Anti-Ice, Rain -System Description 737 Flight Crew Operations Manual
YA613, YA626, YC153 - YC413, YK101 - YK104 Pitot probes, the total air temperature probe and the alpha vanes are electrically heated. Static ports are not heated. When operating on standby power, only the captain’s pitot probe is heated, however, the CAPT PITOT light does not illuminate for a failure.
Note:  The pitot probe for standby airspeed is not heated when the airplane is on standby power.
Engine Anti–Ice System
Engine bleed air thermal anti–icing prevents the formation of ice on the engine cowl lip. Engine anti–ice operation is controlled by individual ENG ANTI–ICE switches. The engine anti–ice system may be operated on the ground and in flight.
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 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.
Copyright . The Boeing Company. See title page for details.

Anti-Ice, Rain -System Description

Engine Anti–Ice System Schematic
COWL  COWL 
ANTI-ICE  ANTI-ICE 
COWL VALVE  COWL VALVE 
OPEN  OPEN 

Copyright . The Boeing Company. See title page for details.
3.20.8  June 1, 2005

Anti-Ice, Rain -System Description 737 Flight Crew Operations Manual
Wing Anti–Ice System
The wing anti–ice system provides protection for the three inboard leading edge slats by using bleed air. The wing anti–ice system does not include the leading edge flaps or the outboard leading edge slats.
The wing anti–ice control valves are AC motor–operated. With a valve open, bleed air flows to the three leading edge inboard slats, and is then exhausted overboard. The wing anti–ice system is effective with the slats in any position.
Wing Anti–Ice System Operation
On the ground, positioning the WING ANTI–ICE switch ON opens both control
valves if thrust on both engines is below the setting for takeoff warning activation
and the temperature inside both wing distribution ducts is less than the thermal
switch activation temperature.

Both valves close if either engine thrust is above the takeoff warning setting or
either temperature sensor senses a duct overtemperature. The valves automatically
reopen if thrust on both engines is reduced and both temperature sensors are cool.

With the air/ground sensor in the ground mode and the WING ANTI–ICE switch
ON, the switch remains in the ON position regardless of control valve position.
The WING ANTI–ICE switch automatically trips OFF at lift–off when the
air/ground sensor goes to the air mode.
Positioning the WING ANTI–ICE switch to ON in flight:

. opens both control valves
. sets stall warning logic for icing conditions.
Note: Stall warning logic adjusts stick shaker/minimum maneuver speed bars
on airspeed indications. FMC displayed VREF is not adjusted
automatically.
Note: Stall warning logic remains set for icing conditions for the remainder
of the flight, regardless of subsequent WING ANTI–ICE switch
position.
Valve position is monitored by the blue VALVE OPEN lights. Duct temperature and thrust setting logic are disabled and have no affect on control valve operation in flight.
Copyright . The Boeing Company. See title page for details.
Anti-Ice, Rain -System Description

Wing Anti–Ice System Schematic

Copyright . The Boeing Company. See title page for details.
3.20.10  June 1, 2005

Controls and Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10.1
Mode Control Panel (MCP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10.1 Speed Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10.2 Vertical Navigation  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10.6 Lateral Navigation  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10.12 Autopilot / Flight Director . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10.18 Autopilot / Autothrottle Controls . . . . . . . . . . . . . . . . . . . . . . . . 4.10.21 Autopilot / Autothrottle Indicators . . . . . . . . . . . . . . . . . . . . . . . 4.10.22 Thrust Mode Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10.23 Flight Mode Annunciations (FMAs)  . . . . . . . . . . . . . . . . . . . . .  4.10.25
　
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