Supermarine S.4

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Supermarine S.4

The Supermarine S.4, an aircraft crafted in 1920s Britain, was a single-engined monoplane produced by Supermarine. The design process was led by a team under the direction of the company’s chief designer, R. J. Mitchell, with the specific aim of entering the 1925 Schneider Trophy contest.

Mitchell’s design was nothing short of revolutionary. He recognized the significance of minimizing drag to enhance speed, leading to the creation of a floatplane that stood in stark contrast to the flying boats previously developed by Supermarine. Constructed from wood and featuring an unbraced cantilever wing, the aircraft was powered by a Napier Lion engine designed to deliver 700 horsepower (520 kW) for short bursts during races. The S.4 exhibited both aerodynamic prowess and visual appeal, although its cockpit placement had a potential safety drawback, limiting the pilot’s visibility. Within less than a month of its inaugural flight on August 24, 1925, the aircraft set a new world seaplane speed record at 226.752 miles per hour (364.922 km/h).

However, at Bay Shore Park in Baltimore, the chosen venue for the 1925 contest, the S.4 sustained damage to its rear due to a falling pole during a gale preceding the event. After being repaired and undergoing navigation trials on October 23, the aircraft was performing well. Yet, for reasons not fully understood, it suddenly lost control and plunged into the sea from a height of 100 feet (30 m) during the trials, resulting in the destruction of the plane and injuries to its pilot, Henri Biard.

The practical insights gleaned from the S.4 project significantly informed Mitchell’s subsequent work on its immediate successor, the Supermarine S.5.

Supermarine S.4





First flight


Number built

 Racing floatplane

United Kingdom


R. J. Mitchell

24 August 1925

Destroyed 23 October 1925








Maximum speed



26 ft 7+3⁄4 in (8.122 m)

30 ft 7.5 in (9.335 m)

11 ft 8.75 in (3.5751 m)

2-bladed fixed-pitch propeller

239 mph (385 km/h, 208 kn)

0.21 hp/lb (0.35 kW/kg)

Creation and Development

In the year 1925, R. J. Mitchell, the chief designer at Supermarine, was deeply engrossed in developing a novel aircraft for participation in the upcoming Schneider Trophy race. The decision to embark on this design endeavor was reached through a collaborative effort between Napier and Supermarine on March 18, 1925. Having witnessed the impressive performance of the American entrants in the preceding contest, Mitchell was acutely mindful of the imperative to minimize drag forces in order to enhance speed. Supermarine’s fresh concept revolved around a mid-wing, cantilever floatplane, resembling the French monoplane, the Bernard SIMB V.2, which had broken the flight airspeed record in December 1924. This innovative design stood in stark contrast to the flying boats that Mitchell had conceived for the prior Schneider Trophy races, where the Supermarine entries had secured victory in 1922 and secured a third-place finish behind the American Curtiss CR seaplanes in 1923.

The designation “S.4” was personally chosen by Mitchell, with the “S” representing Schneider. In his view, the earlier Schneider Trophy contenders (the Supermarine Sea Lion series) were S.1, S.2, and S.3. The S.4 marked a significant turning point as the first Schneider Trophy entrant to receive support from the British government. This support came in the form of an agreement to purchase the aircraft if Supermarine and Napier should bear the initial costs of development and construction. In this endeavor, the British Air Ministry offered more latitude to the British teams than their US counterparts experienced from their government.

Characterized as a monoplane seaplane, the S.4 showcased an unbraced cantilever wing and a semi-monocoque fuselage. It derived power from a specially engineered variant of the Napier Lion engine, a water-cooled powerplant developed to deliver 700 horsepower (520 kW) for brief racing intervals. Predominantly fashioned from wood, the aircraft featured a single-piece unbraced wing fortified with two spars, plywood webs, and spruce flanges. This wing was enveloped with plywood and bolstered by stringers. The fuselage was cloaked in diagonally arranged spruce planks secured over plywood formers, forming a framework around a pair of steel A-frames. These frames facilitated the attachment of the engine bearers and wing spars and supported the floats. Crafted from metal, the single-step floats bolstered the aircraft’s aquatic capabilities. Notably, while the S.4 lacked the then-unavailable newly designed surface radiators, its overall design was distinguished by its aerodynamic and visually pleasing aspects. The radiators, which were positioned beneath the wings, constituted the sole elements protruding from the fuselage.

