boeingggg 737 ice and rain protection

7/24/2019 Boeingggg 737 Ice and Rain Protection

1/12

CopyrightSmartcockpit.comLudovic ANDRE / version 00

Smartcockpit.com BOEING 737 SYSTEMS REVIEW Page 1

ICE & RAIN

1. GENERAL

The systems provided for ice and rain protection are Thermal Anti-icing (TAI) & electrical anti-icing.

All 737 Classics pitot-static probes, 737 NG pitot probes, the Total Air Temperature probe, the 737Classics angle of airflow sensors and 737 NG alpha vanes are electrically heated to prevent theformation of ice. Static ports are not heated.

2. COCKPIT WINDOWS

The cockpit windows are provided with electrical heating for anti-icing and defogging.

Heating the windows No. 1 and No. 2 also improves the impact strength of the windows for bird-strikeprotection.

Air from the air-conditioning system can be used to defog the No. 1 cockpit windows.

The windows No. 1 & No. 2 consist of glass panes laminated to each side of a vinyl core. The innerglass pane is the primary load carrying member. The vinyl core also acts as a backup load carryingmember. The outer pane has no structural significance but provides a scratch resistant surface. Aconductive coating on the outer pane permits electrical heating to prevent ice build-up and windowfogging. B737 NG : A permanent rain repellent coating is applied to the windows.

Windows No. 3, 4 and 5 are similar in construction in that both consist of glass panes laminated toeach side of a vinyl core. A conductive coating on the inner glass pane permits electrical heating toprevent fogging. Window No. 4 has an additional vinyl layer and acrylic sheet laminated to the insidesurface.

The FWD Window Heat Switches control heat to window No. 1. The SIDE Window Heat Switchescontrol heat to windows No. 2, 3, 4 & 5.

Temperature sensors, through control units, maintain windows No. 1 & 2 at the correct temperature.Power is automatically removed if an overheat condition is sensed. (Temperature controller appliesvoltage gradually to windows 1 & 2 L & R so as not to cause delamination.

A thermal switch on windows No. 3 & 5, maintains the correct temperature of windows No. 3, 4 & 5.

3. ANGLE OF ATTACK SENSORS

Two 737 Classics Angle-Of Airflow sensors, 737 NG Alpha Vanes are installed on the forwardfuselage. They provide angle-of-attack information to the stall warning system, autopilot, autothrottleand auto slats. They are anti-iced by heating elements, controlled by the Pitot Static Heat Switches.


2/12



4. WINDSHIELD WIPERS

The windshield wipers are designed for use during takeoff, approach, and landing.

Windshield wipers are provided to maintain a clear area on the cockpit No.1 windows during takeoff,approach and landing, in rain or snow. Windshield wipers should not be used on a dry windshield.

Each wiper is operated by a separate system to ensure that clear vision through one of the windowsis maintained in the event of a system failure.

Both wiper systems are electrically operated and controlled 737 Classics : by a common switch, 737NG: by separate switches located on the overhead panel. The switch(es) provide(s) a selection ofspeeds and control(s) the stowing of the wiper blades in a PARK position when the system is not in

use.

5. ENGINE THERMAL ANTI-ICE

Engine bleed air thermal anti-icing is provided for ice protection of the wing leading edge slats andengine cowl lip. On 737-800/900, the outboard leading edge slats are not anti-iced.

Engine anti-ice operation is controlled from the cockpit by individual Engine Anti-ice Switches. Theengine anti-ice system may be operated on ground and in flight.

Positioning the Engine Anti-Ice Switches ON sends an open signal to the engine cowl anti-ice valvesand to the main engine control.

Each cowl anti-ice valve is electrically controlled and pressure actuated. An open cowl anti-ice valvepermits the cowl leading edge to be anti-iced by engine bleed air.

If there is a disagreement between the anti-ice switch and the cowl anti-ice valve position, the COWLVALVE OPEN Light remains illuminated bright blue and 737 NG an amber TAI indication is displayedabove the engine N1 indication.

The amber COWL ANTI-ICE Light illuminates due to :- 737 Classics : excessive temperature or pressure.

- 737 NG : excessive pressure.

Note :- adjusts stick shaker & minimum maneuver speed bars on airspeed indications. FMC displayed

VREF is not adjusted automatically- stick shaker logic & airspeed indications return to normal when engine anti-ice is positioned to OFF

if wing anti-ice has not been used in flight.


3/12



6. WING ANTI-ICE

General The wing anti-ice system provides protection for the leading edge slats by using bleed air from the

main pneumatic manifold. The system does not include the leading edge flaps and 737 NG outboardslats.

The wing anti-ice control valves are AC motor operated. Valve position is monitored by the blueValve Open Lights. With a valve open, bleed air flows through the wing distribution duct in theleading edge, through a telescoping duct to each slat, and is then exhausted overboard. The winganti-ice system is effective with the slats in any position.

Ground-Enabled Wing Anti-ice

On ground, positioning the WING ANTI-ICE Switch ON opens the wing anti-ice control valves if thruston both engines is below the setting for take-off warning activation and provided the temperature inthe distribution duct does not exceed a certain limit.

Both valves close if thrust increases above the take-off warning setting or in case of overheat,however, the switch remains in the ON position. If thrust or temperature is reduced, the valves re-open automatically. The switch trips to OFF at liftoff.

The terminal switches and thrust setting logic are disabled in flight.

Ground-inhibited Wing Anti-ice

The air/ground sensor prevents the wing anti-ice control valves from opening on the ground exceptduring ground test. A ground overheat thermal switch in each wing closes the wing anti-ice controlvalves in case of overheat during ground test. Activation of either thermal switch closes both valves.

