Bionic design of flying robots based on natural models has become a hot topic in mechanical engineering. The research going on in this direction considers that there is a lot to learn from flying animals such as birds, insects, and bats, from walking on the ground to getting enough power to be airborne. To get an efficient design of flying robots, we must better understand the origin of flight. This paper focuses on the review of avian flight and its possible application in the design of flying robots. Different hypotheses have been proposed to tackle the origin and evolution of avian flight from cursorial dinosaurs to modern birds, including the famous ground-up and tree-down theories. During the past decade, discoveries of feathered and winged dinosaurs from Liaoning, China, strongly supported the theory that birds originated from theropod dinosaurs. The transition from running on the ground to maneuver in the sky involves various stages of flights and plumages, which can be now illustrated by several representative paravian dinosaurs from Liaoning. Those fossils provide good research bases for the design of flying robots. Microraptor is one of those important transitional stages in the evolution of flight. This paravian dinosaur is characterized by the presence of pennaceous feathers along both its arms and its legs, but how it could actually fly is still debated. It is of course difficult to evaluate the flight performances of an extinct animal, but aerodynamics of a four-wing robot can be developed to get some knowledge about its flying capacity. Fossil and living flying animals with different morphologies, stability, and control mechanism can be a source of inspiration for designing socially relevant products.

Among the different models that have been proposed to explain the origin of avian flightfrom terrestrial predators, the cursorial and arboreal hypotheses remain the most discussed.However, the fossil data at hand show that, taken separately, both theories have significantlimitations in explaining the origin of flight in bird lineage. Here, we describe an aerodynamicsprinciple that fills in the gaps between those apparently contradictory models. The upslope wind inmountain areas and strong wind in plains provided the meteorological conditions allowingfeathered paravians to glide. The results suggest that smaller, feathered paravians could be lifted toglide down to trees on mountain slopes or even to glide up to high trees in plain areas when meetinga strong airflow as they were pursuing a prey or escaping from a predator. The development ofmore aerodynamical limb feathers was a key factor for gliding down the trees because of thedependency of the resultant force on the surface area of a paravian’s body. Later in the evolutionprocess, paravians learned to change the orientation of their wings to gain higher lifts. The proposedprinciple and the results obtained in the present research help to better estimate the aerodynamicbehavior of extinct species and will also help to design an efficient and beneficial system for futureflying robots.