The static stability of an aircraft is generally the first type of stability that a designer evaluates in a new aircraft configuration. Static stability criteria for the three rotational modes of the aircraft (pitch, roll, and yaw) must be considered individually. Accepted design practice for most aircraft has been to achieve some degree of static stability for each of these rotational degrees of freedom. A tradeoff typically exists between static stability and maneuverability. A high degree of static stability would normally result in an aircraft that was easy to fly but that had low maneuverability (trainer aircraft, for example). Fighter aircraft designs would incorporate low levels of static stability so that enhanced maneuvering capabilities could be achieved. However, with the advent of high authority fly-by-wire control systems in aircraft such as the F- 16, the Space Shuttle, and the X-29, acceptable levels of both static stability and maneuverability can be achieved. Some degree of static instability in the basic airframe design is intentionally incorporated in these aircraft to achieve enhanced maneuvering capabilities, while the fly-by-wire system provides automatic control inputs to achieve the appearance of static stability from the pilot perspective. Static stability concepts provide a first step in achieving a design with acceptable flying qualities.