Engine Anti–Ice System Operation
Each cowl anti–ice valve is electrically controlled and pressure actuated.
Positioning the ENG ANTI–ICE switches to ON:
Note: Stall warning logic adjusts stick shaker and minimum maneuver speed
bars on airspeed indications. FMC displayed VREF is not adjusted automatically.
Note: Stall warning logic, airspeed indications, and minimum maneuver speeds
on the airspeed indicator return to normal when engine anti–ice is positioned
OFF if wing anti–ice has not been used in flight.
If the cowl anti–ice valve fails to move to the position indicated by the ENG ANTI–
ICE switch, the COWL VALVE OPEN light remains illuminated bright blue and an
amber TAI indication illuminates on the CDS after a short delay.
The amber COWL ANTI–ICE light illuminates due to excessive pressure in the
duct leading from the cowl anti–ice valve to the cowl lip.
Each cowl anti–ice valve is electrically controlled and pressure actuated.
Positioning the ENG ANTI–ICE switches to ON:
- Allows engine bleed air to flow through the cowl anti–ice valve for cowl lip
anti–icing.
- Sets stall warning logic for icing conditions.
Note: Stall warning logic adjusts stick shaker and minimum maneuver speed
bars on airspeed indications. FMC displayed VREF is not adjusted automatically.
Note: Stall warning logic, airspeed indications, and minimum maneuver speeds
on the airspeed indicator return to normal when engine anti–ice is positioned
OFF if wing anti–ice has not been used in flight.
If the cowl anti–ice valve fails to move to the position indicated by the ENG ANTI–
ICE switch, the COWL VALVE OPEN light remains illuminated bright blue and an
amber TAI indication illuminates on the CDS after a short delay.
The amber COWL ANTI–ICE light illuminates due to excessive pressure in the
duct leading from the cowl anti–ice valve to the cowl lip.
