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The Blackburn Sydney was the first large monoplane flying boat to be produced in Britain, but only one prototype of the military version and one of the similar civilian Blackburn Nile were ever built.
The Sydney was designed in response to Air Ministry Specification R.5/27. It was based on the successful Blackburn Iris II, a biplane flying boat with an all-metal hull. The new design used a modified version of the Iris hull, with the monoplane wing carried above the fuselage on a tubular steel pylon. This allowed the engines to be carried in roughly the same position as on the biplane.
On 23 February 1928 Blackburn received a contract to build one Sydney, powered by three 510hp Rolls-Royce Falcon X engines. The engine was changed twice, and it was completed with three higher powered Rolls Royce Falcon F.XIIMS engines. Blackburn also decided to build a civil airliner version of the same design, which became the Blackburn C.B.2 Nile.
The Nile and the Sydney were built alongside each other on the Iris production line. The Nile was designed to be used on the Cobham-Blackburn Air Line route between Alexandria and Cape Town. It would carry a crew of three, fourteen passengers and their baggage and air mail. It was powered by three 515hp Jupiter IX geared engines. The passenger compartment was given square windows, replacing the circular military portholes. The hull of the Nile was completed in time to be put on display at the Olympia Aero Show of 16-27 July 1929. Many of the internal details were incomplete at the time, but a comfortable passenger compartment, with seating provided by leather armchairs in facing pairs was installed. The aircraft also carried a toilet and steward’s pantry.
After the airshow the Nile returned to Brough to be completed. It had almost been completed by February 1930 and the future for the type looking promising, with Canada interested in buying the type. However soon after this the British Government decided that Imperial Airways should be responsible for all Empire air communications. As most of the passengers on the route would have been Government and Colonial officials, this removed the commercial basis for the Nile and work on it stopped. The hull remained in the Brough works until 1935 when it was destroyed in tests to discover the strength of stressed skin construction.
The military Sydney did at least reach the completed prototype stage. The large main wing had a parallel chord centre section, with metal walkways around the engines. The wing had slight dihedral. The outer panels of the wings tapered, and carried Frise ailerons. The three engines were carried in nacelles mounted in and just above the top of the wings. Fuel came from a 560 gallon tank carried in the wing pylon. The tail had three rudders, with no fixed fins. It was equipped with an unusual venting system, which injected air into the front of the step in the hull in an attempt to reduce the time it took to take off.
The Sydney was armed with .303in Lewis guns in nose, amidships and tail positions. It could carry two 550lb bombs, four 250lb bombs or two 1,850lb Mk VIII or Mk X Whitehead torpedoes under the wings (the first British flying boat to carry torpedoes).
The Sydney made its maiden flight on 18 July 1930. A series of further tests followed, before it was delivered to the M.A.E.E. at Felixstow on 9 December 1930. A number of minor changes were made at Felixstow. Tests with the vented step found that it offered little benefit. The Sydney suffered from poor serviceability which reduced the number of tests that could be carried out. Plans were put in place to produce a second aircraft with more powerful Rolls Royce Kestrel engines, but these were scrapped. The Sydney was struck off charge in 1934.
Engine: Three Rolls-Royce F.XIIMS
Power: 525hp each
Crew:
Span: 100ft
Length: 65ft 7in
Height: 20ft 4in
Empty weight: 17,065lb
All-in weight: 23,350lb
Max speed: 123mph at 5,000ft
Climb Rate: 390ft/ min
Service ceiling: 16,500ft
Endurance: 7.5 hours
Armament: Three .303in machine guns
Bomb load: Two 500lb bombs, four 250lb bombs or two 1,850lb Mk VIII or Mk X Whitehead torpedoes