Work continued by Porte, now focused on bringing a modified Curtiss H-12 aircraft to a Royal Navy standard. The H-12 was a dimensionally larger system and saw its first flight in June of 1914. Some 478 of the type would be built before the end and both the United States and United Kingdom would take the aircraft into their respective inventories. Again the same limitations of the H-4 were encountered in the H-12 but the already-completed work on the former helped to usher in a revised design for the latter producing the Felixstowe F.2. Changes included use of a Porte-designed hull with the wings of the Curtiss H-12 though an all-new tail section was added and power came through 2 x Rolls-Royce "Eagle" series engines. First flight of the F.2 was recorded in July of 1916.
The Royal Navy, content with the improved Curtiss H-12, purchased 100 F.2s during the war and original models were designated as "F.2a". These carried Rolls-Royce Eagle VIII engines (345 horsepower each) as well as a 460lb bomb load and were defensed by up to seven .303 Lewis machine guns on flexible mounts (at least one in the nose and three around center mass of the aircraft was typical). Bombs were carried externally under the wings. Performance specifications included a maximum speed of 95 miles per hour with a service ceiling reaching 9,600 feet. Endurance was six hours giving the aircraft good "legs" for over-water patrolling. A standard operating crew was four.
The design of the F.2 was typical for flying boats of the period and the primary physical characteristics were its boat-like hull and large biplane wing arrangement. The wings were held high on the fuselage and incorporated a larger upper wing element set over a smaller lower one. Large parallel struts and cabling braced the wings along their spans with the engine nacelles set between the upper and lower wing units straddling the fuselage. The cockpit/crew area was seated just ahead of the wings with a gunner's / observer's cockpit fitted ahead of it at the nose offering a commanding view of the oncoming terrain below. The hull held a smooth appearance required of it for water-borne landings and takeoffs and the tail unit featured a sold vertical fin with high-mounted horizontal planes. The general arrangement of the F.2 was one carried over from the original F.1 and into the future F.3 and F.5 designs.
In practice, the F.2 served through the Royal Navy and no fewer than twelve Royal Air Force squadrons. Its primarily role was that of maritime patrol in hunting enemy naval vessels, in particular, submarines though the F.2 held enough performance and firepower to engage Zeppelins and even disrupt fighter formations through its defensive machine gun network. Pilots certainly commented on the F.2's maneuverability for an aircraft of its size.
The United States Navy eventually joined the UK in utilization of the F.2 and Chile became the only other notable operator. Beyond the wartime 100 examples was a further seventy added later and the "F.2c" mark became two Felixstowe-constructed F.2s given a lightened hull. Wartime manufacture was aided by contributions from Saunders, Aircraft Manufacturing Co Ltd, and May, Harden, & May. 175 F.2s were built in all.
The Felixstowe "F.3" became the next offering in this flying boat line, made dimensionally larger and heavier than the preceding F.2 so as to carry a greater bomb load while also exhibiting increased operational ranges. However, these changes resulted in a less-than-maneuverable aircraft which was, on the whole, not as well appreciated as its predecessor. First fight was in February of 1917 and 100 of the type were completed. The culmination of the F-series flying boats finally came in the late-war "F.5" which first flew in May of 1918 but did not see service in the conflict. 280 of this model were produced (F5L being U.S.-built aircraft with Liberty engines).
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