The Gloster Gladiator is a biplane fighter aircraft designed and produced by the British aviation firm Gloster Aircraft Company, Ltd.. It was the last biplane fighter to be flown by the Royal Air Force (RAF) as well as being the first to be provisioned with an enclosed cockpit; it was also operated by the Fleet Air Arm (FAA) as the Sea Gladiator variant, as well as being exported to numerous other air services during the late 1930s.
The Gladiator was developed during the mid 1930s as a private venture, being initially referred to the Gloster SS.37 and derived from the Gloster Gauntlet. Mid-way through development, it was decided to adapt the aircraft towards fulfilling Air Ministry Specification F.7/30. Changes over the Gauntlet included the use of wing-design techniques developed by Hawker Aircraft, the adoption of the Bristol Mercury M.E.30 radial engine, and the fitting of a cantilever main undercarriage. First flown on 12 September 1934 and entering service with the RAF in 23 February 1937, the Gladiator was quickly rendered obsolescent by newer monoplane designs even as it was being introduced. While frequently pitted against more advanced fighters during the early days of the Second World War, it acquitted itself reasonably well in combat.
The Gladiator saw action in almost all theatres during the Second World War, with a large number of air forces, some of them on the Axis side. The RAF deployed its Gladiators into front line combat on numerous fronts, including France, Norway, Greece, the defence of Malta, the Middle East, and the brief Anglo-Iraqi War (during which the Royal Iraqi Air Force was similarly equipped). Other countries deploying the Gladiator included China against Japan in the Second Sino-Japanese War; Finland (along with Swedish volunteers) against the Soviet Union in the Winter War and the Continuation War; Sweden as a neutral noncombatant (although Swedish volunteers fought for Finland against the USSR); and Norway, Belgium, and Greece resisting Axis invasion of their respective lands. The top Gladiator ace was South African pilot Marmaduke "Pat" Pattle, having scored 15 victories while flying the type.Thomas 2002, p. 91.Mason 1966, p. 10.
Design and development Origins
During the 1920s, Britain's air defences had been based around interceptor aircraft capable of flying only for short ranges and at speeds of , but by 1930, figures within the Air Ministry were keen to supersede these aircraft. In particular, some dissatisfaction had arisen with the level of reliability experienced with the 'one pilot, two machine guns' design formula previously used; the guns were often prone to jams and being unreliable.Mason 1966, p. 3. The Air Ministry's technical planning committee formulated Specification F.7/30, which sought a new aircraft capable of a maximum speed of at least , an armament of no fewer than four machine guns, and such handling that that same fighter could be used by both day and night squadrons. Gloster, being already engaged with development of the Gloster Gauntlet, did not initially respond to the specification, which later proved to be beneficial.Mason 1966, pp. 3-4.
The specification had also encouraged the use of the new Rolls-Royce Goshawk evaporatively cooled inline engine; many of the submissions produced by various aviation companies in response accordingly featured it.Mason 1966, p. 4. However, the Goshawk proved to be unreliable, mainly due to its overcomplex and underdeveloped cooling system, and unsuited to use on fighter aircraft and this outcome stalled development of the aircraft intended to use it. A further stumbling point for many of the submitted designs was the placement of the machine gun breeches within arm's reach of the pilot. At the same time, the development of monoplane fighters such as the Hawker Hurricane and Supermarine Spitfire cast doubt over the future viability of the requirement altogether.
Gloster recognised that instead of developing an all-new design from scratch, the existing Gauntlet fighter could be used as a basis for a contender to meet Specification F.7/30. Development of what would become the Gladiator began as a private venture, internally designated as the SS.37, at Gloster, by a design team headed by H.P. Folland, who soon identified various changes to increase the aircraft's suitability to conform with the demands of the specification. Making use of wing-design techniques developed by Hawker Aircraft,By 1934 Hawker was parent company of Gloster the new fighter adopted single-bay wings in place of the two-bay wings of the Gauntlet, and two pairs of interplane struts were also dispensed with as a drag reduction measure. The Bristol Mercury M.E.30 radial engine, capable of generating , was selected to power the SS.37, which provided a performance boost over the preceding Gauntlet. Another design choice was the fitting of a cantilever main undercarriage, which incorporated Dowty internally sprung wheels, allowing for more simple rigid landing gear struts.Lumsden 1992, p.10.James 1971, p. 206.
Prototype
In spring 1934, Gloster embarked on the construction of a single SS.37 prototype. On 12 September 1934, the SS.37 prototype conducted its maiden flight, piloted by Gloster chief test pilot Gerry Sayer. Initially powered by a Mercury IV engine, the prototype was quickly re-equipped with a more powerful Mercury VIS engine. During flight tests, the prototype attained a top speed of while carrying the required four machine guns (two synchronised Vickers guns in the fuselage and two Lewis guns under the lower wing). According to aviation author Francis K. Mason, the Air Ministry was sceptical about the aircraft achieving such performance from a radial engine design, so funded a protracted series of evaluation trials.
