No matter how good a person is at flying kites, a kite would never get off the ground without airflow, explains John Anderson. He’s an aeronautical engineer—someone who designs and studies aircraft—and the curator of aerodynamics at the Smithsonian’s National Air and Space Museum in Washington, D.C. To keep a kite aloft, “there has to be airflow both under the kite and over the top of it,” he says.
Airflow isn’t the only thing a kite needs to soar. A kite cannot fly flat. It must have an angle of attack with its nose angled upward (see Kite-Flying Physics). This way, the airflow underneath the kite exerts more pressure than the air moving over the top of the kite. This pressure difference pushes the kite skyward, says Anderson, and “presto, you’ve got lift!” This upward force works against the downward pull of gravity.
A kite often looks like it’s floating stationary in the sky. But to stay up, a kite must be moving forward. The kite needs a pushing force called thrust. To propel a kite forward, a flier can be standing still, but they must apply tension by pulling on the kite’s strings. This also maintains the kite’s angle of attack and helps it overcome the slowing force of drag, explains Anderson. Drag occurs when air molecules push against the surface of a moving object. Unlike a traditional single-line kite, multi-line sports kites can be maneuvered so they fly vertically in the air. This steeper angle of attack means a sport kite’s surface catches more wind—so much so, says Dylan, that “I’ve been pulled down the beach!”