C.Barnes Bristol Aircraft since 1910 (Putnam)

The Bristol Scouts E and F

   In the autumn of 1916, before the Bristol Fighter had been issued to the Royal Flying Corps squadrons in France, desperate efforts were being made to produce single-seater fighting Scouts capable of outflying their German opponents, in the struggle to gain local air superiority over the artillery lines. A limit had almost been reached in the power available from rotary engines and attention turned to various alternative designs, both in-line and radial. Typical of the former was the Hispano-Suiza, but its reliability was poor and supplies of serviceable engines so limited that they were reserved for the officially-designed S.E.5a Scout, the first prototype of which flew in December 1916.
   Designers looked hopefully around for other engines, and Capt. Barnwell was informed of a proposal by Harry R. Ricardo and Frank B. Halford for a ten-cylinder two-row watercooled radial of 200 h.p., the 'Cruciform'. This engine gained no official support and was not built even as a prototype, but nevertheless Barnwell designed round it two alternative single-seater schemes, one a tractor biplane and the other a pusher. The latter, drawn by W. T. Reid on 25 January 1917, remained a preliminary layout only, and showed a conventional equal-span two-bay biplane with the pilot's cockpit in a nacelle mounted high up, as in the contemporary Vickers F.B.26; armament comprised two Lewis guns. The tractor design, drawn by Barnwell himself, was dated two days earlier and showed a neat single-bay biplane combining the aerodynamic refinement of the M.1C with the compact layout of the Scout D. The wings had rounded raked tips as in the monoplane and four small strut-linked ailerons of equal area. The fuselage was a wire-braced structure aft, but a Warren girder forward of the cockpit. The undercarriage was a simple Vee type with rubber-sprung cross-axle, and the engine was installed with a annular radiator forward, to which air was admitted through a large diameter annular spinner surrounding a cone at the centre; this arrangement foreshadowed the low-drag cowling developed 30 years later by Napiers for the Hawker Tempest. Armament consisted of a single synchronized Vickers gun recessed into the top of the fuselage ahead of the pilot and a Lewis gun on the top centre section which could be elevated through 45 degrees from its lowest position, which was arranged just to clear the airscrew.
   A fair amount of design work was done on the tractor project, Scout E, during February and March 1917, and sequence number 2844 was reserved for a prototype; but then it became apparent that the Cruciform engine would not be built, and early in May the Company was promised a few 200 h.p. Hispano-Suiza engines and a contract for six prototypes of a modified design. Barnwell at once revised Scout E to suit the Hispano-Suiza and changed the wing arrangement to one of unequal span with ailerons only on the top wing; at the same time the Lewis gun was deleted and two synchronized Vickers guns were arranged side-by-side in place of the single one. The revised project was named Scout F and retained the rear fuselage and tail unit of Scout E almost unchanged, but the deeper front end necessitated a new, shorter undercarriage. When the contract was issued on 4 June it specified the Sunbeam Arab engine, because of the shortage of Hispano-Suizas, and this was accommodated without much difficulty, but the cooling system gave some trouble and the header tank had to be raised to a position where it made a slight bulge in the top of the cowling. The radiator layout of Scout F matched that of Scout E in neatness and imagination, for it comprised a rectangular block mounted in an under-belly tunnel fairing, with two independent shutters, which could be set to various angles to maintain optimum water temperature. This permitted a low-drag nose design with a conical spinner over the airscrew boss. A good many revisions were made in cockpit details, flying controls and gun installation while construction of the prototype proceeded, and the design was not completed until November 1917, by which time the first few Sunbeam Arabs had begun to demonstrate the incurability of their vibration trouble. It was therefore decided to complete only the first two Scouts F, Nos. 2845 and 2846 (B3989 and B3990), with Arabs and to seek a better alternative engine for the others.
   The first Scout F was flown in March 1918 and had a remarkably fine performance, reaching 138 m.p.h. at sea level and 128 m.p.h. at 10,000 ft. The second Scout F was flown at the Central Flying School by all the most experienced fighter pilots of the day, amongst them Major Oliver Stewart, who rated it as a better aerobatic machine than the S.E.5a; but it was condemned by its engine and no attempt seems to have been made to revert to the Hispano-Suiza version. By this time, however, a new and promising small-diameter radial engine had arrived; this was the Cosmos Mercury of 315 h.p. designed originally for an Admiralty application by A. H. R. Fedden and L. F. G. Butler of Brazil Straker and Co. Ltd. of Fishponds, Bristol, who had been awarded a contract for 200 production engines of the type. Seeking a suitable aeroplane in which to install the Mercury engine for flight testing, Fedden approached Barnwell, who was looking for a substitute for the Sunbeam Arab and was predisposed in favour of a radial since his study for Scout E. The upshot of this meeting was the modification of the third Scout F, No. 2847 (B3991), to take the Mercury, which was installed in a low-drag cowling with only the cylinder heads and exhaust stubs exposed.
   Known as Scout F.l, B3991 was flown for the first time at Filton on 6 September 1918 and on 26 October it became the first Bristol prototype to be flown by the Company's new test pilot, Cyril F. Uwins, who had joined the staff the day before. Although the Armistice put an end to any hope of production of the Scout F.1, it was very successful in its trials and in December 1918 was delivered to Farnborough. There, in April 1919, it put up unofficial records by climbing to 10,000 ft. in 5·4 min. and to 20,000 ft. in 16·25 min.; its maximum speed at sea level was 145 m.p.h. After these trials no further development took place because the Cosmos Mercury contract had been cancelled; the fourth Scout F, No. 2848 (B3992), was completed as a spare airframe, but the last two aircraft of the order were still unfinished in April 1919; the question did arise of completing one of them with a Hispano-Suiza for offer to Senor Juan Pombo instead of the Scout D he had asked for, but he accepted the alternative offer of an M.1C, as recorded earlier. The mainplanes of B3992 were the subject of static strength tests at the RA.E. in 1919, and as late as March 1921 Capt. Barnwell suggested adapting this airframe as a flying test-bed for a new Curtiss engine, but this proposal was not approved.

