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since the first airplane flight in 1903

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flying in winter has been a problem

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because of dangerous situations created

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by ice formations on aircraft

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during the 1920s and 30s when aviation

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was still in its infancy the limitations

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of winter flying were very apparent

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one example was the attempt to establish

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transatlantic routes between the united

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states and europe over the north

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atlantic which were considered much too

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dangerous to fly

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during the second world war more than

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100 c-46 aircraft were lost while flying

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over the himalayas between india and

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china

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this route was known as the hump

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responding to this need the national

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advisory committee for aeronautics naca

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directed that an icing research tunnel

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be constructed at the aircraft engine

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research laboratory which was the former

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name of the lewis research center

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the icing research tunnel was designed

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and constructed from 1942

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to 1944 for six hundred seventy thousand

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dollars

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the first icing test was run on june 9th

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1944

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the icing research within naca first

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started in the 1920s at langley research

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center in virginia

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icing research was also conducted at

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ames research center in california prior

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to the research at lewis research center

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in the 1940s

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soon naca turned to nasa

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and their attention from aeronautics to

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space

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the icing technology developed through

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the 40s and 50s at naca nasa formed the

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basis of what the u.s aircraft industry

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used to solve various icing problems

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dr joe shaw deputy chief for applied

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dynamics at the nasa lewis research

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center

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explains the icing research program

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the icing research program at lewis was

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begun in the early forties it was felt

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that an icing research activity

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including

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the construction of a ground icing test

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facility or the icing research tunnel

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was needed to address the wartime icing

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problems that that the military was

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having there was expressed a need for an

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icing test facility ground test facility

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that would accurately and adequately

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duplicate natural icing conditions

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and you need to generate a cloud in that

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tunnel an icing cloud that simulates the

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right amount of liquid water content and

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droplet size distribution to be typical

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of those you might find in natural icing

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as well as you need to control the

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temperature of the airflow in the tunnel

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so again that you would be able to

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simulate accurate conditions that you

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would expect to see in flight it is not

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the weight of the ice on the various

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parts of the aircraft that causes the

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problem

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but the altered aerodynamics that change

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the performance stability and control

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characteristics of the airplane

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the ice forms may be small but they do

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have a significant effect on the

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airplane and its actions when ice

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secretes or grows on the surfaces of the

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airplane wings tails fuselage whatever

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the

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become severe enough

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the stability and control of the

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aircraft can be completely lost and your

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craft cannot be controlled

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the irt is similar to other subsonic

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wind tunnels in that a wing or other

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aircraft component when placed in the

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test section may be subjected to various

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air speeds

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the airflow being created by a motor

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driven fan

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the irt has several unique features to

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simulate icing conditions a heat

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exchanger and a refrigeration plant to

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achieve the desired temperature and a

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unique spray system to generate a cloud

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of microscopic droplets of unfrozen

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water

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this makes the irt capable of

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duplicating the icing conditions that an

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aircraft might encounter

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all aircraft whatever their size can be

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susceptible to icing

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general aviation aircraft can be more

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susceptible to icing because they have

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smaller wing sections

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ice at a faster rate than larger wing

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sections

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helicopters also have icing problems

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because helicopter rotors are small and

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are spinning at high speeds

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they therefore tend to build up ice

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quickly and it does not take long before

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you get some severe icing conditions on

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the helicopter rotor

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now dr shaw will tell us about

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anti-icing

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using some technique which prevents the

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buildup of ice that is when the water

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droplets hit the surface and

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of the airplane of course they're in the

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liquid state and they remain in the

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liquid state de-icing means that you

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allow the ice to grow that is you form

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an ice accretion or an ice growth and

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then you get rid of or de-ice

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that ice accretion before it it reaches

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a size that can significantly impact the

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aerodynamic performance and stability

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and control performance of that airplane

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in the 1970s the aircraft industry

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realized that there was a need for

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additional icing technology

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and nasa reinstituted an icing research

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program to meet the new icing technology

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needs which occur as a result of the

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ever-changing aircraft design problems

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from basically 1950 through 1957 when

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the knack or nasa program was concluded

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a tremendous icing technology database

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was developed and the technology being

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used today

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on today's aircraft came from largely

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from that program examples of that would

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be the hot gas anti-icing system that is

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used by all transports today for ice

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protection

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today about 90 percent of the smaller

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general aviation aircraft certified for

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flight into forecast icing conditions

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are using the pneumatic boot system for

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de-icing

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it was developed in the 1930s by the bf

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goodrich company

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the pneumatic boot is a rubber boot

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placed over the leading edge of the wing

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or tail

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when the ice secretes or grows a

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pneumatic air source is used to inflate

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the boot which destroys the ice aircraft

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surface bond to clean the surface of the

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craft

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the nasa lewis icing research tunnel was

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named an international historic

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mechanical engineering landmark in 1987.

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it is the oldest and largest

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refrigerated icing wind tunnel in the

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world

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two major achievements of this

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installation are the unique heat

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exchanger and the spray system that

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simulates a natural icing cloud of tiny

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droplets

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icing is no longer a major problem for

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many of today's aircraft because of the

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ice protection systems technology

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largely developed in the nasa lewis

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research center icing research tunnel

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as new aircraft are developed and

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operating practices are changed the

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recently modernized irt will continue to

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lead the way