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We've already mentioned the many types of meteorological conditions that can affect

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aviation operations.

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For the remaining portion of this program though, we're going to learn our focus on

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one type, icing.

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Icing can have a profound effect on both the in-flight and ground operations of aircraft.

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Let us visit two NASA research centers that are involved in various icing research studies.

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We'll start our icing travels by visiting NASA Lewis Research Center in Cleveland, Ohio

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and its Icing Research Tunnel.

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Now this facility is the world's largest refrigerated wind tunnel.

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So bundle up, let's go visit this giant cooler and have a closer look at icing effects on

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aircraft and the icing research being conducted.

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Listen to learn how one measures the effects of ice on aircraft performance.

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Thanks, Shelley.

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My name is Dr. Judy Foss-Vanzanti and I'm standing in the test section of the Icing

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Research Tunnel.

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Right now it's nice and warm in here, but later on it's going to get really cold.

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What this tunnel was built for was to simulate down here on the ground what it's like for

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an airplane to fly through an icing cloud up there.

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We do this by creating a cloud that mimics what you see up there.

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As one of the research engineers, I asked the operators to select five parameters.

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One is the airspeed coming past the model.

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One is the temperature, how cold it is, always below freezing.

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Two parameters are about the cloud density, how much water I have in the cloud, and also

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how big each drop size is.

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The final parameter I select is the time that I'll be flying through that cloud.

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I select the cloud conditions, I select the model, I either select an engine, which provides

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the airplane forward thrust, or I select a wing, which provides the plane lift, and I

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want to see one of three things.

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One is what kind of ice do I grow on my model?

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What does it look like for the given cloud condition?

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Another thing I might want to look at is how to keep ice from growing on that, an ice

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protection system.

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And a third thing I might want to look at is to see how well I can predict what the

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ice shape is going to look like using a mathematical model and a computer.

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All these three functions are done in the tunnel.

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I use this tunnel along with Tom Ratfosky for the tailplane icing program.

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What we did there was to see how ice contamination affects the operation of the tailplane.

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Let's take a look at what the tailplane is and how it affects the aircraft operation.

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What we have here is an animation of an airplane in flight.

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The forces acting on this airplane are the weight, which acts through the center of gravity,

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the upward lift is provided by the wing, and the tailplane on the right side of the screen

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provides a downward lift.

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In equilibrium flight, we've got the following force and moment balances to consider.

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We've got the weight, which acts through the center of gravity, which is also the aircraft's

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pivot point.

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That's always forward of the wing's center of lift.

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Those two forces acting together create a nose-down pitching moment.

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The tail comes in to provide a downward lift.

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As you can see, that's a simple geometry problem.

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The plane acts an awful lot like a seesaw.

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The tailplane icing project that Tom and I worked on investigated the question, what

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happens if you move that wing's center of lift further back?

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How does that affect the tailplane if you've got an ice shape on it?

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We at NASA Lewis Research Center took this information and gave it to the pilots so they

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can make better and safer operating decisions.

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Back to you, Shelley.