SPECIFICATION AND DATA
Type: Scout F
Manufacturers: The British & Colonial Aeroplane Co. Ltd., Filton, Bristol
Power Plants: One 200 hp Sunbeam Arab
   One 315 hp Cosmos Mercury
Span: 29 ft 7 in
Length: (Arab) 20 ft 10 in
   (Mercury) 20 ft
Height: 8 ft 4 in
Wing Area: 260 sq ft
Empty Weight: 1,440 lb
All-up Weight: (Arab) 2,200 lb
   (Mercury) 2,260 lb
Max. Speed: (Arab) 138 mph
   (Mercury) 145 mph
Climb to 10,000 ft: (Arab) 9t min
   (Mercury) 5 1/2 min
Accommodation: Pilot only
Production: 4
Sequence Nos.: 2845-2848

P.Lewis The British Fighter since 1912 (Putnam)

During the Summer of 1917 Bristol’s designer Frank Barnwell set to work on the design of a new single-seat fighter, the Scout F, to use the water-cooled 200 h.p. Sunbeam Arab II engine. The Scout F materialized as a single-bay biplane with N-type interplane struts and a very clean engine installation which was assisted materially by the location of the radiator between the undercarriage legs. Tests revealed excellent overall performance and flying characteristics bqt the Arab power plant persisted in giving trouble.
   Of the three Scout Fs constructed the third, B3991, was fitted with one of the new radial engines then beginning to appear. This was the 347 h.p. Cosmos Mercury with which B3991, redesignated Scout F.1, made its initial flight during April, 1918. The engine was installed to blend neatly into the F.1’s nose and, with it, the machine turned in a first-class performance, carrying armament of two Vickers guns on the front decking but development of the Scout F.1 was eventually halted.

F.Mason The British Fighter since 1912 (Putnam)

Bristol Type 21 Scout F and F.1

   Throughout 1917 Capt Frank Barnwell had been engaged in advancing his basic Bristol Scout concept, but inevitably had to turn his attention away from the rotary engine when it became generally accepted as having reached the realistic limit of its power. The Scout E was schemed up to accommodate a proposed 200hp ten-cylinder water-cooled radial known as the ‘Cruciform’, but when this failed to materialise, Barnwell altered his design to take the much sought-after 200hp Hispano-Suiza in-line engine. The new design was designated the Scout F.
   When, however, a contract for six prototypes was raised, on 4 June 1917, it was made clear that the Hispano engine would not be available (owing to prior claims for the S.E.5A), and that the 200hp Sunbeam Arab should be used instead. Installation of this engine itself presented little trouble, and Barnwell, by placing the water header tank over the engine, managed to achieve a very clean cowling. His locating of the radiator within a tunnel fairing between the undercarriage V-struts proved exceptionally neat, and became an established position for this cumbersome component of water-cooled engines. Another unusual feature, though not unique at the time, were the N-type interplane struts which obviated the need for incidence cable bracing.
   Although the first Scout F prototype, B3989, was completed in November 1917, it was not flown until March the following year, mainly because of troubles being experienced by the Arab engine, early examples displaying severe vibration which seemingly defied cure. While efforts were being made to rectify these problems, numerous improvements were made in the cockpit and armament installation on the Scout. However, despite putting up an excellent performance during trials (138 mph at sea level, and climb to 10,000 feet in 9 minutes 20 seconds), the manufacturer decided to cast around for yet another engine and to abandon the existing design. Only two Scout Fs were completed, the second being flown at the Central Flying School.
   It is likely that Barnwell was already aware of the engine designs of Alfred Hubert Roy (later Sir Roy) Fedden and L F G Butler at the Bristol company of Brazil Straker. These two engines, the two-row, fourteen-cylinder Mercury and the single-row, seven-cylinder Jupiter radials, were to become subjects of fairly large production orders after the Brazil Straker company was bought by the Cosmos Engineering Company. Attracted by the Mercury’s high power output and low overall diameter, Barnwell decided on this engine for his revised Scout F.1, B3991. Indeed, the Mercury had only been bench run in about February 1918. When installed in the F.1, extreme care was taken to keep drag to an absolute minimum by enclosing it in a compound curved cowling, through which only the cylinder heads protruded. The Scout F.1 was officially tested in September 1918 and produced a top speed of 145 mph at sea level.
   Unfortunately, with the signing of the Armistice, the order for 200 Cosmos Mercury engines was cancelled, and further development of the Scout F.1 also came to an end and, although one further prototype, B3992, only awaited an engine, it too was dismantled - although the wings underwent structural strength tests at Farnborough in 1919.


   Type: Single-engine, single-seat, single-bay biplane fighter.
   Manufacturer: The British & Colonial Aeroplane Co Ltd, Filton, Bristol.
   Powerplant: Scout F. One 220hp Sunbeam Arab II water-cooled in-line engine. Scout F.1. One 347hp Cosmos Mercury fourteen-cylinder air-cooled radial engine.
   Dimensions: Span, 29ft 7 1/2 in; length, (Scout F) 20ft 10in, (Scout F.1) 20ft 0in; height, 8ft 4in; wing area, 260 sq ft.
   Weights: Scout F. Tare, 1,436lb; all-up, 2,210lb.
   Performance: Scout F. Max speed, 138 mph at sea level; climb to 10,000ft, 9 min 20 sec; service ceiling, 21,000ft. Scout F.1. Max speed, 145 mph at sea level; climb to 10,000ft, 5 min 25 sec.
   Armament: Twin synchronized 0.303in Vickers machine guns on upper nose decking.
   Prototypes: Six prototypes ordered, B3989-B3994. B3989 and B3990 were built as Scout Fs; B3991 was begun as a Scout F but completed as Scout F.1; B3992-B3994 were not completed. No production.

W.Green, G.Swanborough The Complete Book of Fighters

BRISTOL SCOUT F UK

   Originally intended for a 200 hp Hispano-Suiza engine, the Scout F was initiated by Frank Barnwell in June 1917, subsequently being redesigned to take a 200 hp Sunbeam Arab II eight-cylinder water-cooled engine. This power plant had been ordered into large-scale production in January 1917, before adequate testing had been undertaken. Six prototypes of the Scout F were ordered, the first of these flying in March 1918, by which time it had been decided to complete only the first two aircraft with Arab engines. The Scout F possessed excellent flying qualities, but its Arab engine proved totally unreliable. Nevertheless, the second prototype was completed and flown, flight testing continuing into 1919. Armament comprised two synchronised 0.303-in (7,7-mm) Vickers guns.

