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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
Ð 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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