On 3 April 1935, the prototype was transferred to the RAF, receiving the designation K5200, and commenced operational evaluations of the type. Around the same time, Gloster proceeded to plan a further improved version, featuring an Mercury IX engine, a two-blade wooden fixed-pitch propeller, improved wheel discs, and a fully enclosed cockpit.James 1971, pp. 206–207. K5200 was later used to trial modifications for production aircraft, such as the addition of a sliding hood for the pilot.
In June 1935, production plans for the aircraft were proposed; two weeks later, a production specification, Specification F.14/35, had been rapidly drawn up, partially prompted by events in continental Europe, such as the invasion of Abyssinia by Fascist Italy and the rise of Adolf Hitler to power in Germany, in response to which the British government mandated an urgent expansion of the RAF to counter the emerging threats. This culminated in an initial order for 23 aircraft. On 1 July 1935, the aircraft formally received the name Gladiator.Lumsden 1992, p. 12.
Production Manufacturing of the Gladiator was started at Gloster's Hucclecote facility. Production of the initial batch was performed simultaneously, leading to many aircraft being completed around the same time. On 16 February 1937, K6129, the first production Gladiator, was formally accepted by the RAF; on 4 March 1937, K6151, the last aircraft of the initial batch, was delivered. In September 1935, a follow-up order of 180 aircraft was also received from the Air Ministry;James 1971, p. 207. this order had the proviso that all aircraft had to be delivered before the end of 1937. Variants The first version, the Gladiator Mk I, was delivered from July 1936, becoming operational in January 1937. When difficulties with Rolls-Royce Merlin combustion chamber threatened to postpone the readiness of the next-generation fighters, the Air Ministry hedged its bets by procuring hundreds of Mk II Gladiators as a stopgap via Specification F.36/37 (the delivery of 252 planes took until April 1940). The main differences were a slightly more powerful Mercury VIIIAS engine with Hobson mixture control boxes and a partly automatic boost-control carburettor, driving a Fairey fixed-pitch three-blade metal propeller, instead of the two-blade wooden one of the Mark I. All MK II Gladiators also carried Browning .303-inch machine guns (licence-manufactured by the BSA company in Birmingham) in place of the Vickers-Lewis combination of the MK I.
Variant: the Sea Gladiator A modified Mk II, the Sea Gladiator, was developed for the Fleet Air Arm, with an arrestor hook, catapult attachment points, a strengthened airframe, and an underbelly fairing for a dinghy lifeboat, all for operations aboard aircraft carriers.Barber 2008, p. 6Matricardi, Paolo. Aerei Militari: Caccie e Ricognitori. Milano: Mondadori Electa, 2006. Of the 98 aircraft built as, or converted to, Sea Gladiators, 54 were still in service by the outbreak of the Second World War.
Last British biplane The Gladiator was the last British biplane fighter to be manufactured, and the first to feature an enclosed cockpit. It possessed a top speed of about , but by the time it was introduced, it was already being eclipsed by new-generation monoplane fighters, such as the RAF Hawker Hurricane and Supermarine Spitfire, and the Luftwaffe Messerschmitt Bf 109. In total, 747 aircraft were built (483 RAF, 98 RN), with 216 being exported to 13 countries, some of which were from the total allotted to the RAF.Mason 1964, p. 128.Spencer 2003, pp. 10, 12. Gladiators were sold to Belgium, China, Egypt, Finland, Free France, Greece, Iraq, Ireland, Latvia, Lithuania, Norway, Portugal, South Africa and Sweden.
Operational history Introduction to service
In February 1937, No. 72 Squadron, based at Tangmere, became the first squadron to be equipped with the Gladiator; No. 72 operated the type until April 1939, longer than any other home-based frontline unit.Mason 1966, p. 5. Between March and April 1937, No. 3 Squadron at Kenley also received Gladiators from the remainder of the first production batch, replacing its obsolete Bristol Bulldogs. Initial service with the type proved the Vickers guns to be problematical; the Gladiator was quickly armed with .303 in (7.7 mm) Browning machine guns, which were substantially more popular, leading to the other guns often only being resorted to if deemed necessary. On 27 March 1937, No. 54 Squadron at Hornchurch became the first unit to receive Browning-armed Gladiators.
By September 1937, all eight Gladiator squadrons had achieved operational status and had formed the spearhead of London's air defences.Mason 1966, pp. 5-6. Difficulties with introducing the type had been experienced. Although the Gladiator was typically well-liked by pilots, the accident rate during operational training on the type was so high that a small replacement batch of 28 Gladiator Mk IIs was hurriedly produced. Most accidents were caused by pilots being caught out by the fighter's increased wing loading, and many aviators had little experience in landing aircraft with such a wide flap area. The aircraft had a tendency to stall more abruptly, frequently dropping a wing while doing so. The Gladiator very easily entered a flat spin, and great skill was needed to recover.Håkan & Slongo 2012.
The first use of RAF Gladiators on active service was during the 1936–1939 Arab revolt in Palestine. From September to December 1938, 33 Squadron RAF flew Gladiator strafing missions in support of British Mandate security forces. These were often in mountainous areas, and the aircraft came under substantial rifle fire. Three aircraft were destroyed and two pilots killed in these operations.Thomas 2002, pp. 9-10.