Max speed, 138 mph (222 km/h) at sea level, 128 mph (206 km/h) at 10,000 ft (3 050 m).
Time to 10,000 ft (3 050 m), 9.35 min.
Empty weight, 1,436 lb (651 kg).
Loaded weight, 2,210 lb (1002 kg).
Span, 29 ft 7 1/2 in (9,03 m).
Length, 20 ft 10 in (6,35m).
Height, 8 ft 4 in (2,54 m).
Wing area, 260 sqft (24,15 m2).


BRISTOL SCOUT F.1 UK

   The shortcomings of the Arab engine led, at an early stage in the development of the Scout F, to an investigation of possible alternative power plants, and it was decided to adapt the third prototype airframe to take a new 14-cylinder two-row Brazil-Straker (later Cosmos Engineering) Mercury radial of 347 hp. Designated Scout F.1, the aircraft was first flown on 6 September 1918, and proved to possess an excellent performance, establishing new unofficial climb records in April 1919. By that time, further development of the Mercury engine had been abandoned and no more work on the Scout F.1 was undertaken.

Max speed, 145 mph (233 km/h) at sea level.
Time to 10,000 ft (3 050 m), 5.45 min.
Loaded weight, 2,260 lb (1 025 kg).
Span, 29 ft 7 1/2 in (9,03m).
Length, 20 ft 0 in (6,09m).
Height, 8 ft 4 in (2,54 m).
Wing area, 260 sq ft (24,15 m2).

J.Bruce British Aeroplanes 1914-1918 (Putnam)

Bristol Scout F and F.1

  IN the design of the Bristol Scout F, Captain Barnwell gave further evidence of advanced thinking. Work on the design began in June, 1917, but the aeroplane would not have been accounted old-fashioned more than a decade later.
  In an age when most liquid-cooled aero-engines had their radiators installed car-fashion as a vertical surface immediately behind the airscrew, the Scout F represented a complete breakaway from contemporary practice with its radiator mounted under the fuselage. This position of the radiator allowed the cowling of the engine to be made commendably clean, and the aerodynamic entry of the aeroplane was unusually good.
  Structurally the Scout F was fairly typical of its period. The rear portion of the fuselage was a conventional wire-braced fabric-covered wooden structure, while the forward section was a plywood-covered box girder. The wings were of unequal span and chord, and both interplane and centre-section struts were of N configuration, thus eliminating the more usual incidence wires. Ailerons were fitted to the upper wings only.
  In the air the Scout F had excellent handling qualities, and was considered to be superior to the S.E.5a in some respects. Its performance was good, but it had a built-in liability in its Sunbeam Arab engine. When the Scout F was designed, it was not known that the Arab was going to prove so incurably unsatisfactory. All the troubles experienced with this engine in the Bristol Fighter were repeated with the Scout F, and there can be little doubt that the Arab was the chief reason why the machine did not go into production. Vibration was so severe that damage was caused to the engine bearers.
  Serial numbers were allotted for six machines, but in fact only three were completed and construction of a fourth did not proceed beyond the making of the bare airframe. The design was so promising that the British & Colonial Company did not wish to abandon it completely, and therefore sought an alternative power unit.
  The opportunity was taken to fit the Scout F with a new and untried radial engine, the Cosmos Mercury. This engine had been designed to fulfil the Air Board specification known as Scheme A, which had been issued on April 5th, 1917. Inspired by the Admiralty, Scheme A called for a stationary air-cooled radial engine not more than 42 inches in diameter and capable of delivering at least 300 h.p.
  Designs were submitted by Brazil, Straker & Co., Ltd., of Fishponds, Bristol, by Siddeley-Deasy, by Vickers, and by A.B.C. Motors Ltd. The winning design was the fourteen-cylinder two-row radial submitted by Brazil, Straker & Co., Ltd., and a production order for 200 engines was placed. The engine was named Mercury, and was designed by L. F. G. Butler, Brazil Straker’s chief designer, under the direction of A. H. R. (later Sir Roy) Fedden, who was the company’s chief engineer.
  The design of the Mercury was completed in July, 1917, and the first bench run was made early in 1918. At about that time the Brazil, Straker concern changed hands and was renamed the Cosmos Engineering Company.
  The Cosmos Mercury, as the engine was now known, was flown for the first time in April, 1918, installed in the third Bristol Scout F airframe, B.3991. With this engine the aircraft was designated Scout F.1. Despite the completely different configuration of the Mercury engine, care was again taken to keep drag down to a minimum. The day of the Townend ring and low-drag cowling had not yet arrived, but the Mercury was provided with a circular cowling through which the cylinder heads protruded.
  The performance of the Scout F.1 was excellent, particularly in rate of climb, but it was too late upon the scene to be considered for production. Moreover, the Cosmos company decided in the autumn of 1918 to concentrate on the development of their new single-row radial engine, the Jupiter, and the Mercury was virtually shelved. When the Armistice was signed, the contract for the 200 engines was cancelled, but testing continued into 1919. In April of that year the Bristol Scout F.1 set new climbing records when it reached 10,000 feet in 5-4 minutes and 20,000 feet in 16-25 minutes.


