AIRFOIL DESIGN FOR SAILPLANES AND UTTRALIGHT AIRCRAFT

Abstract

ONERA has been involved over the last twenty years in different studies related to sailplanes and the objective of this paper is to present the main contributions in airfoil design. The OAP airfoil family was designed to obtain a very high lift-to-drag ratio mainly in thermal flight. These airfoils were used to define the wings of Pegasus and Marianne sailplanes produced by Societe Nouvelle Centrair. More recently, airfoils with flaps have been designed with thickness-to-chord ratio between 13 and18%. Two airfoils devoted to ultralight aircraft and general aviation are also presented. For these applications, the paper describes the flow phenomena which have to be considered for the design (transition of the boundary layer separation bubbles, stall behaviour), the design process and the performances of the different airfoils.