H.King Sopwith Aircraft 1912-1920 (Putnam)
Its close relationship to the Hippo notwithstanding, the Bulldog - especially in its very compact single-bay form was a fighter (or fighter-reconnaissance machine) of great individuality, the reconnaissance function implicit in the 'R' after the ‘F' having been envisaged in a possibly earlier, though more or less contemporary, design. This design was likewise Hippo-related, but was Hispano-Suiza powered, and was called Sopwith FR.2; it had two-bay wings with positive stagger and a slightly greater span than the Hippo, the measurement being 40 ft 3 in (12.2 m). Thus it would have been amenable to high-altitude operation with the camera and wireless that were specified for it, especially so as armament was to be lighter than that of the Bulldog in the form wherein this type materialised, the pilot having only one Vickers gun instead of two as actually fitted. A point of special interest is that, as in the earlier Armstrong Whitworth F.K.3 reconnaissance aircraft, the pilot (seated near the top-wing trailing edge) shared the same cockpit as the observer; and hardly less noteworthy is the fact that during the period 1917/18 new Sopwith two-seaters were built both with pillar-mounted rear armament (as on the F.K.3) and with the Scarff ring-mounting (as on the F.K.8).
In the form wherein it materialised, the Bulldog was designed during August/September 1917 - confusingly then called Buffalo, and allotted the construction-licence number 14, for like the Hippo, which had Licence No.16, it was a private venture.
The most striking point about this new two-seat fighter (for as a fighter it was primarily regarded, reconnaissance and contact patrol being subsidiary roles) was that it looked for all the world like a variant of the original Snipe, in particular by reason of its single-bay wings, but also in having twin Vickers guns. Certainly, with its span of only 26 ft 6 in (8 m) and length of 23 ft (7 m) it was about the most compact machine that could have borne its four-gun armament; yet even so, its vertical tail surfaces proclaimed descent (however indirect) from its pioneer forebear in the two-seat fighter field, the 1 1/2 Strutter - which, though considerably larger, had mounted only half the weight of armament.
That the stubby little wings were, in fact, too small to be true detracts but little from this first appraisal; and their inadequate surface may, in any case, be partly attributed to leading-edge and trailing-edge centre-section cut-outs (somewhat as in the Hippo) and even more so to the large gap between the spars through which the pilot's head protruded. The depth of the fuselage in this area was accentuated by a 'hump' fairing for the breech casings of the two synchronised Vickers guns; and thus the installation accorded closely with that of the Snipe. For each of the two guns there was a 600-round belt, and - so near the pilot's face were the ends of the breech casings that these were stoutly padded. Separate case and link chutes were let in to the cowling flanks and the windscreen was perforated for an Aldis sight. The apparent absence of trigger motors on the guns is not necessarily indicative of an intention to fit Sopwith-Kauper gear, or some other mechanical or electrical type, as standard; for had the Bulldog been produced in quantity, as was the Snipe, the C.C. hydraulic gear would doubtless have been specified. The matter may in any case have been an academic one, depending on the gun-timing provisions made, or allowed for, on the new Clerget 11Eb engine a powerplant unfamiliar in Britain and one that only the Hippo had in common.
Of greater interest was the gunner's armament, comprising two Lewis guns, one on a pillar mounting at each end of the elongated, forwardly-tapering cockpit. Having quoted from one's own writings in regard to the Hippo's armament, one now accords like treatment to the Bulldog. Thus:
'To extend the field of fire in the forward upper hemisphere, the front pillar was extensible, and, as it was projected upwards, it raised, by means of a connecting tube, a rectangular screen hinged to the rear spar of the upper centre-section. Jointly with a small windscreen, this afforded the gunner a measure of protection. The rear pillar could be traversed from side to side. Possibly in the interests of gun handling, the ammunition drums were of single (47-round) type. In the original armament scheme, which did not materialise, two Lewis guns were to be mounted between the cockpits, capable of firing, like the single gun actually fitted, above the airscrew. An attachment noted on the forward Lewis gun may indicate an intention that this gun could be fired also by the pilot, but this is conjectural.'
The Bulldog's heavy armament, it must be re-emphasised, was distributed over a very large portion of the original tiny single-bay version of the aircraft, and may well have accounted for heaviness both in weight and in control-forces that were clearly manifest by the end of 1917 air-testing having started in November of that year.
It is known that a new set of wings had been fitted as early as 13 November, 1917, but though these were of greater span and area and of two-bay rig, they were not of definitive form - incorporating, for instance, horn-balanced ailerons and probably having been intended as an alternative installation from an early stage. Strength was evidently to be compatible with the greater span, for, although the outer bays were braced by streamline-section 'Rafwires', the inner bays were sustained by stout wire cables. As tested on the Bulldog at Martlesham Heath during May 1918, however, the two-bay wings had no horn balances; nor was this the sole distinction, for the number X3 was now painted on the fuselage, as shown on photo.
