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uh good morning ladies and gentlemen and

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welcome to day two of the naca centenni

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centenary symposium

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um i think we had a great day yesterday

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and i appreciate all your participation

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it's great questions and some great

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panels and i think we got a great lineup

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today as well

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but we started off this morning

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with a keynote address by dr john

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anderson uh curator of aerodynamics at

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the air and space museum here but also

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the legendary aerodynamicist any of you

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who are have studied aerodynamics

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probably have his textbook in one of its

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many versions on your bookshelf

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someplace so uh john's a legend in the

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aerodynamics world and he's going to

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talk to us about

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the naca in the 1930s trailblazing the

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technical world of aerodynamics so join

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well i want to start out by thanking

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bill berry

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and

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all of those who have organized this

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symposium for giving me the opportunity

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to share a few thoughts and say a few

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words with you

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uh

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in honor of this 100th anniversary of

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the creation of the naca and before i

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even get started i want to share with

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you

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for me

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the naca was all about aeronautical

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engineering the

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information the technology

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went around the world

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uh it was seminal in the field of

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aeronautical engineering extremely

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important and i wanted to emphasize that

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it's all about aeronautical engineering

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also the naca is all about

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the

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highly qualified intelligent

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hard-working individuals

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who work for the naca who produce this

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seminal information that made the united

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states and the naca world famous

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worldwide and i think that's important i

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want to i'm sort of giving them a shout

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out even before we start here

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the

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with you

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nope i keep on going back oh hey there's

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a preview man look at that

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let's keep on going back

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one more there

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i wanted that slide because it says the

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1930s this is the naca in the 1930s

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that's what i'm going to emphasize

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and what's magic about the 1930s but i

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by the way i watched every i wasn't

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physically present in this room

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yesterday

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but i watched every presentation in its

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entirety throughout the day on the

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computer at home

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and

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a number of the speakers emphasized the

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importance of the 1930s the 1930s was a

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period of what we call the design

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revolution that's when the nature and

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the configuration

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all aspects of the airplane changed

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due to

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major

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discoveries

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a lot of which were carried out by the

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naca 19 1930s

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i want before i go any further

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i want to share with you two quotes

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that bracket the 1930s first at the

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beginning and then at the end and these

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quotes

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are he'll come up here in a few seconds

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this man that's edward p warner

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now warner's name has been was mentioned

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yesterday several times debbie douglas

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for example in her presentation uh

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brought forth a contribution some of the

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contributions of ed warner but ed warner

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was graduated with with honors

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with a ba in

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in mathematics from harvard

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went to mit and the next year graduated

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with a bs

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in mechanical engineering and then the

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next year an m.a

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he after that immediately

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took a job

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with the naca langley memorial

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aeronautical laboratory and you were

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told this yesterday

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where he was the chief physicist and he

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took over he took charge of the

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aerodynamics program he

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helped to design and construct the first

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wind tunnel at the at langley you saw

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some pictures of that yesterday

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albeit it was basically a copy of a wind

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tunnel the national physical laboratory

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and then in 1920 he went back to mit

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becoming an associate professor of

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aeronautical engineering and he was

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there for six years

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in 1926 he took the job as assistant

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secretary of the navy for aeronautics

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and then in 1957 he became president of

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the icao the international congress of

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uh

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international

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civil aviation organization the icao

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ed warner was a mover and shaker

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in early aaron the first half of the

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century in aeronautics in this country

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and i'm i'm

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going to share with you two quotes

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one that was

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in a book that he wrote it was

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titled airplane design aerodynamics

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published by mcgraw-hill 1927. and in

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this textbook ed warner says the

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following and this is sort of the

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before the 1930s the pioneers of

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aircraft design traveled in a wilderness

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depended upon their own resources at

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every step

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no path was marked for them and the

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illumination along the way was only such

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as they themselves might provide

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of research in this application

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aeronautical engineering there had been

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hardly even a beginning

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in his place that often

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his place had often to be supplied by

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inspiration intuition or in person

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empiricism or go unsupplied and then

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that's sort of really describing the

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woeful state of the art particularly at

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the end of world war one and up into

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part of the 20s and then and then warner

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goes on in the same same paragraph

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the student who embarks upon

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aeronautical studies in 1927

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is subject to some degree to a contrary

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embarrassment

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experimental data inundate him

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the underbrush of obscurity has been

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cleared away the field is even more

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brightly illuminated by the fruits of

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governmental institutional and private

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research

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but listen to this

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yet the very uniformity with which

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enlightened enlightenment is being cast

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over the subject into several parts may

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prove confusing

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leaving the exact course to be followed

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still in dell that was 1927.

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now

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on the other side of that

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we have ed warner in a new book

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this entitled airplane design

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performance published by mcgraw-hill in

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1936

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and here is the other side of that

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period

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quote

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all this refinement

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what refinement well we'll see

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all this refinement becomes increasingly

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more important and engineers become

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increasingly excellent in their demands

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for it for two reasons first

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because as design becomes increasingly

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an exact science and as designers are

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required to subject themselves

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to ever closer specifications and

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advanced guarantees for their products

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performance

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errors are fo of 5 or 10 percent in

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aerodynamic data that might once have

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seemed too small to notice

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come to assume nightmare proportions so

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there's a big change now we have

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airplane designers

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getting up tight because the data is

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only five percent accurate what has

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changed one of the major things that has

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changed in between these two quotes

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is all the work that have been carried

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out by the naca at the langley memorial

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laboratory their technical contributions

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and so i'm going to share with you only

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three

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categories those contributions one is

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going to be the air foil work carried

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out uh

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at langley uh

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and

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the other second one is going to be the

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development of the naca cowling we'll

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say something about that and then

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finally

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shedding the some light on the

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intellectual understanding of what was

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called the compressibility problem for

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high-speed flight

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and debbie who just walked in you

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recognize that guy up there

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i was just quoting him as you were

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coming yet

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okay let's start

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let's start with airfoils

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and

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you know the naca right away when it was

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created

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recognized the

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the almost ad hoc state of the art of

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airfoil design in 1920

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the engine some engineers at the naca

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collected and categorized and and

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compiled

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airfoil data for hundreds of different

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airfoils around the world now what i'm

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showing you just one of these from this

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1920s in any naca tr 93

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this is a lift drag moment data

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for versus angle attack for the

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girding engine guardian 298 airfoil that

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was used for the fokker dr1

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and there are hundreds of these graphs

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and that the naca compiled

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just so that people could see ah this is

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the state of the art of airfoil

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knowledge airfoil design and it was a

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mess

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during the 1920s

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a person by the name of virginia's clark

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now clark i have to this is a group

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photo

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colonel clark is the man standing on the

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right in the back

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and as a matter of fact clark was a

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distinguished graduate of the naval

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academy in 1907. he went to san diego he

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learned to fly for the navy and then

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later on became part of the army

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during world war one

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he became the commander of the

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of the army research center at mccook

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field

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that was mentioned uh every once in a

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while yesterday

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so there he is on the right

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now what's what's important about

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virginia's clark he designed airfoils a

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whole series of airfoils called

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for most famous being the clark y

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airfoil

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and

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by the way this photograph

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clark was sent to mit for one of the

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first classes in aeronautical

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engineering i think it was about nine i

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think the date on this photograph is

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1918

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and

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somewhere in the back i think is

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funsacker

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nevertheless

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clark

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design

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the clark y air force i'm going to put

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that on

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and

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here's what clark had to say

