Induced Drag

[Ref PPL Instruction Kit Vol1 (306) – 9th Edition, V9.2 P.9]

Induced drag – is a result of an airfoil developing lift. Whenever an aerofoil produces lift it also produces “Wingtip Vortices” ,which can explain why induced drag appear

The less the downwash, the more vertical the lift vector for opposing gravity

In a simply way to explain, air tends to flow from the high pressure area below the tip upward to the low pressure area on the upper surface. This creates the downwash. Downwash is titled relative wind and that causes the lift vector titled. Therefore, the less the downwash, the more vertical the lift vector for opposing gravity.

Anytime when AOA increases, induced drag increases proportionally

This explains why the lower the airspeed, the greater the AOA required to produce lift equal to the aircraft’s weight and, therefore, the greater induced drag.

Be noticed that the induced downwash has nothing in common with the downwash that is necessary to produce lift. It is, in fact, the source of induced drag.

 

Note: Induced Drag is only part of the drag on an aerofoil.

 

Read More –

elliptical wing is the ideal subsonic planform since it provides for a minimum of induced drag for a given aspect ratio.

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