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In the Prep Room - Final Test Preparations

By Fanny Zuniga

January 21, 1998

Well, things are really hopping on this test! Where it used to be me and a few other people, now that we are preparing our model there are at least 50 people working to get this test ready for next week. This week we solved our electrical problem with the balance, checkloaded the balance, mounted our model Supersonic Transport on the balance, assembled all of the little pieces that make up the wing flaps, and intalled our pressure instrumentation. WHEW!

The first picture shows our balance being checkloaded early in the week. Remember, we are doing this to make sure our electronics and software are working and "talking" to the balance properly. In the picture, there are three 500 pound weights hanging from our balance. We checkloaded it up to 3000 pounds and confirmed our balance is very accurate. It was only off by 1/4 pound out of 3000!. Imagine they put 12000 pounds on during calibration. By the way, you can tell things are getting busy by how many people are in our prep room! Most of them are studying the signals from the balance.
The next picture shows our model finally in the prep room. It has been attached to the balance, which in turn is attached to the support posts. The calibration block has been removed, so you can finally see the balance (its the cylinder in the middle of the model body).
I've included a closeup to show you the balance. It is the most important instrument in this test. Also this week, mechanics are checking that all the wing parts we plan to test actually fit onto the model. Every part has been attached and removed at least once.

I mentioned some time ago that we have special instruments to measure air pressures on the surface of the wings. Now that it is all installed, I can tell you more about it. Since it is air pressure that generates the loads (or forces) on our model, measuring the pressures help give us a good idea what features in the airflow are responsible for good or bad performance of our wings and flaps. If this all works as planned, we can actually get maps of pressures on the wing like a weather map of pressures on the Earth.

First, the model came to us with hundreds (405 to be exact) of tiny holes on the top and bottom surface of the wings. Here is a picture of one of them. It is covered with clear tape to keep dirt from clogging it up.
Next, these holes are connected to flexible metal tubing which runs inside the wing and comes out into the body of the model. Here is a closeup of the body (or fuselage) section. Can you see all the tubes coming out of the left and right wings?
Finally, the tubes are bundled together and brought to the nose of the airplane where we have put seven "pressure modules," each of which can read the pressure in 64 tubes. The last picture shows how 64 tubes in a bundle are attached to 64 tubes from one of the pressure modules.

All of these modules are calibrated in a laboratory, just like we calibrated our balance. In this case, instead of weight, a known amount of air pressure is applied to each pressure sensor to measure its voltage output. All we have to do in the prep room is make sure we've connected them correctly (each hole on the wing is numbered, as is each tube) to the pressure modules that do the actual measuring. We also have to make sure each line has no leaks. That's a lot of work!

As you can tell, there's a lot going on, but everyone is getting excited about starting the test. And every member of the team knows we are working to a deadline. Our fully checked out model has to go in the tunnel next week! By the way, here is a picture of the wind tunnel we'll be using. The air goes around and around the big loop, and the test section (where the model goes) is inside the big building. Next week I'll post some pictures of our model inside the tunnel and show you the control room.

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