Having transatlantic range and cargo carrying capacity by design, the first H-2 class (soon dubbed
"The Americans" by the
Royal Navy) was quickly drafted into wartime use as a patrol and rescue aircraft by the RNAS, the air arm of the British Royal Navy. The original two "contest" aircraft were in fact temporarily seized by the Royal Navy, which later paid for them and placed an initial follow-on order for an additional 12 – all 14 of which were militarized (e.g. by adding gun mounts) and designated the "H-4" (the two originals were thereafter the "H-2" Models to air historians). These changes were produced under contract from Curtiss' factory in the last order of 50 "H-4s", giving a class total of 64, before the evolution of a succession of larger, more adaptable, and more robust H-class models. This article covers the whole line of nearly 500 Curtiss Model H
seaplane flying boat aircraft known to have been produced, since successive models – by whatever sub-model designation – were physically similar, handled similarly, essentially just being increased in size and fitted with larger and improved engines – the advances in
internal combustion engine technology in the 1910s being as rapid and explosive as any technological advance has ever been. '' 10 March 1914, standing next to a
Model F. The outcome was a scaled-up version of Curtiss' work for the United States Navy and his
Curtiss Model F. Impressed by the capabilities he had witnessed, Porte urged the
Admiralty to commandeer (and later, purchase) the
America and her sister aircraft from Curtiss. By the late summer of 1914 they were both successfully fully tested and shipped to England 30 September, aboard
RMS Mauretania. This was followed by a decision to order a further 12 similar aircraft, one Model H-2 and the remaining as
Model H-4s, four examples of the latter actually being assembled in the UK by
Saunders. All of these were essentially identical to the design of the
America, and indeed, were all referred to as "Americas" in Royal Navy service. This initial batch was followed by an order for another 50. These aircraft were soon of great interest to the
British Admiralty as anti-submarine patrol craft and for air-sea rescue roles. The initial Royal Navy purchase of just two aircraft eventually spawned a fleet of aircraft which saw extensive military service during World War I in these roles, being extensively developed in the process (together with many spinoff or offspring variants) under the compressed research and development cycles available in wartime. Consequently, as the war progressed, the Model H was developed into progressively larger variants, and it served as the basis for parallel developments in the
United Kingdom under
John Cyril Porte which led to the "Felixstowe" series of flying boats with their better hydrodynamic hull forms, beginning with the
Felixstowe F.1 — a hull form which thereafter became the standard in seaplanes of all kinds, just as sponsons did for flying boats. , 1916. Curtiss next developed an enlarged version of the same design, designated the
Model H-8, with accommodation for four crew members. A
prototype was constructed and offered to the
United States Navy, but was ultimately also purchased by the British Admiralty. This aircraft would serve as the pattern for the
Model H-12, used extensively by both the Royal Navy and the United States Navy. Upon their adoption into service by the RNAS, they became known as
Large Americas, with the H-4s receiving the
retronym Small America. As built, the Model H-12s had 160 hp (118 kW)
Curtiss V-X-X engines, but these engines were under powered and deemed unsatisfactory by the British so in
Royal Naval Air Service (RNAS) service the H-12 was re-engined with the 275 hp (205 kW)
Rolls-Royce Eagle I and then the 375 hp (280 kW) Eagle VIII. Porte redesigned the H-12 with an improved hull; this design, the
Felixstowe F.2, was produced and entered service. Some of the H-12s were later rebuilt with a hull similar to the F.2, these rebuilds being known as the
Converted Large America. Later aircraft for the U.S. Navy received the
Liberty engine (designated
Curtiss H-12L). Curiously, the Curtiss company designation
Model H-14 was applied to a completely unrelated design (see
Curtiss HS), but the
Model H-16, introduced in 1917, represented the final step in the evolution of the Model H design. With longer-span wings, and a reinforced hull similar to the Felixstowe flying boats, the H-16s were powered by Liberty engines in U.S. Navy service and by Eagle IVs for the Royal Navy. These aircraft remained in service through the end of World War I. Some were offered for sale as surplus military equipment at $11,053 apiece (one third of the original purchase price.) Others remained in U.S. Navy service for some years after the war, most receiving engine upgrades to more powerful Liberty variants. ==Operational history==