The last and finest of the biplane fighters operated by the Royal Air Force, the Gladiator, was also an excellent example of the biplane fighter at the apogee of its technical development and, with its enclosed cockpit and trailing-edge flaps, was a type which successfully bridged the technical gap between the ‘classic’ biplane fighter (fabric-covered structure, open cockpit and fixed landing gear) and the ‘modern’ monoplane fighter (stressed-skin construction, enclosed cockpit, trailing-edge flaps and retractable landing gear).
The origins of the Gladiator can be traced to the Air Ministry’s F.7/30 requirement, which was issued late in 1930 and called for a day and night interceptor with the powerplant of one Rolls-Royce Goshawk V-12 engine (an evaporatively cooled development of the water-cooled Kestrel), the fixed forward-firing armament of four 0.303 in (7.7 mm) machine guns, a maximum speed of at least 217 kt (250 mph; 402 km/h), a low wing loading, no exhaust glare, and considerable improvements over current fighters in terms of climb, ceiling, manoeuvrability, and fields of vision.
Gloster’s initial response was the SS.19 development of the SS.18B that was an interim step in the evolution of the fighter that finally matured as the Gauntlet, but Henry P. Folland’s design team later started work on a new fighter as a private venture. This new type was clearly inspired conceptually by its predecessor, for by 1933 Folland had decided that the the agility and performance of the SS.18/SS.19/Gauntlet could be materially improved by the revision of the wing cellule to a single-bay configuration with heavier spars for additional strength in the absence of the two inboard sets of interplane struts, and the adoption of cantilever main landing gear units with Dowty internally sprung wheels. Folland calculated that the drag and reduction yielded by removal of two sets of interplane struts, two landing gear struts and the spreader bar, together with all their associated rigging, would boost maximum speed by some 17.5 kt (20 mph; 32 km/h). Folland was also aware that Bristol was developing the Mercury ME.30 air-cooled nine-cylinder radial engine at a rating of 700 hp (522 kW), and firmly believed that a combination of his aerodynamic improvements and Bristol’s more powerful engine would yield a maximum speed of more than 217 kt (250 mph; 402 km/h).
The problem now facing Folland was the need for heavier armament, for it was impossible to combine four machine guns, the planned airframe and the Mercury ME.30 engine in a package that would meet the Air Ministry’s performance requirement. The solution to Folland’s problem was provided by Bristol, which promised a Mercury ME.35 engine rated at 800 hp (596.5 kW) for any production fighter resulting from Gloster’s initiative. Gloster therefore pressed ahead with its private-venture contender, which was the last type proposed for the Specification F.7/30 requirement. The new type received the Gloster designation SS.37, and to speed development the fuselage and tail unit of a Gauntlet was used as the basis of the new machine: the changes effected in the fuselage were the incorporation of a surface oil cooler on the starboard side of the forward decking ahead of the cockpit, a small streamlined headrest for the pilot, the new cantilever main legs for the fixed tailwheel landing gear, and the powerplant of one Mercury VIS engine, rated at 645 hp (481 kW), was initially selected although the engine used in the prototype’s first flight was the Mercury IV rated at 530 hp (395 kW). To the Gauntlet-derived fuselage and tail unit were added the new wing cellule. This was of the staggered type and was based on lower stubs extending from the lower longerons and an upper centre section that was inversely tapered in thickness and chord, and supported above the central fuselage by a wire-braced arrangement of cabane struts: these upper and lower centre sections carried four basically similar wing panels each carrying the trailing-edge combination of an outboard aileron and inboard split flap: the outer wing panels on each side were separated by a single set of parallel interplane struts and braced by the standard arrangement of flying and landing wires.
The SS.37 prototype recorded its maiden flight on 12 September 1934, and was soon revised with the Mercury VIS engine for a maximum speed of 210 hp (242 mph; 389.5 km/h) with an armament of four 0.303 in (7.7 mm) fixed forward-firing machine guns in the form of two Vickers synchronised belt-fed weapons in the fuselage sides and two Lewis unsynchronised drum-fed weapons under the leading edges of the lower wing. Trials revealed the need for only a few minor changes, and showed that the SS.37 had first-class agility and, with an engine rated at a lower power than that proposed for the production version, performance that was little short of the figure demanded by the Air Ministry.
