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
Sequence Nos.: 2845-2848
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.
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).
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.
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.
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.
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.
Flight, January 23, 1919.
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.