Three-Surface Aircraft - A Concept for Future Large Aircraft

Abstract

In this paper the activities of the Institute of Design Aerodynamics within the DLR project "Dreiflächen-Flugzeug (3FF)" - Three-Surface Aircraft, TSA - concerning the investigation of three-surface aircraft configurations are presented. Results of aircraft predesign calculations of the retrofitted wind-tunnel model DLR-F11 show higher performances for the optimised TSA configuration compared to the conventional design. However, the performance increase is coupled with a loss of static stability. Under the boundary condition of equal static stability, the same performance gain is achieved with a conventional design. The possible performance potential of TSA configurations can only be realised if the concept of a "free-floating canard", which does not influence the static stability, is taken into account. Corresponding transonic canard designs demonstrate the aerodynamic feasibility of the canard concept for transport aircraft configurations at high cruise Mach numbers for a backward swept canard at a low aft position and a forward swept canard at a low front position.