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Final week - We're done ! ! ! !

by Fanny Zuniga

March 3, 1998

This test of the Supersonic Transport model is done! We all worked hard and got a lot done in our five weeks in the wind tunnel. The last week we started looking forward to the end of the test because testing is hard work. I get so focused on a project like this, that I have to adjust to a more normal life after that focus goes away. Ending any long, challenging project feels a little funny. Even though a big project is tough, and you're glad to see it end, working towards a goal with a team of people is really rewarding too.

The last week of our test had a different feel than the rest of the test. The knowledge that we had accomplished most of our objectives took a lot of pressure and stress off of everyone. We started the week by wrapping up aerodynamic loads testing. This included testing other "control surfaces." I mentioned that we tested the horizontal tail to see how well it would control the airplane's speed. This week we tested the the other main control surfaces - the rudder and ailerons. We want to know how well they control the skidding and rolling of the airplane.

Then the focus turned toward getting some detailed information about our favorite model configurations. Getting this extra information, flow visualization for example, is slow work so it is reserved for only the best model configurations. We started with model deformation. Checkout data from last week looked like it was working well. So we made some runs this week to get wing bending information. As I mentioned in my fourth journal, this data helps us remove the effect of wing bending and twisting from the aerodynamic data we have collected. Basically, wing deformation is an undesired effect. So we measure it and then we can subtract its effect from the lift and drag data.

Preparing the model for painting with Pressure Sensitive Paint (PSP) began Wednesday afternoon. We changed the model configuration to one of our favorites and cleaned the right-hand wing. The painting team spent the rest of the night putting on a base coat of paint. They had problems getting the paint to stick to the model, so it took until after midnight to finish. They also put reference marks on the wing, measured their location, and finally went home. Measuring the location of those marks is a tricky business, as you can see in the picture below. Why so tricky? The wings are curved so we can't just lay a ruler on it to locate a point.

The actual pressure sensitive part of the paint was sprayed on Thursday morning and the PSP system was finally ready to go by Thursday afternoon. We then spent the rest of Thursday and Friday getting PSP images (see picture below).

In testing, we always have to be planning and working ahead. We were told we could have Monday to finish up. So, while PSP runs were going on, we were getting some colored oil ready for the final study of our test. First we mixed the colored dye into the oil. We used 30 grade motor oil (nothing fancy here) and mixed in a bunch of color to get it to the right thickness. We painted a sample and experimented with different ways to put it on. We were looking forward to having some fun on Monday!

We started off with oil flow first thing Monday morning. We tried to get the right amount of oil on the wings to get a good picture of the flow. We tried little drops, big drops, blobs, and stripes of oil. We got lots of different effects this way as you can see in the pictures. What we are looking for is places where the flow doesn't go straight back on the wing. We also want to see if there are places where the air flow "separates" off the surface of the wing. As you can see, the airflow on the wing is very complicated. These pictures will help us understand why some types (or positions) of the wing flaps worked better than others.

At 8:00 Monday night we made the decision to shut down the tunnel and pull the model out. We had finished our last run - just over 500 runs! We had the model out of the tunnel by midnight.

This was a great test and had great people on it. Now we can go home and get some much deserved rest. All of the out-of-town research staff from Boeing and elsewhere are heading home. The model is being put into its crate and shipped immediately to the model makers in Virginia. They are waiting for it to get it ready for the next test. The balance will also be packed up and shipped out to Langley Research Center, another NASA center, to be re-calibrated and inspected. The next model to use this tunnel is downstairs undergoing final preparations (see photo). It gets installed on Wednesday and then another test team will call the control room home for a while.

Now that we're out of the tunnel, I'll be busy for the next few weeks wrapping things up. I'll tell you about some of that in a week or two in my last journal entry.

Here is our Olympic Flap Changing Team in action. There are six people working on the model. One of them is carrying away a flap piece that was being changed.
Here you can see the PSP team measuring reference marks on the model. It's pretty strange setting up a temporary office inside the test section. Anything we want to do with the model has to be done inside the test section because its too hard to remove and reinstall the model.
Here is a map of pressures on the wing surface as imaged with Pressure Sensitive Paint. The paint's brightness under blacklight (UV) corresponds to pressure. The colors are created with a computer program that associates different colors with paint brightness. The colors are scaled to represent pressures and make it easier for us to study the image.
These three pictures show some results from our oil flow experiments. The airflow is made visible by colored oil which was smeared over the wing by the air. You can see the direction of the airflow on the surface of the wings. Notice how the air doesn't flow nice and straight over the wing. The flow is pretty complicated for wings with this kind of shape. Also notice the other wing looks white - that's the pressure sensitive paint. It looks white to pink in normal light; its only under UV light that it glows according to pressure.
In this picture we have removed our model. The balance is still mounted on the support posts. The next test with this model doesn't use this balance so we took the model out first. Looks kind of lonely to me.
This pictures shows the next model to be tested in this tunnel. It is a model Boeing 777 jet airliner and you can see it is full of instruments just like our model was. It is mounted on posts and has a balance inside it just like our model.


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