This aircraft was first flown by Grp. Cpt. PWS Bulman, Chief Test Pilot of Hawker Aircraft (1925-1945), on 6 November 1935. The prototype F.36/34, K5083, was powered by Rolls Royce Merlin C driving a two-bladed fixed pitched wooden propellor and weighed 5,416 lbs. Structurally the aircraft combined the well-proven tubular metal cross-braced fabric-covered Warren fuselage with a new fabric-covered cantilever, twin-spar wing with Warren girder interspar structure. Many small features, subsequently modified, distinguished K5083 at this time from its later and more familiar outline.
Initially, the undercarriage fairings included wheel door hinged to the top wheel segment covers, but following damaged caused during taxiing over rough ground at Martlesham Heath, these flaps were removed. Also removed were the tailplane struts fitted at first, the slide panels of the sliding hood canopy were unstiffened during K5083 early flights and first one, and later, two vertical frames were added, tail wheel was fully retractable and there was no under-fin. The radiator bath was increased in size and exhaust ejector stubs were soon added. Brief preliminary handling trials were conducted at the Aircraft and Armament Experimental Establishment, Martlesham Heath, early in 1936, and in June of that year (soon after the name Hurricane had been officially adopted), a production order for 600 aircraft, large by any peace-time standards, was received by Hawker Aircraft Limited due principally to a decision to discontinue development of the Merlin I and to concentrate on the Merlin II, the first production Hurricane I did not fly until 12 October 1937, the change in powerplant necessitating redesign of engine controls, mountings and header tank as well as the nose cowlings. From the outset the production rate of Hurricanes was high, some 40 aircraft being completed in the first 3 months. Moreover, inside 2 months, the first aircraft was delivered to the RAF and by Christmas 1937, one flight of the first squadron No.III at Northolt had received its machines, supplanting Gloster Gauntlets.
Production of the Hawker Hurricane Mk I, Hawker built aircraft commenced at Kingston and Brooklands during 1936, the first aeroplanes being completed towards the end of 1937. In 1939 aircraft from the Langley factories began to appear, to be joined a year later by Gloster-built machines. First production batch of 600 aircraft with 8 wing-mounted brownings, 303-inch machine guns, Rolls Royce Merlin II engines and, initially, 2-blade fixed-pitch wooden propellors covered by contract numbers 527112/36, dated 3 June 1936. Squadron No.85 L1604; L1632; L1634; L1637; L1639; L1644; L1648; L1651; L1653; L1656; L1765; L1773; L1775; L1778; L1779; L1833; L1834. We are led to believe that these aircraft were used in the Battle of France.
These early machines were delivered to the Service with rear fuselage contours similar to the prototype, but as a result of spinning trials it was decided to enlarge the rudder and incorporate an underfin, and all aircraft delivered from February 1938 onwards carried this modification.
Build-up of RAF Squadrons continued throughout 1938, No.3 and 56 following No.85 Squadron with Hurricanes. By the end of the year about two hundred machines had been delivered to Fighter Command and despite the urgency to accelerate production and expansion, resulting from the Munich Crisis, Hawker Aircraft Ltd, was able to accept contracts with foreign Governments.
By 1939 several improvements had been made in the standard Hurricane I design, the Merlin II had been superseded by the Merlin III and the first Hurricane, L1562, to be fitted with a two-pitch de Havilland 3-blade propellor had been flown on 29 August 1938. Triple ejector exhaust manifolds were standardised while most of the early aircraft had been retrospectively modified with the underfin.