Multiple-element airfoils (MEA) greatly increase the achievable lift coefficient and stall angle. They are found commonly on commercial airliners, which have wings that can transform between single- and multiple-element airfoils. The multiple-element transformations are used during takeoff and landing, where speeds are lower and a higher lift coefficient is needed.
MEA enable greater lift coefficients by distributing pressures so that for a given level of lift the pressure peaks are lower. High pressure peaks ultimately lead to flow separation. References: http://adg.stanford.edu/aa241/highlift/highliftintro.html http://www.dept.aoe.vt.edu/~mason/Mason_f/HiLiftPresPt1.pdf |