289
00:11:53,750 --> 00:11:50,959
about this aerofoil about the whole

290
00:11:56,069 --> 00:11:53,760
status of of airfoil design and this

291
00:11:58,870 --> 00:11:56,079
really shows the ad hoc nature of

292
00:12:00,870 --> 00:11:58,880
airfoil design this was a quote

293
00:12:03,110 --> 00:12:00,880
it was published in an interview that he

294
00:12:05,190 --> 00:12:03,120
had with aviation magazine now that was

295
00:12:08,710 --> 00:12:05,200
forerunner of what we call aviation week

296
00:12:10,870 --> 00:12:08,720
today it was in october 1927. colonel

297
00:12:12,629 --> 00:12:10,880
clark was asked

298
00:12:14,470 --> 00:12:12,639
how do you go about designing these

299
00:12:15,910 --> 00:12:14,480
airfoils of yours

300
00:12:18,230 --> 00:12:15,920
they've become famous by that time

301
00:12:21,350 --> 00:12:18,240
because so many airplanes were using the

302
00:12:23,110 --> 00:12:21,360
clark uh clark series of airfarms now

303
00:12:24,389 --> 00:12:23,120
colonel clark uh

304
00:12:27,190 --> 00:12:24,399
how do you go about designing these

305
00:12:28,550 --> 00:12:27,200
airfalls of yours what is the secret

306
00:12:30,069 --> 00:12:28,560
clark laughed

307
00:12:32,790 --> 00:12:30,079
and replied

308
00:12:34,389 --> 00:12:32,800
i would gladly tell you the secret if i

309
00:12:36,710 --> 00:12:34,399
knew of any

310
00:12:38,870 --> 00:12:36,720
the airfoil sections just seemed to lay

311
00:12:41,829 --> 00:12:38,880
themselves out and

312
00:12:44,230 --> 00:12:41,839
when good luck attends

313
00:12:46,550 --> 00:12:44,240
fair results are obtained

314
00:12:48,870 --> 00:12:46,560
when good luck attends

315
00:12:52,389 --> 00:12:48,880
fair results are attained that was the

316
00:12:54,550 --> 00:12:52,399
status of airfoil design and development

317
00:12:57,269 --> 00:12:54,560
in the even up at the towards the

318
00:13:03,590 --> 00:12:57,279
beginning of the 1930s

319
00:13:08,629 --> 00:13:07,269
in 1920s oh i should say

320
00:13:09,829 --> 00:13:08,639
if you just go out the hall and look

321
00:13:11,670 --> 00:13:09,839
down in the

322
00:13:13,829 --> 00:13:11,680
milestones of light gallery you see not

323
00:13:15,910 --> 00:13:13,839
hanging there but on the floor now the

324
00:13:18,550 --> 00:13:15,920
spirit of st louis the spirit of saint

325
00:13:20,389 --> 00:13:18,560
louis uses a clark y air force for

326
00:13:23,269 --> 00:13:20,399
example

327
00:13:27,829 --> 00:13:25,430
this person

328
00:13:29,670 --> 00:13:27,839
walked in the front gates

329
00:13:32,710 --> 00:13:29,680
of langley memorial aeronautical

330
00:13:33,829 --> 00:13:32,720
laboratory a year after he had graduated

331
00:13:35,509 --> 00:13:33,839
from

332
00:13:37,670 --> 00:13:35,519
university of california berkeley and

333
00:13:40,150 --> 00:13:37,680
mcken with a bachelor's degree in

334
00:13:42,550 --> 00:13:40,160
mechanical engineering this is eastman

335
00:13:45,670 --> 00:13:42,560
jacobs his name was mentioned several

336
00:13:47,509 --> 00:13:45,680
times in some presentations yesterday

337
00:13:50,310 --> 00:13:47,519
now jacobs

338
00:13:54,150 --> 00:13:50,320
within a few years became director of

339
00:13:56,389 --> 00:13:54,160
the variable density wind tunnel

340
00:13:57,350 --> 00:13:56,399
dick hellion said some interesting

341
00:13:59,350 --> 00:13:57,360
things

342
00:14:00,949 --> 00:13:59,360
about the variable density wind tunnel

343
00:14:03,670 --> 00:14:00,959
yesterday

344
00:14:05,350 --> 00:14:03,680
and in that tunnel

345
00:14:07,030 --> 00:14:05,360
there it is there's the variable density

346
00:14:09,350 --> 00:14:07,040
wind tunnel let me remind you what that

347
00:14:11,350 --> 00:14:09,360
is is a big pressure tank

348
00:14:13,509 --> 00:14:11,360
and inside that pressure tank is a is a

349
00:14:14,870 --> 00:14:13,519
wind tunnel complete wind tunnel inside

350
00:14:16,949 --> 00:14:14,880
that pressure tank

351
00:14:18,150 --> 00:14:16,959
and that tank was pressurized to 20

352
00:14:21,350 --> 00:14:18,160
atmospheres

353
00:14:23,269 --> 00:14:21,360
so that means that the air pressure

354
00:14:24,470 --> 00:14:23,279
in the airstream flowing over the model

355
00:14:27,829 --> 00:14:24,480
in that wind tunnel was at 20

356
00:14:28,629 --> 00:14:27,839
atmospheres high density air and that

357
00:14:31,030 --> 00:14:28,639
in

358
00:14:32,629 --> 00:14:31,040
aerodynamics parlance that means the

359
00:14:34,710 --> 00:14:32,639
reynolds number was high the reynolds

360
00:14:36,710 --> 00:14:34,720
number was almost equivalent to that

361
00:14:38,069 --> 00:14:36,720
encountered in free flight and so

362
00:14:42,710 --> 00:14:38,079
measurements

363
00:14:45,509 --> 00:14:42,720
this variable density tunnel

364
00:14:47,910 --> 00:14:45,519
were reasonable representations of what

365
00:14:50,470 --> 00:14:47,920
you could experience in full-scale

366
00:14:53,189 --> 00:14:50,480
flight particularly in those days so

367
00:14:56,710 --> 00:14:53,199
here we have eastman jacobs

368
00:14:58,949 --> 00:14:56,720
running that tunnel now and he begins a

369
00:15:01,269 --> 00:14:58,959
whole series

370
00:15:01,990 --> 00:15:01,279
of

371
00:15:07,509 --> 00:15:02,000
in

372
00:15:09,590 --> 00:15:07,519
designs now this is what was a if i had

373
00:15:11,910 --> 00:15:09,600
a laser pointer and i have a little red

374
00:15:14,629 --> 00:15:11,920
dot there but if if you look at the

375
00:15:17,350 --> 00:15:14,639
bottom picture that's an airfoil

376
00:15:20,310 --> 00:15:17,360
and you'll see that there's a curved

377
00:15:21,910 --> 00:15:20,320
line at midway in the middle of that

378
00:15:25,509 --> 00:15:21,920
airflow that's called the mean camera

379
00:15:30,389 --> 00:15:28,389
that airfoil is designed by first coming

380
00:15:32,629 --> 00:15:30,399
up with the camber line and then

381
00:15:34,710 --> 00:15:32,639
wrapping around it a symmetrical

382
00:15:37,110 --> 00:15:34,720
thickness distribution and that picture

383
00:15:39,670 --> 00:15:37,120
up on the top is the symmetrical

384
00:15:41,110 --> 00:15:39,680
thickness distribution so you combine

385
00:15:43,430 --> 00:15:41,120
the camber line with that thickness

386
00:15:46,069 --> 00:15:43,440
distribution and presto you've got an

387
00:15:46,949 --> 00:15:46,079
airfoil and you have an airfoil that is

388
00:15:50,150 --> 00:15:46,959
sort of

389
00:15:52,949 --> 00:15:50,160
designed in a systematic way

390
00:15:56,230 --> 00:15:52,959
this led to a whole series of airfoils

391
00:15:59,990 --> 00:15:56,240
which was called the naca

392
00:16:02,230 --> 00:16:00,000
four digit airfoil series

393
00:16:04,389 --> 00:16:02,240
which will come up here in a minute

394
00:16:06,870 --> 00:16:04,399
and there they are

395
00:16:08,790 --> 00:16:06,880
these airfoils not only were they

396
00:16:11,670 --> 00:16:08,800
systematically designed they were

397
00:16:14,389 --> 00:16:11,680
effective airflows the naca

398
00:16:16,949 --> 00:16:14,399