In June 1935 Gloster submitted to the Air Ministry a proposal for the definitive production model with its all-metal structure revised to the well tried Hawker system, a redesigned tail unit, a fully enclosed cockpit with access provided by a rearward-sliding canopy section, improved Vickers Mk V machine guns, and the powerplant of one Mercury IX engine rated at 830 hp (619 kW) for a maximum speed estimated at 219 kt (252 mph; 405.5 km/h) at 14,000 ft (4565 m). The threat of German aggression, revived by the Nazi party’s accession to power in 1933, was now being taken more seriously as a result of revelations about the expansion and re-equipment of the German military machine, and the UK was belatedly responding with its own programme of expansion and re-equipment. One of the major threats posed by German aggression was deemed to be strategic bombing, so a major element in the RAF’s re-equipment effort was a larger number of fighter squadrons with more modern aircraft. There were advanced types such as the Hawker Hurricane and Supermarine Spitfire monoplane fighters in the offing, but in an attempt to bridge the technical gap until the advent of these two types in large numbers, the Air Ministry decided to adopt the SS.37 as an interim type that could be brought into service quickly. In June 1935, therefore, the Air Ministry responded to Gloster’s proposal with an initial order for 23 aircraft that received the name Gladiator in the following month.
By September 1935 and the beginning of flight tests of the prototype upgraded to virtual production form, Gloster had received orders for a further 180 Gladiator fighters for delivery by the end of 1937, and production of the Gladiator Mk I finally reached 378 aircraft (231 of them for the RAF and the others for export customers) delivered by 1938. The trials included assessment of performance with the Mercury IX engine driving a two-blade Watts wooden propeller or a three-blade Fairey-Reed metal propeller, each of the fixed-pitch type, and as a result of this effort it was decided that later production aircraft should have the Fairey-Reed propeller as this offered a higher maximum speed at the expense of marginally reduced take-off performance.
As these trials were being undertaken, production of the first 23 aircraft was proceeding for delivery in a period of little over two weeks during February and March 1937. The first unit to equip with the Gladiator Mk I was No. 72 Squadron, and during the rest of the year another eight squadrons received Gladiator fighters. By this time the Vickers gun had been superseded as the RAF’s primary fixed weapon by the new licence-built 0.303 in (7.7 mm) Browning gun, and two of these weapons (each with 600 rounds) were used as the fuselage-mounted guns of all Gladiators. Supplies of the new gun were limited in the mid-1930s as Birmingham Small Arms got its production effort under way, so the wing-mounted guns on the first 60 Gladiator Mk I fighters were two 0.303 in (7.7 mm) Lewis guns each with a 97-round drum and on the next 10 aircraft two 0.303 in (7.7 mm) Vickers ‘K’ guns each with a 100-round drum before the 161st aeroplane introduced the standard arrangement of two 0.303 in (7.7 mm) Browning guns with 400 rounds per gun.
There was only one major problem with the Gladiator Mk I, namely an overspeeding of the Watts propeller in a dive resulting in vibration that made it difficult to hold a target in the sight, and this led to the adoption of the Fairey-Reed propeller as soon as possible. From March 1938 a number of British-based Gladiator Mk I squadrons were able to start conversion to the more advanced Hurricane, and the aircraft these units relinquished were used for the re-equipment of a few home-based Gauntlet squadrons, five home-based Auxiliary Air Force squadrons, and several squadrons in Egypt and the Middle East where the Gladiator Mk I provided a much needed boost in British air power. The Gladiator Mk I was used operationally in northern Europe over Norway and France, suffering relatively heavy losses, but was more gainfully employed in the Mediterranean Middle East and North Africa.
