Bristol Biplane / Bristol Boxkite

The Boxkite (officially the Bristol Biplane) was the first aircraft produced by the British and Colonial Aeroplane Company (later known as the Bristol Aeroplane Company).

A pusher biplane based on the successful Farman III; it was one of the first aircraft types to be built in quantity.

As the type was used by Bristol for instruction purposes at their flying schools at Larkhill and Brooklands many early British aviators learned to fly in a Boxkite.

Four were purchased in 1911 by the War Office and examples were sold to Russia and Australia.

It continued to be used for training purposes until after the outbreak of the First World War.

The Boxkite was a two-bay biplane with an elevator carried on booms in front of the wings and an empennage consisting of a pair of fixed horizontal stabilisers, the upper bearing an elevator, and a pair of rudders carried on booms behind the wing.

There were no fixed vertical surfaces. Lateral control was affected by ailerons on both upper and lower wings.

These were single-acting, the control cables arranged to pull them down only, relying on the airflow to return them to the neutral position.

The wings and fixed rear horizontal surfaces were covered by a single layer of fabric: the other surfaces were covered on both sides.

Power was usually provided by a 50 hp (37 kW) Gnome rotary engine, although other engines were also used.

The engine was mounted on a pair of substantial wooden beams mounted above the lower wing: these continued forward to carry the seats, which were arranged in tandem, with the pilot sitting over the leading edge of the wing.

The undercarriage consisted of a pair of long skids, each bearing a pair of wheels sprung by bungee cords, and a single sprung tailskid mounted below the leading edge of the lower tailplane.

The first two Boxkites, assigned works numbers 7 and 8, differed in detail from the later production aircraft; the front outrigger booms were braced by a pair of vertical struts and were attached to the ends of the interplane struts.

This arrangement was inherited from the Zodiac, being necessary in that aircraft because the front spar of the wing did not also form the leading edge.

Additionally, the rear elevator had a straight trailing edge.

No. 8 also had double-surfaced wings; the wings of No. 7 were single-surfaced with the ribs enclosed in pockets, like production aircraft.

No. 7 was initially fitted with a 50 hp (37 kW) Grégoire, but for its first flight this was replaced by a Gnome, although the Grégoire was later refitted for trial purposes: No. 8 had a 50 hp (37 kW) E.N.V.

The first examples built had upper and lower wings of equal span, although most of the aircraft eventually produced had an extended upper wing and were known as the Military Version.

The examples of this type sold to the Russian government and the first aircraft sold to the British Army were fitted with a third rudder hinged to the centre leading-edge interplane strut of the tailplane, but this was not made standard.

Two modified Boxkites were produced for competition purposes.

The first, No. 44, was a single seater built to compete in the 1911 Circuit of Europe air race and had reduced wingspan and a nacelle for the pilot, similar to the Bristol Type T.

The second, No.69, was a redesign by Gabriel Voisin, who was employed as a consultant by Bristol.

This had no front elevator, monoplane tail with a single rudder, and a reduced gap between the wings.

It was tested at Larkhill in February 1912, but was evidently unsuccessful since it was soon rebuilt as a standard Boxkite and was to crash in November 1912.

Production continued until 1914, with a total of 78 being built: 60 of these were the extended Military Version, one was a racer (No. 44) and another the Voisin variant (No. 69); all but the last six aircraft were built at Filton.

These were built at Brislington by Bristol Tramways.

38 ft 6 in (11.73 m)
47 ft 8 in (14.53 m)
46 ft 6 in (14 m)
11 ft 10 in (3.61 m)
Wing area
517 sq ft (48.0 m2)
Empty weight
900 lb (408 kg)
Gross weight
1,150 lb (522 kg)
1 × Gnome Omega 7-cylinder air-cooled radial piston engine,
50 hp (37 kW)
Alternative Engines
50 hp (37.3 kW) Grégoire-Gyp 51hp 4-cyl in-line
50 / 60 hp (37.3 / 44.7 kW) E.N.V. Type A
60 hp (44.7 kW) Renault
70 hp (52.2 kW) Gnome Gamma
2-bladed fixed-pitch pusher propeller
Maximum speed
40 mph (64 km/h, 35 kn)
Wing loading
2.22 lb/sq ft (10.8 kg/m2)
0.043 hp/lb (0.071 kW/kg).

Share on facebook