tested them extensively so there was a

399
00:16:19,749 --> 00:16:16,959
lot of experimental data available to

400
00:16:23,910 --> 00:16:19,759
airplane designers on these airfoils and

401
00:16:26,949 --> 00:16:23,920
so a very large number of airplanes

402
00:16:32,150 --> 00:16:26,959
during the 1930s used the naca

403
00:16:36,470 --> 00:16:33,829
for example

404
00:16:38,470 --> 00:16:36,480
not only just in the united states

405
00:16:40,470 --> 00:16:38,480
but

406
00:16:43,030 --> 00:16:40,480
when r.j mitchell was designing the

407
00:16:46,590 --> 00:16:43,040
spitfire

408
00:16:50,629 --> 00:16:46,600
that airplane uses an naca

409
00:16:53,829 --> 00:16:50,639
2213. it's a 13 thick aerofoil at the

410
00:16:55,910 --> 00:16:53,839
root tapers to a 22.05 five percent

411
00:16:58,550 --> 00:16:55,920
thick at the tip

412
00:16:59,829 --> 00:16:58,560
the spitfire used in naca four dision

413
00:17:02,550 --> 00:16:59,839
airfoil

414
00:17:05,990 --> 00:17:02,560
its major protagonist in the battle of

415
00:17:08,549 --> 00:17:06,000
britain the messerschmitt 109 also used

416
00:17:09,669 --> 00:17:08,559
an nac air foil it was sort of a strange

417
00:17:11,510 --> 00:17:09,679
one

418
00:17:13,029 --> 00:17:11,520
it was uh it was

419
00:17:16,870 --> 00:17:13,039
essentially called a

420
00:17:18,710 --> 00:17:16,880
2r comma 12 airfoil now you're gonna if

421
00:17:21,029 --> 00:17:18,720
you look for data for that airfoil it's

422
00:17:23,510 --> 00:17:21,039
hard to find because

423
00:17:25,990 --> 00:17:23,520
the naca felt that was not a very good

424
00:17:28,549 --> 00:17:26,000
airfoil very quickly after testing they

425
00:17:31,909 --> 00:17:28,559
found that that airfall it had low drag

426
00:17:33,830 --> 00:17:31,919
that was a big advantage it also had a

427
00:17:36,070 --> 00:17:33,840
low maximum lift coefficient and

428
00:17:38,549 --> 00:17:36,080
prematurely stolen

429
00:17:39,990 --> 00:17:38,559
so the naca

430
00:17:41,510 --> 00:17:40,000
recommended that

431
00:17:43,830 --> 00:17:41,520
here in the united states recommended

432
00:17:47,110 --> 00:17:43,840
people don't use it

433
00:17:49,590 --> 00:17:47,120
the engineers the designers the me109

434
00:17:53,190 --> 00:17:49,600
like that low drag feature and they use

435
00:17:57,029 --> 00:17:53,200
that airfoil on the 109. so i mean just

436
00:17:59,830 --> 00:17:57,039
it's just an example of how the airfoil

437
00:18:02,070 --> 00:17:59,840
were carried out by the naca by people

438
00:18:03,830 --> 00:18:02,080
like eastman jacobs and his

439
00:18:07,669 --> 00:18:03,840
and his colleagues

440
00:18:08,789 --> 00:18:07,679
provided a major change a major

441
00:18:09,750 --> 00:18:08,799
improvement

442
00:18:14,390 --> 00:18:09,760
in

443
00:18:15,590 --> 00:18:14,400
basically of air airfoil performance and

444
00:18:18,310 --> 00:18:15,600
giving

445
00:18:21,270 --> 00:18:18,320
airplane designers the opportunity to

446
00:18:24,230 --> 00:18:21,280
use effective airfoils on the airplane

447
00:18:27,510 --> 00:18:24,240
set this is one of the big deals during

448
00:18:33,669 --> 00:18:27,520
the 1930s from the naca well jacobs

449
00:18:37,750 --> 00:18:35,350
and i'm waiting for the next one to come

450
00:18:41,029 --> 00:18:39,029
i should say

451
00:18:43,669 --> 00:18:41,039
there is a jacob's had a colleague at

452
00:18:46,310 --> 00:18:43,679
langley theodore theodorsen theodores in

453
00:18:48,470 --> 00:18:46,320
the 1930s was the most respected

454
00:18:52,150 --> 00:18:48,480
theoretical aerodynamicist

455
00:18:54,390 --> 00:18:52,160
for the naca and theodorsen in parallel

456
00:18:55,830 --> 00:18:54,400
with these airfoil measurements being

457
00:18:57,669 --> 00:18:55,840
carried out in the variable density

458
00:19:00,789 --> 00:18:57,679
tunnel

459
00:19:02,150 --> 00:19:00,799
came up with a theoretical method

460
00:19:04,310 --> 00:19:02,160
for

461
00:19:07,990 --> 00:19:04,320
calculating the pressure distributions

462
00:19:09,990 --> 00:19:08,000
over airfoils of arbitrary shapes and

463
00:19:11,510 --> 00:19:10,000
arbitrary thickness that was a big that

464
00:19:13,190 --> 00:19:11,520
was a big improvement

465
00:19:15,350 --> 00:19:13,200
and it was i'll show you one of his

466
00:19:16,710 --> 00:19:15,360
results

467
00:19:19,590 --> 00:19:16,720
this is a result

468
00:19:21,430 --> 00:19:19,600
actually on a clark y airfoil showing uh

469
00:19:25,029 --> 00:19:21,440
pressure distributions or the bottom of

470
00:19:27,029 --> 00:19:25,039
the top of the airfoil and

471
00:19:29,190 --> 00:19:27,039
there are two curves shown there

472
00:19:31,190 --> 00:19:29,200
one is the theoretical measurement i

473
00:19:32,950 --> 00:19:31,200
mean the calculation of the pressure and

474
00:19:34,950 --> 00:19:32,960
one is the experimental measurement of

475
00:19:38,630 --> 00:19:34,960
the pressure distribution and you'll see

476
00:19:40,630 --> 00:19:38,640
that especially uh the uh over the top

477
00:19:43,430 --> 00:19:40,640
the lower pressures are plotted on the

478
00:19:45,430 --> 00:19:43,440
upper part of that graph and you'll see

479
00:19:47,590 --> 00:19:45,440
there's a little bit discrepancy there

480
00:19:50,150 --> 00:19:47,600
now to give you some idea of the kind of

481
00:19:51,990 --> 00:19:50,160
person theodorson was

482
00:19:53,590 --> 00:19:52,000
he looked at that and he said the

483
00:19:56,150 --> 00:19:53,600
trouble is with the experimental

484
00:19:57,669 --> 00:19:56,160
measurements the experimentals ought to

485
00:19:59,669 --> 00:19:57,679
take another look

486
00:20:00,789 --> 00:19:59,679
uh

487
00:20:02,950 --> 00:20:00,799
in my

488
00:20:05,830 --> 00:20:02,960
experience all the beginning you know

489
00:20:09,190 --> 00:20:05,840
right from the start even when i was

490
00:20:10,630 --> 00:20:09,200
educated in engineering

491
00:20:14,070 --> 00:20:10,640
you know

492
00:20:15,110 --> 00:20:14,080
you always accepted experimental data as

493
00:20:16,630 --> 00:20:15,120
the

494
00:20:21,909 --> 00:20:16,640
major

495
00:20:24,149 --> 00:20:21,919
any theoretical calculations if there

496
00:20:26,149 --> 00:20:24,159
was disagreement about that you would

497
00:20:28,230 --> 00:20:26,159
suspect the theoretical calculations but

498
00:20:30,470 --> 00:20:28,240
not theodore but i just wanted to throw

499
00:20:32,710 --> 00:20:30,480
this in that at the same time that these

500
00:20:35,270 --> 00:20:32,720
air form measurements were being made

501
00:20:38,310 --> 00:20:35,280
the naca had their most expert

502
00:20:40,070 --> 00:20:38,320
theoretician working on calculating

503
00:20:42,470 --> 00:20:40,080
particularly the pressure distributions

504
00:20:45,590 --> 00:20:42,480
over arbitrary airfalls of arbitrary

505
00:20:51,909 --> 00:20:49,190
one last aspect of this airfoil design

506
00:20:54,149 --> 00:20:51,919
eastman jacobs toured

507
00:20:55,590 --> 00:20:54,159
europe in 1935.

