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13. Ice & rain protection

13.1. Wing anti-ice
13.2. Engine anti-ice
13.3. Window heat
13.4. Probe heat
13.5. Other

13.1. Wing anti-ice

The three outboard slats of each wing are anti-iced using hot bleed air from the pneumatic system. APU bleed air must not be used for wing anti-icing. Each wing has a single electrically (DC ESS SHED) operated valve that controls flow of air to the slats. Both valves are controlled by a single WING button on the anti-ice panel. The valves fail closed in the event electrical power is lost.

Selecting wing anti-ice causes the FADECS to decrease N1 limit and increase idle N1.

If a hot air leak is detected, the wing anti-ice valve on the affected side automatically closes.

If the WING button is pushed on the ground, a 30 second self test of the wing anti-ice system is initiated. If left on, the valves will open automatically once airborne.

13.2. Engine anti-ice

The engine air intakes are anti iced using an independent air bleed from the HP compressor. For each engine, hot air is routed via an electrically controlled (DC1 and DC2), pneumatically operated engine anti-ice valve to the intake. These are controlled by the ENG1 and ENG2 buttons on the anti-ice panel. The valves close if no air is available, but fail open if electrical power is lost.

The fan blades are not anti-iced. If icing conditions last longer than 30 minutes or significant icing induced engine vibrations occur, the fan ice can be shed by running the engines up to 70% N2 for 30 seconds [FCOM] (n.b. parking brake limitation of 75% N1 [FCOM]). This run up should also be carried out just prior to takeoff if conditions require it. In freezing rain, freezing fog or heavy snow, ice shedding can be enhanced by momentary run ups to 70% at intervals of less than 10 minutes.

13.3. Window heat

The windshield and side windows are heated electrically. Each side has an independent Window Heat Computer (WHC) that automatically regulates the system and provides overheat protection and fault detection. The window heat operates whenever at least one engine is running. On the ground, the windshield heat operates in a low power mode, with an automatic changeover to normal power once airborne. The windows only have one heating level. If window heat is required before engine start it can be switched on manually with the PROBE/WINDOW HEAT button on the anti-ice panel.

13.4. Probe heat

The pitot heads, static ports, AOA probes and TAT probes are elecrically heated. The Captain's probes, F/O's probes and standby probes each have an independent Probe Heat Computer (PHC). These provide automatic regulation, overheat protection and fault detection. The probes are heated whenever at least one engine is running. On the ground, the pitot heating operates at low level and the TAT probes are not heated. Changeover to normal heating is automatic once airborne. If probe heat is required before engine start it can be switched on manually with the PROBE/WINDOW HEAT button on the anti-ice panel.

13.5. Other

Each front windshield has a two-speed electric wiper controlled by a rotary selector. The maximum speed for wiper use is 230kt [FCOM 3.1.20].

In moderate to heavy rain only [FCOM], rain repellent can be applied to the windshield. Each windshield has an independent RAIN RPLNT button that applies a measured quantity when pressed. The rain repellent is stored in a nitrogen pressurised bottle in the rear cockpit. If the pressure gauge is in the yellow or the REFILL float is visible, the bottle needs replacing. A smell of orange peels in the cockpit may indicate a toxic leak of rain repellent fluid. A smell of pine needles may indicate a non-toxic leak [FCOM].

An external lighted visual ice detector is installed between the two windshields.

The water drain masts are electrically heated. This heat is reduced when on the ground.