SPECIFICATION
  Manufacturers: The British & Colonial Aeroplane Co., Ltd., Filton and Brislington, Bristol.
  Power: Scout F: 200 h.p. Sunbeam Arab II. Scout F.1: 347 h.p. Cosmos Mercury.
  Dimensions: Span: upper 29 ft 7 1/2 in., lower 26 ft 2 in. Length: Scout F, 20 ft 10 in.; Scout F.1, 20 ft. Height: 8 ft 4 in. Chord: upper 5 ft 7 in., lower 4 ft 11 in. Gap: 5 ft 1 in. Stagger: 2 ft. Dihedral: 0°. Incidence: 1°. Span of tail: 10 ft 6 in. Airscrew diameter: Scout F, 9 ft 2 in.
  Areas: Wings: upper 150 sq ft, lower i 10 sq ft, total 260 sq ft. Ailerons: each 15-25 sq ft, total 30-5 sq ft. Tailplane: 15 sq ft. Elevators: 14-5 sq ft. Fin: 4-1 sq ft. Rudder: 5-3 sq ft.
  Weights and Performance: No. of Trial Report on Scout F: M.185. Date of Report: March, 1918. Type of airscrew used on trial of Scout F: P.3041. Scout F: weight empty: 1,436 lb. Military load: 319 lb. Pilot: 180 lb. Fuel and oil: 275 lb. Weight loaded: 2,210 lb. Scout F.1: weight loaded: 2,260 lb. Scout F: maximum speed at ground level: 138 m.p.h.; at 5,000 ft: 135 m.p.h.; at 10,000 ft: 128-5 m.p.h.; at 15,000 ft: 117-5 m.p.h. Climb to 6,500 ft: 5 min 20 sec; to 10,000 ft: 9 min 20 sec; to 15,000 ft: 17 min 20 sec. Service ceiling: 21,000 ft. Scout F.1: maximum speed at ground level: 145 m.p.h. Climb to 10,000 ft: 5 min 25 sec; to 20,000 ft: 16 min 15 sec.
  Tankage: Scout F. Petrol: main tank 29 1/2 gallons; service tank 3 gallons; total 32 1/2 gallons. Oil: 5 gallons. Water: 1 1/2 gallons.
  Armament: Two fixed Vickers machine-guns mounted on top of the fuselage and synchronised to fire forward through the revolving airscrew.
  Production: Three Scouts F were completed, and a fourth airframe was built. They were ordered under Contract No. A.S.3423.
  Serial Numbers: B.3989-B.3994. B.3991 was modified to become the Scout F.1; only the airframe of B.3992 was built; B.3993 and B.3994 were not built.

H.King Armament of British Aircraft (Putnam)

Scout F. The two Vickers guns of the Scout F (1917) were mounted externally on top of the fuselage, the land-service handle blocks flanking the windscreen. There was a ring-and-bead sight, the bead being positioned just ahead of the windscreen and the ring almost level with the front of the cooling jackets. Beneath the short ejection chutes were access panels to the belt boxes. The external fitting of the guns was regrettable, if unavoidable (because of the small fuselage dimensions), for the Scout F was of unusually clean aerodynamic design.

Jane's All The World Aircraft 1919

   The Bristol scout, type Fl. is a recent production of the Bristol firm and was about to be put in production when the Armistice was signed. The fuselage is very deep and carried in its nose a 200 Sunbeam " Arab." The main planes show the principal departure from standard Bristol practice in that the lower plane is of smaller chord than the upper one so as to improve the pilot's range of vision downwards. One set of three struts, in the form of an N, are fitted on either side of the fuselage and are inclined outwards from the base. Ailerons arc fitted to the upper plane only. The tail plane and undercarriage are of normal type. Armament consists of two fixed Vickers guns fitted on top of the fuselage and firing through the propeller with the usual form of fire-control gear. The machine shows a speed of 128 m.p.h. at 10,000 feet, to which height it climbs in 8 1/2 minutes.
   A later edition with a "Cosmos" engine of 315 h.p. has given a much better performance.
  
  
  
Specification.
Type of machine Single-seater Biplane.
Name or type No. of machine Scout F.
Purpose for which intended Fighting and Reconnaissance.
Span Top 29 ft. 6 In.,
   bottom 26 ft. 2 In.
Gap 5 ft. 1 In.
Overall length 80 ft. 10 In.
Maximum height 8 ft. 4 in.
Chord Top 5 ft. 7 in.,
   bottom 4 ft. 11 In.
Total surface of wings 260 sq. ft.
Area of ailerons 30 sq. ft
Total area of tail 15 sq. ft.
Span of tail 10 ft 6 In.
Area of elevators 14.5 sq. ft.
Area of rudder 5 sq. ft
Area of fin 4.1 sq. ft
Engine type and h.p. 200 h.p. Sunbeam "Arab"
Airscrew, diam., pitch and revs. 9 ft 2 ins., 9 ft., 1,155 r.p.m.
Weight of machine empty 1,300 lbs.
Load per sq. ft. 8.08 sq. ft
Weight per h.p. 10 lbs.
Petrol tank capacity in gallons 32 gallons.
Oil tank capacity in gallons 5 gallons.
Performance.
   Speed low down 138 m.p h.
   Speed at 5,000 feet 135 m.p.h.
   Speed at 10,000 feet 128 m.p.h.
   Landing speed 49 m.p.h.
   Climb.
   To 5.000 feet 3.7 minutes.
   To 10,000 feet 8.5 minutes.
   To 15,000 feet 16 minutes
Disposable load apart from fuel 450 lbs.
Total weight of machine loaded 2,100 lbs.

C.Owers British Aircraft of WWI. Vol.7: Experimental Fighters Part 3 (A Centennial Perspective on Great War Airplanes 81)

