In a flying boat, the main source of buoyancy is the fuselage, which acts like a ship's hull in the water. Most flying boats have small floats mounted on their wings to keep them stable. All large seaplanes have been flying boats, their great weight supported on their hull.
The Curtiss Models F made up a family of early flying boats developed in the United States in the years leading up to World War I. Widely produced, Model Fs saw service with the United States Navy under the designations C-2 through C-5, later reclassified to AB-2 through AB-5. Several examples were exported to Russia, and the type was built under licence in Italy.In Italy, the Curtiss representative Enea Bossi secured rights for local licence-production of the Type F by the Zari brothers, who built eight examples at their workshop in Bovisia, near Milan. The first of these was demonstrated to the Italian Navy on Lake Como on 22 September 1914.
In configuration, these were biplane flying boats powered by a single engine mounted amongst the interplane struts and driving a pusher propeller. The pilot and a single passenger sat side-by-side in an open cockpit. The wing cellule was derived from the Model E landplane and was of two-bay, unstaggered, equal-span construction with large ailerons mounted on the interplane struts and extending past the span of the wings themselves. The earliest examples of this design were built and sold by Curtiss in 1912 without any designation applied to them; the Model F name only coming into use the following year. Confusingly, Curtiss also used the designation Model E to refer to some early machines in this family, although these were quite distinct from Curtiss landplanes that bore this same designation and all but identical to the Model Fs.
Model Fs built from 1918 featured a revised, unequal-span wing that incorporated the ailerons into the upper wing and sponsons on the sides of the hull to improve the aircraft's handling in water. These were known as the Model MF (for Modernised-F), and years later as the Seagull in the post-war civil market.
The Macchi L.3, or later Macchi M.3, was an Italian biplane flying boat developed from the earlier L.2.
Over 200 M.3s were built and delivered to the Italian Navy and were used on a variety of missions which including bombing, reconnaissance, patrol and escort. For a short period in 1917, it was also used as a fighter. Several aircraft were used in commando-style operations behind Austrian lines. The aircraft were highly regarded by the Italian Navy and they were used on bombing raids and pioneered the Italian use of aerial photography. After the war, the type was used by training units until 1924.
The company had learnt about flying boat design from copying an Austrian flying boat to produce the Macchi L.1 and improving it to produce the L.2. The result was the L.3, which was renamed the M.3 in 1917 to recognise the change in design from Lohner influenced to a Macchi design. Only the unequal-span biplane wings were inherited from the L.2 a new and refined hull and strut-mounted tailplane were designed. Powered by a single Isotta-Fraschini engine strut mounted between the two wings and driving a pusher propeller. It was armed with a single machine gun on a trainable mounting and could also carry four light bombs. In 1916, one aircraft gained the world altitude record for a seaplane when it climbed to 5,400 m (17,700 ft) in 41 minutes.
The Macchi M.5 was an Italian single-seat fighter flying boat designed and built by Macchi-Nieuport at Varese. It was extremely manoeuvrable and agile and matched the land-based aircraft it had to fight.
The first prototype of a single-seat sesquiplane fighter was the Type M which first flew in 1917. Developed by engineers Buzio and Calzavera it had single-step hull and an open cockpit forward of the wings and was similar to the earlier Macchi M.3. It was followed by another prototype with a revised tail unit designated the Ma and further developed as the M bis and Ma bis.
The production aircraft was designated the M.5 and like the prototypes were powered by a single Isotta-Fraschini V.4B engine in pusher configuration. Deliveries soon commenced in the summer of 1917 to the Aviazone per la Regia Marina (Italian Navy Aviation). Late production aircraft had a more powerful Isotta-Fraschini V.6 engine and redesigned wingtip floats, they were designated M.5 mod. Macchi produced 200 aircraft and another 44 were built by Societa Aeronautica Italiana.
The M.5 was operated by five Italian maritime patrol squadrons as a fighter and convoy escort, and some were embarked on the Giuseppe Miraglia. Towards the end of World War I, the aircraft were flown by both United States Navy and United States Marine Corps airmen. Ensign Charles Hammann won the first Medal of Honor awarded to a United States naval aviator in an M.5.