NACA-ARR-3L10

Abstract

<strong>INTRODUCTION</strong> <br>An extensive investigation of various hlgh-llft devices has been undertaken by the&#160;NACA to furnish in-formation applicable to the aerodynamic design of wihg- flap combinations for improved safety and performance of airplanes. A high-lift device capable of producing high lift with variable drag for landing and high lift with low drag for take-off and Initial climb Is believed to be desirable. Other desirable characteristics are: no increase In drag with the flap neutral, small change in pitohlng moment with flap deflection, low forces required to operate the flap, and freedom from possible hazard due to icing. <br>Aerodynamic data on the NACA 23012 airfoil have been made available for single slotted flaps in references 1 and 2, for a Fowler flap having a chord 30 percent of the airfoil chord (0.30c) in reference 3, and for a 0.40c double slotted flap In reference 4. <br>The data presented in reference 4 indicated that the double slotted flap gave higher lift than the single slotted flap and had lower drag at high section lift coefficients, The double slotted flap also had higher lift than the Fowler flap. <br>Although an investigation essentially the same as that reported herein had been planned at LMAL several years ago, no tests were made at that time because of other projects of greater interest. Renewed Interest of designers and manufacturers in devices capable of Producing very high lift on combat airplanes, however, led to the present investigation In which tests were made of a 0.30c double slotted flap on the NACA 23012 airfoil (fig.1). It was believed that this device. would combine the advantageous aerodynamic characteristics of the 0.40c double slotted flap (reference 4) with the structural advantages of the small single slotted flap (reference 1)0 The small size of the fore flap would also allow the use of simpler doors for sealing the break in the airfoil lower surface with the flaps retracted