During World War 1, the aviation world was still in its infancy. Designers were still figuring out
what did or didn’t work, and this produced some…interesting results:
One of these was the Twin Blackburn. In 1915 the British Admiralty was looking
for a solution to the Zeppelin menace. At the time the Airships of the German army and Navy
were floating through the British skies in relative safety; the power, climb rate,
and range of British fighters not being quite enough to get at them. As a result of this the
Admiralty issued a requirement for a two-seat plane, capable of long endurance and an ability
to reach an altitude of at least 12,000 feet. In terms of armament, this new aircraft was not
intended to use guns to shoot down the Zeppelin…it would instead fly up over the airship and
bomb it. This would be achieved with the use of the Ranken incendiary dart, which when dropped
would pierce the airships outer envelope and ignite the explosive gas bags within.
At this time the Blackburn company was very new to the aviation field, their main experience
thus far had been building Farnborough-designed BE2s and Sopwith Cuckoos, but they had rapidly
developed a good working relationship with the admiralty and felt confident enough to
submit their first true military design. Known as the TB – or Twin Blackburn – it
was a curious design, being a biplane that had not one but two fuselages. These were joined
at the front by a 10 foot centre section and at the rear by a single large tailplane. From
the outset it was designed as a seaplane, and the fuselages were supported on the water by two pairs
of floats on bungee-sprung mounts. These floats were set forward of the centre of gravity and so
a pair of small floats were also attached to the bottom of the tail to keep it out of the water.
The two wings were arranged without stagger, constructed of spruce spars and ribs, and the
ailerons were placed on the upper wing only. The upper wing also had a considerably greater span,
and because of this it had to be braced using wired kingposts.
To make design and construction of the aircraft easier – and because they had the parts – the
twin fins and rudders were taken from the BE2 which was already being produced by Blackburn.
The choice of a twin-fuselage design had been made on account of the requirement for long range,
as having two fuselages meant you had double the fuel capacity,
and providing your engines were efficient enough you would therefore have better range.
This need for efficiency meant that Blackburn were very interested by the Arrival of the American
John W Smith, who brought with him the design for a 10-cylinder radial engine; an engine he claimed
that would only weigh 380lbs and produce 150hp whilst maintaining a very low fuel consumption.
Apparently, the Admiralty was in a generous (or desperate) mood in early 1915, for not
only did they accept an unorthodox design from a company with almost zero military experience,
but they accepted it to be powered by an engine that had never been used – let alone
tested – on British soil. All in all, nine of the TB biplanes were ordered whilst Smith’s new engine
went though a rapid series of bench tests. Unsurprisingly, this new engine with fabled
performance figures turned out to be pretty rubbish. When tested with an experimental
A.D Navyplane and a Vickers FB5, the Smith engine not only proved to be underpowered,
but also pretty inefficient. And so eight of the nine TB seaplanes were completed
with the Gnome Monosoupape rotary engine, and the ninth was fitted with 110hp Clergets.
The first and last models of the production batch of nine were sent to undergo trials at RNAS Isle
of Grain in 1916. This proved to be a somewhat terrifying experience for test pilot J.W Seddon
and his observer E.W Stedman, the latter of which actually recorded the experience in his memoirs.
The pilot sat in one fuselage with all the flying and engine controls,
while the observer sat several feet away in the other, with no controls except the starting
handle for the engine on his side. Starting on the water needed discipline, courage,
and agility, for a pool of excess petrol – which formed on the float when the engine was primed,
promptly ignited when said engine fired. The observer’s job during take-off – in a scene
that wouldn’t be out of place in an episode of Dad’s Army- was to lie on the lower centre section
and put out the fire on the pilot’s side with an extinguisher, scramble into his own cockpit
to start the second engine, and then leap out again to extinguish the second fire on his side,
before finally getting in again for take-ff. Once in the air and hopefully not on fire,
the aircraft proved difficult to handle as the flexing of the wing caused the aileron
cables to slacken which resulted in an almost total loss of lateral control. This design flaw
-though terrifying- was soon fixed, however there was still a disconcerting amount of
relative movement between the fuselages caused by the flexing of the wire-braced centre section.
Along with being uncomfortably wobbly, the TB was still underpowered even with the new engine,
only being able to achieve two-thirds of the desired power output. As a result of this,
the military load had to be reduced to just 70lbs of Ranken darts…not that it ever got a chance to
use its weapons against the Zeppelins. The first major problem was that the crew
of the TB were limited to hand-signalling for communication, not an ideal arrangement
when in action against enemy airships, and the second problem was that of altitude.
By the time the TB was complete, it was clear that the whole idea of attempting to attack approaching
airships with bomber-type planes (which had little margin in the way of speed or manoeuvrability),
was badly flawed…especially when it was discovered that the airships could simply
outclimb the planes by jettisoning ballast and going to an altitude above the planes ceiling.
Within a not too short timeframe, the Admiralty realised that there was
little use for the Blackburn TB. Four were briefly used at RNAS Killingholme,
where they terrified everyone, but by the end of 1916 they were all put in
storage and eventually broken up as scrap in August 1917.
I’d like to say that Blackburn’s next attempt at a military aircraft was more sensible…but
the A.D Sparrow was anything but that. However, that’s a story for another day.
As always thank you all so much for watching, and I’ll catch you all next time. Goodbye.