The Bristol Scout F & F.1

  In April 1917 the RFC Technical Department recorded: Approved and put forward for manufacture.
  The 200 h.p. Engine from Engine Patents Ltd., for which the British and Colonial Aircraft Co. are designing a single seater fighter (for six of which machines they have an experimental order) is not likely to come forward for a few months. The matter was discussed with Captain Barnwell on Friday and will be considered by the Technical Department Committee on the 26th instant. It would seem desirable that the firm should complete the design on which they have started, but for the purpose of utilising the geared Hispano Engine (Pousse type), as this engine is one of few types which should be available in quantities by the end of the year and it is therefore important that machines should be designed to make the best use of its power.
  The aircraft being discussed can only be the Bristol Scout E. This was a single-seat scout designed by Frank Barnwell for the new 200-hp water-cooled radial engine, the Cruciform, designed by Harry R Ricardo and Frank B Halford. In 1915 Harry Ricardo set up the Engine Patents Co that developed the engine that powered the first successful British tank, the Mk.V. In 1917 Ricardo joined the new engine research facility at the Department of Military Aeronautics. The proposed Scout E would have had the engine mounted behind a circular radiator. In the event the engine was not completed and Barnwell abandoned the design.
  In June 1917 Barnwell began work on another single-seat scout intended to take the 200-hp Hispano-Suiza engine but this was changed to the new Sunbeam Arab engine, most probably due to the Hispano-Suizas being in high demand for the S.E.5a then in mass production. Newly constructed S.E.5a fighters were going into storage as there were not enough engines to power them. The Arab had the same output as the Hispano-Suiza and was also a V-eight and so was thought to be a good alternative. Contract No.A.S.3423 was placed for six machines - B3989 - B3994. An early report stated that machine had been inspected at the works and detail of construction found satisfactory.
  The Scout F emerged as a very clean biplane that would not have looked out of place on a 1920’s aerodrome, mainly due Barnwell’s decision to install an underslung radiator between the undercarriage legs that, with the nose spinner, gave the machine a streamline appearance. In a period where most liquid-cooled aero-engines had the radiator mounted immediately behind the airscrew, Barnwell’s innovation was a revolutionary break from contemporary practice enabling him to give a clean aerodynamic entry to the machine.
  A report in connection with the installation of a Sunbeam ‘Arab' in a Scout F Machine noted that the installation of this engine is now complete and the machine has been delivered to the Acceptance Park at Patchway. However, the cowling was criticised. It was constructed in three parts and fastened together by means of bolts and butterfly nuts. The camshaft housings are not cowled in. No doors have been provided in the cowling for quickly getting to the magnetos and the carburetter; both these were asked for when the installation was being discussed with the representatives of the firm. In order to get at the magnetos it is now necessary to remove one of the sections of the cowling.
  The wing bracing was characterised by a centre section and N interplane struts. The wings were of unequal span and chord. Oliver Stewart recorded that the wide gap together with the pointed nose gave the pilot an excellent outlook. The upper wing was in three pieces and both wings were installed without dihedral. Ailerons were fitted to the upper wing only. The interplane and centre-section struts were of N shape. Structurally the machine was a conventional wood and wire-braced girder structure aft with the front portion of the fuselage a ply covered box girder. Unfortunately, the twin Vickers guns were mounted externally on top of the fuselage spoiling the clean aerodynamic lines of the Scout F. Given the limited size of the fuselage there was probably no other option open to Barnwell than to position the guns here. A ring and bead sight was fitted.
  A visit to the British and Colonial Aeroplane factory on 17 September 1917, resulted in the following report on the single-seater scout 200 H.P. Arab Sunbeam.
  The machine is very similar in form to the S.E.5, the fuselage being about the same width, but rather shorter.
  The planes are arranged in the same position, the trailing edge of the upper plane being a foot above the pilot’s head, with the centre section cut away. The trailing edge of the lower plane is in a line with the pilot’s body.
  There is a forward stager and a dihedral on the planes, which are rigged with one bay of struts, the struts leaning slightly outwards towards the top.
  The tail plane is of steel tubular construction, strengthened with wooden ribs; it is adjustable, but not from the pilot’s seat.
  The rudder and fin are of the same shape and construction as those on the B and C Monoplane.
  The undercarriage is of the usual V type.
  The armament consists of two Vickers Guns firing through the propeller, arranged to that they feed from the centre of the machine. A Lewis gun can be fitted to the top plane as in the S.E.5.
  The visibility from this machine is very good to the rear and above. The field of view forward and upwards is hindered by the top plane.
  The fuselage and wings have so far not been covered. No instruments or engine controls are yet fitted, as the engine has not arrived.
  The rudder bar on this machine is of the same pattern as that fitted on the B & C Monoplane, and is of an unsuitable type for a machine of this kind, as it has no definite stops to prevent the pilot’s foot moving along or slipping off the end of the bar. This bar should be redesigned with the usual stops and foot straps.
  A report in December 1917, noted that the firm had been visited and the first machine has been inspected. Repairs to engine bearers have been inspected, and a new oil tank to give gravity feed is being fitted. Machine will then be sent to Martlesham.
  The following reports of the Controller, Technical Department, chart the construction progress of the machine. The Scout F was listed under the heading of ‘Experimental Machines Embodying Features of General Benefit to Aeronautics.’

  F/E 23.01.18. Bristol Type F. 200 hp Sunbeam. Contract for 6 machines. 1st machine should have flown to Martlesham on 22.01.18 for tests. Oil tanks giving gravity feed has been fitted.
  F/E 06.03.18.
   1st machine. Undergoing tests at Martlesham.
   2nd machine. Undergoing maker’s trials.
   3rd machine. Being prepared to take Brazil Streaker experimental engine for flying tests of the engine.
  F/E 20.03.18.
   1st machine. Undergoing tests at Martlesham.
   2nd machine. Now ready for despatch from makers.
   3rd machine. Being prepared to take experimental Brazil Straker engine for flying tests of engine.
  F/E 03.04.18.
   1st machine. Tests at Martlesham complete.
   2nd machine. Delivered to R.A.F. for trials.
   3rd machine. Ready for installation of Brazil Straker engine.
  F/E 01.05.18.
   2nd machine. Undergoing trials at R.A.E.
   3rd machine. Ready for installation of Brazil Straker engine.

  B3989 with Arab engine was the first to be subject to testing and the Aeroplane Data Book recorded that the machine had the following “Peculiarities of Design”: -
  On this machine the interplane struts are built up of three strips of spruce glued together, the grain running from end to end of the strut in each piece. At each end of the strut for a length of about nine inches the centre spruce strip is replaced by three-ply ash. A cross strut takes the place of more usual stagger wired, the three struts being secured at junction points where the two sides of the fittings are riveted through the strut; ash bushes are inserted to take the riveting compression. The whole length of the strut is wrapped with glued fabric. The universal fork joints of the main lift and anti-lift wires are located inside the planes to diminish head resistance. Twin spars are fitted in the top planes which are deeply spindled out. On the inner faces small distance pieces are fitted between spars at each rib, and more substantial pieces at each compression rib and at the inner end of wing. At the joint between the centre section and the top planes the spars are reinforced by steel fittings drilled to take fixing bolts. The radiator is fitted underneath the fuselage, just forward of the pilot’s seat, and there is a small reservoir above the engine.
  The Aeroplane Experimental Station reported in March 1918 that preliminary trials with a fast revving propeller had been carried out and show that with a similar load to an S.E.5 (with “Viper” engine) the Bristol Scout does 125 miles an hour at 15,000 feet and reaches that height in 13.7 minutes. This beats the S.E.5 by 5 miles an hour and 7 minutes. It should be noted that the difference in performance must be largely due to the difference in engine revolutions (about 240), and may be slightly effected by the fact that the S.E.5 was tested with a Lewis Gun mounted on the top plane, while in the Bristol Scout the Lewis Gun was merely tied to the fuselage.
  As noted above the Scout F could have a Lewis Gun mounted in the same fashion as the S.E.5a and this test may have been to determine its performance with a full armament of three machine guns. With the two Vickers machine guns it would have given approximately the same load as that of the S.E.5a.
  Test results of the Scout F compared with the S.E.5a and Sopwith Snipe are given in the table:
  Report M.185A looked at the effect of the spinner on the performance of the Scout. B3990 was the subject aircraft for the trial. The trials were carried out with the spinner fitted, then without the spinner for two trials, and again with the spinner. The results were tabulated as above:
  The load carried was:
   Pilot 180 lbs
   2 Vickers and 1 Lewis guns 86 lbs
   Deadweight 10 lbs
276 lbs
  Airscrew details were:
   Type: D.R.P. 3041
   Weight of spinner 8 lbs
   Diameter of spinner at base 21 5/8 in.
   Depth of spinner from geometrical apex of cone to base 14 1/4 in.

