Aerodynamic, Stability and Flying Quality Evaluation on a Small Blended Wing-body Aircraft with Canard Foreplanes

Abstract

Abstract Blended wing-body (BWB) concept promises up to 30 percent increase in aerodynamic efficiency and reduction in fuel cost by having planform geometry optimized to increase lift and to reduce drag. Many claimed to have achieved the target of increasing lift-to-drag ratio better than current conventionally-configured airplanes either large airliners or small unmanned airplane. However, achieving good balance of aerodynamic efficiency, stability and flying quality is harder then one might expect. Over years of studying small BWB aircrafts in Universiti Teknologi MARA (UiTM), it is found that unconventional behaviour of aerodynamic characteristics leads to limitations to BWB aircraft's flight envelope. In this paper, a short overview of aerodynamic, stability and flying quality of UiTM's BWB aircraft design is highlighted. Lessons learned from its unsusual lift-angle of attack curves, stability reversals, the effect of canard to flight stability and poor longitudinal flying quality (short-period mode and phugoid mode) are discussed. A classical control solution to improve it flying quality has been proposed and simulated and the result shows that both short-period and phugoid modes are able to achieve damping ratios within 0.6 to 0.8 exceeding minimum Level 1 damping ratios of 0.35 and 0.04 respectively. Design flaws of this aircraft and recommendations to be implemented on the next evolution of aircraft design conclude this paper.