A two-seat fighter version of the Hart would provide additional fire-power from the rear cockpit was proposed and two prototypes were prepared for evaluation by modification of Hart bombers. These were each powered by a 417kW fully supercharged Rolls-Royce Kestrel engine. Each was equipped with two synchronised forward-firing Vickers machine-guns and had the coaming of the rear cockpit modified to provide a maximum field of fire for the Lewis gun operated by the observer/air gunner. Known as Hart Fighters, these were evaluated and a small batch of six was ordered.

In 1932 the fighter received the name Demon. A total of 305 Demons were built, made up of the prototypes/pre-production aircraft, 77 with Kestrel IIS engines (seven as instructional airframes and one fitted with a 477kW Kestrel VI engine under the Hawker report number 475), 155 with 436kW Kestrel VI engines and those for Australia.
From late 1936 aircraft coming from the Boulton Paul production line were equipped with a hydraulically operated shield in the aft cockpit and were known as Turret Demons. The segmented metal shield was provided to give the gunner some protection from the slipstream. Many earlier aircraft were modified retrospectively to this standard. In addition to aircraft supplied to the RAF, a total of 64 were produced for the Royal Australian Air Force which procured them as army co-operation fighters each fitted with bomb racks, a message-retrieving hook and other equipment.

An initial 16 Demons were ordered in January 1934 to replace Westland Wapitis with Nos 1 and 3 Sqds. Deliveries began in 1935 and 36 more were ordered at the same time for Army co-operation and then another 10 for target towing and training. They eventually served with 7 RAAF squadron, a few remaining until 1942.

As a fighter with the RAF the Demon was finally superseded from late 1938 by the Blenheim IF, but a few were used as target tugs until replaced by the Hawker Henley.

Hawker Demon
Fighter interceptor, United Kingdom, 1933
Length : 29.593 ft / 9.02 m
Height: 10.4 ft / 3.17 m
Wingspan : 37.238 ft / 11.35 m
Wing area : 348.0 sqft / 32.33 sq.m
Max take off weight : 4465.1 lb / 2025.0 kg
Weight empty : 3067.2 lb / 1391.0 kg
Max. speed : 158 kts / 293 km/h
Service ceiling : 27493 ft / 8380 m
Wing load : 12.92 lb/sq.ft / 63.0 kg/sq.m
Endurance : 3 h
Crew : 2
Armament : 3x cal.303 MG (7,7mm)

Originally designated Hart General Purpose, the pro¬totype Hardy, a converted Hart, first flew on September 7, 1934. Fitted with a message pick up hook and wing racks for supply containers or light bombs, it was slightly longer and its empty weight was substantially higher than that of the Hart.

The first 37 were powered by 530 hp / 391kW Rolls-Royce Kestrel IB engines, the remaining ten by 585 hp Kestrel Xs. The long exhaust pipes resembling those of the Audax, and the Hart’s armament of a Vickers machine gun on the port side of the fuselage and a Scarff mounted Lewis in the rear cockpit were retained.
A total of 47 Hardys were built by Gloster during 1935, the first examples going to 30 Squadron, RAF, in Iraq in April. The type was used in the Middle East for army co operation, dive bombing and reconnaissance and to provide valuable close support to ground troops under pressure. These served with the RAF, latterly as a communications type, until 1941.

Engine: 1 x Rolls-Royce Kestrel IB, 395kW / 523 hp
Max take-off weight: 2270 kg / 5005 lb
Empty weight: 1450 kg / 3197 lb
Wingspan: 11.35 m / 37 ft 3 in
Wing loading: 14.35 lb/sq.ft / 70.00 kg/sq.m
Length: 9.02 m / 29 ft 7 in
Height: 3.23 m / 10 ft 7 in
Wing area: 32.33 sq.m / 348.00 sq ft
Max. speed: 140 kts / 259 km/h / 161 mph
Service Ceiling: 5180 m / 17000 ft
Armament: 2 x .303in / 7.7mm machine-guns
Crew: 2

