The de Havilland DH.103 Hornet, developed by de Havilland, is a fighter aircraft driven by two piston engines. It further exploited the wooden construction techniques that had been pioneered by the de Havilland Mosquito. Development of the Hornet had started during the Second World War as a private venture. The aircraft was to conduct long range fighter operations in the Pacific Theatre against the Empire of Japan but the war ended before the Hornet reached operational squadron status.
The Hornet entered service with RAF Fighter Command where it equipped several day fighter units and was commonly stationed in the British mainland. It saw combat in the Far East, being used as a strike fighter as part of the British military action taken during the Malayan Emergency. A naval carrier-capable version, the Sea Hornet, had been envisaged early on and was procured by the Fleet Air Arm of the Royal Navy.
Development Origins In the autumn of 1941, de Havilland found that it had the spare design capacity to work on a new project. At this point, the Mosquito had entered full-rate production and preliminary work on a jet-propelled fighter aircraft, which became the Vampire, was waiting for the production of prototype engines.Birtles 1967, p. 3. The company promptly recognised a need for a high-speed, unarmed, night bomber powered by a pair of large Napier Sabre piston engines and a design for such an aircraft was first proposed under the designation D.H. 101 in October 1941. A design team led by R. E. Bishop with C. T. Wilkins assisting, was assembled with the aim of developing the D.H. 101, which was initially pursued as a private venture.
The Sabre engine was suffering from availability problems at that point and the DH. 101 was soon replaced by a lower-powered design, with the internal designation D.H. 102. This proposal was intended to be powered by a pair of Rolls-Royce Griffon or Rolls-Royce Merlin engines but either engine would have meant that the aircraft would be somewhat slower and less attractive than the Mosquito.
By November 1942, de Havilland had elected to shelve the night bomber project and concentrate on producing a long-range fighter, the D.H. 103, that would make the maximum possible use of the Merlin engine. The D.H. 103 resembled a small Mosquito, with a single seat; it was intended to take on other single-seat fighter aircraft, particularly those operated by Japan, while still being capable of conducting very long range missions to be of use in the Pacific Theatre. The long range requirement led to the fuselage being highly streamlined. An independently developed version of the Merlin engine which possessed a low frontal area was selected for use on the D.H. 103.
By the end of 1942, a mock-up of the D.H. 103 had been completed at de Havilland's Hatfield facility and was soon afterwards demonstrated to officials of the Ministry of Aircraft Production. Due to the war, the ministry did not immediately issue permission to construct the D.H. 103. In June 1943, the project stopped being a private venture when the Ministry released Specification F.12/43, which had been written around the D.H. 103 proposal; soon after, the D.H. 103 project received the name Hornet.
It was envisaged that the Hornet could be adapted for naval use and operated from the flight decks of aircraft carriers. Priority was given early on to ensuring that such adaptation could be readily done: measures for ease of control, especially when flown at low speeds, were incorporated and attention paid to providing the pilot with a high level of visibility.Birtles 1967, p. 6. The two propellers were driven in opposite directions to improve take-off and landing characteristics and high-drag flaps were integrated to provide for greater power during approaches.
Prototypes and refinement
By January 1944, the fuselage shell for the first prototype D.H. 103, RR915, was under construction on production jigs at Hatfield; RR915 was rolled out for engine runs on 20 July 1944. On 28 July 1944, only thirteen months after the official sanction to proceed with development, RR915 conducted its maiden flight, piloted by Geoffrey de Havilland Jr., the company's chief test pilot.Bowman 1997, p. 52. Flight tests of RR915 led to it achieving a recorded speed of 485 mph (780 km/h) in level flight. Within two months, over fifty flight hours were accumulated by RR915. The second prototype, RR919, was more representative of production aircraft, having provision for a pair of 200-gallon drop tanks and a pair of 1,000 lbs bombs on hard points underneath the wings.Birtles 1967, pp. 3–4.
Towards the end of 1944, the assembly line for the Hornet F.1, the initial production model, was being established at Hatfield and orders had already been received for the Royal Air Force (RAF).Birtles 1967, p. 4. On 28 February 1945, PX210, the first of 60 production F.1 aircraft was delivered to the Aeroplane and Armament Experimental Establishment (A&AEE) at RAF Boscombe Down. On 29 October 1945, a production Hornet F.1, PX237, was used for the type's first public appearance at an open day at RAE Farnborough.
Additional prototypes were used for the development of improved variants of the Hornet. PX312, participated in the development of an improved fighter model to succeed the F.1, the Hornet F.3. PX212, PX214, and PX219, were converted by the Heston Aircraft Company from Hornet F.1 standard aircraft to represent and test aspects of the initial naval version, later named Sea Hornet F.20. PX212 and PX214 were only partially naval, being outfitted with arrestor hooks but lacking the wing-folding mechanisms of subsequent production aircraft; PX219 was the full naval version and later conducted carrier deck trials on board the aircraft carrier .
