Not like birds and airplanes, says Dickinson. Birds and airplanes stay airborne on wings whose shape and angle create lower pressure above the wing, which helps lift them. To understand the aerodynamic forces generated by flies, Dickinson built a huge model of the wings of a fruit fly, Drosophila melanogaster . Three motors move the robotic wing back and forth in precise motions determined by a computer. Bubbles pumped into the tank show the aerodynamic patterns.
Sensors measure the forces on the wings during each phase of the stroke.
When the insect sweeps its wing forward, a whirlpool or vortex of air is created on top of the wings. This vortex seems to create a low-pressure zone that produces lift. The team also discovered that two previously unknown forces occur at the end of each half-stroke. Like a tennis ball with backspin, the wing is pulled upward by lower pressure. The wing actually passes through a spinning vortex wake from the previous stroke.