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ANTI ICING & DEICING IN AIRCRAFTSBY Siranjivi

Why icing is a problem ??Icing is serious flight safety concernMost serious during take-offs and landings (high lift demands)With ice, must fly at higher angles of attack (higher drag)Ice causes early separation Lift drops drasticallyFlow no longer in contact with control surfaces

ACCREATION OF ICEShape, amount and type of ice determined by:VelocityTemperatureLiquid Water Concentration (LWC)Droplet Size Ice Accretion Time (t)

AIRFOILCLOUD OF SUPERCOOLED WATER DROPLETS

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Where is ice ??Ice is usually found within 5000 feet above the freezing levelUsually only about 2000 - 3000 feet thick between 0 C and -15 CMore rain means more ice when below freezing

VULNERABLE PLACES

TYPES OF ICE FORMED RIMEhas a rough milky white appearance and generally follows the surface closelyCLEARCan look very transparent and glass-like to a very tough opaque surface. Clear ice is formed when large super-cooled water droplets collide with the air frame and freeze slowly after impact.MIXEDa combination of rime and clear ice forms at intermediate temperatures (about -5 deg C to -15 deg C) and has characteristics of both types.

TEMPERATUREIcing types and their forming temperatures include :Clear (0 to -5 degrees CelsiusClear or mixed (-5 to -10 deg C)Mixed or rime (-10 to -15 deg C)Rime (-15 to -20 degrees Celsius)

DIFFERENCE (ANTI ICING & DEICING)Anti-icing (ice prevention):Heated wings-Hot compressor bleed air is directed into sections of the wing increasing its surface temperature.Weeping wings-Fluid (a water and glycol mix) is pumped through a mesh panel on the wings leading edge.Clean wings can also be sprayed with glycol based fluids to protect against freezing for a limited time.

Deicing (ice removal):Pneumatic boots-attached to wings and are inflated with air in order to break off any ice that has accumulated on them.If wings have accumulated ice, a heated glycol and water mix is sprayed on the wings to remove it.

Cont.Anti-icing (ice prevention):Includes: thermal heat, prop heat, pitot heat, fuel vent heat, windshield heat, and fluid surface de-icers

Deicing (ice removal):Includes surface de-ice equipment such as boots, weeping wing systems, and heated wings

Techniques usedPropeller Anti IcersWindshield Anti - IcersThermal HeatHeatersBleed AirBootsWeeping WingElectro Impulse Deicing

Propeller Anti - icersIce usually appears on propeller before it forms on the wingCan be treated with chemicals from slinger rings on the prop hubGraphite electric resistance heaters on leading edges of blades can also be used

WINDSHIELD AINTI - ICERS

Liquids used include: ethylene glycol, propylene glycol, Grade B Isopropyl alcohol, urea, sodium acetate, potassium acetate, sodium formate, and chloride saltsChemicals are often bad for the environmentUsually uses resistance heat to clear windshield or chemical sprays while on the ground

THERMAL HEATAir HeatedBleed air from engine heats inlet cowls to keep ice from formingBleed air can be ducted to wings to heat wing surface as wellIce can also build up within engine, so shutoff valves need to be incorporated in designUsually used to protect leading edge slat, and engine inlet cowlsResistance heaterUsed to prevent ice from forming on pitot tubes, stall vanes, temperature probes, and drain masts

bootsInflatable rubber strips that run along the leading edge of wing and tail surfacesWhen inflated, they expand knocking ice off of wing surfaceAfter ice has been removed, suction is applied to boots, returning them to the original shape for normal flightUsually used on smaller planes

Weeping WingFluid is pumped through mesh screen on leading edge of wing and tailChemical is distributed over wing surface, melting iceCan also be used on propeller blades and windshields

Electro Impulse deicingElectromagnetic coil under the skin induces strong eddy currents on surfaceDelivers mechanical impulses to the surface on which ice has formed Strong opposing forces formed between coil and skinResulting acceleration sheds ice from the surfaceCan shed ice as thin as 0.05

GROUND OPERATION - REMOVING ICE

Truck PlatformFixed Gantry Platform

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