|
|
The Blackburn Cubaroo was a very large torpedo bomber designed in the 1920s for coastal defence but that only reached the prototype stage.
The Cubaroo was designed in response to Air Ministry Specification 16/22 which called for a long-distance coastal defence aircraft that could carry a 21in torpedo or the equivalent weight in bombs. Avro and Blackburn both produced aircraft to fulfil this specification.
Blackburn’s design was powered by a single 1,000hp Napier Cub sixteen cylinder water cooled engine, one of six prototypes of this engine that had been ordered in 1919 (no more were produced). This was used to power a very large aircraft, with an 88ft wingspan, making it one of the largest aircraft in the world at the time (although the First World War Zeppelin-Staaken R.VI had been much larger).
The structure followed the standard Blackburn pattern also used in their Swift, Dart and Blackburn, with a tubular steel framework. The central part of the fuselage was built as a single unit, with two tubular steel girders projecting from the bottom on either side to carry the undercarriage. They were also used as the front and rear spars of the central section of the bottom wing. The central section of the fuselage was very tall, almost filling the gap between the wings. The rear was also fairly tall, but did taper down behind the wings.
The aircraft had a biplane tail with two fins with balanced rudders and a large central rudder. The elevators were horn balanced. The two horizontal surfaces were mounted level with the top and bottom of the rear of the fuselage.
The Napier Cub was an unusual engine with four rows of four cylinders arranged in a rather squashed X shape. The upper two rows were slanted at 26.25 degrees from the vertical. The lower rows were 26.25 degrees below the horizontal. This arrangement allowed the upper part of the engine to be fully enclosed within the nose of the aircraft and made the nose narrower to give a better forward view. The aircraft also carried a 5hp gas engine that was used to quickly start the massive Cub engine.
The two bay biplane wings had a span of 88ft and were straight sided with a constant chord of 11ft 6in. The outer sections were had slight dihedral and sweep-back in order to improve stability, and could be folded back along the side of the aircraft to reduce storage space.
The main undercarriage consisted of two separate units, one under each wing. Each carried a pair of 4ft diameter Palmer wheels. The use of two entirely separate units meant that the torpedo could be carried directly below the fuselage without any obstructions.
The pilot and navigator’s cockpit was located just ahead of the leading edge of the upper wing, and over the rear part of the engine, taking advantage of the narrow nose to give a good view down, important for accurate torpedo work.
An enclosed cabin was located below the cockpit, accessed by a hatch in the cockpit floor. This contained the chart table, radio gear, a bomb aimers winder and two prone positions for gunners firing below the aircraft. A ladder at the rear of the cabin led up to a ring mounted gun carried behind the wings with a good field of fire above the fuselage.
The massive aircraft could carry 2 tons of fuel and 3.5 tons of useful load including the 1.5 ton 21in torpedo.
The Cubaroo remained secret for some time. It was first mentioned in the Italian aviation paper Notiziarro di Aeronautic late in 1923, and wasn’t officially revealed until 21 August 1924 when it was shown to the Press and representatives from the governments of Spain, Japan, Greece and the United States.
The Cubaroo made its maiden flight in the summer of 1924. Despite its large size and heavy weight the test pilot Flt L P.W.S. Bulman reported that it was no more tiring to fly than the D.H.9A and its manoeuvrability was reminiscent of a Bristol Fighter!
A second prototype was built in 1925, with a modified radiator but otherwise identical. It was displayed at the RAF display at Hendon on 27 June 1925 in the New Types Park.
Late in 1925 the Air Ministry decided against using large single engined aircraft in favour of twin engined designs. By 1927 Blackburn had come up with three possible designs for twin engined versions of the Cubaroo – the Mk II powered by two 650 Rolls-Royce Condor IV engines carried between the wings, the Mk III using geared Condor III engines and the Mk IV using Condor IV engines in nacelles on the lower wings. None of these were ever built.
The first prototype was used as an experimental hack until it was damaged when the port undercarriage collapsed on 16 July 1925.
The second prototype survived at least into 1927 when it was being used as a flying test bed for the 1,100hp Beardmore Simoon Mk I eight-cylinder inline inverted water-cooled engine.
Although the Cubaroo never entered production, the experience gained helped Blackburn with the design of the Iris flying boat, which did see service, although in small numbers.
Avro came up with the Avro 577 Ava, powered by two Rolls-Royce Condor III engines. This had an even larger 96ft 10in wingspan, and was similar in size and weight, although with a much slimmer looking fuselage. Two prototypes of this aircraft were built, the first as the torpedo bomber, the second in 1927 to satisfy a heavy bomber specification, but no production followed.
Engine: Napier Cub or Beardmore Simoon Mk I
Power: 1,000hp or 1,100hp
Crew: 4 (pilot, navigator, bomb-aimer/ wireless operator, gunner
Span: 88ft
Length: 54ft
Height: 19ft 4in
Empty weight: 9,632lb
All-up weight: 19,020lb
Max speed: 115mph
Climb Rate:
Absolute ceiling: 11,800ft
Maximum Range: 1,800 miles
Endurance:
Armament:
Bomb load: