Flight Test of Stable Automated Cruise Flap for an Adaptive Wing Aircraft

摘要

Cruise flaps are trailing-edge flaps that are adjusted to minimize drag by moving the location of the low-drag region of an airfoil drag polar to match the current coefficient of lift. Previous research explored the use of a wing-based pressure-differential ratio called ΔC'_P to automate cruise flaps. Rigid-aircraft simulations showed the effectiveness of a controller implementing multiple functions using ΔC'_p. The gust-alleviation function reduced coefficient-of-lift perturbations, the ΔC'_p -optimization function reduced drag, and the ΔC'_p -maintenance function maintained the current trim ΔC'_p in the presence of pilot elevator inputs. In this research, the ΔC'_p-optimization and ΔC'_p-maintenance functions were implemented using low-cost microcontrollers and pressure transducers. Flight tests were performed using a radio-controlled sailplane with a wing span of 100 inches. Although direct measurement of drag for aircraft of this size is difficult and was not attempted, analysis of the data showed that the ΔC'_p -optimization function was effective in producing pressure differentials that would have reduced drag. The effectiveness of the ΔC'_p-maintenance function could not be determined because of large sample-to-sample variations in measured ΔC'_p values. It remains unknown whether this high-frequency content actually represented rapidly varying pressures on the airfoil surface or if it was the result of noise in the measurement system.