Comparison of Five STOL Concepts for Runway Independent Aircraft

Abstract

One approach to reducing airport congestion is to use taxiways at large airports or the shorter runways available at general aviation airports. Aircraft that could use these shorter runways require the high lift coefficients that are only available from powered lift. Aero/propulsion characteristics and relative performance capabilities are presented for five STOL concepts that could operate as runway independent aircraft (RIA). Data obtained using powered wind tunnel models are identified and compared. The STOL aircraft concepts examined include turbojet engine powered internally-blown flap (IBF), externally-blown flap (EBF), and uppersurface blown flap (USB). For these concepts the longitudinally trimmed powered performance are compared. In addition, the deflected slipstream (DSS) and tilt-wing (TW) propeller powered STOL are examined. For these two concepts the reports selected did not provide sufficient data to provide trimmed aero/propulsive characteristics. The lift-drag polars are presented for the takeoff configurations using a 6° climb path and for the landing configurations using a 6° descent path. These data are then used to determine the required thrust to weight ratio as a function of wing-loading. It is found that the configurations that spread their powered lift across the full wing span have the lowest thrust to weight ratio requirement. These configurations include the internally-blown flap, the deflected slipstream, and the tilt-wing powered lift concepts. Also examined is one concept for power augmented low flight speed (or high lift coefficient) longitudinal-directional control. When this concept is combined with the suggested appropriate power augmented lateral control, a powered-lift airplane concept for low-speed flight is described. It is noted that such a concept will require further development and flight demonstration.