Engine Anti–Ice System Operation
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 (Common Display System) 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.