One of the first adaptations of the Hart day bomber involved fairly minor changes to satisfy an Army cooperation requirement, with the RAF needing a replacement for Armstrong Whitworth Atlas and Westland Wapiti aircraft. For this role the Hart was provided with a message pick-up hook and other equipment changes.
About 652 Audax biplanes were ordered for the RAF, including those purchased by South Africa and those transferred to Malaya for the Straits Settlement Volunteer Air Force. Others were constructed for Persia (with Bristol Pegasus and Pratt & Whitney Hornet engines), Iraq, Canada, Singapore and Egypt. The Egyptian aircraft with Armstrong Whitworth Panther X engines and supplied to allow Egypt to share with Britain the defence of Egypt, the Sudan and the Canal zone under the terms of the Anglo-Egyptian Treaty.
RAF Audaxes entered service in 1932 and some based overseas were still flying in 1941-42. An Audax squadron was used as fighter cover at the Digboi air station in north east Assam, India in 1942. Most of the remaining Audaxes were operated during the early war years as Hotspur glider tugs and trainers, 18 having previously been converted into Hart Specials.

Engine: 1 x Rolls-Royce “Kestrel IIS”, 385kW
Max take-off weight: 1987 kg / 4381 lb
Empty weight: 1336 kg / 2945 lb
Wingspan: 11.4 m / 37 ft 5 in
Length: 9.0 m / 29 ft 6 in
Height: 3.2 m / 10 ft 6 in
Wing area: 32.4 sq.m / 348.75 sq ft
Max. Speed: 274 km/h / 170 mph
Cruise speed: 240 km/h / 149 mph
Ceiling: 6400 m / 21000 ft
Range w/max.fuel: 600 km / 373 miles
Armament: 2-4 .303 MG (7,7mm) machine-guns, 250kg of bombs
Crew: 2

Hawker Audax
Engine: Rolls Royce Kestrel II B, 523 hp
Length: 29.593 ft / 9.02 m
Height: 10.4 ft / 3.17 m
Wingspan: 37.238 ft / 11.35 m
Wing area: 348.000 sqft / 32.33 sqm
Max take off weight: 4385.7 lb / 1989.0 kg
Weight empty: 2939.3 lb / 1333.0 kg
Max. speed: 148 kts / 274 km/h
Service ceiling: 21506 ft / 6555 m
Wing load: 12.71 lb/sq.ft / 62.00 kg/sq.m
Endurance: 4 h
Crew: 2
Armament: 2x .303 MG (7,7mm) machine-guns, 4x 9kg Bomb / 2x 51kg Cont.

The task of redesigning the Woodcock was undertaken by W G Carter, who retained little of the original design apart from the fundamental fuselage structure. A new single-bay wing cellule was adopted, with marginally increased incidence and chord, and reduced sweepback. The fuselage decking was recontoured, tail surfaces were redesigned and the armament was repositioned. Powered by a 380hp Bristol Jupiter IV nine-cylinder radial like that eventually installed in the original Woodcock, but featuring individual cylinder heads, a new prototype designated Woodcock II was flown early in 1924. The redesigned fighter overcame most of the shortcomings of its progenitor, and a contract was placed on behalf of the RAF before the end of 1924.
Similarly armed to the original fighter prototype, the Woodcock II was awarded successive contracts, a total of 62 being built, with deliveries being completed in 1927. The type served with two RAF squadrons until 1928, some late production examples being fitted with the Jupiter IV uprated to 416hp.

Max take-off weight: 1351 kg / 2978 lb
Empty weight: 913 kg / 2013 lb
Wingspan: 9.91 m / 32 ft 6 in
Length: 7.97 m / 26 ft 2 in
Height: 3.02 m / 9 ft 11 in
Wing area: 32.14 sq.m / 345.95 sq ft
Max. speed: 227 km/h / 141 mph
Cruise speed: 166 km/h / 103 mph

As a result the Air Ministry Specification 12/26 for a new light bomber required an improvement upon the performance of the Fox.
Hawker’s submission for this requirement, which eventually became known as the Hart, was evolved in conjunction with Rolls-Royce, and when submitted in late 1926 proved sufficiently attractive for construction of a prototype to be authorised. Sidney Camm’s design utilised what became known in later years as ‘Hawker’s patent metal construction system’, a lightweight and robust structure with fabric covering. From Rolls-Royce came a new engine – known then as the F.XI, a development of the Falcon engine -which had weight-saving six-cylinder monoblocs instead of individual cylinders.
The airframe design was that of an uncluttered single-bay biplane, streamlined fuselage, a conventional Hawker tail unit, and fixed landing gear with tailskid. The biplane wings were of unequal span, the lower wing of constant chord and with a straight leading edge. The upper wing was slightly swept back and incorporated the ailerons and Handley Page leading-edge slots.

