Abstract
Inspired by a dragonfly, which sometimes appears to quit wing-beating, a possibility of a flight with either fore-wing or hind-wing beating of our four-winged flapping vehicle in order to achieve the more efficient flight. The wind-tunnel tests were carried out to determine which wing was appropriate to quit, by measuring the lift force on the fixed wing, which was placed in front of or behind the flapping wing. It revealed that the generated lift on the fixed fore-wing showed the dependency inversely to the flapping of the hind-wing. The visualized flow indicated that the flow separation over the upper surface of the fore-wing was suppressed by the flapping of the hind-wing. The prototype of the hind-wing flapping vehicle with the fore-wing fixed, successfully exhibited the steady flight, as well as saving 70 percents of the required energy for a flight of the four-winged flapping one.
