and spring-actuated to the closed position andserve as system shutoff.With the pressure regulator valves in theenergized position, bleed air flows throughducting to the cyclic valves. Any time theempennage pressure regulator valve is open, theram air scoop ejector is provided with acontinuous flow of bleed air for anti-icing. Thecyclic valve solenoid, when energized, portspressure to the inlet side of the cyclic valve, andvents the outlet side of its pilot valve toatmosphere. Pneumatic pressure from the inletside causes the cyclic valve to open. Bleed air willthen flow through the ducting for that segmentto the respective piccolo tube, where it is directedto flow onto the inner skin surface to raise theskin temperature above freezing. On the wing,bleed air flows along the contour of the skin, andis vented overboard between the leading edge flaplower seal and the fixed wing. For the horizontalstabilizer, the bleed air, after leaving the piccolotube, flows spanwise in the leading edge plenum,and flows overboard at the tips.To ensure that the flow of bleed air is directedto the appropriate points regardless of thepositions of movable surfaces such as leading edgeflaps and the horizontal stabilizer, extension ductsand leakproof rotary joints are incorporated.Also, a special wing fold seal permits wing foldingwhile providing a leakproof junction when thewings are spread.The timing control provides electrical signalsto operate the pressure regulator valves and thecyclic valves in the proper sequence. The sequenceis as follows: left outboard wing, right outboardwing, left center wing, right center wing, leftinboard wing, right inboard wing, left horizontalstabilizer, and right horizontal stabilizer. Electricpower (28 Vdc) is applied to the timing controlby setting the deice switch on the environmentalpanel on the center console to WING EMP forcontinuous operations, or to SINGLE CYCLE foroperation of the system, through one completesequence. Setting the deice switch to WING EMPenergizes the solenoids on the pressure regulatorvalves, which causes all three pressure regulatorvalves to open if a bleed-air pressure of 30 psi ormore is available. This pressure allows bleed airto flow to the eight cyclic valves. If the wings arefolded, the wing pressure regulator valves will notbe energized because the wing fold interruptswitch will be in the open position. When thewings are extended, the timing control energizesthe cyclic valves in proper sequence. Each solenoidis energized for 30 seconds, which causes eachcyclic valve to be pneumatically opened by bleedair, to allow hot bleed air to flow through thepiccolo tube for 30 seconds or until the skinreaches 60°± 3°F (15°± 1.6°C) as sensed by thetemperature sensor. When the skin temperatureexceeds 60°±3°F, the temperature sensorprovides a signal to the timing control tode-energize the solenoid for that cyclic valve.For in-flight operation, setting the deice switchto SINGLE CYCLE will cause the system tooperate in the same way as it does when the deiceswitch is set to WING EMP except that uponcompletion of one sequence, the switch will returnto the OFF position. For ground operation andcheckout of the deice system, setting the deiceswitch to SINGLE CYCLE will permit the systemto function through one complete cycle even ifthe skin temperatures exceed 60°±3°F. Theinterrupt feature of the temperature sensors isdisabled only in the single-cycle mode and onlywhen the aircraft is on the landing gear.If a cyclic valve fails to fully open whenscheduled, a mechanical position switch signalsthe timing control, which causes the DEICE FAILindicator light on the annunciator panel on thecenter instrument panel to come on. This indicatorlight will go off when the 30-second interval forthat cyclic valve is completed. If the pressureregulator valve fails in the closed position, bleedair will not be available to actuate the cyclic valve.Again, the DEICE FAIL indicator light will comeon for each cyclic valve downstream from themalfunctioning pressure regulator valve.If a temperature sensor fails or a cyclic valvefails while open, which results in the skintemperature exceeding 200°± 5°F (93°± 2°C), athermo switch closes, and the DEICE HOTindicator light on the annunciator panel comes on.The WING EMP deicer system is functionalduring all normal flight operating conditions.During the engine-start cycle and during single-engine operations, the deice system is functionallyinhibited. Normal deicing becomes available whenboth engines are operating. When operating ona single engine, deice can be recovered by settingthe air-conditioning and deice switches on theenvironmental panel to OFF/RESET and WINGEMP, respectively.1-13
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business