Long before airplanes took to the skies, birds such as this have been soaring around with a naturally engineered ease. As the diagram shows, there are four main forces acting: Lift, Drag, Thrust and Weight.
For flight to be possible, thrust must be more than the drag. In aircraft this is achieved by expelling gas at high velocities and being propelled by the reaction force. In birds, thrust is cause by the power of the wings pushing air back. A major advantage to the bird is that it has a tiny amount of drag; drag is caused by air resistance to the bird and its extremely streamlined shape lessens this. The skeleton of the bird is also lightweight by using hollowed bones with tiny holes to lower weight which helps to achieve greater thrust.
Birds can glide like the one shown by relying on wing shape, the shape causes a higher pressure of air below the wing by diverting air to a longer route along to the top of it. This causes a greater lift force up than the force of wind down onto it.
Photo by Martin Phipps, March 09
Post by Tom Corbett
No comments:
Post a Comment