Curtiss HS

In late 1916, the Curtiss Aeroplane Company produced a new twin-engined flying boat, which was smaller than both the current Curtiss H-12 being built for Britain's Royal Naval Air Service and the earlier Curtiss H-4, with the new design given the factory designation Model H-14, although its design was unrelated to earlier Model H variants. The H-14 was a conventional unequal-span, unstaggered biplane, powered by two 100 hp (75 kW) pusher Curtiss OXX engines mounted between the wings. An order for 16 was placed by the United States Army before the prototype flew, but the prototype was disappointing and the US Army cancelled its order for H-14s. The prototype was converted to a single-engined aircraft powered by a 200 hp (149 kW) Curtiss V-X-X engine, also in a pusher configuration, during 1917, being redesignated as the Curtiss HS-1 (for H model with single engine). While Curtiss's V-X-X engine proved to be inadequate, as it did in its larger Model H cousins, the Liberty proved more suitable, and large orders were placed by the US Navy for the HS-1L. Again, Curtiss specified one of their own engines, and again, the Navy substituted this with the Liberty engine in the definitive HS-2L. The HS-3 was a further improved version with a new, wider, flat-sided hull, that eliminated the typical Curtiss sponsons. The end of the war brought an end to plans to mass-produce this version, only six being built. ==Operational history==

The HS-1L began to enter service early in 1918, flying anti-submarine patrols from a number of Naval Air Stations on the Eastern Seaboard of the United States, and from the Panama Canal Zone. Two HS-1Ls operating from Chatham, Massachusetts, made the only confirmed aircraft attack on a German in American waters on July 21, 1918, but this was unsuccessful, with bombs failing to explode and the submarine escaping. From August 1918, in order to compensate for Canada's lack of patrol aircraft, US Navy HSs operated from two bases in Nova Scotia. Twelve HS-2Ls were donated to Canada at the end of the war. in the 1920s. Large numbers of HS boats were also used by US Navy forces in France, with deliveries starting on May 24, 1918, flying their first patrols on June 13. About 160 HS-1Ls and -2Ls were deployed to France. Following the Armistice, the HS boats based in Europe were scrapped apart from four aircraft based in the Azores, which were acquired by Portugal, while the US Naval Air Service shrank considerably, with many Naval Air Stations closing, resulting in considerable numbers of HS boats becoming surplus to requirements and available for sale at $200 to $500 without engines. HS-2Ls continued in use by the US Navy as a patrol aircraft and a trainer until 1928. As many as 83 HS boats were used by the United States Army Air Service for communications and survey purposes from overseas bases, although they were not given US Army serial numbers. ==Variants==

• HS-1 - prototype with Curtiss engine. • HS-1L - early production version of HS-1 with Liberty engine and short span (62 ft 1 in (18.92 m)) wings. • HS-3L - Canadian modified version of HS-2L with modified wings (Clark Y section). At least three converted. ==Operators==

; • Argentine Naval Aviation ; • Canadian Air Board - acquired 12 HS-2L from the US Navy following closure of its Naval Air Station Halifax. Likely transferred to Canadian Air Force in 1923. • Canadian Air Force - obtained HS-2L beginning in 1920. 12 likely transferred from Air Board when it disbanded and in total operated 30. All retired in 1928. ; ; Philippine Islands • Philippine Air Service - operated three HS-2Ls between 1920 and 1921. ; • Portuguese Naval Aviation - took over four ex-US Navy HS boats based in the Azores after the end of World War I, using them for training. Retired 1931. ; • United States Army Air Service operated in total 83 HS-2L • United States Coast Guard operated 11 until 1926 • United States Marine Corps • United States Navy ==Specifications (HS-2L)==