Bristol B.105 Bulldog
In 1926, the British Air Ministry issued F.9/26 specification for a radial-piston engine fighter design that could operate during the day or night, armed with twin Vickers-type machine guns, and capable of engaging the top enemy bombers of the day. Bristol responded with the Bulldog I as a private venture, designed by Frank Barnwell, which was used as a developmental model to ultimately become the Bulldog II.
The Bristol Jupiter engine, which in the initial production Bulldog II was a 328kW Jupiter VII, was mounted in a streamlined nose with its cylinders projecting uncowled but with streamlined fairings and cooling baffles. The propeller had two wooden blades. Features included Frise ailerons on the large upper wing and an adjustable trimming tailplane.
The Bulldog II had an all-metal fuselage with a fabric skin covering. The biplane wings were equal span with single bays and a single pair of parallel support struts. Armament consisted of 2 x 7.7mm Vickers machine guns with their breeches accessible to the pilot, synchronized to fire through the spinning propeller via an interrupter gear. Four 9 kg bombs could be carried under the small lower wing.
The undercarriage was fixed with a tail skid and both were designed to operate from grass runways. The pilot sat behind and underneath the upper wing in an open cockpit, with an oxygen supply for high altitudes and a short-wave two-way radio. Optional armament included 4 x 20lb bombs under the wings.
From the first flight on 17 May 1927, it was entered in the F9/26 competition at Martlesham Heath against the officially sponsored Armstrong Whitworth Starling, Boulton-Paul Partridge, Gloster Goldfinch and Hawker Hawfinch. The Bulldog was well liked by the RAF test pilots and could be dived to terminal velocity without damage to its robust steel structure. The only criticism involved the spin recovery which was overcome with a longer fuselage, larger fin and rudder.
Because of the closeness of the competition between the Bulldog and the Hawfinch the British Government ordered a single Bulldog II for further trials. The Bulldog II had a longer rear fuselage to overcome the spin deficiency of the prototype. First flown on January 21, 1928, the Bulldog II was tested against the Hawfinch at Martlesham, but the competition proved so close that a final decision was reserved until service pilots could assess both types. Eventually the decision was based on the ease of maintenance and here the Bulldog, with its single-bay wings as against the twin-bay wings of the Hawfinch, won. This Mk II prototype modification made cross-wind landings and taxiing more difficult.
Nine Bulldogs were ordered, deliveries to 3 Squadron RAF, starting on May 8, 1929.
The first batch comprised 25 aircraft, of which 23 went to RAF fighter squadrons beginning with No 3 in 1929. Altogether 92 Bulldog II were built, one of which was retained for trials with Mercury engines in more advanced forms of cowling. Seventeen went to Latvia, eight to the RAAF, two to the US Navy, two to Siam, 12 to Estonia, three to Sweden and one to Chile.
The Bulldog II entered RAF service in June of 1929 and effectively replaced the aging Gloster Gamecock and Armstrong Whitworth Siskin fighters then in frontline use.
It was successively upgraded, the Bulldog IVA with the Bristol Mercury VIS 2 engine being the last version to be built in quantity.
A civil demonstrator flown in June 1930 was stressed for greater gross weight and led to the main production version, the Bulldog IIA, the usual engine of which was the 365kW Jupiter VIIF with forged cylinder heads. By November 1933 Bristol had built 262 of this model, of which eight went to Sweden and 253 to the RAF. Four more, called Bristol 105D, were supplied to Denmark with Madsen guns and other changes. Two improved and much faster aircraft with the Mercury engine and Townend ring cowl were designated Bulldog IIIA, leading to the strengthened four-aileron Bulldog IVA, with a 477kW Mercury VIS2 and full-length cowl. This was beaten by the Gladiator for RAF orders, but 17 were built for Finland in the first two months of 1935.
The Australian Air Board approved the purchase of the six Bulldogs on Januany 17, 1929, at an estimated cost of £34,700. In May it was noted that Order No.244 was "held up in London owing to argument between Air Ministry, our Liaison Officer and the Bristol Company in regard to price."
