TM 1-1520-238-102-60Section IX.UTILITY SYSTEMS2.42 DEFOGGING SYSTEM.The CANOPY DEFOG switch on the pilot ANTI ICE panelallows the pilot to direct pressurized air (with ECS on oroff) to diffuser outlets at each canopy side panel. Whenthe CANOPY DEFOG switch is set to ON, 28 vdc from theNo. 1 essential dc bus through the ECS CANOPY ANTIICEcircuit breaker causes the defog valve to open. Thisallows hot air from the pressurized air system to flowthrough the shutoff valve to the air mixers. The hot pres-surized air mixes with the crew station conditioned air inthe air mixers. This partially cooled air is directed againstthe canopy side panels to defog them.PILOT ANTI-ICE PANELAUXANTI–ICEADSSOFFSTBY FANOFFTADS/PNVSGNDONOFFW WIPERCPGPILOTCPG AUX / ANTI-ICE PANELM01-018Figure 2-33.Pilot and CPG Anti-Ice Control Panels2.43 ANTI-ICING AND DE-ICING.Multiple anti-icing and de-icing protection is available forthe windshields, pitot tubes, air data sensor, pilot night vi-sion sensor (PNVS), target acquisition designation sight(TADS), engine inlets, nose gearboxes, and main and tailrotor blades. The 30mm weapon and the wing pylons arealso susceptible to icing and may be de-iced by periodicflexing in azimuth or elevation. The pilot and CPG haveANTI-ICEpanels on their left consoles (fig 2-33).2.43.1 Windshield Anti-Ice/De-Ice.The two wind-shields, one in front,and the other directly above theCPG, have built-in transparent anti-ice elements that areheated by 115 vac to prevent ice accumulation. The pilotactivateswindshield heating by setting a two-positionCANOPY HTRtoggle switch on his ANTI-ICEpanel toON. In the ONposition, the CANOPY HTR switch pro-vides 28 vdc from the No. 1 essential dc bus through theCANOPY ANTI-ICE CONTRcircuit breaker on the pilotoverhead circuit breaker panel to turn on the windshieldanti-ice control unit. When the control unit is operating,115 vac from the No. 2 essential ac bus through the CAN-OPY ANTI-ICEcircuit breaker on the pilot overhead circuitbreaker panel is provided to the control unit. The 115 vacis distributed by the control unit to the window heater ele-ments. The control unit is provided with temperature con-trol and fail-safe features. When there is a failure in thewindshield anti-ice system, the control unit will remove the115 vac power from the unit. If the cause for the failure isan overheat or false temperature sensor signal, the con-trol unit can be reset by turning the CANOPY HTR switchOFFand then back ON. Whenever the control unit, cano-py heaters, canopy temperature sensors, or input powerfails, or if the canopy overheats with the CANOPY HTRswitch in the ON position, the CANOPY ANTI-ICE FAILlight on the pilot caution/warning panel will illuminate.2.43.2 Pitot Tube and Air Data Sensor Anti-Ice/De-Ice.The pitot tubes, installed outboard on the leadingedge of both wings, and the air data sensor, attached tothe top of the main rotor de-ice distributor are protectedfrom ice accumulation by internal heating elements. ThePITOT AD SNSRswitch, located on the pilot ANTI-ICEpanel, is a dual function switch. In the ON position, theright hand pitot heater receives 28 vdc from the emergen-cy dc bus through the PITOT HTRcircuit breaker. Thesecond function of the switch provides 28 vdc from the No.3 essential dc bus through the
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