Naval Officer Lt. Charles Dennistoun Burney had the original idea of a seaplane that would use hydrofoils rather than floats, to provide support when on the water, with the supporting struts for the hydrofoils being termed ‘hydropeds’.
However, Burney lacked the resources to develop his ideas and so the entered into a relatively secret arrangement with the British and Colonial Aeroplane Company. The Admiralty had unofficially promised further support the project and so a separate office was set up, known to just a handful of people as the 'X Department'. Scottish designer Frank Barnwell headed the Design Team with Clifford Tinson as his assistant.
Their first proposal (delightfully codenamed Bristol-Burney X.1) was an adaption of the Bristol GE.1 biplane.
It featured a watertight hull and five streamlined airbags under the wings, both provided to support buoyancy whilst at rest. For take off, the craft would be accelerated using water propellers and the hydrofoil principle, recently pioneered by Enrico Forlanini. This utilised three sets of hydrofoils, each consisting of a central leg bearing a stack of lifting planes, an assembly referred to as a 'hydroped'. Once plaining was achieved, the propellers would disengaged, using the main engine to drive a conventional airscrew for the actual take-off. After a number of failed attempts and trials, the proposal was abandoned.
Barnwell then designed and built two machines (Bristol-Burney X.2 and X.3) both being strikingly clean monoplanes.
Having abandoned the Bristol-Burney X.1, Barnwell produced a proposal for a two-seat monoplane with an inflatable wing, using eight tubes of rubberised fabric running span-wise in place of spars.
Although experiments were made with this idea, it proved too heavy and so it was modified to use a more conventional wing structure, utilising three spars used for wing-warping for lateral control. These were mounted on top of the fuselage, which featured rounded 'boat-like' lower section, planked with mahogany and covered with varnished sailcloth. This acted like a flying boat hull, providing buoyancy until enough speed was achieved for the hydrofoils to provide lift.
There were two hydropeds, angled out from below the leading edge of the wing, each with a water propeller driven by a shaft contained within the leg. Meanwhile, a third hydroped supported the rear fuselage.
Power was provided by an 80 hp (60 kW) Canton-Unné water-cooled radial engine, driving both the air and water propellers, via a pair of Hele-Shaw clutches. Dual controls were fitted in the cockpit, in which the crew sat side-by-side.
The aircraft was completed in May 1912, and transferred by boat for testing at to Dale near Haverfordwest on the Pembrokeshire Peninsular.
Initial trials showed the aircraft accelerated well under the power of the water propellers although disastrously, the streamlined fairing of the hydropeds were torn away after only a short run. This signalled the immediate end of testing.
Static investigation revealed a vibration problem in the main drive and while this was examined, further trials were made by towing the aircraft behind a torpedo boat. Stability issues were partially cured by small adjustments to the parafoil lifting planes as well as the addition of a controllable water elevator and rudder to the aft hydroped. This resulted in much improved towing performance although, when the water propellers were engaged, their torque reaction caused the aircraft to heel over.
Taxying trials (initially with an 80hp Gnome engine and dummy outriggers fitted instead of lifting wings) took place at Dale in August 1913. These trials were promising in terms of taxying performance and stability under tow.
In September 1912, flight trials were carried out, towing the aircraft behind a boat. For the initial tests the valuable engine was removed and replaced by ballast. On 21st September and whilst being towed by a torpedo boat, the controls were set for level flight and locked. It lifted off at around 30 knots (35 mph, 56 km/h). It assumed a dangerous nose-high attitude where it stalled, side-slipped and eventually crashed. It was carrying George Dacre, onboard to monitor the instruments and happily he escaped without injury.
In June 1914, the aircraft was prepared for flight trials (using the Canton Unné engine) when unfortunately it was seriously damaged after it ran aground on a submerged sandbank. With finances being eaten up by the war effort, the secret project came to an end.
The X.2 was not repaired although in March 1913, the Admiralty funded a second machine, X.3 (given a build no 159) and which was of larger dimensions and fitted with a 200 hp Canton Unné engine.
In March 1913, work began on another aircraft, allocated the Bristol sequence number 159.
This was incrementally larger than the Bristol-Burney X.2, with a fuselage covered in Consuta plywood, a form of construction of watertight hulls for boats and marine aircraft. The character of the water propellers was altered, with the contra-rotating propellers, mounted centrally in tandem, now eliminating the torque effect. The wing-warping method was also replaced by ailerons and the design was powered by a 200 hp (150 kW) Canton-Unné water-cooled radial engine, which had been loaned by the Admiralty.
Initial taxying trials were conducted with outriggers supporting the wing tip floats, replacing the wings. Bearing in mind the value of the loaned engine, an 80 hp (60 kW) Gnome was used.
The trials were concluded to be satisfactory although the type had a tendency for the nose to dip when the airscrew was engaged. To offset this an additional front-mounted elevator was added.
For the following trials, the Gnome engine was removed and replaced by the Canton-Unné . The wings were also fitted.
Disastrously and before flight testing could commence, the aircraft was severely damaged when it was grounded on a sandbank, necessitating extensive repairs. Bristol applied to the Admiralty for more substantial financial support but this was refused. Faced with growing costs and little prospect of success, the the program was abandoned.
The Bristol-Burney X.3 was returned to Filton, where it was eventually scrapped in 1920.
Charles Burney went on to exploit his experience with the Bristol X Planes at HMS Vernon during 1915, developing the Paravane, a form of towed underwater 'glider' with a warhead that was used in anti-submarine warfare.
|Powerplant||80 hp Canton Unné||200 hp Canton Unné|
|Span||55 ft 9 in||57 ft 10 in|
|Capacity||Two crew||Two crew|
Variants and number built
Two experimental prototypes only: X.2 (Bristol build number 92) and X.3 (build number 159).