Sopwith Dolphin

The Sopwith 5F.1 Dolphin was a British fighter aircraft manufactured by the Sopwith Aviation Company. It was used by the Royal Flying Corps and its successor, the Royal Air Force, during the First World War. The Dolphin entered service on the Western Front in early 1918 and proved to be a formidable fighter. The aircraft was not retained in the postwar inventory and was retired shortly after the war.

Design and development

In early 1917, the Sopwith chief engineer, Herbert Smith, began designing a new fighter (internal Sopwith designation 5F.1) powered by the geared 200 hp Hispano-Suiza 8B.Franks 2002, p. 7. The resulting Dolphin was a two-bay, single-seat biplane, with the upper wings attached to an open steel cabane frame above the cockpit. To maintain the correct centre of gravity, the lower wings were positioned forward of the upper wings, creating the Dolphin's distinctive negative wing stagger.Cooksley 1991, p. 34. The pilot sat with his head through the frame, where he had an excellent view. This configuration sometimes caused difficulty for novices, who found it difficult to keep the aircraft pointed at the horizon because the nose was not visible from the cockpit. The cockpit was nevertheless warm and comfortable, in part because water pipes ran alongside the cockpit walls to the two side-mounted radiator blocks. A pair of single-panel shutters, one in front of each radiator core and operated by the pilot, allowed the engine temperature to be controlled.

The first Dolphin prototype was powered by a geared 150 hp Hispano-Suiza 8B-series V-8 engine and featured a deep "car-type" frontal radiator.Mason 1992, p. 104.Davis 1999, p. 126.Bruce 1969, p. 15. Test pilot Harry Hawker carried out the maiden flight on 23 May 1917.Robertson 1970, p. 102. In early June, the prototype was sent to Martlesham Heath for official trials. On 13 June, the prototype flew to Saint-Omer, France, where the aircraft's unfamiliar shape prompted Allied anti-aircraft gunners to fire on it. Several pilots, including Billy Bishop of No. 60 Squadron, evaluated the prototype and reported favourably.Davis 1999, pp. 126–127. On 28 June 1917, the Ministry of Munitions ordered 200 Dolphins from Hooper & Co.Davis 1999, p. 127. Shortly afterwards, the Ministry ordered a further 500 aircraft from Sopwith and 200 aircraft from Darracq Motor Engineering Company.

The second prototype introduced upper wing radiators in lieu of the frontal radiator and large cut-outs in the lower wing roots, to improve the pilot's downward vision. These features proved unsuccessful and were omitted from subsequent aircraft.Davis 1999, p. 128. The third and fourth prototypes incorporated numerous modifications to the radiator, upper fuselage decking, fin and rudder.Franks 2002, p. 8. The fourth prototype was selected as the production standard. Series production commenced in October 1917, with 121 Dolphins delivered by the end of the year.

Operational history

The Dolphin Mk I became operational with Nos. 19 and 79 Squadrons in February 1918 and Nos. 87 and 23 Squadrons in March. The Dolphin's debut was marred by several incidents in which British and Belgian pilots attacked the new aircraft, mistaking it for a German type.Franks 2002, p. 11. For the next few weeks, Dolphin pilots accordingly exercised caution near other Allied aircraft.

New pilots also voiced concern over the Dolphin's wing arrangement, fearing serious injury to the head and neck in the event of a crash.Franks 2002, p. 21. Early aircraft were often fitted with improvised crash pylons consisting of steel tubes over the cockpit to protect the pilot's head. Experience showed that fears of pilot injury from overturning were largely unfounded. Crash pylons disappeared from frontline aircraft, though they were often retained on trainers. Night-flying Dolphins of No. 141 Squadron, a Home Defence unit, had metal loops fitted above the inner set of interplane struts.Lamberton 1960, p. 62.

Despite early problems, the Dolphin proved successful and generally popular with pilots. The aircraft was fast, manoeuvrable, and easy to fly, though a sharp stall was noted. In his memoir ''Sagittarius Rising'', Cecil Lewis described a mock dogfight between his S.E.5 and a Dolphin: "The Dolphin had a better performance than I realised. He was up in a climbing turn and on my tail in a flash. I half rolled out of the way, he was still there. I sat in a tight climbing spiral, he sat in a tighter one. I tried to climb above him, he climbed faster. Every dodge I have ever learned I tried on him; but he just sat there on my tail, for all the world as if I had just been towing him behind me."

When functioning properly, the Dolphin's Hispano-Suiza engine afforded excellent performance at high altitude. Accordingly, the Dolphin was often sent against German reconnaissance aircraft such as the Rumpler C.VII, which in its specialized ''Rubild'' photo-reconnaissance version routinely operated at altitudes above . No. 87 Squadron explored the use of equipment to supply pilots with oxygen at high altitude but the experiment was abandoned after trials showed that the oxygen tanks exploded when struck by gunfire.

Four Royal Air Force squadrons operated the Dolphin as their primary equipment, while other squadrons used it in small numbers. No. 1 (Fighter) Squadron, a Canadian Air Force unit, formed with Dolphins at RAF Upper Heyford.Milberry 1984, p. 16. The unit became operational shortly after the Armistice. In October 1918, the American Expeditionary Force purchased five standard Mk Is for evaluation, sending four back to the United States.

The highest-scoring Dolphin unit was No. 87 Squadron, which shot down 89 enemy aircraft.Robertson 1970, p. 106. Pilots of No. 79 Squadron shot down 64 enemy aircraft in the eight and a half months that the aircraft was at the front. The top two Dolphin aces served in No. 79 Squadron. Captain Francis W. Gillet, an American, scored 20 victories in the type.Franks 2002, p. 31. Lieutenant Ronald Bannerman, a New Zealander, scored 17 victories.Franks 2002, p. 32. The third-ranking Dolphin ace was Captain Arthur Vigers of No. 87 Squadron, who attained all 14 of his victories in the same aircraft, serial no. C4159.Franks 2002, p. 53. Another notable ace, Major Albert Desbrisay Carter

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