Felixstowe F.5

The Felixstowe F.5 was the last in a series of flying boats developed by John Porte based on earlier Curtiss boats, and served with the RAF after the First World war and entered production in American as the Curtiss F-5L.

The Felixstowe flying boats were descended from the Curtiss H-1, a pre-war twin engined biplane flying boat that had been built to try and fly across the Atlantic. After the outbreak of war, John Porte, a former Royal Naval officer and member of the H-1 team, returned to Britain and rejoined the Navy, where he was appointed as commander of the Felixstowe Naval Air Station. He convinced the Navy to purchase the two H-1s and the similar H-4, which became the first large flying boats in British service. However the Curtiss boats weren’t well suited for operations on the North Sea, so Porte and his team developed a new hull. This was combined with the flying surfaces from one of the H-4s to produce the sole Felixstowe F.1. This performed much better on the water, and retained the H-1’s good performance in the air. The H-4 was followed by an order for a larger flying boat, designated as the H-8 by the RNAS. This performed even worse on the water, so the sole prototype was combined with another of Porte’s hulls to produce the Felixstowe F.2. This entered production with a more powerful engine as the F.2A. This version entered service early in 1918, operating alongside the Curtiss H-12, Curtiss’s own attempt to improve the design.

The F.2A was followed into service by the Felixstowe F.3. This had a longer wingspan, which allowed it to carry double the bomb load of the F.2A (four 230lb bombs, up from two), making it a better anti-submarine warfare aircraft, but at the cost of making it less agile. 

The prototype of the F.5 made its maiden flight in November 1917, just after the F.3. It had a slightly deeper two step hull, and an entirely new wing with a greater wing span. The crew were carried in two open cockpits in front of the wing. Power was provided by a slightly improved version of the Rolls-Royce Eagle VIII used in the F.3m which produced 350hp (up 5hp). In flight tests the prototype performed better than the F.3, but it was decided that the increase in performance wasn’t enough to justify the expense of such a major redesign.

The design was thus modified to use as many components from the F.3 as possible, including a very slightly modified F.3 wing with an extra 1ft 8in of span. However the F.5 did introduce a wooden skin for the fuselage, replacing the fabric covering of the decks and rear sides of the earlier models. As a result the production aircraft performed worse than the F.3, with a lower service ceiling and top speed. However endurance did increase, and its handling in the air and on the water remained good.  A shortage of Eagle VIII engines meant that some F.5s were completed with the 325hp Eagle VII, with a resulting drop in performance.

Although the prototype was tested in November 1917, the F.5 didn’t enter service until after the end of the First World War. However it then became the new RAF’s standard flying boat, until it was replaced by the Supermarine Southampton in August 1925. As with the earlier models, the F.5 was produced by several different companies, including the Gosport Aviation Company, Airco, May, Harden and May, Phoenix, Saunders and Short. Boulton & Paul also built a number of hulls. The following serial numbers are recorded as being assigned to F.5s - N90, N127, N177-N178, N4037-N4049, N4118-N4149, N4184-N4229, N4580-N4729, N4780-N4879

Curtiss F-5L on seaplane barge
Curtiss F-5L on seaplane barge

The F.5 was also produced in America. This version was powered by a Liberty engine, and was modified to American production standards. Although the largest number of the resulting F-5Ls were produced by the Naval Aircraft Factory, it is generally known as the Curtiss F-5L. Like the F.5 it remained in service until the mid 1920s. A number of British serial numbers were allocated to the Felixstowe F5L (N128, N4730-N4779), possibly for Curtiss F-5Ls exported to Britain.

Sixteen F.5s were sold to Japan. These aircraft were built by Shorts, and were followed by fifty built under licence in Japan by Aichi. The first Short built aircraft were delivered in August 1921, and the type remained in Japanese service until 1929. Aichi went on to be a successful producer of their own flying boats.

Engine: Two Rolls-Royce VIII 12-cylinder V piston engines
Power: 350hp each
Span: 103ft 8in
Length: 49ft 3in
Height: 18ft 9in
Empty weight: 9,100lb
Maximum take-off weight: 12,682lb
Max speed: 88mph
Climb Rate: 305ft/ min
Service ceiling: 6,800ft
Endurance: 7 hours
Armament: Four .303in Lewis machine guns, one in nose, three amidships
Bomb load: 920lb of bombs under wings (four 230lb bombs)

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How to cite this article: Rickard, J (23 February 2021), Felixstowe F.5 , http://www.historyofwar.org/articles/weapons_felixstowe_F5.html

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