ATR 72-500 CBT Ice and Rain Protection HD

Ice and Rain Protection System Overview

Introduction to the Ice and Rain Protection System

• The module covers the aircraft's ice and rain protection system, including its description, components, controls, indicators, and uses.

• This system is crucial for ensuring safe flight operations in icy or rainy conditions.

Components of the Ice Protection System

• The ice and rain protection system consists of a deicing system, an anti-icing system, and windshield wipers.

• Pneumatic air provides ice protection for various parts of the aircraft using inflatable boots that break up ice accumulation.

Types of Boots Used

• Two types of boots are utilized:

• Cordwise Boot: Used on leading edges and engine gas paths.

• Annular Boot: Circular tubes used at engine inlets; inflating these changes their shape to separate ice.

Operation of the Boot System

• Each boot consists of two chambers (Boot A and Boot B) that alternate inflation to enhance ice separation efficiency.

• Inflation is controlled by seven distribution valves corresponding to different sections of the aircraft (e.g., engine intakes, wing leading edges).

Heating Elements in the System

Electrical Heating Components

• Electrical power heats propeller blades, windshields, probes, static ports, and flight control horns to prevent icing.

• Windshield wipers are employed to clear rain from forward windshields; controls are located on the overhead panel.

Ice Detection Mechanisms

Ice Detection Systems Overview

• Icing detection involves an ice evidence probe (IEP) visible from both pilot positions for visual indication of icing conditions.

• The IEP retains ice until it sublimates or melts; it features spanwise ridges for improved efficiency but is not heated itself.

Anti-Icing Advisory System

• The Rosemont ultrasonic ice detector probe alerts crew visually and audibly when icing occurs on its surface through frequency changes as ice accumulates.

• An amber icing light illuminates when 0.5 mm of ice has formed on the probe; this triggers a heat cycle to remove accretion.

Limitations in Detection Capabilities

• The detection system may struggle with large supercooled drops near freezing temperatures due to insufficient heat transfer during contact with the probe.

Engine Anti-Icing Systems

Engine Anti-Icing Functionality

• Combines pneumatic air with AC electrical power for effective anti-icing measures across both engines via pressure-regulating DI I valves located on each side of the aircraft.

Deicing System Operation

Overview of Deicing System Components

• The bleed air valve low pressure port cannot be used for deicing; the deice valves are activated by selecting the airframe air bleed push button to "on."

• Each deice valve can also be opened independently via engine push buttons on the engine Wing deicing panel, maintaining a constant delivery pressure of 20.3 PSI.

• The engine dual distribution valve divides the air supply into two lines, directing it to both the air inlet deicer and gas path deicer boot (throat boot).

• Isolation valves prevent pneumatic error from entering the wing deicing system in case of downstream leaks, connecting each engine's pneumatic bleed supply to a common manifold.

• This common manifold supplies pneumatic air to the DI boots for the airframe deicing system, ensuring operation even if one engine fails.

Control Mechanisms and Cycle Operations

• The operation of the deicing system is initiated by pressing the airframe push button, which signals a multi-function computer to start a deicing cycle.

• The mode select auto push button determines how long boots inflate and deflate; when released, it operates in automatic mode based on data from two air data computers.

• Boots A in both engine intakes inflate first for 5 seconds before deflating; this sequence continues with alternating inflation between boots A and B across various sections.

• After several cycles of inflation and deflation among different boots, there is a pause before repeating the cycle automatically based on temperature conditions.

• If static temperatures exceed -20°C, cycles occur every 60 seconds; otherwise, they extend to 180 seconds with specific dwell periods where no boots inflate.

Manual Override and Independent Operation

• The entire cycle length can be adjusted using the di I mode selector push button while enabling manual control through an illuminated caption on the control panel.

• Pressing this selector forces a 180-second cycle; releasing it reverts back to 60 seconds for normal operations.

• Engine intake and gas paths can be independently selected for deicing by pressing associated engine push buttons that activate their respective valves regardless of other settings.

System Deicing and Anti-Icing Processes

Overview of Deicing and Anti-Icing

• System deicing involves removing ice, while anti-icing prevents ice formation. The ATR 72-500 utilizes electrical systems for both processes on propellers and flight control horns.

Flight Control Horns Anti-Icing

• The elevator and rudder horns are electrically heated using AC wild electrical power from two separate buses (115 volts AC).

• Control of horn anti-icing is managed via a panel on the overhead, powered by the DC emergency bus. Each push button corresponds to specific horns.

• When activated, a blue caption illuminates; however, this system is inhibited when the aircraft is on the ground.