508
00:20:57,110 --> 00:20:55,600
he was over there for the volta

509
00:20:58,630 --> 00:20:57,120
conference which was mentioned yesterday

510
00:21:01,270 --> 00:20:58,640
and i'm going to talk about that later

511
00:21:03,669 --> 00:21:01,280
on but he was there and he took the

512
00:21:05,990 --> 00:21:03,679
opportunity over a space of a couple of

513
00:21:07,909 --> 00:21:06,000
months to tour various laboratories

514
00:21:12,870 --> 00:21:07,919
including in britain he visited

515
00:21:17,669 --> 00:21:15,270
g.i taylor who was the

516
00:21:20,149 --> 00:21:17,679
very noted fluid analysis

517
00:21:22,710 --> 00:21:20,159
and melvil jones who was a very noted

518
00:21:25,270 --> 00:21:22,720
aerodynamicist both at cambridge and

519
00:21:28,470 --> 00:21:25,280
they both told jacob said look

520
00:21:31,110 --> 00:21:28,480
you know we have discovered at cambridge

521
00:21:31,990 --> 00:21:31,120
in the wind tunnel that if you have a

522
00:21:37,590 --> 00:21:32,000
body

523
00:21:39,750 --> 00:21:37,600
pressure keeps going down over the

524
00:21:41,830 --> 00:21:39,760
surface of the body as you flow down the

525
00:21:43,190 --> 00:21:41,840
surface of the body pressure goes down

526
00:21:44,470 --> 00:21:43,200
it's called a favorable pressure

527
00:21:46,549 --> 00:21:44,480
gradient

528
00:21:48,870 --> 00:21:46,559
the boundary layer on that surface will

529
00:21:51,110 --> 00:21:48,880
tend to remain laminar

530
00:21:51,990 --> 00:21:51,120
and only when that pressure starts going

531
00:21:54,710 --> 00:21:52,000
up

532
00:21:56,789 --> 00:21:54,720
do you have a transition to a turbulent

533
00:21:59,909 --> 00:21:56,799
boundary layer now that's that's

534
00:22:03,190 --> 00:21:59,919
important because the skin friction for

535
00:22:05,029 --> 00:22:03,200
a laminar boundary layer is much lower

536
00:22:06,549 --> 00:22:05,039
than the skin friction for a turbulent

537
00:22:07,430 --> 00:22:06,559
boundary layer everything else being

538
00:22:10,830 --> 00:22:07,440
equal

539
00:22:13,590 --> 00:22:10,840
factor of 10 lower uh can be and so

540
00:22:16,789 --> 00:22:13,600
therefore uh there this was a pretty

541
00:22:19,590 --> 00:22:16,799
important uh piece of information that

542
00:22:20,549 --> 00:22:19,600
eastman jacobs took back to langley with

543
00:22:22,630 --> 00:22:20,559
him

544
00:22:26,549 --> 00:22:22,640
and then he sat down and said how in the

545
00:22:32,230 --> 00:22:26,559
world can i design an airfoil shape

546
00:22:34,149 --> 00:22:32,240
to create a long region a wide swath

547
00:22:35,830 --> 00:22:34,159
of favorable pressure grain and

548
00:22:39,110 --> 00:22:35,840
decreasing pressure over the surface of

549
00:22:40,789 --> 00:22:39,120
the airfall to encourage a large region

550
00:22:43,430 --> 00:22:40,799
of laminar flow over there fall and

551
00:22:45,830 --> 00:22:43,440
therefore uh encounter

552
00:22:47,430 --> 00:22:45,840
have a much lower skin friction

553
00:22:49,830 --> 00:22:47,440
coefficient well

554
00:22:52,710 --> 00:22:49,840
that was not easy uh there was there was

555
00:22:54,549 --> 00:22:52,720
no way of doing that and so jacobs took

556
00:22:56,310 --> 00:22:54,559
some of the work that theodorson had

557
00:22:58,390 --> 00:22:56,320
done theodores and said this is

558
00:23:00,549 --> 00:22:58,400
impossible you can't you can't take a

559
00:23:02,870 --> 00:23:00,559
pressure distribution and design an

560
00:23:05,190 --> 00:23:02,880
airfoil that's going to give you that

561
00:23:06,470 --> 00:23:05,200
pressure distribution jacobs went home

562
00:23:09,029 --> 00:23:06,480
for three days

563
00:23:11,750 --> 00:23:09,039
studied theodore since theory came up

564
00:23:13,590 --> 00:23:11,760
with a technique for designing an

565
00:23:16,149 --> 00:23:13,600
airfoil that indeed

566
00:23:17,990 --> 00:23:16,159
would create a given pressure

567
00:23:19,350 --> 00:23:18,000
distribution

568
00:23:20,789 --> 00:23:19,360
whoops

569
00:23:22,549 --> 00:23:20,799
i'm going to go back

570
00:23:24,149 --> 00:23:22,559
and what you see there

571
00:23:26,549 --> 00:23:24,159
and the top graph

572
00:23:29,510 --> 00:23:26,559
is a standard naca airflow and you see

573
00:23:31,350 --> 00:23:29,520
the pressure distribution uh it's uh

574
00:23:33,590 --> 00:23:31,360
starts at the front of the airfoil and

575
00:23:35,190 --> 00:23:33,600
it drops like a rock reaches a

576
00:23:36,870 --> 00:23:35,200
minimum

577
00:23:38,630 --> 00:23:36,880
just downstream the leading edge and

578
00:23:40,390 --> 00:23:38,640
then you have this big

579
00:23:41,830 --> 00:23:40,400
region of increasing pressure the

580
00:23:43,990 --> 00:23:41,840
adverse pressure gradient that

581
00:23:46,310 --> 00:23:44,000
encourages turbulent flow and that was

582
00:23:48,789 --> 00:23:46,320
what was encountered over all all these

583
00:23:51,750 --> 00:23:48,799
standard airfoils basically they had

584
00:23:53,510 --> 00:23:51,760
turbulent boundary layers on them

585
00:23:56,390 --> 00:23:53,520
the bottom graph

586
00:23:57,430 --> 00:23:56,400
is a different shaped air form

587
00:23:59,830 --> 00:23:57,440
and you can see the pressure

588
00:24:02,070 --> 00:23:59,840
distribution there drops like a rock or

589
00:24:05,269 --> 00:24:02,080
going going around the leading edge and

590
00:24:08,149 --> 00:24:05,279
then maintains a decreasing

591
00:24:09,590 --> 00:24:08,159
favorable pressure practically to you

592
00:24:11,510 --> 00:24:09,600
know further downstream and then the

593
00:24:13,190 --> 00:24:11,520
midpoint of the airfoil and then you get

594
00:24:16,950 --> 00:24:13,200
your pressure increase

595
00:24:21,269 --> 00:24:16,960
that airfoil experienced a large region

596
00:24:24,230 --> 00:24:21,279
of laminar flow and therefore had a much

597
00:24:27,269 --> 00:24:24,240
lower skin friction coefficient

598
00:24:28,630 --> 00:24:27,279
that airfoil was called a laminar flow

599
00:24:31,990 --> 00:24:28,640
airfoil

600
00:24:34,870 --> 00:24:32,000
the ana there was a whole series of naca

601
00:24:37,510 --> 00:24:34,880
laminar flow airfoils that were designed

602
00:24:39,830 --> 00:24:37,520
and investigated and measured total

603
00:24:41,750 --> 00:24:39,840
measurements made towards the end of the

604
00:24:45,350 --> 00:24:41,760
1930s

605
00:24:47,909 --> 00:24:45,360
and that work unlike almost all the

606
00:24:50,149 --> 00:24:47,919
previous work at the naca

607
00:24:51,830 --> 00:24:50,159
that work on the laminar flow airflow

608
00:24:53,830 --> 00:24:51,840
was considered to be

609
00:24:56,310 --> 00:24:53,840
so important that it was immediately

610
00:24:58,950 --> 00:24:56,320
classified and so the word didn't get

611
00:25:00,630 --> 00:24:58,960
around very much about these new laminar

612
00:25:03,990 --> 00:25:00,640
flow air falls

613
00:25:07,590 --> 00:25:04,000
but it did get to edgar smooth who was

614
00:25:09,830 --> 00:25:07,600
designing the p51 at north america

615
00:25:10,789 --> 00:25:09,840
and smood had an opportunity first he

616
00:25:14,470 --> 00:25:10,799
had designed

617
00:25:17,430 --> 00:25:14,480
using p51 using a standard airfoil and

618
00:25:19,990 --> 00:25:17,440
then he was visited by several naca

619
00:25:22,070 --> 00:25:20,000
engineers one one day this is what the

620
00:25:23,269 --> 00:25:22,080
naca did they sent people out they

621
00:25:25,830 --> 00:25:23,279
talked to

622
00:25:28,630 --> 00:25:25,840
important people in industry and smooth

623
00:25:30,710 --> 00:25:28,640
learned about this classified

624
00:25:33,190 --> 00:25:30,720
laminar flow airform

625
00:25:35,269 --> 00:25:33,200
