( used by the cabin pressure control system )
These valves are used to control the airflow which needs to be sent out of the fuselage to keep the pressure at the required level inside the aircraft cabin. Two kinds of outflow valves are existing on modern commercial airliners :
1) The butterfly type outflow valves :
They are often installed on the front or on the aft bulkhead of the aircraft fuselage.
They are made of an aerodynamic shaped body including a plate moving around a shaft to open or close the valve depending of its position. This plate called a butterfly is driven by an electrical actuator.
2) The flappers type outflow valves:
They are always installed on the fuselage surface so as to provide an interesting effect : the thrust recovery.
This kind of valve is made of a rectangular housing including two flappers. The aft one can move outward, the forward flapper opens inward. Through these special positions these two flappers create a two dimensionnal nozzle directed as far as it is possible in line with the aircraft speed . The airflow leaving the cabin through this valve creates a small thrust which contributes to a fuel economy, this is what we call the thrust recovery :
MAIN SITE NAVIGATION :
bleed air system / air cooling system / zone temperature control system / cabin pressure control system