FAA Commercial Pilot Airplane (CAX)Aerodynamics and PerformanceEasy
During the landing flare, a pilot notices the airplane seems reluctant to settle onto the runway and floats farther than expected. This is most likely caused by:
- Areduced induced drag due to disruption of wingtip vortices near the ground
- Bincreased parasite drag near the surface
- Cincreased induced drag due to ground effect
- Da decrease in angle of attack caused by ground proximity
Show answer & explanationAnswer & explanation
Correct answer: A. reduced induced drag due to disruption of wingtip vortices near the ground
Ground effect occurs when the wing flies within roughly one wingspan of the surface, disrupting the formation of wingtip vortices and reducing induced drag. This reduction in drag, combined with slightly increased lift efficiency, causes the airplane to float longer during the flare than it would at altitude.
Why the other options are wrong
- B. Parasite drag is largely unaffected by proximity to the ground.
- C. Ground effect decreases induced drag, not increases it.
- D. Ground effect does not directly decrease angle of attack; it changes drag characteristics.
Ground Effect
An aerodynamic phenomenon occurring near the ground where induced drag is reduced due to interference with wingtip vortex formation, resulting in extra lift efficiency.
- Occurs within about one wingspan of the surface
- Reduces induced drag, causing floating during flare
- Can mask an impending stall if airspeed is too low
Memory trick: Close to the ground, vortices lose their pound (of drag).