The Felixstowe F.4 Fury was the last flying boat designed by John Porte, and was a massive triplane flying boat that only reached the prototype stage.
The F.4 was at least partly inspired by the Curtiss Wanamaker Triplane, also known as the model T. Like the original Curtiss H-1, the Triplane had originally been designed in response to an order from the wealthy department store owner Rodman Wanamaker to attempt to fly across the Atlantic. The massive aircraft then attracted the attention of the British Admiralty, which ordered twenty aircraft for use against Zeppelins. The resulting aircraft was a four engined triplane. The four engines were arranged in a row on the middle row, an arrangement that looks entirely logical to modern eyes, used to the four engined heavy bombers of the Second World War. However during this earlier period aircraft designers preferred not to use this configuration, as the lighter aircraft of the period would be directionally unstable if one of the engines failed. A more common layout, and the one used on the later Curtiss NC, was to have pairs of engines in tandem in a single nacelle, each carrying one pusher and one tractor engine. The Model T was the first four engined aircraft built in the United States, although when the fuselage was completed the Curtiss V-4 engine wasn’t ready, so it never flew in the US. Instead it was shipped across to Britain, where it was given four 240hp Renault engines. The most famous photograph of the Model T shows it with these engines installed, and with three wings each of different length - widest at the top, shortest at the bottom. The Model T arrived in Britain late in 1916, but was written off after its maiden flight (presumably late in 1916, but the date eludes me), and the rest of the order was cancelled.
At some point after this Porte began work on his own triplane. The F.4 had much in common with the smaller Felixstowe F boats, which replaced their original Curtiss hulls with a new design developed by Porte and his team at the Felixstowe naval air base. The main part of the hull was built as a simple box girder design, with four longerons and cross braces. The boat part of the hull was then added to it, allowing for easy changes. The F.4 had a two step boat hull. The triplane wings had a span of 123ft on the upper two wings, and a shorter span on the lower wing, which had floats at the tips. It was powered by five engines in three positions, all carried on top of the middle wing. The central position carried a single pusher engine. The outer positions each carried one tractor and one pusher engine.
The first version of the tail had a biplane tailplane, with two rudders carried between the horizontal surfaces and a small third rudder on top. This was later replaced with a normal biplane tailplane with three fins and rudders.
The control surfaces were all given small servo motors to help the pilot, but tests showed that they weren’t needed and they were soon removed.
The crew were carried in three cockpits – a bow gunner’s position, dorsal position for the flight engineer and a side by side two seat cockpit for the pilots. It had an impressive all-up weight of 24,000lb.
The F.4 was the largest British flying boat of the time, and almost inevitably gained the nickname ‘Super Baby’, following on from the almost as large three engined Porte Baby. The single prototype, serial number N123, made its maiden flight on 11 November 1918 with Porte acting as pilot. In later tests it took off with a weight of 33,000lbs, and on one flight carried twenty-four passengers, 5,000lb of ballast and fuel for seven hours. Plans were also in place to attempt a transatlantic flight, but no money was available. It then joined 4 Communications Squadron, but on 11 August 1919 it crashed when taking off at the start of a planned flight to Africa.
After the war Porte worked for the Gosport Aviation Company, where he designed the Gosport G.9. This would have been a 29,000lb mail and freight carrying triplane, based on the F.4 Fury, but Porte died in October 1919 and it was never built.
Engine: Five Rolls Royce Eagle VIIs or Eagle VIIIss
Power: 325hp or 345hp each
Length: 63ft 2in
Height: 26ft 6in
Empty weight: 18,563lb
Maximum take-off weight: 24,000lb
Max speed: 97.5mph
Climb Rate: 550ft/ min
Service ceiling: 12,000ft
Endurance: 8-13 hours
Armament: Positions for four .303in Lewis guns
Bomb load: Bomb positions planned