATA |
| | | | | DOOR | REF. |
| ------------------------------------------------------------------------------- |
| 8039KM SENSOR - COMPRESSOR DISCHARGE PRESS 316 316AR 49-51-19 |
| 8051KM VALVE - BLEED CONTROL 316 316AR 49-51-53 |
3. System Description
A. Primary Components
The bleed and surge air system has the subsequent primary components:
The bleed and surge air system has the subsequent primary components:
- a compressor discharge pressure-sensor,
- an air bypass duct,
- a bleed control valve.
B. Bleed and Surge Air System
The bleed and surge air system supplies the APU bleed air to the aircraft user. The ECB uses signals from the two compressor discharge pressure-sensors to calculate the bleed air flow condition. Then the ECB controls and regulated fuel pressure from the Fuel Control Unit (FCU) operates the bleed control valve to the necessary position. The bleed control valve has a discharge and a delivery position. In the discharge position the air from the load compressor is guided to the APU exhaust system through the air bypass duct. In the delivery position of the bleed control valve, the air from the load compressor is supplied to the aircraft users.
During the APU start sequence or the APU BLEED pushbutton switch is ON but no demand signal is available, the bleed control valve is in the discharge position.
When the APU BLEED pushbutton switch is in the ON position and a demand signal from the aircraft system is available, the ECB commands the bleed control valve in the delivery position.
The bleed and surge air system supplies the APU bleed air to the aircraft user. The ECB uses signals from the two compressor discharge pressure-sensors to calculate the bleed air flow condition. Then the ECB controls and regulated fuel pressure from the Fuel Control Unit (FCU) operates the bleed control valve to the necessary position. The bleed control valve has a discharge and a delivery position. In the discharge position the air from the load compressor is guided to the APU exhaust system through the air bypass duct. In the delivery position of the bleed control valve, the air from the load compressor is supplied to the aircraft users.
During the APU start sequence or the APU BLEED pushbutton switch is ON but no demand signal is available, the bleed control valve is in the discharge position.
When the APU BLEED pushbutton switch is in the ON position and a demand signal from the aircraft system is available, the ECB commands the bleed control valve in the delivery position.
4. Interface
The bleed and surge air system has an interface with:
** ON A/C NOT FOR ALL The bleed and surge air system has an interface with:
- the APU Bleed Air Supply and Crossbleed System (Ref. AMM D/O 36-12-00-00),
- the APU Load Compressor (Ref. AMM D/O 49-23-00-00),
- the APU Fuel Control (Ref. AMM D/O 49-32-00-00),
- the Control and Monitoring System (Ref. AMM D/O 49-61-00-00).
A. Bleed Control Valve (BCV)
The BCV consists of a spherical body with three flanged connections. It has a valve section with a butterfly flap, an actuator and a servo valve. The butterfly flap is driven by the fixed-link linear rotary-actuator. The actuator is controlled by the servo valve which is operated by fuel pressure from the FCU.
The ECB sends control current signals to the two solenoids of the servo valve. This allows the fuel pressure to move the actuator and position the butterfly flap in the demanded position.
A Linear Voltage Differential Transducer (LVDT) transmits position signals to the ECB. The LVDT is located inside the piston of the actuator.
The BCV consists of a spherical body with three flanged connections. It has a valve section with a butterfly flap, an actuator and a servo valve. The butterfly flap is driven by the fixed-link linear rotary-actuator. The actuator is controlled by the servo valve which is operated by fuel pressure from the FCU.
The ECB sends control current signals to the two solenoids of the servo valve. This allows the fuel pressure to move the actuator and position the butterfly flap in the demanded position.
A Linear Voltage Differential Transducer (LVDT) transmits position signals to the ECB. The LVDT is located inside the piston of the actuator.
B. Compressor Discharge Pressure-Sensors
The two compressor discharge pressure-sensors (delta P and P) are contained in one unit. The sensors measure the load compressor discharge air pressure.
The two compressor discharge pressure-sensors (delta P and P) are contained in one unit. The sensors measure the load compressor discharge air pressure.
C. Compressor Discharge Pressure Sensor
The compressor discharge pressure sensor is a unit which contains a static pressure and a differential pressure sensor. It is located at the APU air intake plenum. The pressure sensors are varable resistor devices.
