Experimental Studies on a Propelled Micro Air Vehicle D. Arivoli 1 , Ravi Dodamani 1 , Roshan Antony 2 , C.S. Suraj 2 , G. Ramesh 1 , and Sajeer Ahmed 1 Council of Scientific & Industrial Research – National Aerospace Laboratories, Bangalore, Karnataka, 560037, India An experimental study has been carried out on a typical Micro Air Vehicle of span 300mm having inverse Zimmerman planform. The objective is to get i) the aerodynamic characteristics of the vehicle in the range of incidence and sideslip angle the vehicle expected to encounter during its flight; ii) an understanding of the propeller effect on the aerodynamic data and iii) the control surface (elevon) effectiveness with incidence. Tests were carried out in a low speed wind tunnel at a freestream velocity of 8 m/s and 12 m/s corresponding to a test Reynolds number based on chord of about 120000 and 180000 respectively. Analysis of the aerodynamic data showed significant effect of propeller flow field on the lift, stall angle and drag of the vehicle. The propeller induced flow is seen to increase the lift coefficient at higher angle of attack and delay the stall. Nonlinear variation is observed in the rolling moment indicating the onset of asymmetric flow field at higher incidence. The effectiveness of the elevon is observed to increase linearly with incidence. Nomenclature C L = lift coefficient C D = drag coefficient C M = pitching moment coefficient C S = side force coefficient C YM = yaw moment coefficient C RM = roll moment coefficient C.G = center of gravity LAR = low aspect ratio Re = Reynolds number V = velocity (m/s) α = angle of attack (degree) β = sideslip angle (degree) φ = roll angle (degree) δ = elevon deflection angle (degree) I. Introduction ICRO Air Vehicles (MAVs) are small class of vehicles which fly in the Reynolds number range less than 200,000 at lower atmospheric altitude in the earth’s boundary layer. The small span of the wing requires larger wing area to create sufficient lift to support itself that makes it a low aspect ratio (LAR) wing. These LAR wings at low Re exhibits unique aerodynamic characteristics. Flow over the upper wing surface is prone to separation with a possible turbulent transition in the free shear layer, and then reattachment to the surface, leaving behind a separation bubble 1 . Such flow structures typically result in a loss of lift and an increased drag, which decreases the lift-to-drag ratio of the vehicle 2 . LAR wings exhibits non-linear lift. This non-linearity in lift is due to the formation of wing tip vortices which creates a low pressure on the upper surface of the wing which results in a subsequent increase in lift. These tip vortices strengthen as the angle of attack increases and might be present over most of the wing area due to which the LAR wings stalls at higher angle of attack. Destabilization of tip vortices occur beyond certain angle of attack due to its interaction with the separated flow resulting in a bilateral asymmetry which may cause rolling instabilities 3 . Controllable flight in the lower atmospheric altitude is another problem these M American Institute of Aeronautics and Astronautics 1 1 Scientist, Experimental Aerodynamics Division., CSIR-National Aerospace Laboratories. 2 Scientist, Propulsion Division, CSIR-National Aerospace Laboratories. 29th AIAA Applied Aerodynamics Conference 27 - 30 June 2011, Honolulu, Hawaii AIAA 2011-3656 Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.