The RAAF had previously used a two-seat SE.5a to introduce pilots to single -seat fighters and was interested in increasing the order by adding a two -seat Bulldog. The Liaison Officer had to advise that the type was not being constructed for preliminary instruction for single-seat fighters, two-seat Armstrong Whitworth Siskins were standardised for this purpose.
It was now evident that funds for the eight were available and as it was thought that a better price per unit could be obtained for a larger number, Order No.277 was raised to cover two additional Bulldogs. These aircraft were identical to the RAF Bulldog II except for the choice of engine and supplied under Air Ministry Contracts No.901228/29 for aircraft, and 934691/29 for engines respectively. "As supplied to the Royal Air Force (the Bulldog) is fitted with a Jupiter Mk VII (supercharged) engine for speed at heights above 10,000ft, but as operations at these heights are not called for in our case, as the 'Bulldog' with Mk VI is faster than with the Mk VII below 8,000ft," the RAAF ordered the Bulldog with the Jupiter VI engine.
The eight Australian Bulldogs (Bristol construction sequence numbers 7389-7396) were allocated the serials A12-1 to A12-8. The price quoted for each was £3,750. They arrived in Melbourne, Victoria, aboard the SS Fordsdale on March 14, 1930. Assembly took place at 1 Air Depot, Laverton, and the first was flight tested by F/Lt F R W Scherger on May 1.
The Bulldog was constructed of ribbon steel worked up into suitable corrugated sections. The process was not in operation in Australia and major spares were necessarily obtained from overseas, but items "such as tanks, metal fittings and small parts... [were] obtained locally." The upper wings were of greater span and chord than the lower wings. All fuel was carried in two gravity tanks recessed into the upper wings. The undercarriage featured oleo-dampened rubber in compression legs which were attached to the top longerons. Two Vickers guns were mounted on each side of the cockpit. Provision was made for a wireless transmitter-receiver to be carried in a compartment just behind the cockpit.
The last Bulldog was an all-stainless-steel Mk IIA for the Air Ministry.
Bulldog II's would never saw combat in British service but foreign users of the type did. Finnish pilots used Bulldogs against Soviet invaders in World War 2. Other foreign operators included Spain.
In 1931 a Mk IIA had been rebuilt into a dual-control advanced trainer. In December 1932 a modified trainer, called Bulldog TM (Training Machine), went into production as a standard type for the RAF. By December 1934 no fewer than 60 had been delivered. They were designed so that by fitting different rear fuselages, and adding guns (for which provision was made), they became fighters. Bulldogs remained in full RAF service until 1937, and until 1940 with Baltic air forces.
Bulldog TM 23 June 1934 – TM3181, 450 hp Bristol Jupiter VI
Some 443 examples were produced from 1928 until 1935 including a total of 293 Bulldogs built for the RAF.
The Bristol Bulldog was replaced in RAF service by the Gloster Gauntlet.
Nakajima of Japan produced two examples of the Bulldog as the J.S.S.F.
Bristol Bulldog II
Engine: 1 x Bristol Jupiter VII Radial Piston, 440hp.
Length: 25.00ft (7.62m)
Width: 33.92ft (10.34m)
Height: 9.84ft (3.00m)
Wing load : 11.07 lbs/sq.ft / 54.00 kg/sq.m
Maximum Speed: 174mph (280kmh; 151kts)
Maximum Range: 275miles (443km)
Rate-of-Climb: 1,379ft/min (420m/min)
Service Ceiling: 27,001ft (8,230m; 5.1miles)
2 x 7.7mm synchronized Vickers machine guns
4 x 20lb bombs
Empty Weight: 2,200lbs (998kg)
Maximum Take-Off Weight: 3,490lbs (1,583kg)
Engine: Bristol Jupiter VII F, 490 hp, 360kW.
Span: 33ft. 11 in.
Length: 25 ft
Height 9ft. 10in
Wing area: 28.5 sq.m / 306.5 sq. ft
Weight empty 2,412 lb
Loaded weight: 1600 kg / 3,503 lb
Max. speed: 174 m.p.h
Ceiling 27,000 ft.
Range w/max.fuel: 600 km / 373 miles
Range w/max.payload: 440 km / 273 miles
Armament: 2 x 7.7mm machine-guns, 4 x 9kg bombs