B737 CBT Ice and Rain Protection (legacy)

737 Ice and Rain Protection Systems Overview

Introduction to Ice and Rain Protection

• The 737's ice and rain protection systems are crucial for maintaining clear critical areas of the airplane, utilizing bleed air from the engine to heat various components.

• Key heated areas include engine cowlings, leading edge slats, flight deck windows, and probes which are electrically heated to prevent ice formation.

Icing Conditions

• Icing conditions in-flight occur when total air temperature is at or below 10°C with visible moisture present (e.g., rain, snow). This can also include clouds and fog with visibility under one mile.

• On the ground, icing conditions exist under similar temperature criteria while operating on ramps or runways with surface snow or slush.

Engine Anti-Ice System Operation

Control Mechanisms

• Engine anti-ice is controlled from the flight deck using switches that open the engine cowl anti-ice valve; this allows bleed air to flow into the cowl lip.

• The "Cal Valve Open" light indicates valve status: bright when in transit or disagreement between switch position and dim when open. It extinguishes when closed.

Operational Guidelines

• Engine anti-ice must be activated during all operations in expected icing conditions; visual cues should not be relied upon for activation decisions. Instead, use temperature and moisture criteria as guidelines.

• After confirming operation by checking indicator lights, turn off engine anti-ice once it is no longer needed but avoid using it above 10°C total air temperature.

Non-Normal Conditions for Engine Anti-Ice

Troubleshooting Indicators

• If the "Cal Valve Open" light remains bright after activation, it indicates a malfunction where the valve has not opened; similarly, if it stays bright after deactivation, it suggests a failure to close. Limit thrust accordingly if temperatures exceed safe limits.

• In case of duct pressure issues indicated by warning lights, reduce thrust until indicators reset as necessary for safety compliance.

Wing Anti-Ice System Functionality

Activation Procedures

• Wing anti-ice is controlled via a single switch on the overhead panel; there’s no protection for outer slats or leading-edge flaps during operation. Ensure proper indication lights illuminate during activation checks on ground operations under icing conditions.

Ground Operations Considerations

• Use wing anti-ice during ground operations to prevent frost accumulation but remember that it complements rather than replaces deicing procedures performed on the ground. Thrust settings can influence valve operation based on duct temperatures detected by sensors during takeoff preparations.

Flight Operations of Wing Anti-Ice

Methods of Operation

• There are two operational methods for wing anti-freeze: primary (deicer mode) allows ice accumulation before activation providing optimal airflow efficiency while secondary mode continuously prevents ice formation but consumes more fuel—use only in severe icing scenarios like holding patterns due to potential drawbacks such as increased fuel consumption and possible ice runback issues.( t = 613 s)( t = 649 s)( t = 665 s)

Wing Anti-Ice and Window Heat Management

Wing Anti-Ice System Operations

• The engine or wing should not be operated in icing conditions when the total air temperature exceeds 10 degrees Celsius.

• If the left wing valve open light remains bright while the wing anti-ice is activated, it indicates that the valve is stuck closed, necessitating avoidance of icing conditions.

• When deactivating the wing anti-ice, if the valve stays open, control of bleed air must be managed using both the isolation valve switch and engine number one bleed switch.

Window Heat Control Procedures

• Window heat can be controlled from the flight deck via switches located on the forward overhead panel; these switches have distinct on/off positions for windows numbered one through five.

• In addition to electric heating, conditioned air circulates across the inner surface of forward windows to prevent fogging; this is adjustable using windshield air control knobs on both captain and first officer panels.

• All window heat systems should be activated at least 10 minutes prior to takeoff to ensure maximum strength against potential bird impacts during flight. The system should remain active throughout flight operations but turned off during shutdown or after prolonged ground time exceeding 30 minutes.

Monitoring and Safety Features

• Temperature controllers monitor windows one and two for overheating; if a window overheats, both master caution and anti-ice system enunciator lights will illuminate as a warning signal.

• Upon detecting an overheat condition, electrical power is removed from the affected window automatically by the temperature controller, extinguishing its corresponding light indicator. This process resets once window heat is turned off for that specific window.

Probe Heating System Overview

• The probe heating system includes components such as Pito probes, elevator probes, alpha vein sensors, and total air temperature probes; these are crucial for accurate flight instrument readings under icy conditions.

• Probe heat controls are located on an overhead panel with separate switches managing left and right system heaters; activation occurs post-engine start and deactivation happens during taxiing procedures.

Windshield Wiper Operation Guidelines

• The windshield wiper removal system consists of wipers paired with a rain repellent coating designed for use in adverse weather conditions like rain or snow during critical phases such as taxiing or landing. Caution: operating wipers on dry windshields can damage this coating significantly.