Deice Pressure Regulating Valve

Engine and engine nacelle inlet anti-icing (fig. 1-11) is accomplished by 14th stage bleed air, which is separated, in each engine pylon, from 14th stage air being used for other environmental control system (ECS) purposes. The anti-ice switch on the environmental panel on the center console, when set to the ENG & PITOT position, opens both engine anti-icing valves by de- energizing their solenoids to direct 14th stage bleed air, regulated to 22.5 ± 2.5 psi, to the engine nacelle leading edges and engine anti-icing systems. The position of each anti-ice valve is shown on the copilot’s advisory panel; 1 A-ICE ON and 2 A-ICE ON indicator lights come on whenever the anti-ice valves are open. The engine anti-ice switch also opens the empennage pressure regulator valve to provide a source of constant bleed air to the ram air inlet duct anti-icing shroud (unless the deice system is being operated, the empennage cyclic valves will remain inactive/ closed). The engine anti-icing valve activates the entire deice system. The deice system cannot be operated until the anti-ice switch is set to the ENG & PITOT position. The bleed-air deice/anti-icing system consists of deice pressure regulating valves, bleed-air solenoid valves, a WING & EMP deice timing controller, a probe sensor temperature trans- mitter, and a deice thermostatic switch. Deice Pressure Regulating Valve The system (fig. 1-12) uses three pressure regulating valves. One pressure regulating valve Figure 1-11.—Engine anti-icing system. 1-14