Sopwith Dolphin prototype with car-type radiator
The Dolphin prototype with its original "car-type" frontal radiator.
Designed in 1917 by Sopwith Aviation Company Chief Engineer, Herbert Smith, the Sopwith Dolphin was the company's first attempt to produce a high-altitude fighter although the initial intention had been to design an aircraft that would provide the pilot with a greater field of vision than any other contemporary fighter.
The span of the Sopwith Dolphin's wings was increased beyond that of its predecessor, the Sopwith Camel  A two-bay wing configuration was adopted and was used to provide great structural strength without significantly increasing the aircraft's weight. At the same time the interplane gap was also reduced and forming the most outstanding characteristic of the new fighter, a negative stagger whereby the lower wings being positioned forward of the upper wings. The stagger of 12in was adopted to maintain the correct centre of gravity.
The pilot's head was in the rectangular space between the upper wing spars, affording an excellent view unobscured by the upper wing. Pilots initially experienced difficulties in keeping the aircraft pointed at the horizon as because of this the nose could not be seen from the cockpit.
Armament comprised a pair of moveable Lewis guns, mounted on the forward cabane crossbar, firing at an upward angle above the arc of the propeller. Additionally, it featured two fixed Vickers machine-guns, partly faired into the engine cowling forward of the cockpit, firing through the propeller disc.
The prototype Sopwith Dolphin was powered by a geared Hispano-Suiza V8 engine with a tall 'car-type' frontal radiator. It made its first flight in the hands of test pilot Harry Hawker, on 22nd May 1917.
Following official testing at Martlesham Heath, the prototype was then sent to France during mid-June 1917, for evaluation in the field. It was found to be fast, agile, relatively easy to fly and capable of delivering a hefty punch in terms of firepower.
As a result, a contract for 500 Sopwith Dolphins was awarded to Sopwith aircraft Company that same month, with further contracts being issued to the company and sub-contract manufacturers Hooper & Co and Darracq.
Sopwith Dolphin port front production
The Dolphin's radiators were relocated the radiator to the flanks, leaving a more streamlined nose.
The second Sopwith Dolphin prototype introduced a revised radiator configuration, with the tall frontal radiator divided into two parts and placed one on each side of the fuselage, level with the cockpit. The nose was tapered and the tail surfaces enlarged and these modifications became standard on production examples.
The Sopwith Dolphin entered service with the Royal Flying Corps in early 1918, although its unusual shape led to numerous early 'friendly fire' incidents with Allied pilots mistaking it for a new German type.
Despite early engine problems, the Sopwith Dolphin proved popular with its pilots and enjoyed particular success against high-flying German Rumpler reconnaissance aircraft, often at altitudes of 20,000ft-plus. Engine reliability problems were addressed by replacing the geared Hispano-Suiza engine with a direct-drive variant, examples of which were built in Britain as the Wolseley Viper and designated Dolphin Mk IIIs.
The Sopwith Dolphin's success continued after the establishment of the Royal Air Force (RAF) in April 1918.
Unfortunately, it never achieved the iconic status of its arguably more photogenic stable-mate, the Sopwith Camel, despite being an equally formidable fighter. For example, on 30th October 1918, nine Sopwith Dolphins were escorting a flight of DH9A bombers when they were attacked by 30 enemy fighters. 11 of aggressors were shot down at the cost of five Dolphins and three of the RAF pilots were later recovered uninjured.
When the Armistice with Germany was signed in November 1918, Sopwith Dolphins were being built under-licence by the French government's Société Anonyme des Constructions Aéronautique, for use by the French air arm and the US Army Air Service. Powered by 300hp Hispano-Suiza 8F direct-drive engines, these were designated Sopwith Dolphin Mk IIs. They also incorporated adjustable tailplanes and additional strengthening to allow for the increase in power.
The Sopwith Dolphin also saw service with the Polish Air Force during the Polish-Soviet War of 1919–20. During the conflict, some ten examples were used briefly as ground-attack machines from the summer of 1920 until the lack of spare parts saw the Dolphin force grounded. Later that same year, two of the Polish Sopwith Dolphins were loaned to the Ukrainian Air Arm to fight against the Soviets although both were returned to Poland in early 1921.
It is thought that nearly 2,100 Sopwith Dolphins had been built by the time production ended in August 1919. The type was retired surprisingly quickly after the end of the First World War and was declared obsolete by 1921.
Sopwith Dolphin C3988 RAF Museum
The Dolphin C3988 displayed at the RAF Museum uses parts from a number of original aircraft.
There are no complete Sopwith 5F.1 Dolphins still in existence today, although a magnificent composite aircraft comprising various surviving parts of original machines is on display in the Grahame White Hangar at Royal Air Force Museum Hendon. A replica Dolphin was also built by the Old Rhinebeck Aerodrome Flying Museum in New York State during 1977. Sadly, it has not flown since a forced landing in 1990 and it remains under restoration to non-airworthy status.
Little-known and still much under-rated, the Sopwith Dolphin nevertheless played a significant part in the latter stages of the Great War and was one of the fledgling RAF's first state-of-the-art fighters.
Wing Commander M.M. Fry, who flew the type, recalled 'Looking back, the Dolphin was a splendid machine; strong, easy on the controls, no flying vices and, owing to its large wing surface, it had an excellent performance high up. I fact, I should think at the time it had a better performance at, say, over 15,000ft, than any other British or German machine'.
Sopwith Dolphin three view drawing
Sopwith three-view drawing of the Dolphin, dated November 1917.



Dolphin Mk I  
Main production version. Powered by geared 200hp Hispano-Suiza 8B
Dolphin Mk II            
Manufactured under licence in France by Société Anonyme des
Constructions Aéronautique. Powered by direct-drive 300hp Hispano-Suiza 8F
Dolphin Mk III
Production version powered by direct-drive 200hp Hispano-Suiza 8B
or Wolseley Viper

Specification (Dolphin Mk I)

One 200hp V8 Hispano-Suiza 8B geared or 220hp Hispano-Suiza
direct-drive or 300hp Hispano-Suiza 8F or 200hp Wolseley Viper
water-cooled piston engine.
32ft 6in
Maximum weight
Capacity & Armament
One pilot; two fixed 0.303in Vickers machine-guns and one
or two Lewis machine-guns; provision to carry four 25lb Cooper bombs
Maximum speed
136 mph at sea level, 122 mph at 10,000ft; 114 mph at 15,000ft

Survivors & Replicas

Royal Air Force Museum Hendon, London, UK.
The airframe is based on an original 6ft length of rear fuselage from serial C3988, and incorporates original parts from serials D5329 and C4033.

Other information

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