The Gladiator proved most effective in the Middle East, where it was employed in the imperial policing role before the outbreak of World War II. This raised local demands for an improved version, and 24 of the last 28 Gladiator Mk I fighters were completed to the Gladiator Mk II standard deemed better suited to this theatre. The changes included the Mercury VIIIA engine rated 830 hp (619 kW) and built by a Bristol ‘shadow factory’ as the Mercury VIIIAS sub-variant with the three-blade propeller, a partially automatic boost control carburettor, a Vokes air filter over the carburettor air inlet, an electric starter, storage for desert survival equipment, and improved instrumentation.
During 1938 Gloster received an order for an initial 50 Gladiator Mk II fighters at the beginning of a production effort that saw the eventual delivery of 270 aircraft (231 to the RAF and the others to export customers) in 1938 and 1939. The Gladiator Mk II was dimensionally identical to the Gladiator Mk I except for its height of 11 ft 7 in (3.52 m), but differed in details such as its empty weight of 3,444 lb (1562 kg), maximum take-off weight of 4,864 lb (2206 kg), maximum speed of 223 kt (257 mph; 414 km/h) at 14,600 ft (4450 m), climb to 10,000 ft (3050 m) in 4 minutes 30 seconds, and service ceiling of 33,500 ft (11570 m). Despite the fact that it was somewhat heavier than the Gladiator Mk I, therefore, the Gladiator Mk II had slightly better performance and proved an invaluable asset in the Mediterranean theatre after Italy’s entry into the war in June 1940.
The type proved more than a match for the Italian air force’s biplane fighters in the North African campaign, and in the Greek campaign was also successful, although to a slightly less comprehensive extent, against the Italian air force’s first-generation monoplane fighters. Even after the Germans intervened from April 1941, the Gladiator Mk II was not wholly outclassed and was flown by the most successful RAF fighter pilot of World War II, Flight Lieutenant M. T. St. J. Pattle, a South African who scored most of his victories (an unknown number certainly in excess of 40 and possibly over 50) in the Gladiator. The RAF withdrew its last Gladiator Mk II fighters from first-line service in September 1941, but the type’s life was far from over as the Gladiator was then used by 12 meteorological reconnaissance flights and one meteorological reconnaissance squadron: the Gladiator made its last meteorological flight in January 1945.
Other second-line tasks included airfield defence, communications, radar calibration, flying training and army co-operation training. Some 30 of the RAF’s Gladiator Mk II fighters, it should be noted, were transferred to Finland in December 1939 for use in that country’s defence against the Soviet invasion of the ‘Winter War’ (1939/40). In March and April 1939, the Egyptian air force received 18 ex-RAF Gladiator Mk I fighters brought up to Gladiator Mk II standard, and in 1941 some 27 ex-RAF Gladiator Mk II fighters were also transferred: a few of the aircraft were later taken back on British charge. The final transfers of ex-RAF fighters to a Middle Eastern nation took place in 1940/42 and March 1944, in both instances to the Iraqi air force: the first transfer involved nine Gladiator Mk I fighters and the second five Gladiator Mk II fighters. The last of these Iraqi aircraft was retired only in 1949. Finally, in April 1941 11 ex-RAF Gladiator Mk II fighters were transferred to the South Africa Air Force to supplement one Gladiator Mk I handed over in January 1939 for evaluation purposes.
In 1937 the Admiralty woke up to the belated realisation that its carrierborne warplanes were not just obsolescent but indeed obsolete by current landplane standards. The Fleet Air Arm’s standard fighter at this time was the Hawker Nimrod biplane, and in 1937 the Admiralty asked the Air Ministry for information about which of the RAF’s current or forthcoming fighters could most readily be adapted for carrierborne deployment pending the arrival of the Fairey Fulmar monoplane fighter in FAA service. The Air Ministry decided that the Gladiator, now well proved and in full though limited production, was ideally suited to the task as it offered significantly higher firepower and performance than the Nimrod, yet was agile and with a stalling speed of little over 43 kt (50 mph; 80.5 km/h) was already fairly compatible with carrier operations.
