The VX-1 KittyHawk strikes a marked contrast with the Falcon. Its blended wing body features wings that are smoothly blended into an airfoil-shaped fuselage, achieving a 50 percent greater lift-todrag ratio than conventional designs. Skillen points out that the most efficient airfoil is elliptical, like a Spitfire. “This is exactly the top profile of the KittyHawk,” he adds.
At full scale, the plane will measure 26 ft/8m in length with a span of 22.5 ft/7m and a body height of 4 ft/1.25m, offering significantly more usable internal volume than other aircraft of similar gross weight. (Empty weight will be ~750 lb/340 kg, using 100- to 125-hp engines). “It will offer a 7-ft/2m cockpit width, which is unique in this size aircraft.” As a UAV, its larger internal volume permits more payload and sensors. In the manned light aircraft market, it means more cockpit comfort, and greater cargo and fuel capacity. There are also no wings to break off upon landing, improving aircraft recovery for UAVs, and it offers the option to be powered by compressed natural gas (see “A UAV fueled by CNG?” sidebar, bottom of p. 61).
With support from North Carolina State University (NCSU, Raleigh, N.C.), computational fluid dynamics (CFD) analysis and wind tunnel testing were completed in October and November 2013, managed by Dr. Richard D. Gould, chair of the Mechanical Engineering and Aerospace Department. According to Skillen, results have exceeded expectations. The aircraft generates 20 lb/44 kg of lift at 0° angle of attack (i.e., no tilt relative to the airflow direction), which equates to 100 ft/ sec (31 m/sec) at 68 mph/109 kph. In other words, the aircraft generates lift quickly without requiring a lot of speed to take off. “That’s almost twice as aerodynamically efficient as most other light aircraft,” says Skillen. It also demonstrates good dynamic stability (ability to recover after disturbance from normal flight), and no further modifications will be needed prior to flight testing. NCSU will help here as well, says Skillen, by flying the 1:4 scale aircraft with a telemetry package to map out all of its flight characteristics and, thus, verify the CFD analysis.