Characterizing Stability and Control of Subscale Aircraft from Wind-Tunnel Dynamic Motion

This paper outlines a process of determining the stability and control characteristics of small-scale aircraft from wind-tunnel experiments which aim to emulate flight tests. Scaled aircraft models with representative control surfaces are flown in semifree flight on a test rig allowing motion in 4 degrees of freedom. The motion is measured and system identification and parameter estimation techniques are used to obtain a mathematical description of the dynamics of the model. Previous work has relied on the rise of potentiometers to measure the model's attitude about its pivot point with other motion variables being generated analytically using these measurements and well-known kinematic relationships. However, it is now possible to mount sensors within the model as advances in technology have produced microelectromechanical system packages of small size, lightweight, low cost, and low power consumption. The current work is investigating the effectiveness of using microelectromechanical system inertial sensors to measure motion of the model. An example of the system identification process carried out on a one-twelfth scale BAe Hawk model is also presented. Parameter estimation is performed in the frequency domain using the equation error and output error methods.