Supermarine S.4 Creation and development

Supermarine S.4 Creation and development
Supermarine S.4 Creation and development

In the month of September in the year 1925, the publication Flight provided the following observation:

It is perhaps fitting to characterize the Supermarine-Napier S.4 as a creation that appears to have been conceived in a moment of inspiration, yet bearing within it all the qualities emblematic of British craftsmanship meticulously integrated into its minutiae. It is undeniable that the design exudes a sense of audacity, and we hold in high regard Mr. R. J. Mitchell, the chief designer at the Supermarine Aviation Works, for his audacious departure from conventional approaches and his bold venture into entirely uncharted realms.

— “The Schneider Cup Seaplane Race,” Flight (September 25, 1925)


Assigned with the civil registration G-EBLP and the Air Ministry serial number N197, the S.4 achieved its inaugural flight on August 24, 1925. This historic event was witnessed by none other than Mitchell himself, who embarked on a motorboat excursion alongside Lord Mountbatten. The testing phase was conducted at Calshot, chosen due to the significant distance required for successful take-offs.

Supermarine’s esteemed chief test pilot, Henri Biard, reportedly harbored reservations about the S.4. He expressed dissatisfaction with the unbraced wings and the cockpit’s placement, situated well behind the wings. The cockpit’s positioning posed a potential danger, as it impeded the pilot’s forward visibility, especially during critical moments like take-off and landing. In fact, during its maiden flight, the S.4 narrowly avoided a collision with an ocean liner due to this very issue.

Remarkably, on September 13, 1925, traversing a straight course spanning 1.864 miles (3.0 km) over Southampton Water, the S.4 succeeded in elevating the world’s seaplane speed record (alongside setting the British speed record) to an astonishing 226.752 miles per hour (364.922 km/h). This feat reverberated across the press, generating considerable sensation upon its revelation a month later.

Henri Biard and R. J. Mitchell in front of the S.4

Henri Biard and R. J. Mitchell in front of the S.4
Henri Biard and R. J. Mitchell in front of the S.4

Trophy competition of 1925

Carrying high aspirations for a British triumph in the upcoming Schneider Trophy competition at Bay Shore Park in Baltimore, the S.4, accompanied by two Gloster III biplanes, embarked on a journey to the US aboard the SS Minnewaska, enjoying a waived shipping fee. However, during the voyage, Supermarine’s pilot, Biard, sustained a wrist injury while playing tennis.

Unfavorable weather conditions hampered the practice opportunities for the already-present Schneider Trophy competitors. The aircraft remained confined within their crates, awaiting the erection of canvas hangars on the beach for their accommodation. Amid these circumstances, Biard fell ill with influenza, although he managed to recover sufficiently to partake in the competition. Unfortunately, strong winds had toppled the hangar housing the S.4, resulting in damage to the aircraft’s rear section caused by a falling pole. The S.4 was repaired in time for navigation trials on October 23, 1925.

During these trials, the S.4 initially performed well, yet upon its return to shore, a violent oscillation of the control column ensued, leading Biard to lose control of the aircraft at high speed. The S.4 entered a stall before descending abruptly into the sea from a height of 100 feet (30 m). Biard, initially rendered unconscious while still strapped to the airplane, managed to surface from the depths and grasp onto floating debris. Regrettably, the first rescue launch dispatched to him encountered engine troubles, necessitating his salvation by a second launch. Amid the rescue, Mitchell, who was aboard the rescuing boat, jestingly inquired of the injured pilot, “Is the water warm?” Subsequent examination revealed that Biard had suffered two broken ribs.

The Supermarine S.4 (left of centre) prior to the start of the 1925 Schneider Trophy competition

The Supermarine S.4 (left of centre) prior to the start of the 1925 Schneider Trophy competition
The Supermarine S.4 (left of centre) prior to the start of the 1925 Schneider Trophy competition

Although parts of the wrecked aircraft were salvaged, the exact cause of the accident remained uncertain. While flutter was commonly suggested as the cause, an official inquiry conducted later failed to definitively establish the reasons behind the tragic crash.

