Abstract

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 wingbased pressure-differential ratio called C0 p to automate cruise flaps. Rigid-aircraft simulations showed the effectiveness of a controller implementing multiple functions using C0 p. The gust-alleviation function reduced coefficient-of-lift perturbations, the C 0 p-optimization function reduced drag, and the C 0 p-maintenance function maintained the current trim C 0 p in the presence of pilot elevator inputs. In this research, the C 0 p-optimization and C 0 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 C0 p-optimization function was effective in producing pressure differentials that would have reduced drag. The effectiveness of the C0 p-maintenance function could not be determined because of large sample-to-sample variations in measured C0 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. Nomenclature CL = aircraft lift coefficient