by Robert Jercinovich
July 9, 1999
We have been assembling the instrumentation for this test to measure lift and drag during the test. We have also been installing the instrumentation that will measure the air pressure on the wings. Which instruments we need and how they would fit inside the model was all planned out over the last couple of weeks.
The balance is the instrument which measures lift and drag, forces acting on the model when the wind blows on it are measured by strain gages in the balance, simulating the forces that act on planes when they fly. The balance was calibrated at Langley, then checked at Ames calibration lab and then transferred to the tunnel data system. To calibrate the balance you have to hold on to one end of the balance, hang some "known" weight on the other end, and measure the output voltage.
The balance has been attached to the model and a new bayonet pitch block was installed. The test manager and the computer programmer were checkloading the balance. This took quite a while because we had some problems with the way the balance calibration was transferred from Langley to the 12-foot data system (SDS). In addition, we had some noise (EMF) from the bi-pod motors, which control the angle of attack of the model, to reduce. When we say noise we mean the electromagnetic interference which affects the quality of the data recorded during the wind tunnel test.
We've been hooking up all the stainless lines which run from tiny holes on the surface of the model to polyurethane tubes which are then connected to the PSI modules which have already been installed. This activity took two technicians two days to complete because there are hundreds of them.
Two instrumentation technicians and two mechanics have been working to put the model together. It traveled to Ames in pieces. Next week we are going to be hooking up the tilt sensors, the rest of the psi sensors, and the strain gauges in the wing. Then we will start trying to test things out in the data system. However we don't have the complete computer program we need yet to collect the data we want from the test. It will be unavailable until we move into the test section.