Aftermath of the Crash

Two days following the S.4’s tragic crash, the victory in the race was secured by Lieutenant James Doolittle, piloting a Curtiss R3C, achieving an average speed of 232.573 mph (374.443 km/h). This speed surpassed the S.4’s world record set just a month earlier. The success of the American team emphasized to other participating nations that a comprehensive approach to the contest, involving thorough pilot training and meticulous aircraft development testing, was imperative. Mitchell highlighted this necessity in a lecture he delivered to the Royal Aeronautical Society in 1927. Starting from 1925, the Air Ministry adopted a policy that entailed conducting wind tunnel tests to assess the performance of their high-speed aircraft productions.

Supermarine S.4 Aftermath of the crash

Supermarine S.4 Aftermath of the crash
Supermarine S.4 Aftermath of the crash


The Supermarine S.4 emerged as a groundbreaking aircraft that stood years ahead of its era, pioneering design principles that would endure throughout the 1930s and 1940s. Its technological advancements were remarkable, with state-of-the-art floats and a bracing-wire-free wing that marked a departure from Supermarine’s earlier aircraft models. John D. Anderson, an aviation historian, observes that the S.4 embodied Mitchell’s willingness to integrate novel technology while adhering to a proven conceptual design approach. This aircraft represented a revolutionary shift in airplane design that profoundly influenced subsequent Schneider racing planes. The victorious Italian Macchi M.39 from the 1926 Schneider competition bore distinct similarities to the S.4. Mitchell drew on his practical insights from the S.4’s development when crafting its successor, the Supermarine S.5, which is often regarded as his initial major achievement.

Drawings and archival footage chronicling the S.4’s construction, along with a five-minute film capturing its inaugural takeoff and flight, have been preserved in the biographical movie about Mitchell, “The First of the Few” (1942), directed by Leslie Howard.

The design of the S.5 incorporated features aimed at mitigating wing flutter, a factor that was believed to contribute to the S.4’s demise. The S.5’s monoplane wings were braced with wires, its fuselage cross-section was reduced, and streamlined floats were added—all intended to enhance speed over its predecessor. The most significant speed enhancement, approximately 24 miles per hour (39 km/h), was achieved by introducing surface radiators to cool the engine. These radiators notably minimized drag forces acting on the aircraft. Testing conducted on a model of the S.4 at the National Physics Laboratory post-crash revealed that the Lamblin radiators accounted for one-third of the aircraft’s drag and that without them, the S.4 would have ranked as the “cleanest” monoplane globally.

A screenshot taken from the British film "The First of the Few" (1942), featuring a scene of the Supermarine S.4 during takeoff.

A screenshot taken from the British film "The First of the Few" (1942), featuring a scene of the Supermarine S.4 during takeoff.
A screenshot taken from the British film "The First of the Few" (1942), featuring a scene of the Supermarine S.4 during takeoff.


  • Crew: 1
  • Length: 26 ft 7+3⁄4 in (8.122 m)
  • Wingspan: 30 ft 7.5 in (9.335 m)
  • Height: 11 ft 8.75 in (3.5751 m)
  • Wing area: 139 sq ft (12.9 m2)
  • Empty weight: 2,600 lb (1,179 kg)
  • Gross weight: 3,191 lb (1,447 kg)
  • Powerplant: 1 × Napier Lion VII W-12 liquid-cooled piston engine, 680 hp (510 kW) at 2,000 rpm
  • Propellers: 2-bladed fixed-pitch propeller
  • Maximum speed: 239 mph (385 km/h, 208 kn) [12]
  • Wing loading: 23 lb/sq ft (110 kg/m2)
  • Power/mass: 0.21 hp/lb (0.35 kW/kg)


Who Won the Schneider Trophy in 1925?

The 1925 Schneider Trophy was impressively won by Jimmy Doolittle, an American pilot who would later gain fame for his role during World War II. Doolittle flew a Curtiss R3C-2 racer, which stood out for its cutting-edge design and remarkable speed.

What Planes Did Supermarine Make?

