Anti-Ice

Question 1

WING ANTI-ICE VALVE OPEN lights (L and R)

Answer 1

extinguished

• switch is OFF and corresponding wing anti-ice control valve is closed
• normal ops
• illuminated (dim)
• switch is ON and corresponding wing anti-ice control valve is open
• normal ops with WAI operating
• illuminated (bright)
• corresponding wing anti-ice control valve is in transit, or
• the position of the valve is contrary to the position of the wing anti-ice switch (disagreement lights)

Question 2

ENG ANTI-ICE switches

Answer 2

OFF
- engine anti-ice valve closes and the COWL VALVE OPEN light goes out
ON
- opens corresponding engine anti-ice valve (illuminates the cowl valve open light), signals EEC for high idle, and signals the FMC to bias fuel schedules for bleed loads.
- adjusts stick shaker and minimum maneuver speed bars on airspeed indicators
- FMC displayed VREF is not automatically adjusted.
- stick shaker and minimum maneuver speed indications return to normal when engine anti-ice is positioned off if wing anti-ice has not been used in flight
- approach idle is selected in flight if flaps are in landing configuration or engine anti ice is ON for either engine
- 72-79% N2

Question 3

COWL VALVE OPEN lights (blue)

Answer 3

• illuminated (bright) = corresponding control valve is in transit, or if not in transit, the position of the valve is contrary to the position of the associated Engine Anti-Ice switch (disagreement lights)
• illuminated (dim) = corresponding control valve is open (switch on)
• extinguished = corresponding control valve is closed (switch off)

Question 4

COWL ANTI-ICE light

Amber

Answer 4

• illuminated indicates an overpressure

Question 5

WING ANTI-ICE switch

Answer 5

OFF
- wing anti-ice control valves are closed
- VALVE OPEN lights are extinguished
ON (on the ground)
- VALVE OPEN lights illuminate bright then dim
- look for slight decrease in both duct pressure gauges
- 2nd segment climb consideration - turn on after 1000’ AGL
- adjusts stick shaker and minimum maneuver speed bars on airspeed indicators
- FMC displayed Vref is not automatically adjusted
Note: stick shaker and minimum maneuver speed bars on airspeed indicators remain set for icing conditions for the remainder of the flight, regardless of subsequent wing anti-ice switch position
CAUTION: use above approximately FL350 may cause a dual bleed trip