The Curtiss HS-1 was a single engined flying boat that was used as a coastal patrol aircraft in American and French waters, and was one of the most significant American designed combat aircraft of the First World War.
The HS-1 was developed from the Curtiss H-14. This was originally built as a twin engined flying boat with unequal span wings, powered by two 100hp Curtiss OXX-2 pusher engines (the same layout as the first version of the Curtiss H-1 America, before a third tractor engine was added). The US Army ordered sixteen H-14s, but cancelled the rest of the order after testing the first aircraft.
Curtiss modified the sole H-14 by giving it a single 200hp Curtiss VX-23 engine. The modified design interested the US Navy, which ordered sixteen aircraft (included the modified H-14). Work on the H-14s on order had been quite advanced, so some of the Navy’s aircraft were completed with partly built H-14 hulls. The new aircraft was redesignated as the HS, or Model H, Single engine.
The HS-1 had a single-step hull, with a wide planning bottom with lateral sponsons to improve its stability on the water. It had unequal span three bay biplane wings. The HS-1 was a three seater.
The HS-1 was followed by the HS-1L and HS-2L, both of which were powered by a Liberty engine. The HS was produced in large numbers, with a total of 675 built by Curtiss and 417 by five other firms by the time production was ended after the Armistice. A total of 1,092 were built, making it far more numerous than any of the larger H or Felixstowe F models. Production aircraft were all Liberty powered HS-1Ls or HS-2Ls.
The Standard Aircraft Corporation received an order for 250 aircraft, of which the last 50 were cancelled. Lowe, Willard and Fowler were given an order for 200 aircraft, and again the last 50 were cancelled. Gallaudet built 60 aircraft. Boeing received an order for 50 aircraft, and built 25. Loughhead (later to become Lockheed) built two.
Before the end of the First World War 182 HS-1L and HS-2L flying boats reached France (probably mainly HS-1s), where they carried out coastal patrol and convoy escort duties. Eight HS-1s were the first American built aircraft to join the US Naval forces in France, with eight arriving at Pauillac on 24 May 1918. They flew their first combat mission on 13 June, and were eventually operated from ten Naval Air Stations in France. They also operated from naval air stations along the US Coast, and from bases in Nova Scotia.
On 21 October 1917 a HS-1 was used on the first flight of the 12-cylinder Liberty engine, one of the most important American contributions to aviation during the First World War. This early version produced 375hp, but the fully developed version produced 420hp.
After the end of the war most became training aircraft, before finally being scrapped in 1928.
The first HS-1L was produced in October 1917 by fitting a 360hp Liberty engine in an existing HS-1. It quickly replaced the HS-1 on the production lines. As well as the new engine it introduced horn-balanced ailerons on both wings. It could carry 360lb of bombs or two 180lb depth charges. The HS-1 had a decent endurance of 4 hours 30 minutes, but a rather poor service ceiling of only 1,725ft!
The HS-2L had longer upper and lower wings, with a new central section on the upper wing and extra panels between the fuselage and lower wings. This added 12ft to the wingspan, increasing the payload that could be carried. A further boost came from the introduction of 400hp Liberty engines, and with both changes the HS-2L could carry two 230lb depth charges or 460lb of bombs. The new engine also saw the service ceiling treble, to 5,200ft
The HS-3 was a joint US Navy and Curtiss project to improve the HS-2. The hull was significantly altered and a new fin and rudder developed. The HS-3 entered production just before the end of the war, and only six had been completed when the Armistice ended production.
Engine: One Liberty 12 engine
Span: 62ft 1in
Length: 38ft 6in
Height: 14ft 7in
Empty weight: 4,070lb
Maximum take-off weight: 5,910lb
Max speed: 87mph
Service ceiling: 1,725ft
Endurance: 4 hours 30 minutes