So I am designing a biplane,I know the weight.I want to know what is the lift formula , volume ratio and aspect ratio for a biplane? I know the formulas for monoplane
closed as unclear what you're asking by Dan Hulme, Ralph J, fooot, SMS von der Tann, David Richerby Sep 2 '18 at 21:38
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They are the same, but you have to use the total area of both wings multiplied by an interference factor that will be $<1$ to represent the loss of efficiency due to interference between both wing planes.