An Airfoil Fitted With a Slotted Flap

THE use of the slotted flap on an airfoil has been found to be very advantageous in recent tests conducted in the seven by ten foot wind tunnel of the University of Detroit. A slotted flap of 30% chord fitted on a Gottingen 398 (modified) airfoil shows a large increase in lift with a very small added drag for small flap deflections. A large reduction in take off speed with good rates of climb were found obtainable at speeds below the minimum speed for the normal airfoil. Satisfactory air braking is available at high flap deflections. Low relative drag was obtained at zero flap angle by closing the slot entirely in this condition.