ICE AND RAIN PROTECTION SYSTEM

The ice and rain system allows the aircraft to be operated in heavy rain and icing conditions. Hot bleed air is used for wing and engine anti-icing and, electrical heating is used for the windshields, sensors, pitot probes, static ports and drain masts. The windshields also have windshield wipers and rain repellent.

Wing anti-ice 

The three outboard slats are anti-iced with hot air form the pneumatic system. The wing anti-ice pb on the ANTI ICE panel controls the opening and closing of the pneumatic valves in each wing. On the ground, the valves will open for testing purposes but will close again after 30 seconds.The valves close automatically if a leak is detected, after landing and if there is an electrical failure.

Engine anti-ice 

The engine anti-ice valves are electrically controlled and pneumatically operated. Each engine nacelle is anti-iced by an independent air bleed from the high pressure compressor. The engine anti-ice valves are operated by their respective switches on the ANTI ICE panel. The engines must be running for the system to work, and in the event of an electrical failure, the valves will open and remain open until electrical power is restored.

When either anti-ice valve is opened the following occurs: 

• Maximum N1 is limited 

• Continuous ignition is applied 

• Minimum idle RPM is increased to provide adequate bleed air pressure.

Window heat 

Electrical heating is used for anti-icing each windshield and for de-misting the cockpit side windows. Two window heat computers (WHC); one on each side, automatically regulate the temperature and provide overheat protection.

Window heat automatically comes on when: 

• At least one engine is running or the aircraft is in flight 

• Manually before engine start, if the PROBE/WINDOW HEAT pb is pressed.

Low heat is provided on the ground and normal power in the air. The windows have a constant heat output with no changeover.

Probe Heat 

The pitot probes, static ports, angle of attack sensors, total air temperature (TAT) are all electrically heated. Three independent probe heat computers (PHC) automatically control and monitor the: 

• Captain probes 

• F/O probes 

• STBY probes 

The probes are heated automatically when: 

• At least one engine is running or the aircraft is in flight 

• Manually before engine start, if the PROBE/WINDOW HEAT pb is pressed.

On the ground the TAT probes are not heated, and the pitot heating operates in low heat until the aircraft is airborne. 

Drain masts 

The drain masts are electrically heated whenever there is electrical power on the aircraft. On the ground they operate at low heat and normal levels in flight.

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