. Stability

Most airplanes are designed to be aero­dynamically stable. A stable airplane is one that is steady in the air. If it is rocked by a gust of wind, it steadies itself without the pilot having to do any­thing. Stability makes an airplane safer and easier to fly, but it also makes it more difficult to maneuver. Stable air­craft are designed to fly straight and level. That stability works well for a plane like an airliner, because passengers want to fly in planes that feel steady and turn gently.

A fighter plane that performed like an airliner, however, would not last long in an air battle. Fighters have to be able
to maneuver fast to chase other planes and escape danger. The way to make fighter planes more maneuverable is to make them less stable.

The latest fighters are highly unsta­ble. Sometimes, a pilot needs to make a sudden turn, climb, or dive. A fighter plane’s instability enables it to respond quickly to controls and make such a move much faster than a more stable aircraft. In fact, these extraordinary planes are able to fly only with the help of computers that constantly make

FLYING WINGS

Most planes have the same basic layout, with a pair of wings sticking out from a central fuselage (body) and a small tail unit at the back. The B-2 bomber (below) is different. It is a type of aircraft called a flying wing. The whole plane is one big wing. There is no tail. A flying wing is very streamlined, but it is also very unstable. If the nose of a flying wing tips up or down even a little, the plane can suddenly flip over. Most planes have a tail unit that prevents this from happening. A flying wing needs a control system to keep it under control in the air.

Flying wing aircraft have been built since the 1930s, but they never became very popular or widespread, because their lack of stability made them difficult to fly. The control systems available then were not able to tame their wild behavior. Control systems developed since the late 1980s work much better. The B-2 bomber, which first flew in 1989, relies on four flight computers to stop it from tumbling out of con­trol. The pilot operates the computers, and the computers fly the plane.

split-second adjustments to keep them under control. Without their flight com­puters, these planes would be impossible to control.

Scientists know a lot more about aerodynamics today than they did in the early days of aviation, but there is still a lot to learn. The development of new aircraft and faster aircraft, together with the use of new materials, continue to
present aerospace engineers with new challenges in aerodynamics.

SEE ALSO:

• Aircraft Design • Bird • Glider

• Lift and Drag • Materials and Structures • Wind Tunnel • Wing

• Wright, Orville and Wilbur

_____________________________________________ /