The Hawker Hart Trainer stemmed from a need to provide dual instruction for pilots who were to ily the basic Hart and its many planned variants. The concept of such a modification was by no means new, as the RAF had already flown dual versions of various aircraft‘ mainly at Flying Training Schools. Some were conversions of machines already in service, such as the Sopwith Snipe (dual). Others were specially built on the production line, such as the Armstrong Whitworth Siskin lll (DC) and the Fairey IIID (T) and Fairey IIIF (DC),
The original l-lart bomber first appeared in prototype form in 1928‘ and was rnost advanced for its time The straightforward design for a single-engined bomber proved capable of adaptation, and from it came a long line of two-seat aircraft for various duties, including the Osprey, Demon, Audax, Hardy and Hind, as well as single engined fighters from the same stable, These were all powered by the Rolls Royce Kestrel engine, which proved very reliable in service. Designed by Sydney Camm, later responsible for such famous aircraft as the Hurricane, Typhoon and Tempest, the Hart was an immediate success on its introduction into service, It had been designed to a competitive 1926 specification requiring a top speed of 160 mph, which at that date was quite exceptional, To meet this demand, the Hawker design team worked closely with Rolls-Royce, the original proposal being to install a Falcon Fl engine.
New construction techniques were necessary if the specification was to be met, and consequently the fuselage was built on the Warren tubular steel girder system, the nose having a pleasing and effective streamlined appearance‘ By the time of the first flight. the more powerful Rolls-Royce F.XlB engine had become available. It was lighter than the original engine, being cast in a single piece‘ and was later christened the Kestrel. The engine and fuel tank were completely enclosed with quick-release panels‘ and the honeycomb-type radiator could be retracted in flight‘
There were two spacious and comfortable cockpits in the rear fuselage, which was fabric-covered and faired-in to retain the streamlining‘ The pilot had a 303 in Vickers Mk ll gun in a trough on the port side of his cockpit, synchronised to fire safely through the propeller blades, whilst the observer had a movable 303 inch Lewis Mk III gun mounted on a Hawker’ designed gun ring‘
The unequal span single-bay wings were also of metal construction, the spars being of drawn steel strip and the ribs of duralumint Differential ailerons of similar construction were fitted to the upper wings, Production machines had a conventional cross-axle undercarriage‘ although a divided-axle type had been tried on the prototype‘
From the start‘ the aircraft had excellent flying qualities‘ the controls were reported as being light over the whole range of normal flight and very effective at the stall. Aerobatics presented no difficulties, and it would go into a spin easily, evenly and fast ln a dive it would remain steady‘ without any vibration‘
Harts first entered service with 33 squadron in 1930‘ and in the Air Exercises of that year they outpaced the contemporary Siskin fighters. They were equally successful in the annual inter-squadron bombing competition‘ and no time was lost in placing further orders for this outstanding and versatile aircraft‘
The advent of this fast new machine led to the need for an appropriate training syllabus, but existing slower types of dual control trainer were inadequate for the purpose. Official thinking was, therefore, that a new design was required‘ The simplest means of providing this would be to base it on the Hart‘ and in February l932 Hawkers were asked to build such a machine for trials. Rather than build an entirely new machine, they decided to take a partially completed Hart variant off the production line, and consequently the second production Audax (K1996) was deleted from its contract and completed in the dual control trainer configuration.
K1996 made its first flight on Z0 April 1932‘ only SlX weeks after receipt of the contract, and differed little from the early standard production I-lart bombers. The main variations were removal of the gunner’s ring in the rear cockpit, which was fitted with dual control, and duplication of the instruments and other equipment except for the fuel gauge‘ which could be a problem as it was not easy to read from the back seat‘ Maintenance facilities were excellent‘ with greatly improved access compared with the normal Hart, removable panels being fitted at each side aft of the cockpit‘ as well as each side under the tail and under the bottom of the rear cockpit. A modification introduced on later machines was a long Osprey-type exhaust extending under the lower starboard mainplane. A tailwheel was also fitted to later production aircraft in place of the original tailskid.
Tests on K1996 found the controls to be effective and reasonably light, being somewhat lighter than those of the standard Hart‘ Both cockpits were comfortable, though they could become stifling in summer conditions at low altitude‘ The rear windscreen came in for some criticism‘ being so large as tomake it impossible to look over or round it‘ which could cause problems if it became obscured by oil‘ and by deflecting the airflow it also had the effect of accentuating the summer overheating problem.
The test report considered the aircraft very suitable as a training type, being easy to fly and controllable at very low speeds. lts flying characteristics were very similar to those of the standard Hart. and aerobatics could be performed easily and cleanly. Several modifications were recommended, however, on the production version. Brakes should be controllable from both seats, the rear cockpit fitted with a duplicate petrol gauge, the windscreen size reduced and parachute grips provided. ln addition the harness in both cockpits came in for criticism, and it was recommended that the leg straps be anchored further forward. Take off and initial climb proved to be quite good, and landing was slow and easy. There was, however some tendency to turn into wind whilst taxiing, especially when travelling across wind.
Two further test machines were completed, K2474 and K2745 having been laid down as Hart bombers, and these flew later in 1932 as Hart Trainers (Interim). The trials having proved the success of the concept, Specification 8/32 was issued, and initial production orders placed. Several of the early deliveries went to the RAF College at Cranwell, where they started to replace Atlas Trainers from lune 1933, and others went
to the Central Flying School Hart Trainers were also issued to No 25 and 43 Squadrons. Replacing now-unsuitable dual Siskins in these Hawker Fury’ equipped units, and others went to Hart-equipped auxiliary squadrons, Further large orders enabled the Flying Training Schools to replace their ageing Atlas and Bulldog Trainers, and eventually 473 machines were built, many being sub-contracted by Armstrong Whitworth and Vickers, ln addition, a further 32 conversions were made by Glosters from Hart bombers,
Early Hart Trainers had the 535 hp Kestrel lB, but some were later fitted with the derated 510 hp Kestrel V(DR), this latter engine being replaced by the similarly rated Kestrel X(DR) in the Series 2 version, which was produced from 1934, Several of the later aircraft had tropical radiators fitted, and quite a number of Hart Trainers served overseas, including many with N0 4 Flying Training School at Abu Sueir in the Egyptian Canal Zone. When first introduced into service, they were finished in the normal silver paint/aluminium overall. ln 1935, however, they changed to the new all—yellow scheme adopted in that year for all RAF training aircraft. The Munich crisis of 1938 led to the upper surfaces being camouflaged in brown and green, this later replacing the yellow entirely,
By the outbreak of the Second World War, the Hart Trainers were obsolescent, being largely replaced by the Harvard and Master, Nevertheless, shortage of these types meant that many Hart Trainers continued in service until as late as the end of l94l. Quite a number ended their days as ground instructional airframes.[2]
Notes[]
Sources[]
- ↑ Ray Sturtivant’s collection
- ↑ The History of Britian's Military Training Aircraft. Ray Sturtivant. Haynes Publishing Group. 1987. ISBN 0-85429-579-8. Pages 69 to 72