Combined Lateral and Longitudinal Control of Parafoils Using Upper-Surface Canopy Spoilers

Precision placement of guided airdrop systems necessarily requires some mechanism enabling effective directional control of the vehicle. Often this mechanism is realized through asymmetric deflection of the parafoil canopy trailing-edge brakes. In contrast to conventional trailing-edge deflection used primarily for lateral steering, upper-surface bleed air spoilers have been shown to be extremely effective for both lateral and longitudinal (i.e., glide slope) control of parafoil and payload systems. Bleed air spoilers operate by opening and closing several spanwise slits in the upper surface of the parafoil canopy, thus creating a virtual spoiler from the stream of expelled ram air. The work reported here considers the autonomous landing performance of a small-scale parafoil and payload system using upper-surface bleed air spoilers exclusively for both lateral steering and glide slope control. Landing accuracy statistics computed from a series of Monte Carlo simulations in a variety of atmospheric conditions and experimental flight tests were found to be in good agreement. Median miss distances for the combined lateral and longitudinal control logic are on the order of 13 m, indicating an improvement in landing accuracy of nearly 50% over similar systems employing only lateral steering control.