NATURAL-LAMIMAR-FLOW AIRFOIL FOR GENERAL-AVIATION APPLICATIONS

A natural-laminar-flow airfoil, the NLF(1)-0115, has been recently des igned for general-aviation aircraft at the NASA Langley Research Cente r. During the design of this airfoil, special emphasis was plated on e xperiences and observations gleaned from other successful general-avia tion airfoils. For example? the flight lift-coefficient range is the s ame as that of the turbulent-flow NACA 23015 airfoil. Also, although b eneficial for reducing drag and producing high lift, the NLF(1)-O115 a irfoil avoids the use of aft loading, which can lead to large stick fo rces if utilized on portions of the wing having ailerons. Furthermore, not using aft loading eliminates the concern that the high pitching-m oment coefficient generated by such airfoils can result in large trim drag if cruise flaps are not employed. The NASA NLF(I)-0115 airfoil ha s a thickness of 15% chord. It is designed primarily for general-aviat ion aircraft with wing loadings of 720-960 N/m(2) (15-20 lb/ft(2)), Lo w-profile drag as a result of laminar flow is obtained over the range from c(l) = 0.1 and R = 9 x 10(6) (the cruise condition) to c(l) = 0.6 and R = 4 x 10(6) (the climb condition), While this airfoil can be us ed with flaps, it is designed to achieve a c(l,max) of 1.5 at R = 2.6 x 10(6) without flaps, The zero-lift pitching moment is held to c(m,0) = -0.055. The hinge moment for a 20% chord aileron is fixed at a valu e equal to that of the NACA 63(2)-215 airfoil, c(H) = -0.0022. The los s in c(l,max) due to leading-edge roughness at R = 2.6 x 10(6) is 11% as compared with 14% for the NACA 23015.