  It was found that the performance was improved by the use of the spinner by 100 feet per minute in rate of climb (1 1/2 minutes less in time to 15,000 feet) and by 4 m.p.h. in speed at 15,000 feet.
  B3990 went to Martlesham Heath on 30 January 1918, but official trials were delayed by engine troubles and had to await the arrival of a new engine from the Sunbeam Company. The tests at Martlesham Heath had included the comparative tests with and without the spinner as noted above. The Cosmos Engineering Co Ltd advertisements proudly acclaimed A Bristol Scout fitted with a 'Mercury’ engine climbed 10,000 feet in 5 mins. 25 secs., & 20,000 feet in 16 mins. 15 secs., speed at 10,000 feet 143 M.P.H. Official corrected barographfigures. This constituting two British records. B3990 was still at the RAE Farnborough in July 1919. By then the engine bearers had to be reinforced with mild-steel channel strips as they were in a bad condition
  Oliver Stewart found that the little Bristol F was a pleasure to fly and could be made to do ordinary aerobatics. Its Arab engine, designed by Coatalen the car engine designer, was smooth running through most of its range, but had periods when it vibrated violently. There was a crankshaft and airscrew resonance which more than once caused Arab-engined aircraft to shed their propellers while in flight. A Stewart recorded that the control qualities of the machine were between those of the Sopwith Camel and the S.E.5a. The elevator was not so sensitive as that of the Camel, but it was probably more powerful than that of the S.E.5. And in general, the aeroplane felt handier than the S.E.5, but less handy than the Camel.
  Capt Reginald M Charley had served with No.54 Squadron in France before he was sent to Orfordness as a test pilot. On arrival he found his friend Capt Oliver Stewart who had also just arrived the previous evening. The two were to fly the many various machines that came through the experimental centre. Charley made pertinent comments on the aircraft he flew in his log book. He not only recorded serial numbers but engines fitted and the time of the flight. He flew the usual Camel, S.E.5a and Dolphin types as well as experimental types such as the Sopwith Bulldog and Vickers Vampire, all recorded with his impressions. After his first flight in B3990 on 7 April 1918, Charley was enamoured with the little Bristol Scout. In a later letter he wrote that he had flown the most wonderful scout in the world: it flew at 140 mph and Climbed to 10000 ft in seven minutes or under. Charley’s logbook entries covering the Bristol B3990 are listed below: -
  7.04.18. Time 2.45 PM. 50 min, 14,000 ft. [P]erfectly super wonderful machine; colossal performance: lovely clouds.
  3.05.18. Time 9.35 AM. 90 min, 22,000 ft. [H]eight record to date; felt very dizzy; fought B.F at 18,000ft. fine machine.
  15.05.18. Time 9.15 AM. 25 min, 10,000 ft. [T]hrough several layers of cloud; engine not running very well.
  15.05.18. Time 9.15 AM. 20 min, 6,000 ft. [W]ith new radiator shutter & seat: more comfortable to fly but engine bad.
  30.05.18.Time 10.15 AM. 35 min, 15,000 ft. [M]achine is really fine engine now O.K. & machine wonderful 10000 ft. in 8 1/2 mins. 112 m.p.h. at ground.
  31.05.18. Time 10.0 AM. 40 min, 10,000 ft. [E]ngine gets rather hot in hot weather; radiator shutter does not keep it warm.
  4.06.18.Time 3.10 PM. 40 min, 10,000 ft. [G]ets hot if climbed too steeply; air press, went dud; machine otherwise O.K.
  6.06.18. Time 10.15 AM. 60 min, 20,000 ft. 20,000ft. in 20 mins, engine gets very cold coming down. 145 m.p.h. near ground.
  10.06.18. Time 9.20 AM. 50 min, 10,000 ft. [O]il pressure varied a great deal but engine kept very cool.
  13.06.18 Time 18.10 AM. 55 min, 10,000 ft. O.S. on Camel & I fought A.E.3. I went up through a lot of cloud.
  13.06.18.Time 3.55 PM. 35 min, 8,000 ft. O.S., Duncan & I fought A.E.3 & it had not got a hope; very bumpy.
  14.06.18. Time 10.00 AM. 55 min, 10,000 ft. [T]hrough 4000 ft. of solid cloud; made a hoppy landing.
  17.06.18. Time 11.40 AM. 20 min, 11,000 ft. [B]oth guns gave stoppages I could not correct.
  26.06.18. Time 3.15 PM 5 min, 1200 ft. [T]o show General how it climbed, but engine conked & I had to land.
  26.06.18.Time 3.40 PM. 25 min; 10,000 ft. [P]ut machine to full test & it went well; went through clouds.
  26.09.18. Time 10.00 AM. 30 min, 12,000 ft. [E]ngine going very well & machine very nice to fly pitot dud but made good landing.
  27.09.18.Time 2.40 PM. 50 min, 10,000 ft. [F]ive machines to attack a Flying Boat which did not turn up. [W]e fought an Aldebungh (illegible) engine.
  9.12.18. Time 20 min, 2000 ft. [B]est flight I had for a long time; doing 140 m.p.h. zoomed up almost vertical.
  23.01.19. Time 40 min, 2,500 ft. [A]wful job to get it started; engine was not so good, one mag cut out altogether
  06.02.19. Time 15 min, 2,000 ft. Rev. Howard was over. I flew down over Crag Farm & Renie & Mrs Madeles saw me.
  25.02.19. Time 50 min, 4,000 ft. MacKerrow was in F.E. and took pictures of me in many positions with aerial camera; fine results.
  10.05.19. Time 15 min, 1,000 ft. [T]est flight before it was sent to Farnborough; lovely machine, going fine.

