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Gloster Gamecock

The Gloster Gamecock was a biplane fighter of the Royal Air Force, a development of the Mk III Grebe.

The Gamecock was a development of the earlier Grebe Mk III, an early interwar fighter procured by the Royal Air Force (RAF).

Work on the type commenced in 1924 as a response to Air Ministry Specification 37/23.

The principal difference between the two aircraft was the adoption of the Bristol Jupiter radial engine for the Gamecock in the place of the somewhat unreliable Armstrong Siddeley Jaguar.

Various other structural improvements were also made to the fuselage, the armament was also revised to include internally mounted machine guns.

On 22 February 1925, the prototype Gamecock performed its maiden flight.

Evaluation flights at RAF Martlesham Heath resulted in considerable praise for the aircraft; few changes were made as a result.

During September 1925, the Air Ministry placed an initial order for 30 production aircraft to fulfil Specification 18/25.

Further orders would quickly follow; the first production Gamecock flew in March 1926 and was delivered two months later.

While the type was often praised for its manoeuvrability and speed, it suffered a high rate of accidents in service, leading to a relatively brief flying career with the RAF.

The aircraft served considerably longer with the Finnish Air Force; it was produced under license for the service under the local name Kukko and saw action during the Winter War of 1939–1940 against the Soviet Union.

The origins of the Gamecock can be found in the earlier Gloster Grebe.

During the mid-1920s, this fighter had proven itself to be relatively popular amongst the pilots of the Royal Air Force (RAF), which typically praised it for its high maximum speed for the era and its manoeuvrability.

However, it was also clearly recognised that the Grebe also had some shortcomings even in its later models.

One prominent one was the unsatisfactory performance of the Armstrong Siddeley Jaguar engine, which had developed a reputation with ground crews for its poor reliability as well as being difficult to service.

Accordingly, Gloster became keenly interested in the replacement of the Jaguar with another engine and took an interest in the promising Bristol Jupiter radial engine that could deliver similar performance to the Jaguar while being both lighter and considerably less complex.

During the summer of 1924, the Air Ministry issued Specification 37/23, which was tailed around the development of a Jupiter-powered version of the Grebe.

Gloster commenced work on the project immediately thereafter.

Gloster’s design team, headed by Henry Folland, had also identified numerous improvements, typically relating to the aircraft’s structure, that could be made.

The fuselage was composed almost completely out of wood, although steel tie-rods were used for internal bracing, as well as a combination of aluminium and asbestos for a fireproof bulkhead at the back of the engine bay.

One of the more distinctive changes on the new aircraft was the adoption of internally mounted machine guns in place of the Grebe’s external armament arrangement along the top of the fuselage.

Less than six months from the specification’s issuing, Gloster had completed construction of the prototype, J7497, which was fitted with the Jupiter IV engine; by this time, orders for a further two prototypes had been ordered.

On 20 February 1925, it was delivered to RAF Martlesham Heath to commence a comprehensive evaluation; its maiden flight was performed two days later.

Within weeks of its arrival, the prototype’s Grebe-style unbalanced rudder was replaced by a redesigned horn-balanced counterpart.

It was determined to possess excellent manoeuvrability, in part due to its engine being placed so close to the aircraft’s centre of gravity, and the trials were considered to be a clear success.

By July 1925, in excess of 50 flight hours had been attained with the first prototype; no major changes were made at this stage of the aircraft’s development as no major flaws or concerns were being reported. 

Having been sufficiently convinced, in September 1925, the Air Ministry placed an initial order for 30 production aircraft to meet Specification 18/25, which were given the name Gamecock; these were to be powered by the improved Jupiter VI engine, as fitted to the third prototype.

During March 1926, the first production aircraft performed its maiden flight; delivered of the type commenced two months later.

During July 1926, a follow-on order from the Air Ministry for 40 more Gamecocks was received by Gloster; in November of that same year, another 18 aircraft were also ordered.



Prototype to Air Ministry Specification 37/23 powered by a Jupiter IV engine and first flown in February 1925.


Prototype with Jupiter IV engine.


Prototype with Jupiter VI engine.

Gamecock Mk I

Production single-seat fighter aircraft for the RAF, 90 built.

Gamecock Mk II

Single-seat fighter aircraft with revised wing and tail.

One new built for RAF with another Mk I converted to Mk II standard.

There were three exported to Finland in 1928, with a further 15 built under licence in Finland from 1929–1930 as the Kukko.

The type remained in Finnish service until 1944.

Gamecock Mk III

One RAF Gamecock Mk II modified with lengthened fuselage for spin trials.


A carrier-based version of the Gamecock produced as a private venture.

Manufactured under licence for the Imperial Japanese Navy as the Nakajima A1N.

About 150 were operated from 1929 to 1935 and saw combat during the Shanghai incident in 1932.

108 aircraft were built.





19 ft 8 in (5.99 m)


29 ft 9.5 in (9.081 m)


9 ft 8 in (2.95 m)

Wing area

264 sq ft (24.5 m2)

Empty weight

1,930 lb (875 kg)

Gross weight

2,860 lb (1,297 kg)

Fuel capacity

50 imp gals (60 US gal; 230 L)


1 × Bristol Jupiter VI,

9-cylinder air-cooled radial piston engine,

425 hp (317 kW)


2-bladed Watts wooden fixed-pitch propeller,

9 ft 0 in (2.74 m) diameter


Maximum speed

155 mph (249 km/h, 135 kn) at 5,000 ft (1,524 m)

145 mph (126 kn; 233 km/h) at 10,000 ft (3,048 m)


365 mi (587 km, 317 nmi)


2 hours 30 minutes

Service ceiling

22,100 ft (6,700 m)

Rate of climb

7,066 ft/min (35.90 m/s) at 1,000 ft (305 m)

Time to altitude

10,000 ft (3,048 m) in 7 minutes 36 seconds

Wing loading

10.8 lb/sq ft (53 kg/m2)


0.15 hp/lb (0.25 kW/kg)



2 × 0.303 in (7.7 mm) Vickers machine guns.



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