Aerodynamic design optimization trim analysis of canard conventionalconfigurations

A design study has been conducted to optimize trim cruise flight of high performance general aviation canard aircraft which achieve minimum drag. In order to investigate the advantages and disadvantages of canard configured aircraft, corresponding conventional tail-aft aircraft were designed and used for comparison. Two-dimensional coupled lift and drag coefficient predictions of the canard and wing airfoil shapes were obtained by coupling inviscid results from a vortex panel multielement program to a momentum integral boundary layer analysis. By using the results of the two-dimensional vortex panel analysis, a vortex lattice method was employed to predict the finite wing results. The analysis utilized a turbulent airfoil and a natural laminar airfoil, which are two NASA state-of-the-art airfoil sections. The canard aircraft designs give quantitative results of wing and canard loadings, wing-to-canard moment arm ratios, and aspect ratio effects for trim cruise flight for a wide range of wing-to-canard area ratios. Both canard and baseline aircraft achieved a 25-30% improvement in performance over typical current technology aircraft, but high canard loading necessary for trim resulted in slightly poorer cruise performance of the canard aircraft for equal fuel as compared to the baseline designs. However, when takeoff gross weight was held the same by reducing the fuel payload, the canard designs achieved longer ranges than the baselines. The required positive decalage angle between the canard and the wing guarantees that the canard will stall first, thereby preventing the wing from stalling, and thus having a stall- and, hence, spin-proof configuration.