Abstract: Recent interest in the development of micro air vehicles has led to a renewed interest in flapping-wing propulsion due to the spectacular performance of small birds and insects in this flight regime. Small flapping-wing models, no bigger than 15 centimeters in any dimension, are designed, built and tested in a low speed wind-tunnel. The composite models weigh as little as 6 grams, and flap at frequencies in excess of 38Hz. Both qualitative and quantitative data are obtained. A smoke-wire is used to visualize the highly unsteady, three-dimensional flowfields, providing some insight into the complicated nature of the flow, with comparisons to numerical models where possible. Operating in the Reynolds number range below 24,000, flow visualization indicates separated flow over most of the flapping cycle. Direct thrust measurements are made for several configurations, and illustrate the advantages of aeroelastic tailoring of the structure. While many of the model's aerodynamic characteristics still need further investigation, the present model produces sufficient thrust to hover, and it overcomes its own drag at speeds up to 5.5 meters per second.

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