At the time of the Martlesham Heath tests Bulldog X3 still had its two pillar-mounted Lewis guns, though a Scarff ring-mounting with a twin-gun attachment (or 'carrier' as the lining was called) was in prospect for a second specimen of the aircraft then in the Sopwith works. Another intended installation was that of an A.B.C. Dragonfly radial engine, of higher power than the Clerget 'Type 11 No. 3' to which a much-overgenerous output of 260 hp was credited for the official tests just mentioned.
As a potential replacement for the Bristol Fighter, and as such competitive with the Avro 530, the Bulldog was unleashed in mock combats against a 'Brisfit' and was found to be just about as manoeuvrable. Clearly, however, any worthwhile improvement in speed and climb must await the fitting of the Dragonfly, and a Clyno-built example of that engine was duly installed in Bulldog X4, the new combination being ready for testing in the second half of June 1918. By this time production of the Bulldog as a fighter was no longer contemplated, and X4 - or the Bulldog II as it was otherwise styled, to distinguish it from the Clerget-engined X3 Bulldog I was manifestly a flying test-bed. Not only was all armament deleted, but the coaming for the rear cockpit was carried high to make the occupant snug if not safe - for the Dragonfly-Bulldog was deplorably unreliable. Even so, this aircraft was flying at the Royal Aircraft Establishment, Farnborough (after undergoing various powerplant 'fixes' and at least one complete engine-change) as late as March 1919, having first arrived there on 25 June, 1918.
Although a third Bulldog had once been in prospect, work on this had long been stopped.
Bulldog I (200 hp Clerget 11Eb)
Span 33 ft 9 in (10.23 m): length 23 ft (7 m); wing area 335 sq ft (31 sq m). Empty weight 1.441 lb (653 kg); maximum weight 2,495 lb (1.132 kg). Maximum speed at 10.000 ft (3.050 m) 109 mph (175 km/h); maximum speed at 13,000 ft (3,960 m) 101.5 mph (163 km/h); climb to 5.000 ft (1.525 m) 6 min 5 sec: climb to 10.000 ft (3,050 m) 15 min 35 sec; climb to 15.000 ft (4.570 m) 38 min 55 sec; service ceiling 15,000 ft (4,570 m); endurance 2 hr.
N.B. All performance data for the Bulldog II Dragonfly test-bed would obviously vary greatly according to engine state, but the much-improved climb is implicit in the recorded time to 15,000 ft (4,570 m) of only 16 min 28 sec.
H.King Armament of British Aircraft (Putnam)
Bulldog. Designed as a high-performance fighter-reconnaissance aircraft, this two-seater of 1918 had an unusual and heavy armament. For the pilot there were two synchronised Vickers guns, with 600 rounds each, mounted Snipe-fashion, with their padded breech casings all but touching the pilot's face. The windscreen was perforated for an Aldis sight, and there were separate case and link chutes in the cowling flanks. For the gunner there were two Lewis guns, one on a pillar mounting at each end of the elongated cockpit. To extend the field of fire in the forward upper hemisphere, the front pillar was extensible, and, as it was projected upwards, it raised, by means of a connecting tube, a rectangular screen hinged to the rear spar of the upper centre-section. Jointly with a small windscreen, this afforded the gunner a measure of protection. The rear pillar could be traversed from side to side. Possibly in the interests of gun handling, the ammunition drums were of single (47-round) type. In the original armament scheme, which did not materialise, two Lewis guns were to be mounted between the cockpits, capable of firing, like the single gun actually fitted, above the airscrew. The second (two-bay) version of the first Bulldog was armed as the first, but the second machine (Dragonfly engine) was unarmed, although a Scarff ring-mounting had been intended for it.
An attachment noted on the forward Lewis gun may indicate an intention that this gun could be fired also by the pilot, but this is conjectural.
P.Lewis The British Fighter since 1912 (Putnam)
The prolific Sopwith design office’s output was increased by yet another machine which appeared in 1918 - the 2FR.2 Bulldog two-seat biplane. Intended for fighter reconnaissance, low-set on its landing-gear and heavy-jowled, the weightily-armed Bulldog was aptly named. The first prototype had single-bay wings and the 200 h.p. Clerget 11 E.B. rotary for power. Twin Vickers guns were provided in front of the pilot, while the aft cockpit was fitted with two Lewis guns, one firing forwards and the other to the rear.
A second prototype was built with two-bay wings of larger size and initially had horn-balanced ailerons which were later replaced by revised wings with plain ailerons.
Following the Bulldog Mk.I with its Clerget engine came another version, the Mk.II with the ill-starred 360 h.p. A.B.C. Dragonfly Ia radial for its power plant, but neither type of Bulldog was developed further.
F.Mason The British Fighter since 1912 (Putnam)
Sopwith 2FR.2 Bulldog
Design of the Sopwith FR.2 started in August 1917, soon after the licensing regulations came into effect, and the Sopwith company was issued with Licence No 2 to build four prototypes, X2- X5. The aircraft was intended as an ultimate replacement for the Bristol F.2B Fighter and, as the designation implied, was to be a reconnaissance fighter. As originally designed, the private venture two-seat FR.2 was to be powered by the 200hp Hispano-Suiza but, as the delivery of these engines fell further and further behind schedule, Herbert Smith changed the design to take the eleven-cylinder 200hp Clerget rotary, and this was re-termed the 2FR.2 Bulldog Mk I.
