Development of UAV Wings - Transonic Designs

Abstract

Development of UAV started to deviate to domain of increased airspeeds and transonic Mach numbers. This is especially evident in development of HALE aircraft, evaluation of transonic flying wings, design of high-speed UAV with enhanced subsonic loitering capabilities and maneuvering transonic air vehicles. Unfortunately, even preliminary stages of design of transonic configurations are complicated because of the lack of suitable airfoils and their performance data. The reason for this is that most existing high-speed airfoils were designed for civil aircraft applications and their specific mission profile. For high-speed UAV, variety of specifications, multi-point design requirements and imposed non-aerodynamic constraints make it unpractical the use of existing transonic airfoils for evaluation work. For these cases, design of new transonic wings is a practically unavoidable choice. This should rely on advanced aerodynamic design concepts that provide significant improvement of performance, help to bridge between conflicting design requirements and consider non-aerodynamic aspects such as structural rigidity, internal volume, wing actuators integrations, etc. While design of transonic NLF airfoils is performed today on a routine basis, a number of evaluation directions in design of high-speed UAV wings require substantial development efforts. This includes design of transonic swept NLF wings with reduced sensitivity to amplification of cross-flow instability of laminar boundary layers, development of highlift airfoils for HALE configurations, evaluation of transonic wings with enhanced subsonic loitering capabilities and improved maneuver performance at medium transonic Mach numbers, etc. IAI experience on development of transonic UAV wings is summarized in this paper by presenting a number of specialized designs, covering a wide range of practical applications.