The prototype (J9052) was flown for the first time in late June 1928 by Flt Lt Bulman and was subsequently flown in competitive evaluation against the Avro Antelope and Fairey Fox II. With superior performance of the Hart confirmed, 15 pre-production aircraft were ordered initially for development and familiarisation, and the first 12 of these entered service with the RAF’s No 33 (Bomber) Squadron in late 1929 or January 1930 and one was sent for trials in India.

In RAF service the Hart was to have a number of variants. These included the 1932 Hart Trainer (483 built, not including conversions of other models); Hart C communications aircraft; and tropicalised versions known as the Hart India and Hart Special. A version was built for the Royal Navy, serving both with wheeled and float landing gear, and this was designated Hawker Osprey. In addition Harts were built for overseas customers which included Estonia, Sweden (also licence-built 42 Pegasus-engined Harts) and Yugoslavia, while ex-RAF aircraft eventually went to South Africa, Egypt and Southern Rhodesia.

Harts remained in service with the RAF on the North-West Frontier in India until displaced by Bristol Blenheims in 1939. Some Royal Navy Ospreys were used for target towing and training until 1940, but so far as is known the last in operational service was a Hart used by the South African Air Force well into World War II. Most extensively built between-wars British military aircraft, a total of 952 had been constructed when production ended in 1937, with Armstrong Whitworth, Gloster and Vickers acting as sub-contractors.
Hawker records also refer to a civil-registered Hart, first flown on 15 September 1932 and known as the Hart II. This was powered in succession by a Kestrel IIS, Kestrel VI and Kestrel XVI, with the latter having an all-up weight of 2,109kg. It was used for demonstrations at air displays and for taking air-to-air photographs of Hawker aircraft, accumulating 627 flying hours in these roles from August 1933.

Powered by a single 525 hp Rolls Royce Kestrel IB, the Hart had a maximum speed of 172 mph (276 km/h) at 10,000 ft (3,050 m.

Hawker Hart Article

The Hart was eventually displaced by a developed version known as the Hind.

Gallery

Engine: 1 x Rolls-Royce Kestrel XDR, 380kW / 525 hp
Max take-off weight: 2066 kg / 4555 lb
Empty weight: 1148 kg / 2531 lb
Wing loading: 13.12 lb/sq.ft / 64.0 kg/sq.m
Wingspan: 11.35 m / 37 ft 3 in
Length: 8.94 m / 29 ft 4 in
Height: 3.17 m / 10 ft 5 in
Wing area: 32.33 sq.m / 348.00 sq ft
Max. speed: 160 kts / 296 km/h / 184 mph
Service Ceiling: 6510 m / 21350 ft
Range: 408 nm / 756 km / 470 miles
Armament: 2 x 7.7mm / .303 in machine-guns, 230kg of bombs
Seats: 2.

The type was designed in 1928, a two-¬seater trainer biplane with a 130 hp Armstrong Siddeley Mongoose III engine with five cylinders, a top speed estimated at 120 miles an hour and a cruising speed of between 85 and 90 miles an hour. As a replacement for the Avro 504N for RAF pilot training, 25 were supplied to the RAF between 1929 and 1931. The last, K1786, was delivered in January 1931. They entered service with No.3 FTS at Grantham and the CFS at Wittering but the type were relegated to communications tasks from 1935. Six Tomtits were used for communications duties during the war and two, as G-ABII and G-AFTA survived post-war. G-ABII was written off in 1948.

A total of 36 were built for the RAF, for civil registration and for export to Canada and New Zealand. The last Tomtits left the RAF in 1938. Civil and ex-RAF Tomtits were fitted with a variety of engines, including the ADC Cirrus Hermes and Wolseley Aquarius and were used by several aero clubs up to the out-break of the war.

Gallery

Engine: 1 x Armtrong Siddeley Mongoose IIIC, 112kW / 150 hp
Max take-off weight: 794 kg / 1750 lb
Empty weight: 499 kg / 1100 lb
Wingspan: 8.71 m / 28 ft 7 in
Length: 7.21 m / 23 ft 8 in
Height: 2.54 m / 8 ft 4 in
Wing area: 22.09 sq.m / 237.77 sq ft
Max. speed: 200 km/h / 124 mph
Ceiling: 5945 m / 19500 ft
Crew: 2