 Differential thrust between the two wings (one on either side of the fuselage) can be used to turn the aircraft around its vertical axis, although conventional tail surfaces may be used as well.Jonathan Edward Caldwell took out a patent on the cyclogyro which was granted in 1927, but he never followed it up.The Schroeder S1 of 1930 was a full-size prototype which used the cyclogyro for forward thrust only.