Wind-Tunnel Investigation of the Lift Characteristics of an NACA 27-212 Airfoil Equipped with Two Types of Flap, Special Report

An investigation has been made in the NACA 7- by 10-foot wind tunnel of a large chord NACA 27-212 airfoil with a 20% chord split flap and with two arrangements of a 25.66% chord slotted flap to determine the section lift characteristics as affected by flap deflection for the split flap and as affected by flap deflection, flap position, and slot shape for the slotted flap. For the two arrangements of the slotted flap, the flap positions for maximum section lift are given. Comparable data on the NACA 23012 airfoil equipped with similar flaps are also given. On the basis of maximum section lift coefficient, the slotted flap with an easy slot entry was slightly better than either the split flap or the slotted flap with a sharp slot entry. With both types of flap the decrease in the angle of attack, for maximum section lift coefficient, with flap deflection is large for the NACA 27-212 airfoil as compared with the NACA 23012 airfoil. Also with both flaps, the maximum section lift coefficient obtained with flaps is much lower for the NACA 27-212 airfoil than for the NACA 23012 airfoil.