Expert: Heiko Hanusch - 2/12/2006

Question
Dear expert,
if airfoil lift is in proportion to its area and drag is in proportion to foils crosssection then it should stand that making 4 smaller foils by scaling down the original by a factor of 2 should result in same combined performance at the half of the original weihght. Since I don't see monoplanes build today means that this reasoning is flawed. Where is a problem ?

Answer
Hi there,

It looks at first that it would reduce weight and drag but it actually does the opposite. Not to get to deep into this the main reason is that each wing would have to be constructed to withstand the loads experienced by the aircraft hence making each wing quite heavy and actually increasing the weight dramatically, also the drag issue is negative because of the close proximation of the wings, drag around them is altered significantly (due to airflow and interference) and produces a lot of extra drag which is undesirable.
This is the problem with multiple wings in a nutshell.

Hope this helps,

H2