he designed a different wing he took two

626
00:25:37,750 --> 00:25:35,279
models up to the wind tunnel at the

627
00:25:39,510 --> 00:25:37,760
university of washington tested

628
00:25:41,669 --> 00:25:39,520
standard wing and tested the wing with

629
00:25:43,990 --> 00:25:41,679
the laminar flow airfoil the laminar

630
00:25:48,230 --> 00:25:44,000
flow airfoil performed much better

631
00:25:49,669 --> 00:25:48,240
presto the p51 is the first airplane in

632
00:25:51,669 --> 00:25:49,679
history

633
00:25:55,510 --> 00:25:51,679
first production line airplane in

634
00:25:58,390 --> 00:25:55,520
history to use a laminar flow airflow

635
00:26:01,029 --> 00:25:58,400
now so this is a big deal is an

636
00:26:03,750 --> 00:26:01,039
important development

637
00:26:05,990 --> 00:26:03,760
a just another follow-on of the kind of

638
00:26:09,750 --> 00:26:06,000
referral work and the

639
00:26:12,870 --> 00:26:09,760
contributions being made by the naca

640
00:26:14,070 --> 00:26:12,880
in aerodynamics in the 1930s

641
00:26:15,990 --> 00:26:14,080
now

642
00:26:17,350 --> 00:26:16,000
the rest of that story by the way is

643
00:26:18,950 --> 00:26:17,360
that

644
00:26:20,710 --> 00:26:18,960
in real life

645
00:26:23,750 --> 00:26:20,720
the laminar flow airfoil didn't really

646
00:26:25,990 --> 00:26:23,760
produce much laminar flow because in the

647
00:26:28,070 --> 00:26:26,000
wind tunnel the variable density tunnel

648
00:26:28,789 --> 00:26:28,080
and other wind tunnels at langley

649
00:26:34,470 --> 00:26:28,799
the

650
00:26:36,310 --> 00:26:34,480
finely polished jewels nice and smooth

651
00:26:38,390 --> 00:26:36,320
in reality when you build something like

652
00:26:40,310 --> 00:26:38,400
a p-51 you have manufacturing

653
00:26:41,830 --> 00:26:40,320
irregularities

654
00:26:43,830 --> 00:26:41,840
you have the airplane flying through the

655
00:26:46,390 --> 00:26:43,840
air encountering all kinds of insects

656
00:26:48,950 --> 00:26:46,400
bug spots on the surface all of that

657
00:26:50,950 --> 00:26:48,960
produces roughness which encourages the

658
00:26:53,669 --> 00:26:50,960
turbulent boundary layer so for all

659
00:26:56,549 --> 00:26:53,679
practical purposes that laminar flow

660
00:26:58,230 --> 00:26:56,559
wing on the p51 did not create laminar

661
00:27:01,029 --> 00:26:58,240
flow but

662
00:27:02,870 --> 00:27:01,039
and here's a case of serendipity in the

663
00:27:05,110 --> 00:27:02,880
history of technology

664
00:27:06,789 --> 00:27:05,120
it turned out that that shape of the

665
00:27:09,750 --> 00:27:06,799
laminar flow airfoil

666
00:27:11,909 --> 00:27:09,760
also had what we call a higher critical

667
00:27:15,029 --> 00:27:11,919
mach number

668
00:27:17,110 --> 00:27:15,039
that wing that airplane could fly faster

669
00:27:18,630 --> 00:27:17,120
before encountering some adverse

670
00:27:21,110 --> 00:27:18,640
compressibility effects which i'm going

671
00:27:24,470 --> 00:27:21,120
to share with you in in just a few

672
00:27:26,630 --> 00:27:24,480
minutes but that was the deal that was

673
00:27:28,950 --> 00:27:26,640
all this airfoil work

674
00:27:30,389 --> 00:27:28,960
culminating in the laminar flow airfall

675
00:27:31,750 --> 00:27:30,399
even

676
00:27:34,549 --> 00:27:31,760
kelly johnson

677
00:27:36,389 --> 00:27:34,559
when he designed the p80

678
00:27:39,190 --> 00:27:36,399
in 1944

679
00:27:42,149 --> 00:27:39,200
used a laminar flow airfoil

680
00:27:44,870 --> 00:27:42,159
so that was that was very important okay

681
00:27:46,230 --> 00:27:44,880
that's it the airflow work being done at

682
00:27:48,789 --> 00:27:46,240
the naca

683
00:27:50,630 --> 00:27:48,799
the langley memorial laboratory was very

684
00:27:52,950 --> 00:27:50,640
important i'm going to quickly go to the

685
00:27:58,630 --> 00:27:52,960
next subject

686
00:27:59,830 --> 00:27:58,640
fred white

687
00:28:02,389 --> 00:27:59,840
took over

688
00:28:04,630 --> 00:28:02,399
a new facility in 1928

689
00:28:07,029 --> 00:28:04,640
at langley it was discussed yesterday

690
00:28:09,669 --> 00:28:07,039
jeremy kinney mentioned it several times

691
00:28:10,710 --> 00:28:09,679
the propeller research time

692
00:28:13,110 --> 00:28:10,720
and

693
00:28:17,750 --> 00:28:14,950
in that tunnel

694
00:28:20,389 --> 00:28:17,760
a new project was initiated and this

695
00:28:22,149 --> 00:28:20,399
this project was initiated really as a

696
00:28:24,950 --> 00:28:22,159
result of meeting the aircraft

697
00:28:27,350 --> 00:28:24,960
manufacturers at langley uh they

698
00:28:31,350 --> 00:28:27,360
encouraged some work on cowlings and

699
00:28:32,789 --> 00:28:31,360
you'll find the 1927 nac annual report

700
00:28:34,789 --> 00:28:32,799
the following quote

701
00:28:37,110 --> 00:28:34,799
one of the problems suggested the study

702
00:28:39,269 --> 00:28:37,120
the effect of cowling and fuselage shape

703
00:28:41,430 --> 00:28:39,279
on the resistance and

704
00:28:43,590 --> 00:28:41,440
and cooling characteristics of

705
00:28:45,990 --> 00:28:43,600
air-cooled engines was promptly

706
00:28:47,110 --> 00:28:46,000
incorporated in the committee's research

707
00:28:49,990 --> 00:28:47,120
program

708
00:28:51,350 --> 00:28:50,000
and so there you have fred weick

709
00:28:55,029 --> 00:28:51,360
in the

710
00:28:59,430 --> 00:28:57,190
see the fuselage there's a one of the

711
00:29:01,190 --> 00:28:59,440
cowlings they were testing on the future

712
00:29:03,830 --> 00:29:01,200
in that prt

713
00:29:05,590 --> 00:29:03,840
and the result of that work

714
00:29:08,789 --> 00:29:05,600
produced something that was called the

715
00:29:10,549 --> 00:29:08,799
number 10 naca cali

716
00:29:12,149 --> 00:29:10,559
there's the lockheed vega

717
00:29:14,549 --> 00:29:12,159
one of the first airplanes to

718
00:29:15,430 --> 00:29:14,559
incorporate the cal that's the that's

719
00:29:20,070 --> 00:29:15,440
that

720
00:29:23,190 --> 00:29:20,080
around the engine the the

721
00:29:24,310 --> 00:29:23,200
the cylinders of the engine and the naca

722
00:29:26,950 --> 00:29:24,320
cowling

723
00:29:28,149 --> 00:29:26,960
not only reduced the drag but also

724
00:29:28,950 --> 00:29:28,159
increased

725
00:29:31,110 --> 00:29:28,960
made

726
00:29:32,310 --> 00:29:31,120
and improved the cooling

727
00:29:36,710 --> 00:29:32,320
of the

728
00:29:39,750 --> 00:29:36,720
and here it is on the lockheed vega the

729
00:29:44,549 --> 00:29:42,070
before the cowling had a top speed of

730
00:29:46,430 --> 00:29:44,559
165 miles an hour

731
00:29:49,029 --> 00:29:46,440
after the cowling was added

732
00:29:50,710 --> 00:29:49,039
190 miles an hour is a top speed that

733
00:29:54,630 --> 00:29:50,720
was dramatic

734
00:29:57,190 --> 00:29:54,640
again another feather in the cap

735
00:29:58,470 --> 00:29:57,200
in the aerodynamic developments of the

736
00:30:01,110 --> 00:29:58,480
naca

737
00:30:02,789 --> 00:30:01,120
at the langley memorial laboratory and

738
00:30:05,510 --> 00:30:02,799
the final feather

739
00:30:10,950 --> 00:30:07,510
has to do with high speed

740
00:30:13,029 --> 00:30:10,960
compressibility problems

741
00:30:17,269 --> 00:30:13,039
we'll start here

742
00:30:18,389 --> 00:30:17,279
in 1918 at mccook field in dayton ohio

743
00:30:20,070 --> 00:30:18,399
the army

744
00:30:21,750 --> 00:30:20,080
put together

745
00:30:23,430 --> 00:30:21,760
a new wind tunnel

746
00:30:24,630 --> 00:30:23,440
dick hallian mentioned that wind tunnel

747
00:30:26,389 --> 00:30:24,640
yesterday

748
00:30:28,149 --> 00:30:26,399
and in fact he even mentioned quite

749
00:30:31,350 --> 00:30:28,159
properly it's a pretty long one tall

750
00:30:34,830 --> 00:30:31,360