PX230 and PX239, were completed for an all-weather night fighter, the Hornet NF.21.Birtles 1967, p. 7. PX239, originally built as a Hornet F.20, was outfitted with power-operated folding wings and a large dorsal fillet, which was later fitted to all production aircraft to comply with a new requirement to provide "feet off" directional stability with one engine stopped. On 25 October 1948, the first deck trials commenced on board ; these were so successful that testing rapidly proceeded to the night trials phase.Birtles 1967, pp. 7–8. On 16 May 1947, PX230 was lost during service trials when the aircraft disintegrated in mid flight; the pilot bailed out following the breakup of the aircraft.Birtles 1967, p. 8.
Hornet F.3, PR.2 and FR.4 The wings of the Hornet F.3 were stressed to carry external weapons; two to four 60 lb (27 kg) RP-3 rockets could be carried under each wing; it was also possible to carry a combination of four rockets with one bomb of up to 1,000 lb (454 kg), or an additional drop tank on each wing, ranging in capacity up to 200 Imp gal (909 L). Internally, the fuel tanks were enlarged from a total capacity of 360 Imp gal (1,636 L) to 432 Imp gal (1,964 L) and additional equipment was added. Larger horizontal tail surfaces were adopted, with larger elevator horn balances. With the evolution of longer-range, jet-powered fighters such as the de Havilland Vampire, de Havilland Venom and Gloster Meteor, the Hornet became obsolete fairly quickly. The F.3 was the last Hornet derivative to see operational RAF service.Hall 1990
The Hornet PR.2 was intended to operate as a long-range photo-reconnaissance aircraft. The Hispano cannon were removed and cameras were mounted in the rear fuselage. Total internal fuel capacity was increased to 528 gal (2,400 L). PX216, PX220 and PX249, were converted from standard Hornet F.1 aircraft, later followed by five more. The requirement for these aircraft lapsed with the end of the Second World War in the Pacific; all were used in arrester barrier trials at Boscombe Down and scrapped before entering RAF service. Twelve Hornet FR.4s were modified from F.3s in much the same way, except that the cannon were retained and the internal fuel capacity slightly reduced from that of the fighter. These FR.4 derivatives saw service with the RAF in Malaya and Hong Kong in the early 1950s.
Sea Hornet F.20, NF.21 and PR.22 The Hornet was designed with the possibility of naval service on carriers firmly in mind. To this end good low-speed handling was required, along with good all-round visibility for the pilot. The basic Hornet design excelled at meeting these requirements. Shortly after the first Hornet prototype flew, Specification N.5/44 was issued to de Havilland, covering the modification of the Hornet for naval service. The Heston Aircraft Company was contracted to carry out the conversion work on three early production F.1s. The work entailed altering the wings to incorporate folding mechanisms so that each outer wing panel, from the aileron/flap line outboard could be folded upwards and inwards at an angle. The hinges were part of the upper wing skin structure while the lower wing skins incorporated securing latches, and Lockheed hydraulic jacks were used to move the wing panels. Slotted flaps were introduced to improve low speed "flaps down" control.
The lower rear fuselage was reinforced with two additional spruce longerons designed to take the stresses imposed by the external "vee" framed arrestor hook, which was flush-mounted below the fuselage. The frame was made up of steel tubing with a forged-steel hook and was held against the fuselage by a "snap gear". Because the Hornet used the American "3-point" system of catapult-assisted takeoff, two forged steel catapult bridle hooks were fitted, one below each wing, close to the fuselage. The de Havilland rubber-in-compression undercarriage legs could not absorb the rebound energies imposed by carrier landings. They were replaced by more conventional hydraulic oleos which embodied torque links.Clark 1987, p. 483.
Merlin 133/134s (derated from to ) were fitted to all Sea Hornets. Other specialised naval equipment (mainly different radio gear) was fitted and provision was made for three camera ports, one on each side of the rear fuselage and one pointing down. Sea Hornet F.20s also incorporated the modifications of the Hornet F.3, although the internal fuel capacity was 347 Imp gal (1,557 L), slightly reduced from that of the F.1. The modifications added some 550 lb (249 kg) to the weight of the aircraft. Maximum speed was decreased by 11 mph (18 km/h).
The Hornet NF.21 was designed to fill a need for a naval night fighter. Special flame-dampening exhausts were installed, and a second basic cockpit was added to the rear fuselage, just above the wing trailing edges. ASH radar equipment was placed in the rear of this cockpit, with the radar operator/navigator seated facing aft. To gain access, a small trapdoor was provided in the lower fuselage; a fixed, teardrop-shaped bubble canopy, which could be jettisoned in an emergency, provided a good field of view. At the front of the aircraft, the nose underwent a transformation with the small rotating ASH radar dish being housed under an elongated "thimble" radome. The horizontal tail units were increased in span. The effect of these modifications on performance was minimal; about 4 mph (6 km/h).
The Sea Hornet PR.22 was a dedicated photo reconnaissance aircraft version of the F.20. The cannon were removed and the apertures faired over. Three cameras were installed in the rear fuselage: two F.52s for night use and one K.19B for day. A total of 23 PR.22s were built, interspersed with F.20s being built at Hatfield.
Civilian Hornet