Design, development and testing of a morphing aspect ratio wing using an inflatable telescopic spar

This paper discusses the design, development and testing of an inflatable telescopic wing that permits a change in the aspect ratio while simultaneously supporting structural wing loads. The key element of the wing consists of a pressurized telescopic spar that can undergo large-scale spanwise changes while supporting wing loadings in excess of 15 lbs/ft. The wing cross-section is maintained by NACA0012 rib sections fixed at the end of each element of the telescopic spar. Telescopic skins are used to preserve the spanwise airfoil geometry and ensure compact storage and deployment of the telescopic wing. A small scale telescopic wing assembly was tested in a free jet wind tunnel facility at a variety of Reynolds numbers (182000, 273000, 363000 and 454000). The telescopic wing was deployed from 7 inches to 15”. Experimental wind tunnel results were compared to rigid fixed wing test specimen to compare the performance of the telescopic wing. Preliminary aerodynamic results are promising for the variable aspect ratio telescopic wing. Overall, the telescopic wing at maximum deployment did incur a slightly larger drag penalty and a reduced lift to drag ratio. Thus, it may be possible to develop UAVs with variable aspect ratio wings using inflatable telescopic spars and skin sections. Graduate Research Assistant, Aerospace Engineering Dept. † Undergraduate Student, Aerospace Engineering Dept. Associate Professor, Aerospace Engineering Dept., Associate Fellow of AIAA Nomenclature a Lift curve slope a0 Theoretical lift curve slope a Angle of attack (degrees) a i Induced angle of attack (degrees) AR Aspect ratio b Wingspan (ft) c Chord length (ft) cf Specific fuel consumption CL Lift coefficient CD Drag coefficient CD,0 Induced Drag coefficient at α = 0 CD,i Induced Drag coefficient e Span efficiency factor E Endurance ID Inside Diameter l Length L Lift force m Mass (lbs) ? Propeller efficiency μ Viscosity OD Outside Diameter P Pressure (Psi) q Dynamic pressure R Range Re Reynolds Number ? Density (lbs/ft ) S Surface area of the wing t Thickness (ft) V Speed (ft/s) W0 Gross weight (with full fuel an payload) W1 Empty weight (lbs) 8 Freestream