The Navy Aircraft Factory/ Curtiss F-5L was an American version of the Felixstowe F.5, which was the final member of a family of Felixstowe boats developed from the Curtiss H-4, and which became the standard US Navy patrol flying boat during the 1920s.
The F-5L had a rather convoluted development history. Before the First World War Curtiss produced the H-1 ‘America’ flying boat, with the help of the British former naval officer and flying boat enthusiast John Porte. After the outbreak of war in 1914 Porte convinced the British to buy the H-1, and a larger number of the similar Curtiss H-4 ‘Small America’. This was followed by the Curtiss H-12 ‘Large America’, a larger version of the H-4. Although the H-4 was generally considered to be good both on the water and in the air, it was underpowered, and the laminated wooden hull turned out to be unreliable. The engine problems were solved by giving it 275hp Rolls-Royce Eagle I engines or 375hp Rolls-Royce Eagle VIII engines, but the hull problems needed a more radical solution.
By this time Porte was serving with the RNAS, and he began work on a new hull for the H-4. This resulted in the Felixstowe F.1, which combined the Curtiss wings and tail with the new hull and Rolls-Royce engines. The new flying boat went through a series of improvements, culminating in the F.5. This included the Felixstowe F.2A, some of which were produced in American by Curtiss as the H-16.
The F.5 also entered production in the United States, where the US Naval Aircraft Factory modified it American standards. Most of the changes are hard to spot, but the use of ailerons with parallel leading and trailing edges instead of the tapering trailing edges of earlier models is one way to tell the F-5L apart from the H-16 (although not the F-5 which had similar wings). The F-5L had open cockpits, while many H-16s had an enclosed cabin. Otherwise it was a similar design to the entire family – a twin engine pusher biplane flying boat.
The modified F-5 entered production as the F-5L, powered by Liberty engines. The F-5L was produced by the Naval Aircraft Factory (138 aircraft), Curtiss (60 aircraft) and the Canadian Aeroplanes Ltd (30), but even though the Naval Aircraft Factory produced the most aircraft, it was generally known as the Curtiss F-5L because of its connections to the earlier H boats. However later post-war versions became known as the Naval Aircraft Factory PN.
Two F-5Ls were later modified with a new vertical tail, becoming the F-6. The F-5L tail was triangular when seen from the side, with the top of the rudder continuing the same line as the top of the fin. On the new tail the fin had a curved top, while the rudder was taller, and the top jutting forward over the top of the fin. The remaining F-5Ls were later given the same new tail.
The Curtiss F-5L and the very similar Curtiss H-16 became the standard Navy patrol boats after the First World War, until they were replaced by Naval Aircraft Factory PN-12s in the late 1920s. This was a direct descendent of the F-5L, but with a metal version of the fuselage, new wings, and radial engines.
Engine: two Liberty 12A inline piston engines
Power: 400hp each
Span: 1-3ft 9 1/4 in
Length: 49ft 3 3/4 in
Height: 18ft 9 1/4 in
Empty weight: 8.720lb
Maximum take-off weight: 13,600lb
Max speed: 90mph
Service ceiling: 5,500ft
Range: 830 miles
Armament: six to eight 0.3in machine-guns on flexible mounts
Bomb load: 902lb bombs