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Supermarine Type 224

The Supermarine Type 224, an inverted gull-wing monoplane fighter aircraft, was meticulously designed by R.J. Mitchell at Supermarine in response to Air Ministry Specification F.7/30.

This specification aimed to procure a fighter aircraft that would surpass the capabilities of the Gloster Gauntlet.

Equipped with the Rolls-Royce Goshawk engine, which incorporated an innovative evaporative cooling system, the Type 224 encountered significant setbacks.

The flaws in this cooling system, coupled with its underwhelming performance, ultimately led to its rejection.

Consequently, the contract for production aircraft was awarded to the Gloster Gladiator instead.

Despite its shortcomings, the Type 224 remains noteworthy due to the invaluable lessons R.J. Mitchell gleaned from its failure.

These lessons played a pivotal role in his subsequent triumph with the iconic Supermarine Spitfire.

Specification F.7/30, which was officially released to the aircraft industry in October 1931, outlined the requirements for a day and night fighter made entirely of metal.

This fighter was expected to be equipped with four machine guns, possess a high top speed and rate of climb, and have a landing speed below 60 mph.

The specification emphasized the significance of providing the pilot with a clear and unobstructed view from the cockpit.

While the use of any power plant was allowed, the Air Ministry expressed a preference for the Rolls-Royce Goshawk, which was undergoing evaporative cooling development at that time.

Out of the numerous proposals submitted by manufacturers, three were chosen for official development as prototypes, with the Supermarine 224 being one of them.

Additionally, privately funded submissions for the competition were also encouraged. R. J. Mitchell, the designer at Supermarine, devised an aesthetically pleasing inverted gull-wing monoplane that was propelled by the 600 hp Goshawk II engine and featured a fixed undercarriage.

The decision to adopt the gull wing configuration was made with the intention of reducing drag by shortening the undercarriage legs.

However, it was well-known that this particular configuration had the potential to cause issues with lateral stability.

To address this concern, an extensive program of wind-tunnel testing using models was conducted prior to finalising the design.

These tests not only confirmed the anticipated problems with lateral stability but also revealed a lack of directional stability.

Consequently, Mitchell made the necessary adjustments by increasing the size of the fin area.

In order to ensure the pilot’s comfort and safety, the cockpit was designed to be open.

To guarantee that the pilot would not experience excessive buffeting, additional wind-tunnel tests were conducted on a full-scale model of the cockpit area.

The fuselage was constructed using a monocoque design, and the armament consisted of one pair of guns mounted on each side of the cockpit, with another pair housed in the ‘trouser’ fairings of the undercarriage.

The wing exhibited an unconventional design, featuring a solitary primary spar positioned at the front.

In front of this spar, the condensers of the engine cooling system were integrated into the entire leading edge of the wing.

This unique combination resulted in the formation of a ‘D-box’ spar, which possessed exceptional torsional rigidity.

Behind the primary spar, the wing was covered with fabric, providing a protective layer.

The system had previously been tested on different aircraft, all of which were biplanes with the condensers and collector tank placed on the upper wing.

However, in the Type 224 aircraft, the collector tanks were located in the undercarriage fairings.

Due to the condensed water being close to boiling point, it was prone to turning into steam with even a slight change in pressure.

This issue often led to the water pumps malfunctioning and stopping their operation.





29 ft 5+14 in (8.973 m)


45 ft 10 in (13.97 m)


11 ft 11 in (3.63 m)

Wing area

295 sq ft (27.4 m2)



NACA 0018



Empty weight

3,422 lb (1,552 kg)

Gross weight

4,743 lb (2,151 kg)


1 × Rolls-Royce Goshawk II,

V-12 evaporative/steam cooled piston engine,

600 hp (450 kW)


2 bladed fixed pitch propeller


Maximum speed

228 mph (367 km/h, 198 kn) at 15,000 ft (4,572 m)

Service ceiling.

38,800 ft (11,800 m) Absolute ceiling

Time to altitude

15,000 ft (4,572 m) in 9 minutes 30 seconds



4 × 0.303 in (7.7 mm) Vickers Mk IV machine guns

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