Design and testing of a pneumatic telescopic-wing for unmanned aerial vehicles

This paper discusses the design, development, and testing of an unmanned aerial vehicle pneumatic telescopic wing that permits a change in the wingspan, while simultaneously supporting structural wing loads. The key element of the wing is a pressurized telescopic spar able to undergo large-scale spanwise changes while supporting wing loadings in excess of 15 lb/ft(2). The wing cross section is maintained by NACA 0013 rib sections fixed at the end of each element of the telescopic spar. Hollow fiberglass shells are used to preserve the spanwise airfoil geometry and ensure compact storage and deployment of the telescopic wing. A full-scale telescopic wing assembly was built and tested in the Glenn L. Martin Wind Tunnel at the University of Maryland. These tests included aerodynamic measurements at a variety of Reynolds numbers. The telescopic wing was tested in three different configurations and experimental results are compared with finite wing theory and results obtained on a rigid fixed-wing counterpart. Preliminary aerodynamic results were promising for the variable wingspan telescopic wing. As expected, the telescopic wing at maximum deployment incurred a slightly larger drag penalty and a reduced lift-to-drag ratio when compared to its solid fixed-wing counterpart. However, the penalty was minimal and thus the development of an unmanned aerial vehicle with a pneumatic variable span wing is feasible.