The Bristol Scout was a single-seat rotary-engined biplane originally designed as a racing aircraft.
Like similar fast, light aircraft of the period it was used by the RNAS and the RFC as a “scout”, or fast reconnaissance type.
It was one of the first single-seaters to be used as a fighter aircraft, although it was not possible to fit it with an effective forward-firing armament until the first British-designed gun synchronizers became available later in 1916, by which time the Scout was obsolescent.
Single-seat fighters continued to be called “scouts” in British usage into the early 1920s.
The Bristol Scout was designed in the second half of 1913 by Frank Barnwell and Harry Busteed, Bristol’s chief test pilot, who thought of building a small high-performance biplane while testing the Bristol X.3 seaplane, a project which had been designed by a separate secret design department headed by Barnwell.
The design was initially given the works number SN.183, inherited from a cancelled design for the Italian government undertaken by Henri Coanda, the half-finished fuselage of which remained in the workshops and the drawings for the aircraft bore this number.
The design was an equal-span single-bay biplane with staggered parallel-chord wings with raked wingtips and ailerons fitted to the upper and lower wings, which were rigged with about half a degree of dihedral, making them look almost straight when viewed from the front.
The wing section was one designed by Coanda which had been used for the wings of the Bristol Coanda Biplanes.
The rectangular-section fuselage was an orthodox wire-braced wooden structure constructed from ash and spruce, with the forward section covered with aluminium sheeting and the rear section fabric covered.
It was powered by an 80 hp (60 kW) Gnome Lambda rotary engine enclosed in a cowling that had no open frontal area, although the bottom was cut away to allow cooling air to get to the engine.
It had a rectangular balanced rudder with no fixed fin and split elevators attached to a non-lifting horizontal stabiliser.
The fixed horizontal tail surfaces were outlined in steel tube with wooden ribs and the elevators constructed entirely of steel tube.
The first flight was made at Larkhill on 23 February 1914 by Busteed and it was then exhibited at the March 1914 Aero Show at Olympia in London.
After more flying at Larkhill the prototype, later referred to as the Scout A, was returned to the factory at Filton and fitted with larger wings, increasing the chord by six inches (15 cm) and the span from 22 ft (6.71 m) to 24 ft 7 in (7.49 m).
These were rigged with an increased dihedral of 1+3⁄4°. Other changes included a larger rudder, a new open-fronted cowling with six external stiffening ribs distributed in symmetrically uneven angles around the cowl’s sides (especially when seen from “nose-on”) and fabric panel-covered wheels.
It was evaluated by the British military on 14 May 1914 at Farnborough, when, flown by Busteed, the aircraft achieved an airspeed of 97.5 mph (157 km/h), with a stalling speed of 40 mph (64 km/h).
The aircraft was then entered for the 1914 Aerial Derby but did not take part because the weather on the day of the race was so poor that Bristol did not wish to risk the aircraft.
By this time two more examples (works nos. 229 and 230) were under construction and the prototype was sold to Lord Carbery for £400 without its engine.
Carbery fitted it with an 80 hp Le Rhône 9C nine-cylinder rotary and entered it in the London–Manchester race held on 20 June but damaged the aircraft when landing at Castle Bromwich and had to withdraw.
After repairs, including a modification of the undercarriage to widen the track, Carbury entered it in the London–Paris–London race held on 11 July but had to ditch the aircraft in the English Channel on the return leg; while in France, only one of the two fuel tanks had been filled by mistake.
Carbury managed to land alongside a ship and escaped but the aircraft was lost.
Numbers 229 and 230, later designated the Scout B when Frank Barnwell retrospectively gave type numbers to early Bristol aircraft, were identical to the modified Scout A, except for having half-hoop-style underwing skids, what appear to be six stiffening ribs positioned around the engine cowl’s exterior circumferential surface (also made with a larger circular front opening for engine cooling when compared to the Scout A) and an enlarged rudder.
Completed shortly after the outbreak of war in August 1914, they were requisitioned by the War Office. Given Royal Flying Corps serial numbers 644 and 648, one was allocated to No. 3 Squadron and the other to No. 5 Squadron for evaluation.
Number 644 was damaged beyond repair on 12 November 1914 in a crash landing.
Impressed by the performance of the aircraft, the War Office ordered twelve examples on 5 November and the Admiralty ordered a further 24 on 7 November.
The production aircraft, later called the Scout C, differed from their predecessors mainly in constructional detail, although the cowling was replaced by one with a small frontal opening and no stiffening ribs, the top decking in front of the cockpit had a deeper curve and the aluminium covering of the fuselage sides extended only as far as the forward centre-section struts, aft of which the decking was plywood.
The single prototype aircraft.
Two manufactured, identical to the modified Scout A except for having half-hoop-style under wing skids and an enlarged rudder.
Type 1 Scout C
Similar to the previous Scout B.
These early Scout Cs, in a total run of 36 aircraft had their main oil tank moved to a position directly behind the pilot’s shoulders, requiring a raised rear dorsal fairing immediately behind the pilot’s seat to accommodate it.
These aircraft used a small-central opening, “dome-fronted” cowl that were only intended for use with the 80 hp Gnome Lambda seven-cylinder rotary engine, curiously the rotary engine choice the Royal Naval Air Service favoured.
Following the initial run of 36 Scout C airframes, later Scout C production batches, consisting of 50 aircraft built for the RNAS and 75 for the RFC, changed the cowl to a flat-fronted shorter-depth version able to house either the Gnome Lambda rotary, or the alternate choice of a nine-cylinder 80 hp Le Rhône 9C rotary engine when the Gnome Lambda was not used, and moved the oil tank forward to a position in front of the pilot for better weight distribution and more reliable engine operation.
The later, relatively “flat”-fronted cowl for the remaining Scout C aircraft still had the small opening of the domed unit, with both cowl designs having a circumferential slot-style cutaway made at mid-cowl depth of about one-sixth the circumference, to the lowest perimeter of the cowl to increase the cooling effect, and to allow any unburned fuel/oil mix to drain away.
A total of some 161 Scout C airframes were produced for the British military as a whole, with the transition to the Scout D standard taking place in a gradual progression of feature changes.
Bristol Types 2, 3, 4 & 5 Scout D
The last, and most numerous production version, the Scout D, gradually came about as the result of a series of further improvements to the Scout C design.
One of the earliest changes appeared on seventeen of the 75 naval Scout Cs with an increase in the wing dihedral angle from 1+3⁄4° to 3° and other aircraft in the 75 aircraft naval production run introduced a larger-span set of horizontal tail surfaces and a broadened-chord rudder, shorter-span ailerons and a large front opening for the cowl, much like that of Scout B but made without the external stiffening ribs instead.
The newer cowl was sometimes modified with a blister on the starboard lower side for more efficient exhaust-gas scavenging, as it was meant to house the eventual choice of the more powerful, nine-cylinder 100 hp Gnôme Monosoupape B2 rotary engine in later production batches, to improve the Scout D’s performance.
Some 210 examples of the Scout D version were produced, with 80 of these being ordered by the RNAS and the other 130 being ordered by the Royal Flying Corps.