Aerodynamics and Spin Awareness 2
PA.IV.C.K4 Ground effect.
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1. Ground effect is most likely to result in which problem?
Answer (A) is correct. (FAA-H-8083-25B Chap 5) Due to the reduction of induced drag in ground effect, the airplane may seem capable of becoming airborne well below the recommended takeoff speed. However, as the airplane rises out of ground effect (a height greater than the wingspan) with a deficiency of speed, the increase in induced drag may result in very marginal initial climb performance. In extreme cases, the airplane may become airborne initially, with a deficiency of airspeed, only to settle back on the runway when attempting to fly out of the ground effect area.
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2. An aircraft leaving ground effect during takeoff will
Answer (A) is correct. (FAA-H-8083-25B Chap 5) During the takeoff phase of flight, ground effect produces some important relationships. The airplane leaving ground effect after takeoff encounters just the reverse of the airplane entering ground effect during landing; i.e., the airplane leaving ground effect will (1) require an increase in angle of attack to maintain the same lift coefficient, (2) experience an increase in induced drag and thrust required, (3) experience a decrease in stability and a nose-up change in moment, and (4) produce a reduction in static source pressure and an increase in indicated airspeed.
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3. What must a pilot be aware of as a result of ground effect?
Answer (A) is correct. (FAA-H-8083-25B Chap 5) Ground effect reduces the upwash, downwash, and vortices caused by the wings, resulting in a decrease in induced drag. Thus, thrust required at low airspeeds will be reduced, and any excess speed at the point of flare may cause considerable floating.
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4. Floating caused by the phenomenon of ground effect will be most realized during an approach to land when at
Answer (C) is correct. (FAA-H-8083-25B Chap 5) Ground effect is most usually recognized when the airplane is within one of its wingspan above the surface. It may extend as high as a full wingspan length above the surface. Due to an alteration of the airflow about the wings, induced drag decreases, which reduces the thrust required at low airspeeds. Thus, any excess speed during the landing flare may result in considerable floating.
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5. What is ground effect?
Answer (C) is correct. (FAA-H-8083-25B Chap 5) Ground effect is due to the interference of the ground (or water) surface with the airflow patterns about the airplane in flight. As the wing encounters ground effect, there is a reduction in the upwash, downwash, and the wingtip vortices. The result is a reduction in induced drag. Thus, for a given angle of attack, the wing will produce more lift in ground effect than it does out of ground effect.
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