it's 18 feet it's a 14 inch test section

751
00:30:37,350 --> 00:30:34,840
uh it's so historic that uh it's

752
00:30:39,990 --> 00:30:37,360
uh belongs to the

753
00:30:42,070 --> 00:30:40,000
museum of the air force in dayton ohio

754
00:30:44,389 --> 00:30:42,080
on display the last time i was there

755
00:30:46,950 --> 00:30:44,399
sort of tucked in a corner but that wind

756
00:30:50,549 --> 00:30:46,960
tunnel you'll see here that wind tunnel

757
00:30:52,070 --> 00:30:50,559
had speeds from 25 to 406

758
00:30:55,310 --> 00:30:52,080
miles an hour

759
00:30:59,590 --> 00:30:55,320
now what airplane in 1918 would fly at

760
00:31:02,310 --> 00:30:59,600
465 miles an hour oh obviously none

761
00:31:04,870 --> 00:31:02,320
and there was nobody in that period of

762
00:31:07,350 --> 00:31:04,880
time who was even thinking about

763
00:31:09,269 --> 00:31:07,360
airplane speeds like that but

764
00:31:11,029 --> 00:31:09,279
they knew that the tip speeds of

765
00:31:13,909 --> 00:31:11,039
propellers

766
00:31:15,830 --> 00:31:13,919
came in in fact excite they exceeded

767
00:31:18,310 --> 00:31:15,840
that velocity

768
00:31:19,830 --> 00:31:18,320
and there were some really strange

769
00:31:22,789 --> 00:31:19,840
things happening

770
00:31:25,029 --> 00:31:22,799
when tip speeds got up close to the

771
00:31:27,830 --> 00:31:25,039
upper pillars got up close to the speed

772
00:31:30,310 --> 00:31:27,840
of sound and these guys frank caldwell

773
00:31:32,870 --> 00:31:30,320
elijah fails in that wind tunnel were

774
00:31:35,830 --> 00:31:32,880
the first to measure

775
00:31:39,350 --> 00:31:35,840
the effect of high speeds on lift prior

776
00:31:42,149 --> 00:31:39,360
to that ballisticians knew that

777
00:31:43,909 --> 00:31:42,159
for on projectiles if you fly up near

778
00:31:45,990 --> 00:31:43,919
the speed of sound suddenly there's a

779
00:31:47,909 --> 00:31:46,000
big increase in drag on the projectile

780
00:31:49,430 --> 00:31:47,919
but nobody had paid any attention to

781
00:31:52,149 --> 00:31:49,440
lift

782
00:31:54,789 --> 00:31:52,159
here's a strange looking graph

783
00:31:56,789 --> 00:31:54,799
as soon as it comes up

784
00:31:58,950 --> 00:31:56,799
from this result

785
00:32:00,870 --> 00:31:58,960
of a cook field what you see there on

786
00:32:03,029 --> 00:32:00,880
the vertical axis is something called

787
00:32:04,950 --> 00:32:03,039
lift coefficient on the horizontal axis

788
00:32:06,710 --> 00:32:04,960
is velocity speed

789
00:32:08,389 --> 00:32:06,720
measuring the wind tunnel and you can

790
00:32:10,310 --> 00:32:08,399
see just pay attention to the right hand

791
00:32:12,149 --> 00:32:10,320
side of that that picture

792
00:32:13,590 --> 00:32:12,159
you'll see that as the velocity

793
00:32:16,070 --> 00:32:13,600
increases

794
00:32:18,870 --> 00:32:16,080
all of a sudden the lift

795
00:32:22,230 --> 00:32:18,880
falls off the cliff it it just

796
00:32:24,549 --> 00:32:22,240
dramatically decreases

797
00:32:26,070 --> 00:32:24,559
an important observation they didn't

798
00:32:27,990 --> 00:32:26,080
have a clue

799
00:32:31,430 --> 00:32:28,000
as to what was causing it but it was an

800
00:32:33,909 --> 00:32:31,440
important observation

801
00:32:34,710 --> 00:32:33,919
a few years later oh by the way i should

802
00:32:38,549 --> 00:32:34,720
say

803
00:32:40,389 --> 00:32:38,559
this work is published in an naca tr

804
00:32:43,750 --> 00:32:40,399
because the naca

805
00:32:44,950 --> 00:32:43,760
funded this work at the cook field

806
00:32:47,909 --> 00:32:44,960
okay

807
00:32:50,070 --> 00:32:47,919
a few years later in the early 1920s the

808
00:32:52,070 --> 00:32:50,080
naca gave a contract in the national

809
00:32:54,230 --> 00:32:52,080
bureau of standards in

810
00:32:55,669 --> 00:32:54,240
a series of tests

811
00:32:57,830 --> 00:32:55,679
one of which

812
00:32:59,909 --> 00:32:57,840
was carried out uh one series carried

813
00:33:02,230 --> 00:32:59,919
out at the edgewood arsenal

814
00:33:06,149 --> 00:33:02,240
up here in maryland

815
00:33:13,190 --> 00:33:08,470
some measurements were made on air foils

816
00:33:16,389 --> 00:33:14,630
well yes

817
00:33:18,310 --> 00:33:16,399
measurements were made actually there

818
00:33:19,990 --> 00:33:18,320
they were made by

819
00:33:22,549 --> 00:33:20,000
hugh dryden

820
00:33:25,190 --> 00:33:22,559
uh and frank caldwell you've heard frank

821
00:33:27,909 --> 00:33:25,200
caldwell's name when jeremy yesterday

822
00:33:28,950 --> 00:33:27,919
talked about variable pitch propellers

823
00:33:33,110 --> 00:33:28,960
and

824
00:33:35,029 --> 00:33:33,120
those guys measured for example

825
00:33:37,269 --> 00:33:35,039
a pressure distribution on the surface

826
00:33:38,870 --> 00:33:37,279
of an airfoil when it was going through

827
00:33:41,029 --> 00:33:38,880
this period where the lift coefficient

828
00:33:42,870 --> 00:33:41,039
is dropping off the cliff

829
00:33:44,950 --> 00:33:42,880
and

830
00:33:46,710 --> 00:33:44,960
that was being called now the critical

831
00:33:47,990 --> 00:33:46,720
speed when the lift coefficient dropped

832
00:33:49,430 --> 00:33:48,000
off the cliff

833
00:33:51,190 --> 00:33:49,440
later on we would call that at a

834
00:33:53,830 --> 00:33:51,200
critical mach number

835
00:33:56,549 --> 00:33:53,840
and the nbs results

836
00:33:58,950 --> 00:33:56,559
showed pressure distribution that were

837
00:34:00,630 --> 00:33:58,960
rather strange you had your decreasing

838
00:34:02,470 --> 00:34:00,640
pressure as the flow expanded over the

839
00:34:05,190 --> 00:34:02,480
top surface of the airflow suddenly

840
00:34:09,190 --> 00:34:05,200
there is a jump in pressure and then a

841
00:34:10,790 --> 00:34:09,200
plateau a flat pressure a plateau in the

842
00:34:12,710 --> 00:34:10,800
pressure distribution

843
00:34:13,909 --> 00:34:12,720
now it was known at that time

844
00:34:17,349 --> 00:34:13,919
that

845
00:34:19,430 --> 00:34:17,359
distribution encountered on an airplane

846
00:34:21,510 --> 00:34:19,440
wing when the airplane was at high angle

847
00:34:24,869 --> 00:34:21,520
attack and the wing stalls and that was

848
00:34:26,869 --> 00:34:24,879
a clear indication of stalling stalling

849
00:34:28,550 --> 00:34:26,879
with a flow separating off the top

850
00:34:29,829 --> 00:34:28,560
surface of the wing

851
00:34:35,190 --> 00:34:29,839
these

852
00:34:36,389 --> 00:34:35,200
phenomena on an airfoil at zero degrees

853
00:34:38,230 --> 00:34:36,399
angle attack

854
00:34:40,389 --> 00:34:38,240
but it was happening at high speeds and

855
00:34:42,550 --> 00:34:40,399
they interpreted

856
00:34:44,069 --> 00:34:42,560
this very bad effect that you see there

857
00:34:46,310 --> 00:34:44,079
the lift coefficient falling off the

858
00:34:48,310 --> 00:34:46,320
cliff the that is called the can be

859
00:34:50,389 --> 00:34:48,320
called the adverse compressibility

860
00:34:52,389 --> 00:34:50,399
effects due to a compressibility burble

861
00:34:54,869 --> 00:34:52,399
they call

862
00:34:57,109 --> 00:34:54,879
that is associated with

863
00:34:58,630 --> 00:34:57,119
separated flow

864
00:35:00,470 --> 00:34:58,640
but again

865
00:35:02,390 --> 00:35:00,480
nobody had a clue

866
00:35:04,630 --> 00:35:02,400
why was the flow separating here you had

867
00:35:06,230 --> 00:35:04,640
a wing it's an airfoil at zero degrees

868
00:35:09,190 --> 00:35:06,240
angle of attack and the flow is

869
00:35:11,109 --> 00:35:09,200
separating at these high speeds what was

870
00:35:12,870 --> 00:35:11,119
going on

871
00:35:14,710 --> 00:35:12,880
well

872
00:35:17,109 --> 00:35:14,720
john stack

873
