NASA-LLIS-0204

Abstract

<strong>Description of Driving Event:</strong> <br>During a test run on a model in a wind tunnel, several components of a wooden test rig could not withstand the loads on them with the tunnel at maximum speed. Stress calculations made prior to the mishap indicated an acceptable factor of safety. However, the assumptions in the calculations for stress neglected to consider the drag force on a flat plate which is a multiplier to the dynamic pressure, resulting in a force 80 percent higher than was used in the calculations. <br>The stress calculations on the model also made certain assumptions that were not consistent with the quality of its material and construction. The investigating committee found that the failed parts were fabricated from inferior wood with numerous knots and that glue was not used to help keep the parts together. The inferior strength of the wood was not noted initially because the model was painted over when delivered to the test site.