The Blackburn T.4 Cubaroo was a British prototype

biplane A biplane is a fixed-wing aircraft with two main wings stacked one above the other. The first powered, controlled aeroplane to fly, the Wright Flyer, used a biplane wing arrangement, as did many aircraft in the early years of aviation. While ...

torpedo bomber A torpedo bomber is a military aircraft designed primarily to attack ships with aerial torpedoes. Torpedo bombers came into existence just before the World War I, First World War almost as soon as aircraft were built that were capable of carryin ...

of the 1920s. Built by

Blackburn Aircraft Blackburn Aircraft Limited was a British aircraft manufacturer from 1914 to 1963 that concentrated mainly on naval and maritime aircraft. History Blackburn Aircraft was founded by Robert Blackburn (aviation pioneer), Robert Blackburn and Jessy ...

and intended to carry a large

torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, such ...

, the Cubaroo was claimed to be the largest single-engined aircraft in the world at the time of its first flight.Jackson, 1990, p.183

Design and development

In 1921, the British

Air Ministry The Air Ministry was a department of the Government of the United Kingdom with the responsibility of managing the affairs of the Royal Air Force and civil aviation that existed from 1918 to 1964. It was under the political authority of the ...

issued Specification 8/21 (previously Directorate of Research type IX) to Blackburn for a ''Coastal Defence Torpedo Aeroplane'', for a long-range torpedo bomber with a range of over and the ability to carry a full size naval

, which was at the time was thought capable of sinking the most heavily armoured warships.Mason, 1994, pp.155-156 Previous torpedo bombers had used smaller, less capable torpedoes. Blackburn Aircraft's chief designer, Major F. A. Bumpus, submitted the Blackburn T.4 Cubaroo, which was a massive

Avro Avro (an initialism of the founder's name) was a British aircraft manufacturer. Its designs include the Avro 504, used as a trainer in the First World War, the Avro Lancaster, one of the pre-eminent bombers of the Second World War, and the d ...

submitted and then withdrew their similarly powered Type 556, and replaced it with the Avro 557 Ava to a revised 16/22 specification which differed mainly in calling for two engines. The Ava was also a large biplane, but powered by two Rolls-Royce Condor V-12 engines.Mason, 1994, p.156 To carry the heavy torpedo weighing over for the required range, the Cubaroo was massive. With a wingspan of , it was claimed at the time to be the largest single-engine military aircraft built, and it had the most powerful aircraft engine then available, the Napier Cub, which weighed over a ton, excluding the

radiator A radiator is a heat exchanger used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in cars, buildings, and electronics. A radiator is always a ...

. The first example, ''N166'', had a curved radiator ahead of the engine in the nose, while the second, ''N167'', had a flat one.Jackson, 1990, p.185 The Cubaroo, with a mainly steel tube metal structure, had an deep

fuselage The fuselage (; from the French language, French ''fuselé'' "spindle-shaped") is an aircraft's main body section. It holds Aircrew, crew, passengers, or cargo. In single-engine aircraft, it will usually contain an Aircraft engine, engine as wel ...

to accommodate the pilot who sat, with a navigator beside him, sitting over the engine. The rear of the fuselage had a triangle cross section to improve the gunner's fields of fire from hatches located near each lower wing root which permitted them to cover the underside of the tail. Bomb aiming was accomplished through a hatch in the floor of the cabin that also contained radio equipment and a navigational chart table. A passage ran aft to a ladder, which led up to another gunner's position, with a gun ring mounted on top of the fuselage just aft of the wing trailing edge. The span, constant chord

folding Fold, folding or foldable may refer to: Arts, entertainment, and media * ''Fold'' (album), the debut release by Australian rock band Epicure * Fold (poker), in the game of poker, to discard one's hand and forfeit interest in the current pot *Abov ...

, two-bay wings had dihedral, and semi-circular wing tips, with inset unbalanced ailerons on all four wings running for about half the span. The

empennage The empennage ( or ), also known as the tail or tail assembly, is a structure at the rear of an aircraft that provides stability during flight, in a way similar to the feathers on an arrow.Crane, Dale: ''Dictionary of Aeronautical Terms, third ed ...

consisted of three balanced rudders, with the outer two having small fins, and an adjustable biplane horizontal stabilizer with a balanced elevator. To carry the torpedo, the Cubaroo was fitted with a split

undercarriage Undercarriage is the part of a moving vehicle that is underneath the main body of the vehicle. The term originally applied to this part of a horse-drawn carriage, and usage has since broadened to include: *The landing gear of an aircraft. *The ch ...

attached to the lower wings, each comprising two sets of two diameter Palmer wheels, with the torpedo or bombs being carried on a crutch under the fuselage, between them.Jackson, 1990, p.184 Due to the change of British

policy favouring twin-engine designs for the role, a new specification, 16/22 was drawn up, and the type was not ordered into service. Although drawings were made for three different versions with two engines, none of these were built.Jackson, 1990, pp.186-187

Operational history

The first prototype (with serial ''N166'') flew in secrecy in the summer of 1924, proving to have good handling characteristics, with the engine not causing problems, as the Napier Cub had already been test flown in an

Avro Aldershot The Avro 549 Aldershot was a British single-engined heavy bomber aircraft built by Avro. Development and design The Aldershot was designed to meet the 1920 British List of Air Ministry Specifications, Specification 2/20 for a heavy long-range d ...

. It was then fitted with a metal, three-blade adjustable-pitch

propeller A propeller (often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working flu ...

and was delivered for testing at

RAF Martlesham Heath Royal Air Force Martlesham Heath or more simply RAF Martlesham Heath is a former Royal Air Force station located southwest of Woodbridge, Suffolk, England. It was active between 1917 and 1963, and played an important role in the development o ...

but was written off after its undercarriage collapsed on 2 February 1925. A second prototype flew in 1925, but the Air Ministry had by then lost interest in single-engine

heavy bomber Heavy bombers are bomber Fixed-wing aircraft, aircraft capable of delivering the largest payload of air-to-ground weaponry (usually Aerial bomb, bombs) and longest range (aeronautics), range (takeoff to landing) of their era. Archetypal heavy ...

s, so the second prototype was used as an engine testbed, flying with the experimental Beardmore Simoon

diesel engine The diesel engine, named after the German engineer Rudolf Diesel, is an internal combustion engine in which Combustion, ignition of diesel fuel is caused by the elevated temperature of the air in the cylinder due to Mechanics, mechanical Compr ...

Variants

;T.4 Cubaroo Mk.I :Both prototypes as built, powered with one X-16 Napier Cub.Jackson, 1990, p.187 ;T.4A Cubaroo Mk.II :Unbuilt 1927 project, powered with two direct-drive V-12 Rolls Royce Condor IV ;T.4B Cubaroo Mk.III :Unbuilt 1927 project, powered with two geared V-12 Rolls-Royce Condor III ;T.4C Cubaroo Mk.IV :Unbuilt 1927 project, powered with two direct-drive V-12 Rolls-Royce Condor IV

Operators

Royal Air Force The Royal Air Force (RAF) is the Air force, air and space force of the United Kingdom, British Overseas Territories and Crown Dependencies. It was formed towards the end of the World War I, First World War on 1 April 1918, on the merger of t ...

- evaluation and engine testbed only.

Specifications (Cubaroo)

References

Bibliography

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Citations

External links

{{Blackburn aircraft Cubaroo 1920s British bomber aircraft Single-engined tractor aircraft Biplanes Cancelled military aircraft projects of the United Kingdom Aircraft first flown in 1924 Aircraft with fixed conventional landing gear Single-engined piston aircraft