Reginald Joseph Mitchell can be considered one of the most important and influential figures in aviation in the 20th century. His creations were at the forefront of the process of aviation evolution, which, in the late XNUMXs, broke with the classic tradition of aircraft construction. It was through one of these projects, the S series of racing seaplanes, that Mitchell would gain international fame, later culminating in the project of his career: the unmistakable Spitfire.
RJ MITCHELL: CREATING A REPUTATION
Mitchell's first involvement with aviation occurred in 1916, when RJ was recruited by the design team of Supermarine Aviation Works, at the time a small company specializing in the construction of prototypes and seaplanes for the British Air Corps.
However, it would be four years before Mitchell produced his first design, called the Commercial Amphibian. The aircraft was an adaptation of Supermarine's own Channel models, which were originally intended for military patrol and anti-submarine reconnaissance purposes.
With the end of the war and surplus of the model, these seaplanes were modified to the civilian enger standard, but had a curved career, due to little comfort and low performance.
At the same time, Supermarine was looking at other ways to showcase its brand to the world. After losing a British government tender to Fairey for the development of a new long-range civil seaplane, the company was forced to resort to alternative means – one of the most interesting being the team's participation in the Schneider Trophy.
The trophy was one of the most important international competitions of the time, taking place annually and bringing together some of the most powerful names in aviation. This competition involved a series of races for high-performance seaplanes, presenting one of the greatest challenges in the aeronautical field.
The representation in these events was enviable, with big names in the hydrofoil segment competing regularly, such as Macchi, Savoia-Marchetti, Curtiss and Sopwith.
Supermarine's first appearance in these races came in the 1919 edition, with the Supermarine Sealion I. Mitchell had little involvement in the development of the aircraft and it is not surprising that the Sealion did not last even a lap in the race.
Despite the failure, the Southampton construction company saw the positive impact on its image that the event had had, which was reflected in a significant increase in sales of Mitchell's own “Commercial Amphibian”. Thus, in 1922, Supermarine returned to the Schneider Trophy, this time with the Sea Lion II model, designed by RJ himself.
Victory in the race against the favourites SM and Macchi elevated the previously unknown Mitchell to one of the most well-regarded names in the aeronautical sector at the time, with the designer later having a key role in the development of the Supermarine Seagull and the Southampton, two very successful projects by the company in the 20s.
Despite his success, Mitchell knew that none of his designs to date had been radical. To get to the forefront of aviation, he knew he needed to innovate, and to do so, the designer turned once again to the Schneider Trophy to test his latest project: the S family of seaplanes.
SCHNEIDER TROPHY: THE RACE FOR AVIATION DEVELOPMENT
The Curtiss CR.III had been the main attraction of the 1923 edition of the trophy. Despite being a seaplane, the machine had superior performance to almost all contemporary aircraft of its time, reaching speeds of over 390 km/h.
For Mitchell, who had the ambition to participate in the next event competitively, a thorough analysis of the American aircraft was necessary, which revealed the need for a significant improvement in the aerodynamics of the Supermarine aircraft and the requirement for an extremely powerful engine.
Taking note of the American project, Mitchell began developing the S.4 seaplane, which was prepared to participate in the 1925 Schneider Trophy. The aircraft broke completely with the lines of the previous Mitchell and Supermarine models, with a clean and elegant design giving the first outlines of the products that the company would produce in the following years.
With a cantilever wing monoplane design, the aircraft was powered by a 700 hp Napier Lion VII engine, an immense thrust for an aircraft of the time. According to technical data, the S.4 could reach over 380 km/h, good enough to take American aircraft into battle.
However, the S.4 was never able to prove its worth. Days before the race, the aircraft was involved in an accident in Baltimore Bay (USA), while training for the race. Crashing into the water after stalling in flight, the S.4 was completely destroyed – the pilot, Henry Biard, walked away from the disaster with only minor injuries.
Despite the total loss of the sole S.4 and the costs associated with the accident, Mitchell decided to move forward and develop an even more improved model of the slender seaplane, which would come to be known as the S.5.
Unveiled in time for the 1927 Schneider Trophy, the S.5 was a far more advanced aircraft than its predecessor. Powered by a 900 horsepower Napier Lion VIIA engine, the aircraft had a top speed of nearly 515 mph (XNUMX km/h).
Other, even more revolutionary details demonstrated that this was the aircraft with which Mitchell hoped to definitively make aviation history: the S.5 was built almost entirely (with the exception of the aircraft's wings) from light metal alloys, particularly duralumin, and almost all of the aircraft's structural elements were optimized for the highest possible performance.
Perhaps the most important point of the S.5 was the extensive use of wind tunnels to improve the aircraft's aerodynamics, something extremely rare at the time for private projects, due to the costs associated with using this technology.
However, the three S.5s built proved to be spectacular machines. In addition to winning the 1927 competition, an S.5 was again entered in the 1929 Schneider Trophy, finishing third. By this time, the S.5s had given way to Supermarine's definitive flying boats, the S.6 series.
SUPERMARINE S.6 AND S.6B: THE ANCESTORS OF THE SPITFIRE
The success of the S.5 proved that RJ Mitchell and Supermarine were on the right track with regard to developing the world's finest racing seaplane, which would be represented by the following series of models.
