The development and flight testing of flapping-wing propelled, radio-controlled micro air vehicles are described. The unconventional vehicles consist of a low aspect ratio fixed-wing with a trailing pair of higher aspect ratio flapping wings which flap in counterphase. The symmetric flapping-wing pair provides a mechanically and aerodynamically balanced platform, increases efficiency by emulating flight in ground effect, and suppresses stall over the main wing by entraining flow. The models weigh as little as 11g, with a 23cm span and 18cm length and will fly for about 20 minutes on a rechargeable battery. Stable flight at speeds between 2 and 5ms-1 has been demonstrated, and the models are essentially stall-proof while under power. The static-thrust figure of merit for the device is 60% higher than propellers with a similar scale and disk loading.
Jones, K. D., Bradshaw, C. J., Papadopoulos, J., & Platzer, M. F. (2005). Bio-inspired design of flapping-wing micro air vehicles. Aeronautical Journal, 109(1098), 385–393. https://doi.org/10.1017/S0001924000000804