FAA Flight Instructor Airplane (FIA)Aerodynamics and Principles of FlightMedium
A student pilot notices that during landing flare, the airplane seems to float and resists touchdown even with power at idle. A CFI explains this is most likely due to:
- Areduced angle of attack caused by wingtip vortices
- Ban increase in parasite drag from ground turbulence
- Can increase in induced drag as the airplane nears the runway
- Dground effect reducing induced drag and downwash near the surface
Show answer & explanationAnswer & explanation
Correct answer: D. ground effect reducing induced drag and downwash near the surface
Ground effect occurs within roughly one wingspan of the surface; it reduces induced drag and upwash/downwash, allowing the wing to produce the same lift at a lower angle of attack or airspeed, which causes floating during flare.
Why the other options are wrong
- A. Ground effect does not directly reduce angle of attack; it changes the drag and lift efficiency at a given AOA.
- B. Ground turbulence is unrelated to the floating phenomenon; ground effect is an aerodynamic, not turbulence, effect.
- C. Ground effect decreases, not increases, induced drag.
Ground Effect
A reduction in induced drag and downwash experienced when the wing operates within approximately one wingspan of the surface, increasing lift efficiency.
- Occurs within about one wingspan altitude
- Reduces induced drag and downwash
- Can cause floating during landing or premature liftoff during takeoff
- Most pronounced with low-wing, wide-span aircraft
Memory trick: 'Cushion of air' near the ground makes wings extra efficient