A floatplane has slender pontoons mounted under the fuselage. Two floats are common, but other configurations are possible. Only the "floats" of a floatplane normally come into contact with water. The fuselage remains above water. Some small land aircraft can be modified to become float planes and in general floatplanes are small aircraft. Floatplanes are limited by their ability to handle wave heights typically greater than 12 inches (0.31 m). These float pontoons add to the empty weight of the airplane, and to the drag coefficient, resulting in reduced payload capacity, slower rate-of-climb and slower cruise speed.
The Curtiss N-9 was a seaplane variant of the Curtiss JN-4 "Jenny" military trainer used during the First World War. As a seaplane, the N-9 was equipped with a single central pontoon mounted under the fuselage. A small float was fitted under each wingtip. With the additional weight of the pontoon, a number of structural and aerodynamic changes were required, the design of which made use of wind tunnel data developed at the Massachusetts Institute of Technology, meaning the N-9 was the first US Naval aircraft to incorporate wind tunnel data directly into its design. The wingspan was stretched an additional 10 ft, the fuselage was lengthened, the tail surfaces were enlarged, and stabilizing fins were added to the top of the top wing. The N-9 was initially powered by a 100 hp (75 kW) Curtiss OXX-6 engine.
Curtiss was awarded an initial contract for 30 aircraft in August, 1916, and an additional 14 were ordered by the US Army, which maintained a small seaplane operation. It became quickly apparent that the aircraft was underpowered, so Curtiss replaces the engine with a 150 hp (112 kW) Hispano-Suiza, manufactured in the US under license by Wright-Martin's Simplex division (later Wright Aeronautical). The aircraft was redesignated N-9H.
A total of 560 N-9s were built during the war, most of which were "H" models. Only 100 were actually built by Curtiss. Most were built under license by the Burgess Company of Marblehead, Massachusetts. Fifty others were assembled after the war by the Navy at the Pensacola Naval Air Station from spare components and engines.
Over 2,500 US Navy pilots received their seaplane training in the N-9s. Besides this primary role, though, the aircraft was also used to help develop ship-borne aircraft operations during the war, especially the development of ship-mounted launch catapults. In 1917, several N-9s were provided to the Sperry Gyroscope Company for conversion to the Hewitt-Sperry Automatic Airplane configuration, flight testing the new autopilot components intended to be used in pilotless "aerial torpedoes".
The N-9s were retired by the Navy in 1927, as more modern trainers became available. Only one example of the type has survived, and is now a part of the National Air and Space Museum collection. Originally on display at Chicago's Museum of Science and Industry, it was transferred back to the Navy pending transport to NASM. It was fully restored in 1966 by the Naval Air Engineering Laboratory in Philadelphia, Pennsylvania.
The Hanriot HD.2 was a fighter aircraft produced in France during the First World War. The design was based on that of the HD.1, but the HD.2 was a purpose-built floatplane. It made use of enlarged tail surfaces and shorter wingspans with greater area. Like its predecessor, though, it was a conventional single-bay biplane with staggered wings of unequal span. The prototype had a twin pontoon undercarriage, with a small third pontoon under the tail. The third pontoon was later discarded on production machines, though.
The HD.2 was developed specifically as an interceptor to defend flying boat bases, but soon was used as an escort fighter to protect French reconnaissance flying boats. The United States Navy also bought 10 examples with wheeled undercarriages, designated HD.2C.
Both the French and United States navies used these aircraft in early experiments in launching fighters from warships. The United States Navy replicated the French trials where a HD.1 had been launched from a platform built atop one of the turrets of the battleship Paris and built a similar platform on the USS Mississippi to launch a HD.2 from. The French Navy converted some of their HD.2s to wheeled configuration and used them for trials on the new aircraft carrier Béarn.
A final experiment in launching a HD.2 from a ship was carried out in 1924 with two new-built examples designated H.29. An unorthodox launching system was developed where the aircraft were equipped with three small pulley-wheels, one on each tip of the upper wing, and one at the tip of the tail fin. These ran along metal rails that had been attached to project horizontally from the mast of the battleship Lorraine. This did not work as hoped, succeeding only in depositing the aircraft into the water below. Further trials were discontinued.
Some newer model Hanriot H.D.1s were supplied to the French Navy. Eventually a few of which were passed to the U.S. Navy. Some naval Hanriots were converted to, or built as, floatplanes. This model was fitted with enlarged tail surfaces. After the war ten Hanriot HD.1s were built (or possibly modified/converted) by the U.S. Naval Aircraft Factory. The U.S. Navy machines were mainly used as trainers, although they were also involved in experiments with takeoff platforms on warships. These Hanriots could be fitted with twin guns, and at least one machine had a hydrovane and flotation bags of the type developed for the Royal Navy
The Curtiss HA (sometimes Dunkirk Fighter) was an American biplane seaplane designed by Captain B.L. Smith of the United States Marine Corps, and built by Curtiss Aeroplane and Motor Company.
The HA was a two-seat biplane with a central float and balancing floats on the wingtips. The fuselage was wood with a fabric covering. The plane was powered by a Liberty 12 engine in the nose. The prototype was ordered in December 1917, and its first flight was on 21 March 1918. During testing the aircraft proved very unstable, with an overly heavy tailplane. The aircraft was destroyed in a crash.
Two more prototypes were ordered, designated HA-1 and HA-2. the HA-1 was constructed of salvaged parts from the original, but its tailplane and radiator were redesigned, and its wings were moved further aft. The HA-1 caught fire during a flight. The HA-2 had a wider wingspan, and performed better, but as the war was almost over, no production order was received.