00:35:18,710 --> 00:35:17,119
1928 graduate of aeronautical

874
00:35:20,310 --> 00:35:18,720
engineering at mit walked through the

875
00:35:22,069 --> 00:35:20,320
doors of the langley memorial

876
00:35:24,950 --> 00:35:22,079
aeronautical laboratory

877
00:35:27,349 --> 00:35:24,960
he soon became involved in a small

878
00:35:28,790 --> 00:35:27,359
high-speed wind tunnel at langley

879
00:35:32,150 --> 00:35:28,800
and stack

880
00:35:35,910 --> 00:35:32,160
measured in 1934 for the first time

881
00:35:37,829 --> 00:35:35,920
really definitive the typical naca kind

882
00:35:39,990 --> 00:35:37,839
of definitive measurements

883
00:35:41,829 --> 00:35:40,000
of

884
00:35:44,630 --> 00:35:41,839
lift coefficient and drag coefficient a

885
00:35:46,950 --> 00:35:44,640
moment coefficient as a function

886
00:35:48,710 --> 00:35:46,960
of velocity

887
00:35:51,109 --> 00:35:48,720
and this happened to be a clockwise

888
00:35:54,150 --> 00:35:51,119
airfoil believe it or not

889
00:35:56,710 --> 00:35:54,160
and indeed it was absolute proof of

890
00:35:58,390 --> 00:35:56,720
these adverse compressibility effects

891
00:36:01,109 --> 00:35:58,400
because the lift as you see it dropping

892
00:36:03,829 --> 00:36:01,119
off when you get to high speed the drag

893
00:36:06,710 --> 00:36:03,839
is going up out of sight that that's the

894
00:36:08,710 --> 00:36:06,720
kind of data that gave rise to the myth

895
00:36:11,190 --> 00:36:08,720
of the sound barrier because you look at

896
00:36:13,190 --> 00:36:11,200
that data and say man we're never going

897
00:36:15,510 --> 00:36:13,200
to be able to fly faster than the speed

898
00:36:19,109 --> 00:36:15,520
of sound because

899
00:36:21,750 --> 00:36:19,119
the drag is going out of sight

900
00:36:24,630 --> 00:36:21,760
and they knew at that time it was due to

901
00:36:27,190 --> 00:36:24,640
flow separation but what was causing the

902
00:36:28,870 --> 00:36:27,200
flow to separate

903
00:36:31,030 --> 00:36:28,880
now i'm going to pass by this is what a

904
00:36:32,630 --> 00:36:31,040
chance john stack

905
00:36:34,390 --> 00:36:32,640
at this period of time

906
00:36:36,950 --> 00:36:34,400
theorized because they couldn't measure

907
00:36:38,950 --> 00:36:36,960
things properly at mach 1

908
00:36:40,790 --> 00:36:38,960
in a wind tunnel that the only way we

909
00:36:44,150 --> 00:36:40,800
could do that is with a real research

910
00:36:46,710 --> 00:36:44,160
airplane in 1934 he was he really was

911
00:36:48,870 --> 00:36:46,720
the first person to suggest

912
00:36:51,670 --> 00:36:48,880
a research airplane to prove this

913
00:36:53,430 --> 00:36:51,680
mysterious range around mach 1 and it

914
00:36:55,349 --> 00:36:53,440
didn't get anywhere that's a graph for

915
00:36:56,950 --> 00:36:55,359
those of you who

916
00:36:58,790 --> 00:36:56,960
have studied airplane performance that's

917
00:37:01,270 --> 00:36:58,800
called a power required curve power

918
00:37:02,630 --> 00:37:01,280
required versus velocity two curves one

919
00:37:04,710 --> 00:37:02,640
with compressibility one without

920
00:37:07,270 --> 00:37:04,720
compressibility only reason i'm showing

921
00:37:09,589 --> 00:37:07,280
this i found this graph in the john

922
00:37:12,950 --> 00:37:09,599
stock our archives

923
00:37:16,310 --> 00:37:12,960
at langley and it was in a manila folder

924
00:37:17,990 --> 00:37:16,320
was in between some of john stack's old

925
00:37:20,069 --> 00:37:18,000
irs forms

926
00:37:22,390 --> 00:37:20,079
and there's even a

927
00:37:24,470 --> 00:37:22,400
rusty paper clip mark on the top of that

928
00:37:27,190 --> 00:37:24,480
graph but he was thinking about these

929
00:37:29,190 --> 00:37:27,200
things even published a paper in the

930
00:37:31,910 --> 00:37:29,200
journal of aeronautical sciences about

931
00:37:34,230 --> 00:37:31,920
this but john stack the really big

932
00:37:35,750 --> 00:37:34,240
contribution came

933
00:37:36,630 --> 00:37:35,760
and

934
00:37:40,230 --> 00:37:36,640
when

935
00:37:43,829 --> 00:37:40,240
in 1934 working for eastman jacobs

936
00:37:45,829 --> 00:37:43,839
eastman jacobs was his boss

937
00:37:48,390 --> 00:37:45,839
jacob suggested since we don't know

938
00:37:50,870 --> 00:37:48,400
what's going on in this flow

939
00:37:53,349 --> 00:37:50,880
why don't we put a schlearn system

940
00:37:55,109 --> 00:37:53,359
across the wind tunnel

941
00:37:57,589 --> 00:37:55,119
at these high speeds

942
00:38:00,390 --> 00:37:57,599
and take a picture and see what is going

943
00:38:01,829 --> 00:38:00,400
on in the flow

944
00:38:04,950 --> 00:38:01,839
they did that

945
00:38:07,510 --> 00:38:04,960
and what you see there in 1934

946
00:38:09,109 --> 00:38:07,520
is the first ever

947
00:38:11,670 --> 00:38:09,119
visualization

948
00:38:13,109 --> 00:38:11,680
of shock waves occurring the flow is

949
00:38:15,430 --> 00:38:13,119
going from left to right over that

950
00:38:18,710 --> 00:38:15,440
airflow there's a shock wave off the top

951
00:38:20,230 --> 00:38:18,720
there's a shock wave off the bottom

952
00:38:22,870 --> 00:38:20,240
first ever

953
00:38:25,430 --> 00:38:22,880
that aerodynamicist had ever seen that

954
00:38:26,630 --> 00:38:25,440
and here this historic photograph is

955
00:38:29,910 --> 00:38:26,640
being taken

956
00:38:34,390 --> 00:38:29,920
by these dedicated intelligent

957
00:38:36,550 --> 00:38:34,400
engineers and scientists at naca langley

958
00:38:38,390 --> 00:38:36,560
this explained

959
00:38:40,790 --> 00:38:38,400
the cause of the separated flow the

960
00:38:42,630 --> 00:38:40,800
shock waves were separating the boundary

961
00:38:45,910 --> 00:38:42,640
layer

962
00:38:47,270 --> 00:38:45,920
flow separation resulted in higher drag

963
00:38:49,430 --> 00:38:47,280
lower lift

964
00:38:51,670 --> 00:38:49,440
that was the explanation it was that

965
00:38:54,710 --> 00:38:51,680
that was a major intellectual

966
00:38:57,829 --> 00:38:54,720
breakthrough in the understanding of the

967
00:38:59,030 --> 00:38:57,839
high-speed compressibility problem and

968
00:39:01,589 --> 00:38:59,040
uh

969
00:39:05,829 --> 00:39:01,599
know it's i don't think the naca gets

970
00:39:08,470 --> 00:39:05,839
enough credit for that now in part

971
00:39:12,390 --> 00:39:08,480
let me quote then this photograph

972
00:39:12,400 --> 00:39:16,790
when this measurement was made

973
00:39:21,510 --> 00:39:19,109
here's a quote from john becker who was

974
00:39:24,470 --> 00:39:21,520
uh became a leading aerodynamicist at

975
00:39:26,470 --> 00:39:24,480
langley later on he says the first tests

976
00:39:28,710 --> 00:39:26,480
were made on a circular cylinder not an

977
00:39:30,710 --> 00:39:28,720
airfoil but a circular cylinder about a

978
00:39:33,349 --> 00:39:30,720
half inch in diameter and the results

979
00:39:35,829 --> 00:39:33,359
were spectacular in spite of the poor

980
00:39:39,190 --> 00:39:35,839
quality of the optics the optics that

981
00:39:40,950 --> 00:39:39,200
they use celluloid for the windows

982
00:39:42,790 --> 00:39:40,960
across the wind tunnel test section so

983
00:39:44,950 --> 00:39:42,800
you're and those of you who've ever

984
00:39:47,270 --> 00:39:44,960
dealt with a certain system

985
00:39:49,990 --> 00:39:47,280
that sounds like heresy

986
00:39:52,069 --> 00:39:50,000
you need high quality optical windows

987
00:39:53,589 --> 00:39:52,079
here's celluloid being used but it was

988
00:39:55,430 --> 00:39:53,599
the beginning

989
00:39:58,230 --> 00:39:55,440
shock waves and intended flow

990
00:40:00,310 --> 00:39:58,240
separations were seen for the first time

991
00:40:02,550 --> 00:40:00,320
starting at subsonic stream speeds about

