Browsing by Author "Ko, Joon Soo"

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    Analysis of the dynamic stability derivatives for high angle of attack aircraft
    Ko, Joon Soo (Virginia Polytechnic Institute and State University, 1985)
    Modern, high performance aircraft are required to be able to fly and be controlled over a wide variety of flight conditions. In order to predict the aircraft behavior and control requirements over the entire flight regime it is necessary to have a proper aerodynamic model. Flight conditions at high angles of attack lead to separated flows making the aerodynamic model more difficult to obtain. In this research wind tunnel experiments are performed on an F-5 air-craft model at high angles of attack, with small oscillations about the body oriented roll axis. In addition the free stream environment can be configured in one of three ways: l) straight uniform flow, 2) curved flow to simulated a horizontal turn, and 3) rolling flow to simulated a roll motion about the relative Velocity vector.
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    Analysis of various forced oscillation techniques for obtaining dynamic stability derivatives
    Ko, Joon Soo (Virginia Polytechnic Institute and State University, 1982)
    Existing subsonic wind tunnel methods for obtaining dynamic stability derivatives for aircrafts at high angle of attack are described. From the general equations of motion of an aircraft in space, the perturbation equations of motion are derived for applying to a wind tunnel aircraft model. Data Reduction and test procedures for important dynamic tests are evolved systematically from the restrained perturbed equations of motion. Emphasis is given to the typical single degree of freedom apparatuses and associated data reduction for routine measurement of dynamic stability derivatives due to pitching, rolling and yawing of the model. The translational and snaking motion apparatuses from which the derivatives, α, β, and p, q, r are measured separately, are also presented. Finally, for the purpose of increasing the capabilities of the Virginia Tech dynamic test systems, a single degree of freedom forced oscillatory rig, which gives the exact sinusoidal displacement of the model and also adjustable to the existing curved and rolling flow facilities, is described with its data acquisition/reduction.