Blackburn TB 1517 |
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The Blackburn T.B. was an unusual twin fuselage aircraft designed as an anti-Zeppelin interceptor, and which saw limited service in 1916.
The T.B. or Twin Blackburn was developed in response to a 1915 Admiralty specification called for a long range Zeppelin interceptor that could operate over the sea at night and carry a payload of Ranken incendiary steel darts, which were meant to be dropped onto the envelop of an airship and ignite the gas inside.
Blackburn responded with the T.B. This had two almost identical fuselages, mounted 10ft apart. Each carried its own rotary engine in the nose. Each fuselage carried a bungee-sprung pontoon float with a single step. It had large three bay biplane wings, with a much longer upper wing. The overhang was supported by wire braces that went back to steel pylons carried above the outer interplane struts. This wing design, with the very long upper wing and shorter lower wing, was kept for the more traditional Blackburn G.P. and the Blackburn Kangaroo landplane of 1918.
The Admiralty ordered nine T.B. seaplanes. The T.B. was originally going to use a new engine, the ten-cylinder Smith radial, which was meant to produce 150hp from a 380lb engine and with very low fuel consumption. This engine passed its bench tests, but when it was tested late in 1915 in the air proved to be unsatisfactory. As a result eight of the T.B. seaplanes were powered by 100hp Gnome Monosoupape engines and the ninth by 110hp Clerget engines.
Three aircraft were sent for trials at RNAS Isle of Grain in 1916. A number of unsatisfactory features were soon discovered. When the Gnome engine was primed ready to start it leaked petrol onto the top of the floats, which would catch fire when the engine was started. The observer’s job was to put out the two fires. The two crew were separated by a gap of 10ft with no means of communication. The only controls in the observer’s side was the starting handle for his engine. Once the aircraft had taken off the wings flexed up, and the aileron control cables no longer worked, so there was no lateral control. This problem was soon fixed by Blackburn. However the biggest problem was the lack of power – 200hp instead of the planned 300hp meant that only 70lb of darts could be carried, and the odds on being able to get above a Zeppelin were low. Seven aircraft were sent to RNAS Killingholme, but they were rarely used and all nine aircraft were soon broken up. Blackburn moved onto the far more conventional Blackburn G.P., which ended up entering production in a land plane version as the Blackburn Kangaroo.
Engine: Two Gnome Monosoupape
Power: 100hp each
Crew: 2
Span: 60ft 6in (upper), 45ft (lower)
Length: 36ft 6in
Height: 13ft 6in
Empty weight: 2,310lb
All-up weight: 3,500lb
Maximum take-off weight:
Max speed: 86mph at sea level
Climb Rate: 12min to 5,000ft
Service ceiling:
Endurance: 4 hours
Armament:
Bomb load: 70lb of steel darts