The ECB uses the sensor output voltage for the calculation of the the air flow and to give the APU BLEED pressure indication for the APU page on the lower ECAM display unit.
The compressor discharge pressure sensor is a unit which contains a static pressure and a differential pressure sensor. It is located at the APU air intake plenum. The pressure sensors are varable resistor devices.
The ECB uses the sensor output voltage for the calculation of the the air flow and to give the APU BLEED pressure indication for the APU page on the lower ECAM display unit.
6. Operation/Control and Indicating
A. Start Procedure of APU Bleed-Air Supply
The start sequence of the APU is complete when the APU acquires 95% speed (Ref. AMM 49-42-00). During the start sequence the bleed control valve is in the discharge position.
Above the acquired 95% speed the APU is obtainable for the supply of bleed-air and electrical power.
Information on the ECAM and the overhead panel shows that the APU is available:
When you push the APU BLEED pushbutton switch and there is a demand signal available:
The start sequence of the APU is complete when the APU acquires 95% speed (Ref. AMM 49-42-00). During the start sequence the bleed control valve is in the discharge position.
Above the acquired 95% speed the APU is obtainable for the supply of bleed-air and electrical power.
Information on the ECAM and the overhead panel shows that the APU is available:
- on the APU page of the lower ECAM display unit, the green AVAIL indication comes on,
- on the APU overhead panel 25VU, (the green AVAIL legend on the APU START pushbutton switch comes on,
When you push the APU BLEED pushbutton switch and there is a demand signal available:
- the blue ON legend in the APU BLEED pushbutton switch comes on,
- the BMC starts a test of the sensing elements on the APU bleed-air duct and the left wing bleed-air ducts. If the test is correct the BMC transmits a signal to the ECB. Then the ECB moves the APU bleed control valve in the delivery position. The necessary air flow is supplied to the aircraft systems.
NOTE: If the BMC 1 finds a leak in the APU bleed-air ducts, while there is a Main Engine Start (MES) signal from the engines, it ignores the leak signal and commands the ECB to open the APU bleed load valve.
(1) Stop of the APU Bleed-Air Supply
To stop the APU bleed-air supply you release the APU BLEED pushbutton switch:
To stop the APU bleed-air supply you release the APU BLEED pushbutton switch:
- the blue ON legend on the APU BLEED pushbutton switch goes off,
- the BMCs removes the 'demand' signal to the ECB,
- the APU bleed control valve turns in the discharge position and the bleed air supply stops,
- on the BLEED and APU pages of the lower ECAM display unit, the APU bleed-valve symbol is shown in the closed position.
NOTE: If an APU emergency shutdown or an APU automatic shutdown occurs, the APU bleed air supply stops automatically.
NOTE: When the APU operates in the APU BLEED OFF condition:
- a random BLEED pressure figure is shown on the ECAM APU page.
- the indication on the ECAM BLEED page must not be more than 4 psi.
B. Indicating
The subsequent status of the bleed and surge air is shown on the lower ECAM display unit:
The subsequent status of the bleed and surge air is shown on the lower ECAM display unit:
- the bleed control valve position,
- the BLEED pressure indication in PSI.
(1) Bleed Control Valve Symbole
The ECB transmits the APU BLEED VALVE FC signal (label 037) from the bleed control valve to the SDACs for the position indication of the APU bleed control valve.
The ECB transmits the APU BLEED VALVE FC signal (label 037) from the bleed control valve to the SDACs for the position indication of the APU bleed control valve.
(2) BLEED Pressure Indication (PSI)
The ECB receives the air pressure signal from the compressor discharge pressure sensor. It convertes the air pressure signal into digital data and transmits the BLEED AIR PRESSURE data (label 166) to the SDACs. The SDACs uses the CORRECTED AVERAGE STATIC PRESSURE data (label 246) from the ADIRS and BLEED AIR PRESSURE data to give the indication for the APU BLEED pressure in PSI.
The ECB receives the air pressure signal from the compressor discharge pressure sensor. It convertes the air pressure signal into digital data and transmits the BLEED AIR PRESSURE data (label 166) to the SDACs. The SDACs uses the CORRECTED AVERAGE STATIC PRESSURE data (label 246) from the ADIRS and BLEED AIR PRESSURE data to give the indication for the APU BLEED pressure in PSI.