 A notable exception is the Stearman PT-17, which has 4° of incidence in the lower wing, and 3° in the upper wing.Considered from an aerodynamic perspective, it is desirable to have the forward-most wing stall first, which will induce a pitch-down moment, aiding in stall recovery.Biplane designers may use incidence to control stalling behavior, but may also use airfoil selection or other means to accomplish correct behavior.