Airbus A320 Pneumatics Flashcards
What are the possible sources of Pneumatic Air?
Engine Bleed
APU Bleed
External HP Air
What 5 purposes has the Pneumatic System?
To provide compressed air as a source for:
- Air Conditioning
- Engine Starting
- Wing Anti Icing
- Water Pressurisation
- Hydraulic Reservoir Pressurisation.
What are BMCs and how many are there?
Bleed Monitoring Computers
( or, sometimes, Bleed Management Computers, ‘Monitoring’ however is the official name.)
There are 2.
How are engine bleed valves signalled and operated?
Signalled electrically from the BMCs.
Operated pneumatically by upstream (i.e. engine side) Engine Bleed Air.
With the engine running, will the engine bleed valve Open?
Yes it will.
Unless electrically signalled Closed, or in order to prevent reverse flow.
What conditions will cause the BMC to signal the Bleed valve closed.
- On-side engine starting
- APU Bleed valve Open
- downstream Overpressure or Overheat
- Leak detected (in the Onside Wing or Pylon only.)
What other electrical signals will cause the Engine Bleed valve to be signalled closed?
- Engine Fire p/b pressed
- Engine Bleed p/b to OFF.
During Climb and Cruise, is Air bled from the IP or the HP stages of the engines?
IP.
The HP valve is only required when IP pressure is low and will maintain Bleed Pressure to 36+- 4 psi.
If the Engine Bleed valve is closed electrically, what happens to the HP Valve?
It too is electrically signalled closed.
To what pressure is bleed air controlled and by which component?
45+- 5 psi.
By the Engine Bleed Air Valve in its Pressure Regulating role.
How is Bleed Air Temperature regulated and to what temperature?
A pre-cooler uses Fan Air to reduce the temperature of the bleed air to 200 deg C.
How is the APU Bleed Air Valve signalled and operated?
Signalled OPEN electrically from either BMC
Operated pneumatically by Upstream APU Bleed Air Pressure.
With the APU able to produce Bleed Air, but in the absence of any control signal, will the APU Bleed Valve open or close.
It will remain closed unless electrically signalled Open by a BMC.
What conditions must be fulfilled before the APU Bleed Valve is signalled open?
- Bleed Switch ON
- APU speed > 95%
- No leaks ( but this is ignored during engine start. )
What is the effect on the pneumatic system when the APU Bleed Valve opens?
- Cross-bleed Opens ( if in AUTO)
- Both Engine Bleed Valves signalled closed.
Note: This action lies at the heart of Pneumatic System functionality:
APU Bleed Valve Open = X-Bleed Valve Open + Engine Bleed Valves Closed
APU Bleed Valve Closed = X-Bleed Valve Closed + Engine Bleed Valves Open.
To which side of the Pneumatic System does the APU Bleed supply connect?
The Left side.
In AUTO mode, APU Air in use, what will cause the X-Bleed Valve to be signalled closed?
Any leak detected (other than during engine start.)
Which areas on the aircraft are monitored for Pneumatic Air Leaks?
- Wing leading edge
- Pylon (Engine)
- APU supply duct.
What will be the effect of a Left Wing Leak being detected?
- FAULT light on Left Bleed p/b
- Appropriate ECAM Caution
- Left Engine Bleed signalled closed
- APU Bleed signalled closed
- X-Bleed signalled closed
NB: During engine start APU & X-Bleed Valves remain open until start complete, the Engine Bleed valve is closed anyway.
What will be the effect of a Right Wing Leak being detected?
- FAULT light on Right Bleed p/b
- Appropriate ECAM Caution
- Right Engine Bleed signalled closed
- X-Bleed signalled closed
NB: During engine start X-Bleed Valve remains open until start complete, the Engine Bleed valve is closed anyway.
APU Bleed valve is unaffected by a Right Wing Leak.
What is the effect of a Pylon (Engine) Leak?
- Onside Bleed Valve FAULT light & ECAM Caution ( except during engine start.)
- Onside Engine Bleed Valve signalled closed
- X-Bleed signalled closed.
What is the effect of an APU Duct Leak?
- APU Bleed p/b FAULT light (and ECAM.)
- APU Bleed Valve signalled closed (except during engine start.)
- X-Bleed signalled closed (except during engine start.)
Note: Closure of the APU Bleed Valve will allow Engine Bleed Valves to open if Engine is running.