36 - Pneumatics Flashcards
The A330 Pneumatic system supplies high pressure air for…
The A330 Pneumatic system supplies high pressure air for the Air Conditioning system, engine starting, wing anti-icing, water tank pressurization, hydraulic reservoir pressurization, and pack bay ventilation turbofan actuation.
The three sources of high pressure air for the pneumatic system are:
engine bleed, APU bleed and two external HP air ground connections.
Pneumatic system operation is controlled and monitored by
two Bleed Monitoring Computers (BMC 1 and 2), the overhead control panel and the ECAM. The APU Electronic Control Box (ECB) controls the APU bleed supply.
The two Bleed Monitoring Computers …
control and monitor each bleed system. In case of failure of one Bleed Monitoring Computer, the other takes over most of the monitoring functions.
What compressor stages feed the bleed systems?
Normally the intermediate pressure stage of the HP compressor supplies air to the pneumatic system. When pressure drops, due to low engine speed for example, the HP valve opens to maintain a pressure of 40 +/- 4 psi.
When the APU bleed valve opens, when does the eng 2 bleed valve closes?
The engine 2 bleed valve closes, when the APU bleed valve opens, only if the crossbleed valve is open.
Describe the precooler.
A precooler uses engine fan air to cool and regulate the temperature of the engine bleed air to 200 °C. The fan air valve is pneumatically operated and electrically controlled.
When does the X-bleed open?
In automatic mode the valve is normally closed and opens when APU bleed air is used.
What are the conditions for the Bleed valves to open?
The engine bleed valve will open if: engine bleed pressure is greater than 8 psi, no onside wing or pylon leak, the APU bleed valve is closed, there are no bleed faults detected, the ENG FIRE pb sw is not released out, and the engine start valve is closed.
ENG BLEED pb FAULT
The ENG BLEED pb sw will show FAULT if: there is a bleed overpressure, a bleed overheat, a wing or engine pneumatic leak, or if the engine bleed valve is not closed either during engine start, or if the APU BLEED pb sw is selected ON. When the fault condition returns to a temperature or pressure below the set limit, and the ENG BLEED pb sw is left ON, the FAULT light will remain illuminated.
The conditions for the APU bleed valve to open are:
The conditions for the APU bleed valve to open are: the APU must be operating at normal speed, there is no leak detected on the APU or left side bleed ducts, and the APU BLEED pb sw must be ON.
Further, the aircraft must be below 25,000 ft during a climb or below 23,000 ft while descending. If a leak should occur on the right side, the crossbleed would close.
What happens when the APU BLEED pb se is selected to ON?
With the APU BLEED pb sw selected ON, the APU bleed valve opens if the APU speed is greater than 95 %. This causes the crossbleed valve to open and the engine bleed valves to close.
What BMC performs APU BLEED LEAK detection?
Only BMC 1 performs APU bleed leak detection.
What happens if the APU BLEED pb sw is selected OFF and engines are running?
If the APU BLEED pb sw is selected OFF both the APU bleed valve and crossbleed valve will close. The engine bleed valves will open if the engines are running and the ENG BLEED pb sw’s are ON.
Where are the leak detection loops?
Leak detection loops are located in the fuselage, pylons, wings and APU duct.
