Private Pilot Flight Training and Instruction Flight Training Article Library | Back To 4VFR.COM Wind and Groundspeed Turning as low levels from a crosswind path to a downwind path can be hazardous. It leads to the terrible downwind turn stall accident. When the aircraft turns from a crosswind to a downwind direction at low altitudes, all at once the ground seems to go by much faster. In actuality, it is, but the reaction to the sensation-illusion is that the airspeed has changed as well. It has not and should not. The wind speed added to your airspeed has caused an increase in your ground speed. Close to the ground fly the airspeed not the ground speed. To allow for student errors in this regard all ground reference should be flown a cruise power in trainers. The downwind turn illusion will be exacerbated if the pilot has developed a (bad) habit of trying to look around the cockpit window post during the turn. (See material on peripheral vision.) As a private pilot you are expected to perform a turn about a point. This means a circle at a constant altitude, of a constant radius with ground speed a variable as affected by the wind. As a commercial pilot you are expected to do a turn on a point. The turn on a point has a constant radius but you are expected to keep the wing tip on the point while flying the circle. This can only be done if you fly a constant ground speed. You should know the difference between the two. Every ground speed has a critical altitude at which a given radius circle will allow the pilot to keep the wingtip on a point. As the circle is flown the wind affects the ground speed differently at every point. To keep the tip on the point the pilot must vary his altitude. Changing altitude will vary the ground speed. Enter a slight dive when the point moves ahead of the wingtip (tailwind component)and a slight climb when the point moves behind the wingtip. Practicing turns on a point at about 640' in a C-150 will give you an idea of how the wind affects ground speed. With this knowledge you will be better prepared to cope with the sensations present in the downwind turn. The best defense is to fly a wide downwind if the wind direction is forcing you toward the runway. When you slow the aircraft on the downwind add some more wind correction. Written by Gene Whitt Flight Training Article Library | Back To 4VFR.COM