Directional Stability

Directional stability keeps a plane flying in a straight line without veering to one side or the other. Early airplanes had lit­tle stability. The pilot had to concentrate extremely hard and constantly make adjustments to keep the plane under control. A gust of wind or a careless maneuver could send the plane spiraling to the ground. Many early aviators died in crashes caused by poor stability and control problems.

A modern plane’s tail fin, or vertical stabilizer, helps to provide directional stability. If the plane’s nose is pushed to one side by a gust of wind, the airflow around the tail fin moves the tail back in line with the nose, so that the plane keeps flying in the same direction instead of veering off course. (Weather vanes keep pointing into the wind for the same reason.)