  On the occasion he flew B3990 to 22,000 feet indicated, it is not surprising he felt the effects of the lack of oxygen. On 25 May he took B3990 up again for another test. The machine had new radiator shutters fitted and a more comfortable pilot’s seat, but the engine’s performance had not improved. On 30th the Arab was running well and he had a good flight in the machine. The next day he found that the Scout F’s engine tended to overheat below 10,000 feet, the radiator shutters having failed to maintain the required temperature. Charley wrote that he and Stewart would engage in using other aircraft that entered their realm as target practice and he records the Scout F was flown against the Bristol Fighter and the luckless R.A.F. A.E.3. Stewart and Charley would ‘scrap’, one flying a Camel, the other the Scout F. Although he enjoyed the trouble-free Rolls-Royce engine of the Martinsyde F.3, he still stated his preference for the Scout F. On 26 June Charley was to demonstrate the Scout F before visiting dignitaries. The Arab engine cut out shortly after take-off and Charley had to land again. The trouble was quickly rectified and he was able to demonstrate the type’s performance when the Arab was behaving as it should.
  The 14-cylinder twin-row Mercury radial from the Brazil, Straker Co, that was coming together under the eye of Roy Fedden, was the engine mentioned in the above Controller’s reports. The engine had been ready for some time for bench testing but this had been held up while the company was reorganised and refinanced as the Cosmos Engineering Co Ltd. A Mercury was finally installed in the third machine, B3991. With this engine the designation was changed to Scout F.1. The fourth airframe was used for structural testing at Farnborough, the results being published in November 1918. Only the first three machines were flown. As mentioned above the Mercury engine was being thought of as a suitable engine for the Scout in March 1918 but the long development period and the changes in the company led to its first test flight in the Scout F.1 being made on 6 September 1918.
  In order to streamline the radial engine a circular cowling through which the fourteen-cylinder heads protruded was installed. Although the performance was improved considerably the handling qualities were adversely affected. Capt Cyril F Uwins was well known to the Company, due to his ferrying Bristol Fighters to France. At the Company’s request he was seconded to the Company as a test pilot, and carried out the second flight on the Mercury powered scout, his first prototype for the British and Colonial Aeroplane Co on 26 October 1918, the day after he joined the Company. The following performance achieved at Farnborough was, for its time, remarkable:
  Climb to
   10,000 ft - 5 min 25
   20,000 ft - 16 min 15
  Speed at 10,000 ft - 143 mph.

  Notwithstanding these results, the F.1 was too late.The Cosmos Company had decided to concentrate on their nine-cylinder Jupiter radial engine and the Mercury was shelved. The Mercury would have needed more time as it only delivered its rated horse-power for short periods and would not have passed the official testing regime. It only ever flew in the Scout F.1. Soon after the Armistice the Air Ministry cancelled the order for the 200 Mercury engines, but testing continued into 1919.
  Writing in 1968, Eugene R McDonald stated that when he arrived at the Armament Experimental Station (Grahame White’s old aerodrome) he was, intrigued to find a machine I did not know, it appears to be smaller than an SE5, had a deep body and a large boss on the prop.
  This was the Bristol Arab, powered by the Sunbeam Arab engine. I was delighted with the performance and found it faster than any SE5 I had ever flown. (This was not an official flight or test). I have no proof of the following statement. I merely understood that the Sunbeam Arab engine had been produced in 1917, and was intended for the Bristol two-seater. It was found that the performance of the 2 seater fighter with the new engine was no better than that given by the existing engine above 16,000 feet, and the engine was discarded. I don’t know who put the Sunbeam Arab Engine in the single seater I flew, but I think it would have been an asset in 1918, had we been able to use it?
  The Scout F had excellent handling qualities and was superior to the S.E.5a in some areas. Keith Knox Muspratt had the opportunity to fly the new Bristol Scout in February 1918, the nicest thing I have ever flown. It was remembered as a great machine let down by its Sunbeam Arab engine. Oliver Stewart summed it up best: - The Bristol F was a machine of quality, and although it never came into general use... those who flew it will remember it with interest, and a certain amount of admiration. It was not a prodigy, but it was a pleasant aeroplane with many good qualities.


Bristol Scout (S.E.5 load) "Viper" S.E.5 Bristol Scout (Snipe Load) Snipe
Load lbs Load lbs Load lbs Load lbs
   Pilot 180 Pilot 180 Pilot 180 Pilot 180
   2 V & 1 L guns 86 1 V & 1 L gun 51 2 V & 1 L guns 86 2 V & 1 L guns 86
   Deadweight 10 Deadweight 55 Deadweight 233 Deadweight 263
   - - - - Petrol 34 gls 245 Petrol 26 gls & Oil 6 gls 245
   Oil 3 gls 30
   Total Load 774 Total Load 774
   Total Weight of machine 1987 Total Weight of machine 1985 Total Weight of machine 2210 Total Weight of
Machine 1992
Height Time RofC RPM Time RofC RPM Time RofC RPM Time RofC RPM
5,000 3.3 1325 2010 4.5 960 1785 3.9 1110 2020 3.6 1165 1220
10,000 7.7 1000 2010 10.8 665 1780 9.25 795 2015 8.75 760 1195
15,000 13.7 665 2000 20.75 370 1770 17.25 475 1995 17.6 400 1160
19,000 - - - - - - 29.2 220 1980 34.4 130 1105
Service ceiling 23,500 ft Service Ceiling 19,500 ft Service ceiling 21,000 ft Service Ceiling 19,000 ft
Height Speed in mph RPM Speed in mph RPM Speed in mph RPM Speed in mph RPM
10.000 - - - - 128 1/2 mph 2265 124 mph 1330
15,000 125 mph 2225 120 mph 1880 117 1/2 mph 2150 113 1/2 mph 1255
Propeller D.R.P.3041 This load is equivalent to the S.E.5 load on the assumption that the Bristol Scout would carry only one Vickers gun & the same amount of petrol as the S.E.5 Propeller A.B.662 P.1800 D.2400 Propeller D.R.P.3041 P.2750 D.2800 Propeller L/4040 P.2490 D.2780


Bristol Scout F Climb Trials
With Spinner Without Spinner
Height Time RofC RPM ASI Time RofC RPM ASI
5,000 3.3 1325 2020 73 3.6 1220 2000 73
12,000 7.7 1000 2010 71 8.4 895 1990 71
15,000 13.7 665 2000 68 15.4 570 1975 67
Speed
Height Speed RPM Speed RPM
15000 125 2225 121 2180
Report M.185A looked at the effect of the spinner on the performance of the Scout. B3990 was the subject aircraft for the trial. The trials were carried out with the spinner fitted, then without the spinner for two trials, and again with the spinner. The results were tabulated as above.


