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Because lift is a function of dynamic pressure ( q ), it is proportional to the square of the airspeed; therefore, small changes in airspeed create larger changes in lift. Likewise, if other factors remain the same while the C$_{L}$ increases, lift also increases. The C$_{L}$ goes up as the AOA is increased. As air density increases, lift increases. However, a pilot is usually more concerned with how lift is diminished by reductions in air density on a hot day, or if operating at higher altitudes. 

All wings produce lift in two ways: 

1. Airfoil shape creates a higher velocity over the top of the wing and a lower velocity over the bottom of the wing with Bernoulli’s venturi effect. 

2. Downward deflection of airflow because of the curvature of the wing with the principle of Newton’s Third Law of Motion: for every action, there is an equal and opposite reaction. 

Both principles determine the lifting force. Review the Pilot’s Handbook of Aeronautical Knowledge to understand Newton’s laws of motion and Bernoulli’s venturi effect. 

Figure 2-14  (top) shows the amount of lift produced along the wing for an airplane wing with an elliptical planform. Notice how the amount of lift generated is smallest at the tips and increases slightly towards the root of the wing. This is known as the “elliptical lift distribution.” 

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The WSC wing lift distribution is different because the wing twist at the root is at a higher AOA than the tips. Most of the lift is produced at the center of the wing with less lift produced at the tips. The WSC lift distribution is compared to the lift distribution for an optimum design elliptical wing in  Figure 2-14. 

##  Drag 

Drag is the resistance to forward motion through the air and is parallel to the relative wind. Aerodynamic drag comes in two forms: 

1. Induced drag—a result of the wing producing lift. 

2. Parasite drag—resistance to the airflow from the carriage, its occupants, wires, the wing, interference drag from objects in the airstream, and skin friction drag of the wing. 

Induced drag is the result of lift, and its amount varies as discussed above for lift. Induced drag creates organized circular vortices off the wingtips that generally track down and out from each wingtip. Refer to the Pilot’s Handbook of Aeronautical Knowledge for additional discussion on wingtip vortices formation. 

These wingtip vortex formations are typical for all aircraft that use wings including WSC, PPC, helicopters, sailplanes, and all fixed-wing airplanes. The bigger and heavier the aircraft, the greater and more powerful the wingtip vortices are. This organized swirling turbulence is an important factor to understand and avoid for flight safety. Refer to the Aeronautical Information Manual (AIM) or the Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25) for additional discussion. 

Parasite drag is caused by the friction of air moving over all the components of the aircraft. Just as with lift, parasite drag increases as the surface area of the aircraft increases, and dramatically increases as airspeed increases (the square of the velocity). Therefore, doubling the airspeed quadruples parasite drag. [Figure 2-15] 

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The WSC aircraft can be designed for the purpose of being a slow fl ying aircraft with a large wing where drag is not a major concern, or can be designed to be a fast fl ying aircraft with a small wing where drag is more of a concern. 

