Reginald Joseph Mitchell CBE FRAeS (20 May 1895 – 11 June 1937) was a British aircraft designer who worked for the Southampton aviation company Supermarine from 1916 until 1936.

[3] He is likely to have played a role in the development of the Baby when in 1919 it was adapted for racing for the Schneider Trophy, and was renamed the Supermarine Sea Lion.

[11] When Supermarine's chief designer William Hargreaves left the company in the summer of 1919, he was replaced by Mitchell, who took up his new duties later that year, leading a team that had in 1918 consisted of six draughtsmen and a secretary.

[12][13] Following his promotion, the 19-year-old returned to Staffordshire and married his fiancée Florence Dayson, an infant school headmistress, who was 11 years his senior.

However, his early promotion was not unusual at that time; other men of Mitchell's age held similar positions in other aircraft companies.

Decades after his death, when approached for information about him, those surviving Supermarine colleagues who had known Mitchell were reluctant to recall their personal memories.

The historian Ralph Pegram notes that the unbuilt Torpedo Carrier reveals the "first true indication of Mitchell's thoughts as a designer".

[34] The Southampton was one of the most successful flying boats of the between-war period,[29] and established Britain as a leading developer of maritime aircraft.

Mitchell dispensed with the complicated curved surfaces for the wings and the hulls of the Air Yacht and the Southampton X, and as a result these aircraft appeared "boxy".

[39] In February 1929, Mitchell submitted patent GB 329411 A, "Improvements in the Cooling System of Engines for Automotive Vehicles", a condenser to be placed within the wings of an aircraft.

[42] Attempts by the company to sell a 5-engined flying boat failed when a contract was cancelled in early 1932, leading to job losses and wage cuts at Supermarine.

[43] However in 1933 the company's fortunes were revived when it received an order for 12 Scarpas (previously the Southampton IV) under the specification R.19/33, the first contract for a new design by Mitchell since 1924.

[46] Following the issuance of Air Ministry specification 5/36, Mitchell worked on a redesigned version of the Walrus, which was given the name Sea Otter.

[48] Mitchell and his design team worked on a series of racing seaplanes, built to compete in the Schneider Trophy competition.

These men were fundamental to Supermarine's success, as was the National Physical Laboratory (NPL), which provided invaluable support, guidance and scientific expertise in the form of detailed reports.

[3][52] There was not enough time for Supermarine to design a new flying boat for the 1923 competition, so the Sea Lion II was borrowed back from the Air Ministry to allow Mitchell to adapt it.

He increased its maximum speed by 10 knots (19 km/h; 12 mph), achieved with the assistance of D. Napier & Son, who supplied the 525 horsepower (391 kW) Lion III engine.

[54] The United States team, flying Curtiss seaplanes, dominated the competition,[3] with the winning pilot, David Rittenhouse, managing to reach a top speed of 177.27 miles per hour (285.29 km/h).

[64] Mitchell understood that a monoplane on twin floats produced lower drag than any other aircraft type of its day, and was convinced by wind tunnel tests at the NPL that the cantilever wing design was too heavy and should be abandoned.

[65] The NPL had demonstrated that flat-surfaced skin radiators reduced drag better than the corrugated variety preferred by American designers, so Mitchell used them to improve the S.5.

[62] Witnessed by the Italian dictator Benito Mussolini, along with a huge crowd gathered on the Venice Lido, the two Supermarine S.5s were the only seaplanes to finish the race, coming first and second.

Rolls-Royce, under pressure to produce an engine in time and that matched S.6's streamlined shape, adopted the partially-developed 825 horsepower (615 kW) Buzzard.

[72] Britain's final entry in the series, the Supermarine S.6B, marked the culmination of Mitchell's quest to "perfect the design of the racing seaplane".

[73] It was sponsored by a wealthy philanthropist, Lady Houston, who donated £100,000 (equivalent to £10 million in 2023)[74] after the British Government decided not to enter an RAF team for the 1931 contest.

[77] Mitchell was awarded the Commander of the Most Excellent Order of the British Empire (CBE) on 29 December 1931 for services in connection with the Schneider Trophy contest.

[82] The final design incorporated an open cockpit, four Vickers machine guns, and a 660 horsepower (490 kW) Rolls-Royce Goshawk engine, along with a fixed undercarriage.

At the time he was not told that, in preparation for a future war, the government had decided to build hard surface runways for the RAF, a decision that meant the modification to the Spitfire was necessary.

Mitchell's achievement lay in the merger of these different influences into a single design, originating from his "unparalleled expertise in high-speed flight... and a brilliant practical engineering ability, exemplified in this instance by the incorporation of vital lessons learned from Supermarine's unsuccessful type 224 fighter".

[58] The Society paid tribute to their colleague, describing him as being "a quiet, subtle, not obvious genius" who had "an intuitive capacity for grasping the essentials, getting to the point and staying there".

[58] Smith, who became Chief Designer at Supermarine after Mitchell's death,[97] said of him that "He was an inveterate drawer on drawings, particularly general arrangements,... [which were] usually accepted when the thing was redrawn.