境界層
Between 1951 and 1955 Cessna used modifications of the 170 and its derivative, the U.S. Army L-19, as test beds for Boundary layer control research, under contract to the Office of Naval Research and the Army Transportation Corps, designating them as the models 309 and 319. The project was done in conjunction with the University of Wichita which conducted extensive wind tunnel tests of the concept. The model 309 utilized the German World War II Arado lift-increasing system in which a jet pump inside the wing sucked in stagnant air from the flap area, energized it and blew the higher-speed air over the ailerons. Various chemicals and enhancements were used to power the jet pump. Better results were obtained by departing from the Arado jet pump method and using an engine-driven generator to power electric motors driving axial fans to move the internal air.