Blackburn T-4 Cubaroo flying
The Blackburn T-4 Cubaroo N166 being flown at Brough on 21 August 1924.

The Blackburn T-4 Cubaroo was a biplane torpedo bomber, designed against Air Ministry Specification 16/22 which sought a long endurance aircraft for coastal defence and able to carry a 21-inch torpedo.


It was constructed at the Blackburn Aeroplane and Motor Co Ltd Olympia Works, Leeds whereafter it was transported for construction and test flying from Brough Aerodrome in East Yorkshire.


Fitted with the 1,000 hp Napier Cub sixteen-cylinder engine, the Blackburn T-4 Cubaroo featured a wingspan of no less than 88 feet, with an all-up weight of just over 19,000 lb, one of the largest aircraft of its day.


Although conventional in layout, the large Blackburn T-4 Cubaroo was not particularly attractive in its appearance and the Editor of The Aeroplane Magazine (CG Grey) described it as ‘looking like a docile cow in a field’. Despite this, when the first aircraft (N166) was publicly demonstrated at Brough on 21st August 1924, its short take off and landing, and its unexpected manoeuvrability were commented on quite favourably.


Blackburn T-4 Cubaroo N166 ground
The 88ft span of the T-4 Cubaroo N166 provides shelter for spectators at a wet Brough.


It was a fabric-covered / steel tube construction and featured two separated two-wheel undercarriages, spaced apart to allow carriage of the torpedo on the fuselage centreline. The wings, with their 11ft 6 in chord, were designed to fold back alongside the fuselage to aid storage.


The pilot and navigator sat in a side-by-side open cockpit, immediately ahead of the upper wing leading edge and directly above the rear of the large engine. There was an enclosed cabin under the centre-section with a chart table, wireless equipment and a bomb aiming window. It also contained accommodation for a gunner / bomb-aimer and one further gunner.


Rearward-firing gun positions were provided at the lower wing roots together with an elevated position equipped with a gun ring that allowed a wide field of fire to the rear.


The prototype (N166) was secretly flown in the summer of 1924, initially with a two-blade wooden propeller, although this was subsequently replaced by a three-blade, all-metal propeller with adjustable pitch.


Blackburn T-4 Cubaroo wings folded
The wings of the Cubaroo were arranged to fold to allow practical hangarage.


A second prototype (N167) was flown in 1925 and differed in having a flat nose radiator, rather than that in the first prototype which was curved to the rear and giving a rounded nose profile. This second machine was shown publicly at the RAF Show at Hendon in June 1925, where during flight it was said to be impressive, both for its size and manoeuvrability.


Before the Blackburn T-4 Cubaroo could exhibit its full potential, the Air Ministry policy changed in favour of twin-engine bombers. Thereafter the two Blackburn T-4 Cubaroo aircraft were used for experimental flying and as engine testbeds.


The first prototype was delivered to the Aeroplane & Armament Experimental Establishment (A&AEE) at Martlesham Heath. Sadly, it was written-off following an undercarriage collapse on 2nd February 1925.


The second prototype was used at Blackburn Aircraft Company at Brough for trials of the eight-cylinder 1,100 hp Beardmore Simoon engine during 1927. Its ultimate fate thereafter is unknown.


Variants & Numbers Built

Two aircraft (N166 and N167)



Powerplant One 1,000 hp Napier Cub sixteen-cylinder engine
Span 88 ft 0 in
Maximum Weight 19,020 lb
Capacity and armament Pilot, navigator, bomb aimer / gunner and second gunner; one 21-inch naval torpedo or four 550 lb bombs, three defensive Lewis guns.
Maximum Speed 115 mph at sea level
Endurance / Range 1,800 miles without weapon load



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