Despite the Royal Air Force's (RAF) involvement in the project, with the institution becoming a major enthusiast and sponsor of Mitchell's designs since his first Schneider Trophy victory in 1922, development of Supermarine's next generation of flying boats took a long time to take to the skies.
Due to the change in suppliers of the aircraft's propulsion, with Napier giving way to Rolls-Royce, the entire flight test schedule had to be rearranged. Both Supermarine, which had its image at stake, and the RAF, which had its own prestige at stake, put pressure on Rolls to have the engine ready in time for the 1929 Schneider Trophy, expected to take place in September.
In May, the first test of the Rolls-Royce R engine was carried out, and despite its good performance, the machine was below expectations, generating “only” 1545 hp. The team from the English manufacturer dedicated itself to studying how to improve the machine, while the clock was getting closer and closer to the deadline.
Meanwhile, Mitchell was putting the finishing touches on the design of the S.6, which, despite bearing a great similarity to the previous model, incorporated major refinements into its design.
The main ones were the all-metal construction of the aircraft, including wings and control surfaces, which were made entirely of high-quality aluminum. The radiators were built in a more aerodynamically efficient manner, below the fuselage and applying a creative oil cooling method, shared with that used by the engine itself.
Other less noticeable features also showed differences between the S.5 and the S.6, such as the use of the aircraft's floats as fuel storage and the 1 meter increase in the aircraft's wingspan.
However, the S.6's star attraction was undoubtedly its engine, which finally achieved the expected performance coefficients at the end of July. Reaching an impressive 1850 hp at maximum torque, the Rolls engine could take the S.6 to over 575 km/h, a record for the time.
Even with delays in engine delivery, two S.6s were ready to compete in the 1929 Schneider Trophy, held in Calshot (England). Lined up by the official RAF team (the High Speed Flight), these aircraft would have as teammates the lone S.5, facing a powerful contingent of Italian competitors, represented by Fiat (C.29), Savoia-Marchetti (S.65) and Macchi (M.52 and M.67).
The British tactic in the race was as follows: let the S.6 piloted by Lieutenant HRD Waghorn go as fast as possible, while the other S.6, commanded by Flight Officer Richard Atcherley, would mark time with the Italian aircraft. The older S.5, under the command of Lieutenant David D'Arcy Grieg, would follow with the peloton, taking advantage of retirements to move up in the classification.
In the case of the race, these tactics were unnecessary: Cadringher (in one of the M.67s) retired on the second lap because he was nearly blinded and suffocated by exhaust fumes, and Monti, in the second M.67, also had smoke problems and was forced to make a forced landing when nearly boiling water began to leak from the engine.
Atcherley also had visibility problems, which caused the driver to miss the entry point to the first corner. The S.6 cut across the inside of the lap marker pylon, being disqualified in the process.
Waghorn, on the other hand, overcame the problems and withstood the pressure from the remaining Macchi, crossing the finish line first; Molin was second in the M.52, and Greig, in the S.5 (as already mentioned), came third.
Mitchell, now intent on becoming the first designer to win three consecutive Schneider Trophies, wasted no time in beginning the design of his definitive seaplane, which would form the basis for all his aircraft to follow.
However, this project faced setbacks in its initial phase, due to the British Air Ministry's refusal to finance the new venture, using the delicate global economic situation at the time as an excuse.
After long discussions, which involved some public blackmail so that the RAF would once again sponsor Mitchell's team, the money to finance the initiative finally reached Supermarine, almost a year late.
Due to the short timeframe for developing a new aircraft, Mitchell had no choice but to update the original S.6 design to a new specification, which would come to be known as the S.6B.
An exterior comparison between the original S.6 and the S.6B may not reveal much to the less attentive observer, as the most significant changes were underneath the aircraft's fuselage.
The first point was to improve the aircraft's cooling, which had proven to be the S.6's biggest problem. To achieve this, an extra set of radiators had been installed on the S.6B's floats, improving not only the aircraft's internal temperatures, but also considerably improving the engine's performance.
Speaking of which, the Rolls-Royce R continued to be the propulsion device of choice for the S.6B. With improved cooling and special upgrades from the English firm, this engine reached an impressive 1931 hp in 2350.
For the 1931 Schneider Trophy, Supermarine would enter the two new S.6Bs, plus two older S.6s upgraded to the updated specification, designated as S.6A.
Despite the expected strong opposition from teams from and Italy, all of these turned out to be empty promises, as manufacturers from both countries had problems developing the aircraft they intended to enter in the race.
Therefore, the 1931 Schneider Trophy was already guaranteed to fall into the hands of Supermarine and Mitchell even before they did anything.
It would be the Supermarine S.6B (tail number 1595) piloted by Lieutenant John Boothman that would cross the finish line first, securing the first three-peat for a team in the history of the trophy.
Thus, from his days as an assistant at Supermarine to becoming head of the company's entire operation, H.J. Mitchell demonstrated his talent for deg performance aircraft that outperformed their rivals in many respects.
Through the creation of the S-class flying boats, Mitchell was laying the foundations for one of his most enduring legacies: the famous Spitfire, which would years later fly the colours of his country, just as the S-class had done a decade earlier.
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