During the early twenties many experimenters in aviation undertook the challenge of making a craft which would rise vertically and hover in the air. Realizing that such a machine would have military value for observation and fire-control, the war department of several nations encouraged such inventions. The de Bothezat Helicopter was developed by the U. S. Air Service, Engineering Division in 1921 with these ideas in mind. Dr. George de Bothezat, a noted Russian aeronautical engineer at the time, designed the helicopter. The de Bothezat was 65 feet long, 65 feet wide, and 10 feet high. It was powered with a 180 h.p. engine and weighed 3,600 lbs. The engine was located at the center above the four-wheeled chassis. Four triangular framework arms extended at right angles, and at their extremity each supported a six-bladed air screw, which is the chief feature of the de Bothezat. Many power tests were made at McCook Field in Dayton, Ohio. The test on December 18, 1922 was notable with a duration in the air of one minute 42 seconds which was attained at a maximum height of six feet.