In aviation, a stabilizer is an aft-mounted wing or surface that provides longitudinal (or pitch) stability, or provides yaw (or directional) stability to an aircraft in flight. A longitudinal stabilizer is surface that provides forces that tend to keep an aircraft flying level and with unchanging "pitch" angles relative to the airstream. (The nose of aircraft is prevented from pitching up or down.) A vertical stabilizer tends to keep the aircraft flying straight ahead with unchanging direction relative to the airstream (yaw stabilization). Stabilizers are always placed at the rear of an aircraft, behind the center of gravity. It is a common misconception that the small forward wing of a "canard" aircraft is a "forward stabilizer".