Supermarine, a British aircraft manufacturer, is best known for creating the iconic Spitfire. However, their repertoire was diverse, including other significant models such as the Supermarine Walrus, the Supermarine S.6B (famous for its Schneider Trophy victories), and the Stranraer, among others.

Where Is the Schneider Trophy Kept?

Today, the Schneider Trophy resides at the Science Museum in London. It’s a testament to the golden age of air racing and represents a period of intense technological advancements in aviation.

When Was the Last Schneider Trophy Race?

The final Schneider Trophy race was held in 1931. The competition ended when Britain won the trophy outright after securing three consecutive wins, which was a stipulated condition from the race’s inception.

Who Offered the £100,000 Required to Enable the RAF to Win the Schneider Trophy Outright in 1931?

Lucy, Lady Houston, a British philanthropist, donated the crucial £100,000 needed for the Royal Air Force to compete in and ultimately win the 1931 Schneider Trophy. Her funding was pivotal in securing the trophy for Britain permanently.

Who Made the Schneider Trophy?

The Schneider Trophy was crafted by the renowned French sculptor Raoul Larche. Larche, known for his Art Nouveau style, created a sleek and stylized depiction of Icarus, fitting for an aviation trophy.

What Was the Fastest Plane in WW2?

The fastest plane in World War II was the Messerschmitt Me 262, a German jet-powered aircraft. Its top speed exceeded 540 mph, a remarkable feat for the time and a significant advancement in aviation technology.

What Replaced the Spitfire?

The Spitfire was eventually succeeded by various models of jets in the Royal Air Force post-World War II, including the Gloster Meteor. The Meteor was Britain’s first jet fighter and a direct evolution from the piston-engine fighters of the war.

What Was the Fastest Spitfire?

The fastest variant of the Spitfire was the Mk XIV. Powered by the Rolls-Royce Griffon engine, it could achieve speeds of up to 448 mph, making it one of the fastest piston-engine fighters ever built.

Where Is the Real World Cup Trophy?

The original FIFA World Cup Trophy, also known as the Jules Rimet Trophy, was stolen in 1983 and never recovered. The current trophy, introduced in 1974, is kept securely by FIFA and only presented to winning nations during the World Cup.

Which Trophy for Football?

The most prestigious trophy in football is the FIFA World Cup Trophy, awarded every four years to the winning country of the World Cup tournament. It is one of the most recognizable sports trophies globally.

What Year Was the First Non-Stop Transatlantic Flight?

The first non-stop transatlantic flight was completed in 1919 by British aviators John Alcock and Arthur Brown. This historic flight covered the Atlantic from Newfoundland, Canada, to Clifden, Ireland.

What Is the Oldest Trophy in Racing?

The oldest trophy in racing is the America’s Cup. Established in 1851, this prestigious yachting competition remains one of the pinnacle events in the sport.

Was Geoffrey Crisp Real?

Geoffrey Crisp is a fictional character and not a historical figure. His name may appear in narratives or fictional settings but does not correspond to a real person in history.

What Was the Schneider Trophy Race in 1925?

The Schneider Trophy race of 1925 was a celebrated event in air racing history, won by American pilot Jimmy Doolittle. The race highlighted advancements in aircraft technology and performance, setting the stage for future aeronautical achievements.

What Was the Last Supermarine Plane?

The last aircraft produced by Supermarine was the Scimitar, a British naval jet fighter. Introduced in the late 1950s, the Scimitar represented the final evolution of Supermarine’s extensive aircraft design experience.

Which Is Better, Spitfire or P-51?

The debate between the Spitfire and the P-51 Mustang is a classic among aviation enthusiasts. Both aircraft were instrumental during WWII and had their strengths. The Spitfire was renowned for its agility and handling, while the P-51 excelled in range and speed, particularly at high altitude.

Who Had the Best Planes in WW2?

Determining who had the “best” planes in WW2 can be subjective, as different countries excelled in various aspects. The United States produced the long-range P-51 Mustang; Britain brought the versatile Spitfire, and Germany developed the technologically advanced Me 262 jet.

What Was the German Famous Plane?

The most famous German plane during World War II was the Messerschmitt Bf 109. It was a staple of the Luftwaffe and served in various roles thanks to its excellent design and adaptability.


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