Lesson 1.6 Ground Effect

1. Ground effect is due to the interference of the ground (or water) surface with the airflow patterns about the airplane in flight.
a. When an airplane is within a distance of its wingspan to the surface, a change occurs in the three-dimensional flow pattern around the airplane because the vertical component of the airflow around the wing is restricted by the Earth’s surface.
1. This change alters the wing’s upwash, downwash, and wingtip vortices.
a. The reduction of the wingtip vortices alters the spanwise lift distribution and reduces the induced angle of attack and induced drag.
2. An airplane leaving ground effect experiences an increase in induced drag and requires more thrust.
3. While in ground effect, an airplane needs a lower angle of attack to produce the same lift as when out of ground effect.
a. If the same angle of attack is maintained in ground effect as when out of ground effect, lift will increase and induced drag will decrease.