GROUP 1Clinton AnocheCarlo Jae Rillera

Jason Clark Alonto

Aircraft Anti-Icing Systems

Anti Icing System

Anti-Icing – Prevention of the formation of ice on a surface. De-Icing – The removal of ice that has formed on a surface. Ice on a propeller blade or wings changes its airfoil shape and

decreases the thrust it produces. Though rare to minimal, it can also create an unbalanced condition which produces vibration that can damage the engine as well as the airframe.

Negative Effects of Ice BuildupDestroys smooth flow of air

over wing, leading to severe decrease in lift and increase in drag forces

Can change pitching momentAs angle of attack is increased

to compensate for decreased lift, more accumulation can occur on lower wing surface

Causes damage to external equipment such as antennae and can clog inlets, and cause impact damage to fuselage and engines

Considered a cumulative hazard because as ice builds up on the wing, it increasingly changes the flight characteristics •http://www.aopa.org/asf/publications/sa11.pdf#search=%22anti-icing%20systems%20aircraft%22

Types of IceRime: “has a rough milky

white appearance and generally follows the surface closely”

Clear/Glaze: “sometimes clear and smooth but usually contain some air pockets that result in a lumpy translucent appearance, denser, harder and more difficult to break than rime ice”

Mixedhttp://virtualskies.arc.nasa.gov/weather/tutorial/images/32clearice.gif&imgrefurl=http://virtualskies.arc.nasa.gov/weather/tutorial/tutorial4.html&h=235&w=280&sz=29&hl=en&start=6&tbnid=NrYdps_943cEmM:&tbnh=96&tbnw=114

Ice Detection

Electronic ice detection common, but can give false readings

GM is developing a mass based ice detection system where ice builds up on external probe

After mass of probe has increased due to additional ice, anti-icing systems are alerted and turned on

This increases fuel efficiency and system life as de-icing systems are only turned on as required by conditions

Types of Ice RemovalAnti-Icing

Preemptive, turned on before the flight enters icing conditions

Includes: thermal heat, prop heat, pitot heat, fuel vent heat, windshield heat, and fluid surface de-icers

De-IcingReactive, used after there has been significant

ice build upIncludes surface de-ice equipment such as

boots, weeping wing systems, and heated wings

Propeller Anti-IcersIce usually appears on

propeller before it forms on the wing

Can be treated with chemicals from slinger rings on the prop hub

Graphite electric resistance heaters on leading edges of blades can also be used

•http://www.aopa.org/asf/publications/sa11.pdf#search=%22anti-icing%20systems%20aircraft%22

The earliest propeller ice control, a system that is still in use, is chemical anti-icing. Isopropyl alcohol is carried in a tank in the aircraft, and when icing conditions are anticipated, some of it is pumped into a slinger ring around the propeller hub. The ring-supply tubes deliver the alcohol to propeller leading edge by centrifugal force and grooved de-icer boots help carry it out of the lenght of the blades.

This is a diagram of a typical system used on a twin turboprop airplane. Current flows from the bus through the 20-amp Auto Prop Deice circuit breakers/switch into the deicer time unit. When the manual-override relays are not energized, this current flows through brushes riding on slip rings mounted on the propeller spinner bulk-head and into the heating elements bonded to the propeller blades. The slip rings are connected to the heater elements through flexible conductors that allow the blades to change their pitch angle

The Timer sends current through the right propeller for about 90 second then switches over and sends current throught the left propeller for 90 seconds. Current cycles of the two propellers are controlled by the timer as long as the propeller Auto Prop Deice switch is ON. Manufacturers limit the operation of the propeller de-icing system on the ground because the inflight air cooling is not present and prolonged use will cause damage.

Windshield Anti-Icers

Liquids used include: ethylene glycol, propylene glycol, Grade B Isopropyl alcohol, urea, sodium acetate, potassium acetate, sodium formate, and chloride salts

Chemicals are often bad for the environment

• Usually uses resistance Usually uses resistance heat to clear windshield heat to clear windshield or chemical sprays while or chemical sprays while on the groundon the ground

•http://www.aopa.org/asf/publications/sa11.pdf#search=%22anti-icing%20systems%20aircraft%22

Thermal HeatAir Heated

Bleed air from engine heats inlet cowls to keep ice from forming

Bleed air can be ducted to wings to heat wing surface as well

Ice can also build up within engine, so shutoff valves need to be incorporated in design

Usually used to protect leading edge slat, and engine inlet cowls

Resistance heaterUsed to prevent ice from forming

on pitot tubes, stall vanes, temperature probes, and drain masts

Airplane Design, Book 4, Roskam

BootsInflatable rubber strips

that run along the leading edge of wing and tail surfaces

When inflated, they expand knocking ice off of wing surface

After ice has been removed, suction is applied to boots, returning them to the original shape for normal flight

Usually used on smaller planes

•http://www.aopa.org/asf/publications/sa11.pdf#search=%22anti-icing%20systems%20aircraft%22

Weeping WingFluid is pumped through

mesh screen on leading edge of wing and tail

Chemical is distributed over wing surface, melting ice

Can also be used on propeller blades and windshields

•http://www.aopa.org/asf/publications/sa11.pdf#search=%22anti-icing%20systems%20aircraft%22

Electro-impulse Deicing Electromagnetic coil under

the skin induces strong eddy currents on surface

Delivers mechanical impulses to the surface on which ice has formed

Strong opposing forces formed between coil and skin

Resulting acceleration sheds ice from the surface

Can shed ice as thin as 0.05”

•http://www.idiny.com/eidi.htmlhttp://www.idiny.com/eidi.html

Typical Anti-IcingC-130:

Engine bleed air used for anti-icing wing and empennage leading edges, radome, and engine inlet air ducts.

Electrical heat provides anti-icing for propellers, windshield, and pitot tubes.

777: Engine bleed air used to heat engine cowl inlets.

If leak is detected in Anti-Ice duct, affected engine Anti-Ice valves close.

Wing Anti-Ice System provides bleed air to three leading edge slats on each wing. Wing Anti-Ice is only available in flight.

References“Airplane Design, Pt 4.” Roskamhttp://www.aopa.org/asf/publications/sa11.pdf#se

arch=%22anti-icing%20systems%20aircraft%22http://www.newpiper.com/promo/PIIPS/images/PIIP

SPropSlingerRing.jpghttp://www.fas.org/man/dod-101/sys/ac/c-130.htmhttp://www.airs-icing.org/AIRS_II/AIAAReno2006/

AIAA-2006-206-739.pdf#search=%22transport%20ice%20%22in%20flight%22%22

www.p2pays.org/ref/07/06047.pdfIce Pictureshttp://www.idiny.com/eidi.html