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The Supersonic Transport Wind Tunnel Test

by Fanny Zuniga

December19, 1997

Welcome to the High-Speed Research Wind Tunnel Test. My name is Fanny Zuniga and I'm the Project Manager for an upcoming test of a future supersonic airliner. Tune in every week to follow this test as we assemble our model, check out all of the instruments on it, install it in the tunnel, and then test it. If you want to know what goes on during a wind tunnel test, this is the place! You might someday fly on a plane like this one we are testing at NASA now.

My test is part of the High-Speed Research Program which is a NASA and industry program studying a new Supersonic Civil Transport design. Over the last several years two different airplane configurations have been studied experimentally and computationally. The experimental work has consisted of testing wind-tunnel models. The major differences in the two configurations were the wing shapes. One wing shape was better for takeoff and landings, while the other performed better during long-range cruising.

The latest model we are about to test has a new wing on it which hopefully captured the best characteristics of the older shapes. It is now my job to test this new wing to study its performance during takeoff and landing which is when the flaps are deployed. Most of my test will involve changing the flaps on the front and back of the wing to determine the best way to use them. I call this my test, but I am working very closely with other researchers from Boeing, Lockheed and other NASA centers including Langley Research Center. It is typical of big tests like this that they involve a big team effort. By the way, the official name of this model is the 5% TCA. The 5% refers to the fact that the model is a 5%-scale version of the real aircraft. The wings on the model are 6.5 feet wide, and we are fitting it in a wind tunnel 12 feet wide. The TCA part of the name stands for Technology Concept Aircraft which refers to this particular new wing shape.

Our test is scheduled in the wind tunnel for late January of next year, but we have been planning this test for eight months already. We are using a model that was already built for a test earlier this year in a different tunnel. New flaps were built for my particular test so this will be the first time that we are testing this model with the new flaps. This test is planned to be in the wind tunnel for five weeks. I want to tell you a bit of what's happened so far during this planning phase, and then give you an update on what's going on right now.

Planning for a test like this is a lot of work. My part in this is to make sure we go into the tunnel with a good plan for testing the right conditions (like speed and model attitude) and the right configurations (like what positions the flaps are in). To do this we (the whole team) have to agree on the the research objectives, or goals, for the test. Then we develop a plan for every "run" we will make in the tunnel. This is called a "run schedule." We want to answer a lot of research questions and at the same time, use our time in the tunnel very wisely. So we try to arrange the runs we want to make in a logical order. The run schedule is always evolving - it can even change during the test because we might start to run out of time and need to eliminate some runs, or because we may learn something interesting and want to add runs to check it out further. We also had to modify the model so we could mount it in our tunnel.

While I am working on this, other members of the test team are very busy too. This test has a test engineer, Rick Giddings, an Instrumentation Engineer (see Robert Jercinovich's bio), a Software Engineer, and a Model Design Engineer (see Rebecca Averill's bio). Rick is spending most of his time assembling the model, making sure we have all the model parts, getting the team members trained on special equipment for this test, and filling out the rest of the test team positions like tunnel operators and model mechanics which will work on the model while its in the tunnel. Robert is now busy installing instruments which measure the lift and drag of the whole model, and other instruments for measuring air pressure on the surface of the wings. Which instruments we need, and how they would fit inside the model, was all planned out over the last couple of months. Meanwhile, Rick and I are writing our requirements for special software which will record all of the measurements (coming from the instruments in the model and tunnel) on a computer so that they can be studied. Soon a programmer will be assigned to this test to write the software.

We had some excitement a few months ago. We always check a model to see if it is strong enough to be tested safely in our tunnels. In this case, we discovered that our model was not strong enough to handle the aerodynamic loads (lift and drag) that it would experience during our test. This meant that we would have to make the model stronger or cut out any runs that created high loads on the model. Since the model was very near completion when we made the discovery, it created a huge problem for us to figure out a way to make it stronger without ruining the design and without missing the test date.

We couldn't just weld more metal on the outside of the model because we didn't want to change its streamlined shape. And there wasn't much room inside for adding reinforcements. So we turned to the run schedule to cut out conditions with the highest loads. It turned out, we would have to cut out so much that the test would not be very useful anymore. In fact, this test was VERY close to getting cancelled. Fortunately, our design engineers found a way to beef up the model. They had to work 24-hours a day and 7 days a week to get it ready in time. Their hard work has paid off because not only did they save the test but we can still run the whole test the way we originally planned. It typically takes good teamwork to overcome the many problems encounted in wind-tunnel testing.

The model was strengthened by Boeing in Seattle, Washington, and then sent here to Ames in mid-November. The picture above shows the model as it is today. We are assembling the model and installing the intruments inside it. The picture below shows some of the instrumentation in the fusilage.

More photos of the model.

Well, that's enough for now. Just one month left to get ready to put our model in the tunnel. I'll keep you posted on progress and tell you more about this test as we go along.


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