Flashcards in Pneumatics Deck (12)
On the SD, when is GND displayed?
Ground HP connected. Displayed in white/green (MSN dependent) when the aircraft is on the ground.
How many BMC’s are there? What happens if left or right BMC fails?
- If one BMC fails, the adjacent BMC takes over the monitoring of the bleed system to issue the following ECAM warnings:
o Over pressure
o Over temperature
o Wing leak.
- BMC 1 lost: (ENG 1) APU bleed leak detection lost.
If CEO (IAE engine):
You also lose the ENG BLEED LEAK warning for the associated engine.
During normal operation when would you expect to see the HP valve OPEN?
- Air is normally bled from the intermediate pressure stage (IP) of engine’s high-pressure (HP) compressor to minimize fuel penalty.
- At low engine speed, when the pressure and temperature of the IP air are too low, the system bleeds air from the HP stage and maintains it at 36+/-4PSI.
- An intermediate pressure check valve downstream of the IP part closes to prevent air from the HP stage from being circulated to the IP stage.
How is the Bleed Air Temperature regulated and to what temperature?
- A pre-cooler downstream of the bleed valve regulates the temperature of the bleed air.
- The pre-cooler is an air-to-air heat exchanger than uses cooling air bleed from the engine fan to regulate the temperature to approximately 200 degrees.
How is the bleed air pressure regulated? What is the normal pressure?
- The bleed valve, which is downstream of the junction of HP and IP ducting, acts as a shut-off and pressure regulating valve.
- It maintains delivery pressure at (45 +/-5 ) PSI.
With the cross-bleed selector in AUTO, what controls the position of the crossbleed valve?
- 2 electric motors, one for automatic, one from manual mode, control the valve.
- In automatic mode, the crossbleed valve opens when the system uses APU bleed air. It closes, if the system detects an air leak, except during engine start.
What happens if a bleed leak occurs with the crossbleed selector in AUTO?
It closes. Except during engine start.
Which bleed (engine or APU) has priority?
Does the overhead panel FAULT light extinguish when the temperature drops following a bleed overheat?
The FAULT light goes out when the ENG BLEED p/b switch is OFF if the fault has disappeared.
When do the bleed air temperature and pressure go amber on the S.D?
- Pre-cooler outlet temperature overheat 290 degrees for > 5sec, 270 degrees for > 15sec, 257 degrees for > 55sec or temperature less than 150 degrees
- or < 4PSI, or if overpressure detected by BMC (threshold 57-60PSI).
Is WAI allowed if only one bleed system is operating?
Yes, if pack on that side is off.
(We think this is to ensure the pre-cooler system can maintain performance (45 PSI output)