STOL CHARACTERISTICS OF A PROPELLER-DRIVEN, ASPECT-RATIO-10, STRAIGHT-WING AIRPLANE WITH BOUNDARY-LAYER CONTROL FLAPS, AS ESTIMATED FROM LARGE-SCALE WIND-TUNNEL TESTS

Research presented relative to the take-off and landing distances possible with a conventional propeller-driven transport-type airplane indicated that if highly effective flaps were used in combination with large amounts of power to augment lift (STOL), the landing and take-off distances would be less than half of the distances for conventional operation. The study is based on the wind-tunnel tests of a model with BLC on the trailing-edge flaps and control surfaces. At the lowest speeds considered (about 50 knots), adequate longitudinal stability was obtained but the lateral and directional stability were unsatisfactory. At these low speeds the conventional aerodynamic control surfaces may not be able to cope with the forces and moments produced by symmetric as well as asymmetric engine power. This problem was alleviated by increasing control effectiveness by use of BLC. Further reductions in the landing and take-off speeds to obtain shorter distances probably will result in the need to supplement the aerodynamic controls, the need for counterrotating propellers, and possibly the need for interconnected shafting on the propellers. (Author)