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Planning a Wind Tunnel Test

By Bob Griffiths

August 6, 1999

Communication is extremely important thing in test planning, especially when the team members are spread across the country within different companies. The original test focal for this test was an engineer at Boeing-Long Beach. The test focal is the one responsible for making sure that everything gets done. To make sure that everybody was working most efficiently, we began having an official teleconference once a week starting about a year ago. These were led by NASA-Ames. Telecons are standard when preparing for a test like this one to ensure that everyone on the test team is on the same page. Early telecons focused on high level topics like test objectives; as the planning progressed the telecons became more and more detailed. As we got closer to the test start date more and more people joined in on the telecons, including the model designers, the model technicians & mechanics, and the test engineers. The telecons ended just before the test started.

One of the issues we discussed in the telecons was whether or not the canards (small movable wings on the airplane forebody, ahead of the main wings) would touch when deflected at high angles. This was a concern because we don't want the canards to run into each other they could be damaged! The solution was found by using a computer aided design (CAD) tool - a computer that we can use to "move" the canards around in a virtual world to look for problems. Turns out the canards will come close but will not touch at the canard angles we will be testing.

This model has been tested before and it is very complicated. It has literally hundreds of parts, with many more new planned for TCA-5. I was responsible for designing some of the leading edge flaps for this test. I did the geometry, the theoretical geometry for the part. When I say geometry I really mean all the mathematical definitions on the computer that describe the parts. Then I did some computational fluid dynamics, CFD, tests on the canards and flaps to see if they met the test objectives. Then we sent the design of the outer mold line (the "OML"), or surface definition, of the flap to the model design shop where they add all the realism, like bolts.

At this point, the contractors have been selected and they have a real good idea of the number and the complexity of parts that will be built. When they get the designs there will be a good deal of discussion back and forth and the fabrication process begins! It turns out that the NASA-Ames model designers will add the realism, but will ask an outside shop to help out with building the parts themselves. The test team tracks the progress of the model parts by e-mails and through the weekly telecons.


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