(1) The butterfly valve is normally closed due to spring load. An inlet pressure pickup for servo air is located about 0.5 inch (12.7 mm) upstream of the butterfly valve. Refer to Figure 2.
(2) When the solenoid valve is energized, the upper chamber is vented to atmosphere through a 0.031 inch (0.79 mm) diameter orifice in the solenoid valve. The pilot valve senses downstream pressure and modulates servo air into upper chamber. This pressure controls position of the actuator and butterfly valve. When downstream pressure changes, due to a change in inlet pressure, the pilot valve compensates by increasing or decreasing modulated pressure. This changes the position of the butterfly valve to maintain regulated pressure in duct.
(3) When the valve is de-energized (closed), pressure in upper and middle chambers of valve assembly are equalized. The pressure differential across the small lower diaphragm, aided by spring pressure, causes the butterfly valve to close.
Two wing anti-ice control-valves are installed on the aircraft, one in each wing leading-edge outboard of the engine pylons. A single ON/OFF switch on the cockpit overhead panel (25VU) operates the two valves.
– isolates the anti-ice ducts from the pneumatic system bleed-air supply when anti-icing is not required
-当不需要防冰时, 隔绝防冰导管和气源系统引气
– controls the pressure of the wing anti-ice bleed-air, supplied by the pneumatic system.
-控制机翼防冰引气压力, 通过气压系统压力。
The valves are selected electrically and actuated pneumatically. If an electrical failure occurs, the valves will automatically go back to the closed position. The valves can be locked in the closed position to let the aircraft operate in non-icing conditions.
When the valve(s) is/are locked in the CLOSED position, the aircraft is not permitted to fly into icing conditions. A microswitch in the anti-ice valve senses when the valve is closed and gives a CLOSED/NOT CLOSED signal to the Environmental Control System Zone Control and Bleed Status Computer (ECS computer) and the Electronic Centralized Aircraft Monitoring (ECAM) system.A visual/mechanical valve position indication is also given.
The wing ice protection system is supplied with hot air from the pneumatic system, downstream of the pre-cooler. The anti-ice control valve (in the wing, outboard of the engine pylon) isolates these two systems. A restrictor downstream of the anti-ice control valve controls the air flow.The hot air goes through a lagged duct that connects the anti-ice control valve to the telescopic duct, inboard of RIB 13. The telescopic duct only attaches to the piccolo ducts in the slat 3. The piccolo ducts 3, 4 and 5 (that connect together with flexible ducts) release the hot air to heat the slats. The piccolo ducts release the air into the slats through holes along their foward length. The air flows around the forward area of the slat then goes through acceleration slots into the rear section. It is then released overboard through the holes in the bottom surface of the slat.
The wing ice protection system prevents ice on the leading edge of the slats 3, 4 and 5. The system, which is the same in the LH and the RH wing, uses hot air from the pneumatic system (Ref. 36-00-00). It is available in all flight conditions. The two engines usually supply the pneumatic system with bleed air. If there is a failure, the cross-bleed valve opens and one engine can supply the two wings.The system is only used during flight, but can be tested on the ground. To prevent heat damage to the slats, the ground test stops automatically after 30 seconds.