992
00:40:04,309 --> 00:40:02,560
six tenths times the speed of sound

993
00:40:07,109 --> 00:40:04,319
visitors from all over the laboratory

994
00:40:09,430 --> 00:40:07,119
from engineering charge hce read

995
00:40:11,030 --> 00:40:09,440
on down

996
00:40:12,710 --> 00:40:11,040
engineer in charge

997
00:40:15,430 --> 00:40:12,720
yesterday it was mentioned when jim

998
00:40:18,230 --> 00:40:15,440
hansen was here one of his first books

999
00:40:20,870 --> 00:40:18,240
is a history of the langley memorial

1000
00:40:22,829 --> 00:40:20,880
aeronautical laboratory the title is

1001
00:40:25,670 --> 00:40:22,839
engineer in charge and it's a double

1002
00:40:28,230 --> 00:40:25,680
entendre because engineer in charge was

1003
00:40:30,069 --> 00:40:28,240
what the director of the lab was called

1004
00:40:32,230 --> 00:40:30,079
and all these

1005
00:40:35,349 --> 00:40:32,240
dedicated intelligent

1006
00:40:39,430 --> 00:40:35,359
motivated engineers and scientists where

1007
00:40:41,030 --> 00:40:39,440
there were themselves in charge of the

1008
00:40:43,349 --> 00:40:41,040
work that they were doing they had the

1009
00:40:46,710 --> 00:40:43,359
professional freedom to do that and that

1010
00:40:47,990 --> 00:40:46,720
was important anyway i don't i i diverge

1011
00:40:49,829 --> 00:40:48,000
on that

1012
00:40:51,109 --> 00:40:49,839
reed came on down came to view the

1013
00:40:53,750 --> 00:40:51,119
phenomena

1014
00:40:56,230 --> 00:40:53,760
langley's ranking theorist theodore

1015
00:40:58,630 --> 00:40:56,240
theodorsen we saw him earlier

1016
00:41:00,870 --> 00:40:58,640
viewed the results skeptically

1017
00:41:02,630 --> 00:41:00,880
proclaiming that since the stream flow

1018
00:41:04,829 --> 00:41:02,640
was subsonic

1019
00:41:09,030 --> 00:41:04,839
what appeared to be shock

1020
00:41:11,589 --> 00:41:09,040
waves was an optical illusion an error

1021
00:41:12,950 --> 00:41:11,599
in judgment which he was never allowed

1022
00:41:15,829 --> 00:41:12,960
to forget

1023
00:41:17,510 --> 00:41:15,839
so sometimes you know everybody makes

1024
00:41:18,550 --> 00:41:17,520
misinterpretation

1025
00:41:21,589 --> 00:41:18,560
finally

1026
00:41:24,470 --> 00:41:21,599
this work the naca didn't sit on this

1027
00:41:26,630 --> 00:41:24,480
one year later eastman jacobs reported

1028
00:41:27,990 --> 00:41:26,640
on this at the fifth volta con

1029
00:41:30,950 --> 00:41:28,000
conference

1030
00:41:33,030 --> 00:41:30,960
for high-speed flight in rome

1031
00:41:34,630 --> 00:41:33,040
this conference was mentioned yesterday

1032
00:41:36,630 --> 00:41:34,640
in fact i think that callion mentioned

1033
00:41:39,109 --> 00:41:36,640
it because that's where adolf bushman

1034
00:41:40,790 --> 00:41:39,119
first suggested the idea of swept wings

1035
00:41:42,710 --> 00:41:40,800
and uh

1036
00:41:45,670 --> 00:41:42,720
also at that conference not so well

1037
00:41:48,790 --> 00:41:45,680
known as the father is the following

1038
00:41:51,270 --> 00:41:48,800
that jacobs gave a paper on this work at

1039
00:41:53,589 --> 00:41:51,280
the volta conference

1040
00:41:56,470 --> 00:41:53,599
and in that paper in keeping with the

1041
00:41:58,309 --> 00:41:56,480
naca's penchant for perfection

1042
00:42:00,150 --> 00:41:58,319
especially in his publications that was

1043
00:42:03,270 --> 00:42:00,160
another thing mentioned yesterday the

1044
00:42:05,510 --> 00:42:03,280
quality of the nac atr's they work they

1045
00:42:07,510 --> 00:42:05,520
strive for perfection so in keeping with

1046
00:42:09,910 --> 00:42:07,520
this pension for perfection

1047
00:42:12,390 --> 00:42:09,920
jacobs apologized for the quality of the

1048
00:42:14,069 --> 00:42:12,400
photographs a fault that detracted

1049
00:42:15,750 --> 00:42:14,079
little from their technical and

1050
00:42:17,990 --> 00:42:15,760
historical importance

1051
00:42:20,390 --> 00:42:18,000
unfortunately the photographs were

1052
00:42:22,150 --> 00:42:20,400
injured this is jacob's going on

1053
00:42:23,990 --> 00:42:22,160
unfortunately the photographs were

1054
00:42:25,829 --> 00:42:24,000
injured by the presence of bent

1055
00:42:27,829 --> 00:42:25,839
celluloid windows

1056
00:42:29,349 --> 00:42:27,839
forming the tunnel walls through which

1057
00:42:31,510 --> 00:42:29,359
the light passed

1058
00:42:33,990 --> 00:42:31,520
the pictures nevertheless

1059
00:42:36,950 --> 00:42:34,000
give fun here this is this is so laid

1060
00:42:40,069 --> 00:42:36,960
back the pictures nevertheless give

1061
00:42:41,910 --> 00:42:40,079
fundamental information in regard to the

1062
00:42:44,230 --> 00:42:41,920
nature of the flow

1063
00:42:46,150 --> 00:42:44,240
associated with the compressibility

1064
00:42:48,630 --> 00:42:46,160
verbal that was an intellectual

1065
00:42:50,309 --> 00:42:48,640
breakthrough in my mind which was a

1066
00:42:52,309 --> 00:42:50,319
first order

1067
00:42:55,190 --> 00:42:52,319
and with that

1068
00:42:58,309 --> 00:42:55,200
the naca high-speed research program was

1069
00:42:59,829 --> 00:42:58,319
not simply on the map it was leading the

1070
00:43:01,510 --> 00:42:59,839
pack

1071
00:43:02,470 --> 00:43:01,520
so this is uh

1072
00:43:05,670 --> 00:43:02,480
and

1073
00:43:08,630 --> 00:43:05,680
ultimately

1074
00:43:11,030 --> 00:43:08,640
helped us and led to the

1075
00:43:14,309 --> 00:43:11,040
the necessary information for the bell

1076
00:43:16,069 --> 00:43:14,319
engineers to to properly design the x1

1077
00:43:17,670 --> 00:43:16,079
which you heard about yesterday and

1078
00:43:20,150 --> 00:43:17,680
which is of course hanging in the

1079
00:43:22,790 --> 00:43:20,160
milestones of light gallery here

1080
00:43:25,030 --> 00:43:22,800
final comment on my own i want to wrap

1081
00:43:26,390 --> 00:43:25,040
this up with the following

1082
00:43:27,270 --> 00:43:26,400
i'm going to read this to make sure i

1083
00:43:28,950 --> 00:43:27,280
get the

1084
00:43:31,670 --> 00:43:28,960
all the words in

1085
00:43:34,470 --> 00:43:31,680
during the 1930s

1086
00:43:37,510 --> 00:43:34,480
no other research establishment

1087
00:43:38,710 --> 00:43:37,520
worldwide and that includes laboratories

1088
00:43:41,430 --> 00:43:38,720
in britain

1089
00:43:42,390 --> 00:43:41,440
prandtl's laboratory and germany the

1090
00:43:44,069 --> 00:43:42,400
labs

1091
00:43:46,390 --> 00:43:44,079
in france etc

1092
00:43:49,430 --> 00:43:46,400
no other research establishment

1093
00:43:51,430 --> 00:43:49,440
worldwide contributed more

1094
00:43:53,829 --> 00:43:51,440
to the advancement of aerodynamics as

1095
00:43:56,309 --> 00:43:53,839
applied to the airplane than did the

1096
00:43:59,030 --> 00:43:56,319
naca you know why did mesher schmidt use

1097
00:44:01,990 --> 00:43:59,040
an naca air force the germans did not

1098
00:44:04,950 --> 00:44:02,000
have any integrated logical airfare

1099
00:44:06,870 --> 00:44:04,960
program they used the naca data

1100
00:44:09,589 --> 00:44:06,880
the engineers and scientists at the

1101
00:44:11,510 --> 00:44:09,599
langley memorial aerodynamic laboratory

1102
00:44:13,829 --> 00:44:11,520
were among the best and i really

1103
00:44:17,349 --> 00:44:13,839
sincerely mean that they were among the

1104
00:44:19,829 --> 00:44:17,359
best and this is a legacy that today's

1105
00:44:22,870 --> 00:44:19,839
nasa engineers and scientists

1106
00:44:25,750 --> 00:44:22,880
can derive great pride from

1107
00:44:28,630 --> 00:44:25,760
and with that i'm going to wrap up this

1108
00:44:30,710 --> 00:44:28,640
discussion of the naca aerodynamic

1109
00:44:33,430 --> 00:44:30,720
contributions in the 1930s and how a