The Curtiss N-9 was a seaplane version of the famous Curtiss JN-4 trainer used by the U.S. Air Service during the First World War. To make the conversion, a single large central pontoon was mounted below the fuselage, with a small float fitted under each wingtip. These changes required a ten-foot increase in wingspan to compensate for the additional weight. Further modifications to the standard Curtiss JN-4 design were required to cope with stability problems that emerged in the N-9. They included lengthening the fuselage, increasing the area of the tail surfaces, and installing stabilizing fins on the top of the upper wing. The N-9 was initially powered by a 100-horsepower Curtiss OXX-6 engine. The U.S. Navy made use of wind tunnel data developed at the Massachusetts Institute of Technology in its redesign the JN-4. The N-9 was the first U.S. Naval aircraft to incorporate wind tunnel data directly into its design.