The first prototype, assumed to be X2 (though the aircraft may not have carried the number), appeared early in 1918 with single-bay wings. The pilot’s cockpit was located squarely beneath the upper wing centre section which featured a large central aperture through which the pilot’s head protruded; immediately forward of this cockpit, in a prominent hump, were mounted the twin Vickers guns with most of their barrel length exposed. The observer/gunner’s large cockpit was situated below and aft of the upper wing’s trailing edge and was provided with a pair of Lewis guns, the forward weapon on a telescopic mounting, the other gun in the rear of the cockpit on a swinging pillar to protect the aircraft’s tail. The upper and lower wings were fitted with plain ailerons, and the fin and rudder were similar to those fitted on the modified Sopwith Dolphin.
The single-bay wings were quickly found to be much too small, and a second aircraft (later marked X3) was quickly produced with much enlarged two-bay wings, being initially fitted with horn-balanced ailerons. In due course these were changed to plain ailerons, and in this form X3 underwent official trials in May 1918. However, its performance was generally disappointing, even though the aircraft was applauded on several counts, not least the crew members’ field of view. With a top speed of only 109 mph at 10,000 feet and a service ceiling of no more than 15,000 feet, the Bulldog fell short of the Bristol Fighter - which it was intended to replace.
The third prototype, X4 (designated the Bulldog Mk II) with the 360hp ABC Dragonfly IA nine-cylinder radial engine, and which started its official trials the following month, was compromised from the start by its engine. No armament was fitted and the rear cockpit reduced in size with a close coaming; the secondary structure was removed from the wing centre section, the carry-through members being plain steel tubes attached to the inner ends of the wing spars. In other respects X4 was similar to X3, but neither was awarded a production contract, and it is believed that X5 was not completed.
Type: Single-engine, two-seat, single- and two-bay biplane reconnaissance fighters.
Manufacturer: The Sopwith Aviation Co Ltd, Kingston-upon-Thames and Brooklands, Surrey.
Powerplant: Mark I. One 200hp Clerget eleven-cylinder rotary engine. Mark II. One 360hp ABC Dragonfly IA nine-cylinder air-cooled radial engine.
Dimensions: Two-bay wings. Span, 33ft 9in; length (Mark I), 23ft 0in; height, 8ft 9in; wing area, 335 sq ft.
Weights: Mark I, two-bay wings. Tare, 1,441lb; all-up, 2,495lb.
Performance: Mark I, two-bay wings. Max speed, 109 mph at 10,000ft; climb to 10,000ft, 15 min 35 sec (Mk II, 9 min 28 sec); service ceiling, 15,000ft.
Armament: Two synchronized 0.303in Vickers machine guns on the nose, forward of the pilot’s cockpit, with 1,200 rounds of ammunition; two Lewis guns on the rear cockpit.
Prototypes: Four ordered, X2-X5. X2 was single-bay Bulldog Mk I; X3 was two-bay Bulldog Mk I; X4 was Bulldog Mk II. X5 was probably not completed. No subsequent production.
W.Green, G.Swanborough The Complete Book of Fighters
SOPWITH 2FR.2 BULLDOG UK
A fighter-reconnaissance two-seater, the Bulldog was a compact aircraft which, in its initial form as first flown late 1917, was a single-bay staggered biplane with a 200 hp Clerget 11Eb 11-cylinder rotary engine and an armament of two synchronised and two pillar-mounted 0.303-in (7,7-mm) machine guns. The Bulldog proved heavier than projected and difficult to control, and in an attempt to improve handling qualities it was fitted with two-bay wings with balanced ailerons, flight test being resumed in March 1918. With the balanced ailerons replaced by plain surfaces, the Bulldog was submitted to Martlesham Heath for official trials on 22 April 1918. There it was found to handle well, but to possess disappointing performance. It was eventually to be re- engined with a Bentley B.R.2. The second prototype was completed with an A.B.C. Dragonfly nine-cylinder radial of 320 hp, being delivered to the RAE at Farnborough on 25 June 1918 as the Bulldog Mk II and serving as an engine test bed. Work began on a third prototype, but the Bulldog’s failure to win official approval led to discontinuation of the programme before this aircraft could be completed. The following data relate to the Clerget-engined Bulldog with two-bay wings and plain ailerons.
Max speed, 109 mph (175 km/h) at 10,000 ft (3 050 m).
Time to 8,000 ft (2 440 m), 8.4 min.
Endurance, 2.0 hrs.
Empty weight, 1,441 lb (654 kg).
Loaded weight, 2,495 lb (1132 kg).
Span, 33 ft 9 in (10,29 m).
Length, 23 ft 0 in (7,00 m).
Height, 8 ft 9 in (2,67m).
Wing area, 335 sq ft (31,12 m2).