Lift/Drag

The enigma of flight is how wing can generate large lift L and the expense of small drag D, with the quotient L/D, also called finesse, larger than 10, with L/D = 15 – 20 for common airplanes and L/D = 70 – 100 for extreme gliders.

The following plots display the distribution of lift and drag on the upper and lower side of a wing for angles of attack 0, 2, 4,10 and 18, and thus reveal the miracle:

Lift distributions (translated) on upper an lower side of a NACA0012 wing.

Drag distributions (translated) on upper and lower side of a NACA0012 wing.

We observe in particular the following features:

  • large lift on top of leading edge
  • smaller high pressure below leading edge
  • negative drag on upper part of leading edge
  • small drag and lift at trailing edge.

which combine to give L/D larger than 10.

See also

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