Air Systems Flashcards
Bleed air can be supplied by what sources?
Engines, APU, Ground Pneumatics .
How are the Engine Bleed Air Valves actuated?
Pressure actuated, remain closed until there is sufficient pressure to cause forward flow.
How is the APU Bleed Air Valve actuated?
Automatic Electric Control, electrically actuated
What is the meaning of a momentary VALVE light on the Pneumatic Panel?
Valve is in transit.
What is the meaning of an illuminated Isolation “VALVE” light?
The valve disagrees with the commanded position.
Describe the function of the ON (flow bar in view) position of the Engine Bleed Air switch.
The engine bleed air valve opens when engine bleed air is available. Valve may close during engine start with APU, Ground Pneumatics air connected or during periods of low engine bleed air demand (packs off).
What is the meaning of an illuminated Engine Bleed Air “OFF” light?
Engine Bleed Air Valve is closed.
System fault, switch is OFF, engine is not running or bleed air pressure has not been sufficient to open the valve
Describe the function of the “OFF” position of the Engine Bleed Air Switch.
Valve is manually closed.
What is the meaning of an illuminated “HI STAGE” light?
The engine bleed system pressure is excessive, the engine high pressure bleed air valve is automatically locked closed.
What is the meaning of the “BLEED” and Engine Bleed “OFF” lights illuminating simultaneously?
Engine bleed air temperature is excessive and the engine bleed valve has closed.
What is the meaning of an illuminated “DUCT LEAK” light? Does anything happen automatically?
A high temperature bleed air leak is detected. Nothing happens automatically because the isolation valve is normally closed.
What is the function of the “STBY - N” position of the Pack Control Selector?
Normal - Regulates pack outlet temperature to a constant, moderate temperature.
What is the function of the “STBY - W” position of the Pack Control Selector?
Warm - Full warm pack operation.
What is the meaning of an illuminated “PACK OFF” light?
The Pack Valve is closed.
What is the meaning of an illuminated pack “INOP” light?
The Pack is overheated.
Fault in the automatic control system.
What is the meaning of an illuminated Pack “INOP” and “PACK OFF” light?
There has been an internal pack overheat and the pack has shut down automatically.
Which temperature zone controls the output of the air conditioning packs during automatic temperature control?
The zone requiring the coolest air.
What is the meaning of an illuminated Compartment Temperature “INOP” light?
Zone temperature failure.
Zone selector in the OFF position.
Trim air switch is OFF.
With a Compartment Temperature Control in the “OFF” position, how is the temperature in that compartment controlled?
That compartment is regulated by pack outlet temperature.
What is the purpose of the trim air system?
To condition (heat) pack air in order to maintain the selected temperature in each zone.
What happens to cabin temperature when the Trim Air System fails or the TRIM AIR switch is OFF?
The packs attempt to maintain all compartments an an average temperature (78*).
What is the purpose of the L RECIRC FAN?
The recirculation fan maintains overall cabin air circulation while allowing a reduction of cabin air ventilation by drawing air through the forward E/E system and returning it to the mix manifold. This allows the packs to be operated at a reduced flow.
Why must the L RECIRC FAN switch remain ON at all times?
Turning the fan off causes the overboard exhaust valve to open. Maintenance action is required to reset the associated STATUS message. It also causes a slight increase in fuel consumption.
What would cause an Equipment Cooling “OVHT” light?
An equipment cooling supply fan/alternate supply fan failure.
Insufficient airflow on the ground.