In March 1938 Gloster received an order for the Sea Gladiator, and the first such aircraft were in fact the initial 38 Gladiator Mk II land-based fighters adapted with naval instruments, radio and a V-type arrester hook under the rear fuselage. Designated Sea Gladiator (Interim) in this form, the aircraft were delivered from December 1938: 13 were retained for initial training and the other 25 were issued to three naval air stations.
Ordered in June 1938, the Sea Gladiator Mk I was the definitive version of the Sea Gladiator. While still based on the Gladiator Mk II as modified with an arrester hook, the Sea Gladiator Mk I introduced changes such as catapult attachment points, an emergency dinghy in a ventral pack, and deletion of the internal spent case and belt link collector boxes in favour of long chutes to jettison these cases and links. The Sea Gladiator Mk I was dimensionally identical to the Gladiator Mk II, but differed in details such as its fuel capacity of 83 Imp gal (99.7 US gal; 377.3 litres), empty weight of 3,554 lb (1612 kg), normal take-off weight of 5,020 lb (2277 kg), maximum speed of 220 kt (253 mph; 407 km/h) at 14,600 ft (4450 m), cruising speed 184 kt (212 mph; 341 km/h) at optimum altitude, climb to 10,000 ft (3050 m) in 4 minutes 45 seconds, and service ceiling of 32,300 ft (9845 m).
Production of 60 aircraft was completed by February 1939, and the aircraft remained in first-line FAA service up to May 1941, seeing operational service over the North Sea, Norway, the Mediterranean and Malta. After their relegation from operational service, the surviving Sea Gladiators Mk I fighters were used for a variety of second-line task up to 1943.
Delivered between September 1937 and May 1938, the 22 aircraft for Belgium were Gladiator Mk I machines essentially identical to their British counterparts. Belgium also considered licensed production of the type by Avions Fairey at Gosselies, but nothing came of this scheme. The Belgian aircraft were involved in the hopeless attempt to stem the German invasion of May 1940, and were all lost in the air or on the ground during this campaign.
In October 1937 the Chinese authorities ordered 36 examples of the Gladiator Mk I as part of its sporadic and hopelessly confused effort to check the Japanese campaign of occupation in China (1932/45). The original plan was for the crated aircraft to be shipped to Hong Kong, erected at Kai Tak airfield and then flown to Canton for onward movement to Chinese bases. In the event the crated aircraft were delivered to Tien Ho airfield at Canton, where they were assembled between late 1937 and late 1938. The aircraft were used in small detachments for the defence of south-western Chinese cities, and were inadequate in numbers and capabilities to check the efforts of the Japanese air forces.
Between 1940 and 1944, the Iraqi air force received from stocks of surplus British aircraft nine and five examples respectively of the Gladiator Mks I and II. The aircraft were generally based at Mosul in the north of the country as used in the counter-insurgency role against dissident Kurds up to 1949, when continued maintenance of these elderly aircraft became uneconomical.
These four Gladiator Mk I fighters were delivered to the Irish Army Air Corps in 1938 and remained in service at Baldonnel airfield until 1941.
In January 1938 a Greek businessman bought two Gladiator Mk I fighters for presentation to the Greek air force. At the end 1940 the Greek government asked for additional aircraft, and a further 17 ex-RAF Gladiator Mk I and Gladiator Mk II fighters were transferred from British stocks in the middle East. All these aircraft were lost in the fighting that resulted in the conquest of Greece by the Italians and Germans.
Ordered in March 1937 and delivered between August and November of the same year, the 26 aircraft for the Latvian air arm were in essence Gladiator Mk I machines with an armament of four 0.303 in (7.7 mm) Vickers Mk VM machine guns. The fate of the surviving aircraft after the USSR’s 1940 annexation of the Baltic republics is uncertain, although some of the aircraft apparently received Soviet markings.
Ordered in March 1937 and delivered between October and November of the same year, the 14 aircraft aircraft for the Lithuanian air arm were in essence Gladiator Mk I machines with an armament of four 0.303 in (7.7 mm) Vickers Mk VM machine guns. The fate of the surviving aircraft after the USSR’s 1940 annexation and assimilation of the Baltic republics is uncertain, although some of the aircraft apparently received Soviet markings.
