A kite is a flying tethered aircraft that depends upon the tension of a tethering system.[1] The necessary lift that makes the kite wing fly is generated when air (or in some cases water)[2][3][4] flows over and under the kite's wing, producing low pressure above the wing and high pressure below it. This deflection also generates horizontal drag along the direction of the wind. The resultant force vector from the lift and drag force components is opposed by the tension of the one or more lines or tethers.[5] The anchor point of the kite line may be static or moving (e.g., the towing of a kite by a running person, boat,[6] or vehicle).[7][8]
Kites are usually heavier-than-air, but there is a second category of lighter-than-air kite called a helikite which will fly with or without wind. Helikites work on a different stability principle to normal kites as helikites are helium-stabilised as well as wind stabilised. They are a stable combination of a helium balloon and kite-sail to create a single aerodynamically sound kite. When flown in wind a helikite will lift far more than its helium alone, and it will fly very well if weighted down to be considerably heavier than air.
Kites may be flown for recreation, art or other practical uses. Sport kites can be flown in aerial ballet, sometimes as part of a competition. Power kites are multi-line steerable kites designed to generate large forces which can be used to power activities such as kite surfing, kite landboarding,kite buggying and a new trend snow kiting. Kites towed behind boats can lift passengers[9] which has had useful military applications in the past.[10]
