Section IX. UTILITY SYSTEMS

TM 1-1520-238-10 2-60 Section IX. UTILITY SYSTEMS 2.42 DEFOGGING SYSTEM. The CANOPY DEFOG switch on the pilot ANTI ICE panel allows the pilot to direct pressurized air (with ECS on or off) to diffuser outlets at each canopy side panel. When the CANOPY DEFOG switch is set to ON, 28 vdc from the No. 1 essential dc bus through the ECS CANOPY ANTI ICE circuit breaker causes the defog valve to open. This allows hot air from the pressurized air system to flow through the shutoff valve to the air mixers. The hot pres- surized air mixes with the crew station conditioned air in the air mixers. This partially cooled air is directed against the canopy side panels to defog them. PILOT ANTI-ICE PANEL AUX ANTI–ICE ADSS OFF STBY FAN OFF TADS/PNVS GND ON OFF W WIPER CPG PILOT CPG AUX / ANTI-ICE PANEL M01-018 Figure 2-33. Pilot and CPG Anti-Ice Control Panels 2.43 ANTI-ICING AND DE-ICING. Multiple anti-icing and de-icing protection is available for the windshields, pitot tubes, air data sensor, pilot night vi- sion sensor (PNVS), target acquisition designation sight (TADS), engine inlets, nose gearboxes, and main and tail rotor blades. The 30mm weapon and the wing pylons are also susceptible to icing and may be de-iced by periodic flexing in azimuth or elevation. The pilot and CPG have ANTI-ICE panels 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 the CPG, have built-in transparent anti-ice elements that are heated by 115 vac to prevent ice accumulation. The pilot activates windshield heating by setting a two-position CANOPY HTR toggle switch on his ANTI-ICE panel to ON. In the ON position, the CANOPY HTR switch pro- vides 28 vdc from the No. 1 essential dc bus through the CANOPY ANTI-ICE CONTR circuit breaker on the pilot overhead circuit breaker panel to turn on the windshield anti-ice control unit. When the control unit is operating, 115 vac from the No. 2 essential ac bus through the CAN- OPY ANTI-ICE circuit breaker on the pilot overhead circuit breaker panel is provided to the control unit. The 115 vac is 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 the windshield anti-ice system, the control unit will remove the 115 vac power from the unit. If the cause for the failure is an overheat or false temperature sensor signal, the con- trol unit can be reset by turning the CANOPY HTR switch OFF and then back ON. Whenever the control unit, cano- py heaters, canopy temperature sensors, or input power fails, or if the canopy overheats with the CANOPY HTR switch in the ON position, the CANOPY ANTI-ICE FAIL light 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 leading edge of both wings, and the air data sensor, attached to the top of the main rotor de-ice distributor are protected from ice accumulation by internal heating elements. The PITOT AD SNSR switch, located on the pilot ANTI-ICE panel, is a dual function switch. In the ON position, the right hand pitot heater receives 28 vdc from the emergen- cy dc bus through the PITOT HTR circuit breaker. The second function of the switch provides 28 vdc from the No. 3 essential dc bus through the