In recent past with the advancements of experimental facilities, an extensive experimental research work was conducted on low aspect ratio wings at slow speeds by. Therefore, lower value of lift to drag ratio made small aspect ratio wings difficult to fly at slow speeds. Therefore, degradation of lift was not only caused by laminar separation bubble bursting at high angles of attack, but also from large value of induced drag. This posed a special problem of three-dimensional flows, where wing tip vortices captured most of the wing area and degraded lift with enhanced drag. In the same era, researchers conducted research in slow moving low aspect ratio wings. Low speed wind tunnel experimentation were also conducted to validate theoretical results along with wake measurements for authentic drag predictions. In early stages of MAV development, extensive studies were conducted in low Reynolds number aerodynamics regime in which research focused on laminar boundary layer separation, transition to turbulent boundary layer and reattachment to form laminar separation bubble. These were battery powered (lithium ion or nickel cadmium) and propeller driven with endurance up to 30 min. Initially designed micro aerial vehicles were fixed wing in flying wing configurations having low aspect ratio wing for lifting characteristics. Since then, many successful micro aerial vehicles were developed and flight tested. Two of the early micro aerial vehicles were “MITE” with its various variants and “Black Widow”. Research and development organization (commonly known as RAND) conducted a workshop for Advanced Research Projects Agency (ARPA) on “Future Technology Driven Revolutions in Military Operations” in 1992 which resulted in the birth of Micro Aerial Vehicles. Interest in small creatures flying at low speeds has increased for the last three decades. FWMAV flew many successful stable flights in which intended mission profile was accomplished, thereby validating the proposed airfoil selection procedure, modeling technique and proposed design. To achieve successful flights, many actions were required including removal of excessive play from elevon control rods, active actuation of control surfaces, enhanced launch speed during take off, and increased throttle control during initial phase of flight. The left roll tendency was found inherent to clockwise rotating propeller as ‘P’ factor, gyroscopic precession, torque effect and spiraling slipstream. Major problems encountered during flight tests were related to left rolling tendency. Since FWMAV was not designed with a vertical stabilizer and rudder control surface, directional stability was therefore augmented through winglets and high wing leading edge sweep. It was found during flight tests that vehicle conducted coordinated turns with no appreciable adverse yaw. Equations of motion for FWMAV have been written in a body axis system yielding a 6-DOF model. Rate derivatives and elevon control derivatives have also been calculated. Static aerodynamic coefficients were evaluated using wind tunnel tests conducted at cruise velocity of 20 m/s for varying angles of attack. The vehicle was fabricated using hot wire machine with EPP styrofoam of density 50 Kg/ m 3. Elevon control surfaces have been designed and evaluated for longitudinal and lateral control. Eppler-387 proved to be the most efficient reflexed airfoil and therefore was selected for fabrication and further flight testing of vehicle. ![]() Airfoil aerodynamic parameters have been calculated using a potential flow solver for ten candidate airfoils. The selection procedure of airfoil has been developed by considering parameters related to aerodynamic efficiency and flight stability. Airfoil selection procedure, wind tunnel testing and an implementation of 6-DOF model on flying wing micro aerial vehicle (FWMAV) has been proposed in this research.
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