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Engine Bleed System
Air is bled from 2 compressor stages: the IP port (5th stage) and the HP port (9th stage). Pressure is regulated and modulated to balance the air flow between the 2 engines on the same wing.
The two systems (engines 1 and 2, engines 3 and 4) are connected via a crossbleed duct which has a crossbleed valve. APU bleed air and external GPU air connect to the left (#1, #2) side of the duct.
There are 4 interconnected BMCs to control and monitor the system. If 1 BMC fails, the adjacent BMC takes over most of its functions. Only BMC 2 performs APU bleed leak detection.
Failures
| FAULT Lights | Valve Closures | |
| Pylon leak | 1 | 2 |
| Wing leak | 2 | 2 |
An APU leak closes the engine bleed valves on the left side of the duct (#1 and #2).
Categories: Airbus A340 | Pneumatic System | Engine Bleed System