In April 1937 the Norwegian air force began negotiation for the purchase of six Gladiator Mk I aircraft as precursor to licensed production. The plan was later revised to the purchase of 12 aircraft, and of these the last six were delivered to Gladiator Mk II standard. The aircraft differed from their British counterparts only in their armament, which comprised a quartet of 0.3 in (7.62 mm) Colt-Browning machine guns. The aircraft were involved in the defence of Norway when the Germans invaded that country in April 1940, and succeeded in shooting down at least four German aircraft before being destroyed in the air, on the ground or, in the case of at least two aircraft, on a frozen lake whose surface broke.
In February 1939, Portugal contracted for 15 Gladiator Mk II fighters that were diverted from RAF orders, and later considered but did not place an order for a further 30 aircraft of the same type.
In 1937 the Swedish air force planned to acquire 55 examples of the Gladiator fighter as 37 Gladiator Mk I and 18 Gladiator Mk II aircraft. Deliveries of the Gladiator Mk I began in June 1937, and the aircraft received the local designation J 8. These differed from their British counterparts in their powerplant of one Mercury engine rated at 640 hp (477 kW) and driving a two-blade Watts wooden propeller of the fixed-pitch type. There followed delivery of the Gladiator Mk II fighters, which entered service with the local designation J 8A and the powerplant of one licence-built Mercury VII engine rated at 740 hp (552 kW) and driving a three-blade Fairey-Reed metal propeller of the fixed-pitch type. Ten of the aircraft were reserved as training and attrition replacement machines, and the other 45 were issued to the three squadrons of the 8.Flygflottilj (wing), which was formed in July 1938. Despite Sweden’s neutrality in World War II, the aircraft saw some service with the Swedish volunteer force that aided Finland in her ‘Winter War’ with the USSR. Many of the aircraft were fitted with Swedish-designed ski landing gear, and had underwing racks for eight light bombs. The aircraft fought in Finland until the end of the ‘Winter War’, losing three of their own number but downing a considerably larger number of Soviet aircraft. The Gladiator was withdrawn from first-line Sweden service in the spring of 1941.
Gloster Gladiator Mk I
Accommodation: pilot in the enclosed cockpit
Powerplant: one Bristol Mercury IX air-cooled 9-cylinder radial piston engine rated at 725 hp (541 kW) for take-off and 830 hp (619 kW) at 14,500 ft (4420 m)
Fuel capacity: 84 Imp gal (100.9 US gal; 381.9 litres)
Performance: maximum level speed ‘clean’ 220 kt (253 mph; 407 km/h) at 14,600 ft (4450 m) declining to 182 kt (210 mph; 338 km/h) at sea level; cruising speed, maximum 195 kt (225 mph; 362 km/h) at 14,500 ft (4420 m) and economical 182.5 kt (210 mph; 338 km/h) at optimum altitude; maximum rate of climb at sea level 2,300 ft (701 m) per minute; climb to 10,000 ft (3050 m) in 4 minutes 45 seconds and to 15,000 ft (4570 m) in 5 minutes 40 seconds; service ceiling 32,800 ft (9995 m); typical range 372 nm (428 miles; 689 km); endurance 2 hours 0 minutes
Weights: empty 3,600 lb (1633 kg); normal take-off 4,592 lb (2083 kg); maximum take-off 4,864 lb (2206 kg)
Dimensions: span 32 ft 3 in (9.83 m); area 323.00 sq ft (30.01 m²); length 27 ft 5 in (8.36 m); height 10 ft 7 in (3.22 m) with the tail down; wheel track 7 ft 2.5 in (2.20 m)
Armament: two 0.303 in (7.7 mm) Browning fixed forward-firing machine guns with 600 rounds per gun in the sides of the forward fuselage with synchronisation equipment to fire through the propeller disc, and two 0.303 in (7.7 mm) Browning fixed forward-firing machine guns with 400 rounds per gun in the leading edges of the lower wing