Experimental Validation of Vertical Lifting Capabilities of Circling Tethered Fixed Wing UAVs

The Electric-Powered Reconfigurable Rotor VTOL Concept (EPR2 ) is a novel type of VTOL aircraft that uses tethered airplanes flying collaboratively along a near circular flight path to lift a payload. The objective of this paper is to experimentally assess the vertical lifting capabilities of a single tethered fixed wing aircraft flying along a circular flight path anchored to the ground using a small-scale testing platform. Results show that the airplane has the ability to lift up to 4 times its empty weight with off-the-shelf components along an unoptimized flight path. This new concept also requires considerably less power than other conventional VTOL aircraft to lift the same payload, reaching a payload-to-power ratio of 13 grams per Watt. The maximum lifting capability and efficiency are then evaluated using a numerical model of the system in a constrained nonlinear multi-objective optimization function. It is shown that the same airframe with minimal modifications could lift up to 8 times its empty weight at a payload-to-power ratio of 26 grams per Watt.