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Moving to the Wind Tunnel

by Fanny Zuniga

January 30, 1998

Tuesday and Wednesday:
Early this week we weren't quite ready to put the model in the tunnel. We had a lot of trouble getting all of the details ready, mostly details about getting our software to talk to every instrument on the model and record the information accurately. We also had trouble with the automatic warning system that we will use to make sure that the model doesn't generate more force than either the balance, the model itself, or the mounting posts can handle. We can't start our test without this important safety system working. Fortunately, the test that is currently in the tunnel wanted more time. So everyone agreed last Friday that we would start a few days late and try to make up the lost days sometime during the five weeks of our test. So we have set our sights on a Thursday move into the tunnel.

Starting last week my team has been working two shifts; we have day and night teams. This is one way we can cover a lot of ground in a short amount of time. In fact, we will operate on two shifts throughout the entire test. That means there are two complete teams of tunnel operators, model mechanics, researchers, electricians, instrumentation technicians, etc! No, we don't clone people, so this demands a lot of communication between all of the people on each shift. We take lots of notes!

Thursday:
On Thursday we were ready to move our model upstairs and install it in the tunnel. There is a lot of stuff going on -- enough to keep 20 people busy 16 hours a day. Installing the model in the tunnel is an exciting moment for a wind tunnel test team! There's no way I can tell you about all of it. We have to take our computer program off of the computers downstairs and copy it to the computers in the control room. Meanwhile, our model was lifted off the bottom half of the supporting posts, leaving the top half of both posts attached to the balance inside the model. All of the electrical cables from our instruments run down through the hollow rear post; they had been connected, under the floor, to the computers in the prep room. Now they are hanging out of the model and will be connected to the computer upstairs. The bottom half of the posts was pulled out of the floor and taken upstairs too.

Next our model was placed on a cart and taken up to the test section in a big freight elevator. You might wonder how we got our big model into the wind tunnel. There is a door in the side of the test section so people can go in and change parts of the model or fix problems. Unfortunately, the model won't fit through that door. So we actually rotated the test section 90 degrees - the whole thing is on a giant turntable. We then put an overhead crane into it, picked up the model with the crane, and carried it in. The bottom halves of the support posts were set into the floor of the tunnel. We held the model over those posts and fed all of the instrument cables through the rear post so they can run out of the tunnel and plug into electronic "black boxes" that will read the electrical signals. After the cables were fed through, we finally mounted the model on the posts and bolted everything down. We next checked that the model could reach the full range of tilt angles (which we call "angle of attack"). Last, we rotated the test section back into line with the rest of the tunnel so the air can flow through the test section. Everyone is glad to have reached this major milestone in our test. The next big milestone is actually turning on the wind after everything is checked out!

Friday:
We moved all of the software onto computers in the control room, and all of our instrument cables were plugged into the electronics as well. We are doing a lot of checks to make sure everything is OK. We even hung some weight on the model to do one last check load to see if our balance was talking properly to the new computer. Cameras, strobe lights, and computers are being put into place for the mini-tuft imaging system. The tufts were glued onto the left hand wing, but didn't stick well enough. The whole job had to be redone.

I'm really tired and looking forward to the weekend! We got a lot done, and with luck we will turn the wind on in the tunnel for the first time next week! By the way, check out http://george.arc.nasa.gov/jit/projects/12FT_WT/ to learn more about this wind tunnel. And for the curious out there, http://aocentral.arc.nasa.gov/ describes some of the other wind tunnels at NASA Ames Research Center (which, by the way, is located near San Francisco, California).

Our model being lifted off the bottom half of the supporting posts. Note the top half of the posts stay attached to the model. You can see the computer terminals used during preparations.
This picture shows our model inside the big freight elevator, on its way up to the test section. Do you see those yellow strips on the tail and the back of the wing? We've added these safety pads to all the back edges of the wing and tail to protect the people working on the model. Can you figure out why? Imagine what happens to the thin back edge of an airplane wing when you scale it down to 5% of its original thickness! Those edges are as sharp as a knife!

This cutaway drawing shows the inside of of the 12-foot wind tunnel. The test section is in the sphere in the middle of the building. The square inset picture (top, right) shows the test section rotated 90 degrees the way it is now, so we can put our model inside.

We are wheeling the model over to the test section. The test section has been rotated away from the rest of the tunnel so we can put in the crane (yellow beam) and lift the model in.
Here's the model on its way into the test section. Remember, we rotated the test section. That's why you see a wall at the end of the test section. All of the electrical cables from our instruments can be seen hanging from the top half of the post.
I told you we had to cram all the cables into the bottom half of the post. Well, it wasn't very easy, so everyone got involved in figuring out how to do it. So, how many engineers DOES it take to screw in a light bulb?
Here we are just ready to mount the model. You can see those pesky cables have been pushed through the rear post.
Done! Ready for checkout! The model is still open on top for access to the instruments, the sharp edges are still covered, and the sharp wing tips are protected by blocks of foam. The test section has been rotated so you are now looking upstream into the wind tunnel.

 
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