Preliminary Investigation of Arc Wing Pitch Characteristics

Abstract

A simple experiment was devised to investigate the pitch characteristics of a single arc wing element. The apparatus consisted of a 24-inch-span arc wing model suspended in the slipstream of a 30-inch-diameter electric fan with a pedestal mount. Details are set forth in this paper, which reports qualitative results on dynamic response and quantitative results on pitch trim point angle of attack. Low-resolution digital video clips exist to document the pitch stability of the tailless wing over a broad angle of attack range. While the test stand was not instrumented to measure lift and drag, yarn tufts on the wing provided circumstantial evidence of substantial lift at extreme angles of attack with respect to the propeller axis. The pitch-response experiment laid the groundwork for the development of a novel control technique that would enable a pilot to abruptly increase the wing angle to 30° or more for tight maneuvers at cruise power settings, or for slow-flight at take-off power. This would be accomplished without incurring the diving moments normally associated with transition from cruise to high lift in conventional wing-with-flap systems. A prototype of the arc wing active incidence (AWAI) system was subsequently installed and tested on the same 24-inch span wing model mentioned above. The paper concludes with a discussion of the effectiveness of the new system.