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Checking out the Model

By Mina Cappuccio

July 28, 1999

By the end of the day Wednesday, the model was installed in the wind tunnel. The wind tunnel test section and control room are on the second floor at the twelve-foot pressure wind tunnel. Using a crane, the model was taken off the bipod in the model prep room and laid on a long, flat table on wheels. The model was brought to the second floor using a huge elevator. The table was rolled over to the front of the test section. A crane was used to lift up the model from the table, move it, and lower it over the bipod for attachment.

Early in the day on Wednesday, the SDS (pronounced suds) data reduction program was installed. There was a bunch of troubleshooting by the data technician to check out the program.

Here you can see how the model is attached to the bipod support.

Most of Thursday and Friday was spent hooking everything up. There is a patch panel where all the connections to the data system are made. They had to connect the balance wires and the three thermocouples on the balance. The digital angle sensors in the model had to be hooked up and calibrated. There are two of these sensors in the model, a primary and a backup instrument. They balanced checkloads by adding weight and did angle checks by pitching the model and calibrating the sensors. These final checks can only be made when the system is connected up in the wind tunnel.

While the instrumentation techs were making all the connections between the data collection system and the model, the mechanics in the wind tunnel were putting the final model parts on, like the vertical tail and nacelles, doing model clean up, and patching holes with a material mix of wax and clay.

On Thursday, we had a little bit of a scare. When the mechanics were cleaning up the model, there was a part of the nose that was missing. We built a new nose for the high mount canard configuration. One of the mechanics came to me and said, "Where's the little nose tip?" He was looking for this part which is a little cone that is very short, about three to four inches long and two to three inches in diameter. I knew that the machine shop was using it to make sure it fit with the new nose part.

When they tried to remove the cone from the new nose model, they couldn't get it off. Somehow when they had attached the nose tip to the new part it was jammed and they couldn't get it off. Every time they put a wrench to the part to take the screw out the wrench would bend.

Finally, they took the part to the metal machine shop that works on big jobs and has heavier equipment. They welded on a drill bit to the head of the screw and then they welded the wrench to the bit. This way they planned to get more torque on the screw. But when they tried this the wrench broke right off at the weld joint.

They welded it again and, happily, this time the screw came right out. Examining the screw you could see that it was all galled up. The hole probably had dust or tiny particles in it which caused the tight fit. We put the cone on the old model Thursday afternoon.

On Friday, the model was pretty much ready, but we were having problems with the checking of the instrumentation system for pressures.

On Monday morning, we had a debriefing meeting on the test. We heard that there were still problems with WICS and model pressures, BLAMS needed to be checked out, turntable limits for yaw needed to be set and needed to do pitch angle checks. The model was ready but the instrumentation was not.

The WICS and model pressure instrumentation problem was due to leaking. It turned out the C1 solenoid needed to be replaced. To calibrate the pressure modules, the module has a sliding switch in two positions: one position allows you to make calibration measurements and the other position allows you to make the test measurements. To slide the control there is a switch. In cal mode, it feeds air to the module at a certain pressure so that the ports, or transducers, read a certain level. Because of the solenoid leak the switch wouldn't slide. Once they figured out that was where the problem was coming from they replaced the solenoid.

Then they had to make leak checks on all the Tygon tubes and discovered leaks in the pressure control tubes which were replaced or repaired as needed. Now both the model pressure system and the tunnel pressure system have been calibrated.

The length of the wires on the balance thermocouples was too short to reach the patch panel, which was at a different distance than the panel they used for the last test. They had to extend these lines.

Hopefully next week I can report that the tunnel is running and I have collected the data on wing one and compared it to the data from the last test.


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