Stall Warning AOA Threshold Adjustment

• Activating horn anti-icing lowers the stall warning angle of attack (AOA) threshold, indicated by a green light as a reminder for crew action regarding speed settings.

• To reset the stall warning AOA threshold to normal values, all horn anti-icing buttons must be deselected after confirming no ice presence.

Propeller Anti-Icing Mechanism

• The inner leading edges of propellers are electrically heated to reduce ice adhesion through centrifugal force. Heat is supplied by resistors near blade surfaces.

• Propeller heating is controlled via two push buttons on the overhead panel; activation results in an illuminated blue caption.

Heating Cycle Details

• The heating cycle alternates between blades every 10 seconds in a low power cycle when temperatures range from 0 to -10°C.

• Manual control of this cycle can be achieved through an anti-ice mode select button that switches between low and high power cycles.

Windshield Heating Systems

Windshield Anti-Icing Features

• Front windshields are heated for defogging purposes using an electrically heated film powered by associated AC wild buses.

Temperature Regulation

• Temperature controllers maintain outer windshield ply above 2°C and inner ply above 21°C to prevent fogging; each window has its own controller.

Side Window Heating Control

• Side windows utilize small wires embedded within glass layers for heating, regulated to keep inner temperatures over 20°C.

Operation Controls

• Windshield heat operation is managed via push buttons on the overhead panel; releasing these buttons deactivates heat supply with visual indicators for faults or loss of power.

Aircraft Anti-Icing and Heating Systems Overview

Push Button Operation for Heating Elements

• The push button activates the heating element, illuminating the blue caption in the side window when selected. Ice buildup indicates severe icing or freezing rain conditions.

• Releasing the push button deselects heat, meaning that only certain portions of the windows are heated, specifically not including the AFT section.

Probe Heating Mechanisms

• AC power heats various probes: captain's, first officer's, and standby pitot tubes; however, static ports have different power sources (DC buses).

• The probe heating control panel allows activation via associated push buttons; releasing a button turns off heat and illuminates an "off" caption.

Fault Monitoring for Probes

• Fault lights above control buttons indicate if a probe is not heated; an amber light will illuminate with a chime sound to alert crew members of issues. This includes faults in heaters or system shutdowns.

• The total air temperature probe heat is automatically inhibited on the ground, and its condition isn't monitored during this time. Static port heat monitoring also ceases while on ground.

Windshield Wiper Functionality

• Each windshield wiper operates via a two-speed DC motor controlled by rotary selectors with three positions: off, slow, and fast (130 cycles/minute vs 80 cycles/minute). Speed limits apply at airspeeds above 160 knots where wipers should not be used.

Ice Detection System Alerts

• The ice detection panel alerts when ice accretion is detected; steady illumination indicates active conditions while flashing signals that one of the anti-icing systems is off. A fault light indicates detector issues or power loss accompanied by caution alerts.

• Testing of the ice detection system can be performed using a dedicated test button which triggers visual and auditory alerts if faults are present during testing procedures.

De-Icing System Control

Engine Deicing and Anti-Icing Systems Overview

Engine Deicing Mechanisms

• Engine deicing can be activated by selecting the engine deice push buttons, which opens the associated deice valve regardless of the airframe air bleed push button's position.

• If the airframe air bleed push button is off, airframe deicing will not be available. An amber fault caption illuminates when there are issues with the operation of the deice valves or isolation valves.

• The fault light extinguishes when the airframe air bleed push button is selected out. If a fault occurs, both master caution lights flash, and an anti-icing alert sounds.

Distribution Valve Control

• Pressing the airframe push button signals the MFC to initiate a deicing cycle; this action also illuminates a blue caption indicating activation.

• The system operates automatically when the mode select push button is released out. Fault conditions trigger an amber fault light if there’s an MFC failure or ADC failure.

Emergency Operation Mode

• An emergency mode can be activated using a guarded override push button, setting a 60-second timing cycle for critical situations where faults are detected.

• When both MFC modules fail in relation to boot control, an amber fault light on the override button indicates incorrect inflation sequences.

Horn and Propeller Heating Controls

• Horn anti-ice systems are controlled via dedicated buttons; pressing activates electrical heating while releasing stops it. A stall threshold is lowered during activation.

• Propeller heat is similarly managed through specific buttons; faults in heating elements trigger alerts including chimes and flashing caution lights.

Anti-Icing Levels for Flight Operations

• For takeoff in icing conditions, level one anti-icing must be selected to activate probe and windshield heaters regardless of atmospheric conditions.

• Level two requires additional selections for propeller heat and other anti-ice systems when operating in known icing conditions during flight.