Bristol Scout F & F.1 Specifications
Source 1.F 2.F 3.F 4.F 6.F 5.F.1 4. F.1
Span top 29 ft 6 in 29 ft 7 1/2 in - 29 ft 7 1/2 in 29 ft 6 in 29 ft 7% in
Span Bottom 26 ft 2 in 26 ft 2 in - 26 ft 2 in 26 ft 2 in 26 ft 2 in
Chord top 5 ft 7 in 5 ft 7 in - 5 ft 7 in 5 ft 7 in 5 ft 7 in
Chord Bottom 4 ft 11 in 4 ft 11 in - 4 ft 11 in 4 ft 11 in 4 ft 11 in
Length 20 ft 10 in - - 20 ft 10 in 20 ft 10 in - 20 ft
Height - - - 8 ft 4 in 8 ft 4 in - 8 ft 4 in
Incidence 1° - - 1° - - 1°
Incidence top - Nil - 0° - - 0°
  “ bottom - 1° 1’ - - - - -
Dihedral - Nil - - - - -
Gap 5 ft 1 in 4 ft 9 1/4 in - - 5 ft 1 in - -
Stagger 2 ft 1 in 2 ft 0 in - - - - -
Tailplane span - 10 ft 4 1/4 in - 10 ft 6 in 10 ft 6 in - 10 ft 6 in
Airscrew dia. - - - 9 ft 2 in 9 ft 2 in - 9 ft 2 in
Wings top 150 - - 150 - - 150
Bottom 110 - - 110 - - 110
Total 260 259 - 260 260 - 260
Ailerons 30.5 16.6 - 30.5 30 - 30.5
Tailplane 15 14 - 15 15 - 15
Elevators 14.5 14.5 - 14.5 14.5 - 14.5
Fin 4.1 3.5 - 4.1 4.1 - 4.1
Rudder 5.3 - - 5.3 5 - 5.3
Empty - - 1,436 1,436 1,300 1,365 -
Fuel & Oil - - 275 275 - 213 -
Military load 270 - 96 319 - 42 -
Crew - - 180 180 - 180 -
Loaded 2,100 - 1,987 2,210 2,100 1,800 2,260
Fuel total 32 - - - 32 - -
main tank - 29 1/2 - 29 1/2 - - -
service tank - 3 - 3 - - -
Oil 5 - - 5 5 - -
Water header tank - 1 1/2 - 1 1/2 - -
Ground level 138 - - 138 138 - 145
at 5,000 ft - - - 135 135 - -
at 6,500 ft - - - - - 143 -
at 10,000 ft 128 - - 128.5 128 136 -
at 15,000 ft - - 125 117.5 - - -
Landing 49 - - - 49 - -
5,000 ft - - - - 3.7 min - -
6,500 ft - - 4.5 min 5 min 20 - - -
10,000 ft 8.5 min - 7.7 min 9 min 20 8.5 min 5.5 5 min 25
15,000 ft 16.0 min - 13.7 min 17 min 20 16 min 9.9 -
20,000 ft - - - - - - 16 min 15
Max Height reached in ft - - - - - 23,760 -
Ceiling in ft - - 23,500 - - - -
Engine Sunbeam Arab 200 Sunbeam Arab Arab Sunbeam 215 BHP 200 h.p. Sunbeam Arab II 200-hp Sunbeam Arab Mercury 347-hp Cosmos Mercury
Source:
  1. “Milestones - The Bristol Machines,” Flight, 23.01.1919. P.100.
  2. Aeroplane Data Book - B3989.
  3. Chart: “Performances of British Aeroplanes March-April-May 1918,” issued by Technical Dept A.P Data from report M.185 of March 1918. Copy in TNA AIR1/708/27/11/03.
  4. J.M. Bruce data.
  5. Chart: “Notable Performances of British Aeroplanes - Single-seat Machines.” Tested at Farnborough in March 1919. Copy in RAF Museum, J.M. Bruce Collection Box 26.
  6. Janes Al the World’s Aircraft 1919.

Журнал Flight

Flight, January 23, 1919.

"MILESTONES"

The Bristol Scout, Type F

The development of the type D scout takes the form of a single-seater tractor, designed for a much more powerful engine than was the type D. In connection with the type F it should be pointed out that whereas the general arrangement drawings and the particulars in the two tables refer to a machine fitted with a 200 h.p. Sunbeam "Arab" engine, the photograph shows a slightly different arrangement, in which the nose of the machine is of different shape, owing to the fact that the engine is a radial air cooled, the Cosmos Mercury engine. In addition to the fact that it is fitted with a different engine, the type F Bristol scout shows variations in nearly all its other component parts, having, in fact, practically no resemblance to the original Bristol scout. Thus it will be seen that the type F has its lower plane of smaller chord and span than the top plane. The wing tips also are of different shape, while the various tail members are totally different in shape. Owing to the deeper nose and generally speaking greater side area in front, a fixed vertical fin is fitted in front of the rudder. The wing bracing is characterised by centre section and inter-plane struts of N formation, and the dihedral angle has disappeared. An examination of the accompanying table of performance, etc., is instructive. It will be seen that while the type D had a wing loading of 6.25 lbs/sq. ft. and a loading of 14.7 lbs. /h.p., the corresponding figures for the type F are 8.08 and 10 respectively. The speed near the ground is 100 m.p.h. and 138 m.p.h. respectively, while the climb to 10,000 ft. occupies 18.5 mins. in the case of type D, and only 8.5 mins. for the type F. It is thus seen that it would appear that "performance" is far more a question of load per h.p. than it is one of wing loading, and that it is in fact only the question of a reasonably low landing speed which prevents one from employing a much higher wing loading than is generally found.