The thermal switches are deactivated in flight.

Wing Anti-ice operation in flight Positioning the WING ANTI-ICE switch to ON in flight :

- opens both control valves- sets stick shaker logic for icing conditions.

Note :- adjusts stick shaker & minimum maneuver speed bars on airspeed indications. FMC displayed

VREF is not adjusted automatically- stick shaker logic remains set for icing conditions for the remainder of the flight, regardless of

subsequent WING ANTI-ICE switch position.

7. CONTROLS & INDICATORS

WINDOW HEAT TEST SWITCH (spring-loaded to neutral)OVHT :

- Simulates an overheat condition. All OVERHEAT Lights illuminate. ON Lights may extinguishimmediately, or remain illuminated for as long as 70 seconds.

- Reset by momentarily positioning the Window Heat Switches to OFF.


4/12



PWR TEST :- Provides a confidence test (Window Heat Switches must be ON).- Controller is forced to full power, bypassing normal temperature control. Overheat protection is still

available.

NOTE : Do not PWR TEST when all green ON lightsare illuminated.

WINDOW HEAT SWITCHON:- Signals the window heat controller to apply heat to the associated window.- The SIDE Switch furnishes power to windows 2, 3, 4 & 5.

OFF :- Window heat not in use.

- Also resets the OVERHEAT Light circuit.

WINDSHIELD / FOOT AIR CONTROLS- Applies conditioned air to the No. 1 windows for anti-fogging.- Applies conditioned air to the pilot's leg positions.

PITOT STATIC HEAT SWITCH / PROBE HEAT SWITCHON :- Power is supplied to heat the respective system.OFF :- Power off.

TAT TEST SWITCH (when installed)PRESS :- Electrical power applied to TEMP PROBE when on ground.

WINDSHIELD WIPER SELECTORPARK: (spring-loaded position)- Stows wiper blades.OFF :- Wipers off.LOW :- Low speed operation.

HIGH :- High speed operation.

L OR R WINDSHIELD WIPER SELECTORPARK :- Stows wiper blades.INT :- Seven seconds intermittent operation.LOW :- Low speed operation.HIGH :- High speed operation.

Depending on aircraft equipment


5/12



ENGINE ANTI-ICE SWITCHON :- Opens corresponding engine anti-ice valve and illuminates the COWL VALVE OPEN light.

Engine anti-ice valve closes and the COWL VALVE OPEN light extinguishes.

WING ANTI-ICE SWITCH (Ground inhibited wing anti-ice)OFF :- Wing anti-ice control valves are closed.- VALVE OPEN Lights are extinguished.

ON (in flight) :- Wing anti-ice control valves are open.- VALVE OPEN lights illuminated dim.

ON (on ground) :- Air/Ground sensor prevents Wing Anti-Ice control valves from opening.

GRD TEST (momentary position) :- Opens wing anti-ice control valves when on the ground.- If duct temperature exceeds a preset limit during test, wing anti-ice control valves close.


6/12



8. FAULTS & INDICATIONS

VALID FORLIGHT INDICATION 300 400 500 600 700 800

900

CAPT AUX PITOT LIGHT(amber)- Related probe not heated

X X X

CAPT PITOT STATIC LIGHT(amber)- Related probe not heated

X X X

CAPT PITOT STATIC / 1 AUX STATIC LIGHT(amber)- Related probe not heated

X X X

COWL ANTI-ICE LIGHT(amber)- 737 Classics : excessive temperature or pressure.

- 737 NG : excessive pressure.

X X X X X X

COWL VALVE OPEN LIGHT(blue)- BRIGHT : related cowl anti-ice valve is in transit, or,

cowl anti-ice valve position disagrees with relatedENGINE ANTI-ICE switch position.

- DIM : related cowl anti-ice valve open (switch ON)- EXTINGUISHED : related cowl anti-ice valve closed

(switch OFF)

X X X X X X

F/O PITOT LIGHT(amber)- Related probe not heated

X X X

F/O PITOT STATIC / 2 AUX STATIC LIGHT(amber)- Related probe not heated

X X X

L ALPHA VANE LIGHT (amber) > idem for Right one- Related probe not heated

X X X X X X

L ELEV PITOT LIGHT (amber) >> idem for Right one- Related probe not heated

X X X X X X

WING ANTI-ICE VALVE OPEN (blue) > idem for Right

- BRIGHT : related WAI control in transit, or, relatedWAI control valve position disagrees with WAI switch

- DIM : related WAI control valve is open (switch ON)

- EXT : related WAI control valve is closed (switch OFF)

X X X X X X

WINDOW HEAT ON LIGHT (amber) X 4

- Window heat controller is applying heat to the

associated window.

X X X X X X

WINDOW OVERHEAT LIGHT (amber) X 4

- Overheat condition removes power to the window &

On light extinguishes.

- OVERHEAT lights will also illuminate if electrical

power to the window is interrupted.

X X X X X X

TEMP PROBE LIGHT (amber)- Related probe not heated X X X X X XTEMPPROB

CAPT P/S1 AUX STATIC

CAPTPITOT

L ELEV

PITOT

AUXPITOT

F/O

PITOT

F/O P/S

2 AUX STATIC

L ALPHA

VANE

OVERHEAT

ON

COWL

ANTI ICE

COWL VALVE

OPEN

L VALVE

OPEN


7/12



B737 CLASSICS


8/12



B737 NG


9/12



COCKPIT WINDOWS


10/12



B737 NG

737 CLASSICS

ANGLE OF ATTACK SENSORS


11/12



B737 NG

ENGINE ANTI-ICE


12/12



WING ANTI-ICE

boeingggg 737 ice and rain protection

Documents