This report represents investigation and analyzes Airbus A318 pneumatic system. On the other hand, aircraft pneumatic systems will be lay-out in this report. The sources of supply in this system both main and standby will also be mention. The last is the pressure and temperature control in this system will be analysed.
The purpose of this report is to analyzing Airbus A318 pneumatic systems and the function of pneumatic systems in Airbus A318.
The function Pneumatic system is used to provide High pressure (HP) for air-conditioning, pressurization, pressurization and anti-icing. Engine bleed, APU and external ground service are used to produce HP.
The engine bleed air is the air taken within the engine compression stage when pressure and temperature regulated prior. High Pressure Compressor (HPC) stages, intermediate Pressure (IP) stages and HP stages are the place where the air is bled.
When the engine in low power condition, the High Pressure Bleed Valve (HPV) will function and supply air to the systems. But, when the pressure inside the IP bleed is sufficient, HPV will closes.
HP Valve (HP VLV)
HP VLV is switch ON when the IP stage is no enough pressure for pneumatically systems (when engine at low speed). The pressure supply is between 8 to 36 psi. HP VLV is force to close when PRV is closed because HP VLV pressure should no more than PRV pressure. If the sense line over the limitation, the system will over pressure and cause malfunction.
The function of Bleed Monitoring Computer (BMC) is to maintain HP VLV closed during the flight.
The HP VLV solenoid will active by BMC when:
The engine is greater than Idle and pressure is over 80psi.
When the Wing Anti Ice (WAI) is OFF condition
The altitude is over 15,000 feet
The pack configuration is act normal.
When solenoid is de-energized, this mean the HP VLV will open. This condition is restrained.
IP check valve
IP check valve is used to prevent the air flow in the anti-direction. When the HP VLV opens, IP check valve will make sure hit air at IP stage wouldn't flow back to the engine.
Pressure Regulating Valve (PRV)
The purpose PRV is used to maintain the bleed pressure between 44 psi. Thermal fuse is used to causes the PRV to close when the engine's case temperature was around 450°C.
Control Solenoid (CTL SOL)
The CTL SOL is located downstream from the precooler. The purpose is to control PRV pressure will going to bleed out. These systems are operated by pneumatic and electric.
The CTL solenoid will energize by BMC when:
Over temperature of the precooler
Over pressure of the PRV
Leak detection surrounding area
APU bleed valve not close
Starter Valve not closed
Overpressure Valve (OPV)
This valve is normally open condition, close when pressure is apply on this valve. This valve closes at 75psi and fully closed at 85. It will open around 35psi.
It is act as a transducer. It is connected to both BMCs and analyzes the pressure from PRV.
This component is also same function as regulated pressure. But it is used to read from HPV and PRV.
Fan Air Valve (FAV)
It is used to control the fan airflow to the precooler and maintain bleed air temperature at 200°C.
FAV Control Thermostat (CTL THERMST)
Act as external servo-control. It is located downstream from the precooler.
Heat Exchanger (Precooler)
It is used to reduce the temperature engine bleed air.
Heat Exchanger Outlet Temperature Sensor
This component is connected to both BMCs. It is use to control temperature downstream from the precooler.
APU Bleed/ External Air
APU is used to bleed air supply for air- conditional and engine start when the aircraft was on the ground. On the other hand, APU also use to provide electrical power to supply the electrical systems. APU bleed act as a backup power for both systems. The both bleed systems are fastening together by a cross bleed duct.
External air also can be use during in flight, depend on the high of the aircraft. When in flight, the APU bleed supply only supplied by the left hand side of the cross bleed duct.
APU bleed valve is used to supply APU is running. The valve is operated by electrically by the Electrical Control Box (ECB) solenoid and pneumatic. When air pressure and electrical power are unavailability, valves spring -loaded will shut off.
Electrical Control Box (ECB)
It is use to monitor the pressure and closes or opens the APU bleed valve.
The function of X-Bleed system is to interconnection of left and right bleed air are system. In the systems, it consists of shut-off valve operated by electrical two DC motors. Primary motor will function in AUTO mode. The position of the shut off valve is controlled by the (BMC) according to the APU bleed configuration. Secondary motor will be used to over dominate the AUTO mode. The position of the valve is manipulated by X-bleed selector.
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Ground Air Supply
It is used so supply air by a ground air cart and connected to the HP ground connector. When ground air cart is connected, only the left hand side of the bleed systems has supply. Left hand side and right hand side bleed system will feed with ground air supply when X-bleed valve selector will be select in the OPEN position.
SYSTEMS OVERVIEW - ENGINE BLEED & APU BLEED/ EXTERNAL AIR
(From MAINTENANCE COURSE BOOK - T1 (CFM56-5B/ME Title: Pneumatic Level) Page 3
Airbus A318 pneumatic systems are supply by engine bleed, APU and the Ground air supply. Engine bleed are used provide air pressure when aircraft engine is low power condition. The pressure is control by the HP valve. After the pressure inside the IP bleed is sufficient, high pressure valve (HPV) will shut down.
APU is used as standby pneumatic system. It is used to provide electrical power to function the electrical and environment systems. It is used when the aircraft on the ground. APU also used when in flight condition depending on the altitude of the aircraft.
It is used so supply air by a ground air cart and connected with HP ground connector. Air only was supply to left hand side of bleed system. So, crossbleed valve will use to feed the air systems to the right hand side of the bleed system.
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