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 , however , and was retired shortly after the war . Design and development . In early 1917 , Sopwith ' s chief engineer Herbert Smith began designing a new fighter ( internal Sopwith designation 5F . 1 ) powered by the geared 200 hp Hispano - Suiza 8 B . The resulting Dolphin was a two - bay , single - seat biplane . The upper wings were attached to an open steel cabane frame above the cockpit . To maintain the correct centre of gravity , the lower wings were positioned 13 inches forward of the upper wings , creating the Dolphin ’ s distinctive negative wing stagger . The pilot sat with his head raised through the frame , where he had an excellent field of view . This configuration sometimes caused difficulty for novice pilots , 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 pipes ran alongside the cockpit walls to the two side - mounted radiator blocks . Shutters in front of each radiator core allowed control of engine temperature . The first Dolphin prototype was powered by a geared 150 hp Hispano - Suiza 8 and featured a deep " car - type " frontal radiator . Test pilot Harry Hawker carried out the maiden flight on 23 May 1917 . 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 favorably on it . On 28 June 1917 , the Ministry of Munitions ordered 200 Dolphins from Hooper & Co . Shortly thereafter , the Ministry ordered a further 500 aircraft from Sopwith and 200 aircraft from Darracq Motor Engineering Co . 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 . The third and fourth prototypes incorporated numerous modifications to the radiator , upper fuselage decking , fin and rudder . 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 . Nos . 87 and 23 Squadrons followed 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 . 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 . Early aircraft were often fitted with improvised crash pylons consisting of steel tubes over the cockpit to protect the pilot ' s head . Operational usage eventually showed that fears of pilot injury from overturning were largely unfounded . Crash pylons thereafter disappeared from front line aircraft , though they were often retained on training aircraft . Night - flying Dolphins of No . 141 Squadron , a Home Defence unit , had metal loops fitted above the inner set of interplane struts . Despite early problems , the Dolphin eventually proved successful and generally popular with pilots . The aircraft was fast , maneuverable , and easy to fly , though a sharp stall was noted . When functioning properly , the Hispano - Suiza afforded the Dolphin excellent performance at high altitude . Accordingly , the Dolphin was often deployed against German reconnaissance aircraft such as the Rumpler C . VII , which routinely operated at altitudes above 20 , 000 ft . 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 . The highest - scoring Dolphin unit was No . 87 Squadron , which shot down 89 enemy aircraft in the type . Pilots of No . 79 Squadron shot down 64 enemy aircraft in the eight and one 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 . Lieutenant Ronald Bannerman , a New Zealander , scored 17 victories . The third - ranking Dolphin ace was Captain Arthur Vigers of No . 87 Squadron , who attained all 14 of his victories while flying the same aircraft . Another notable ace , Major Albert Desbrisay Carter of No . 19 Squadron , obtained approximately 13 of his 29 confirmed victories in the Dolphin . Captain Henry Biziou scored eight victories in the type . 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 . 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 . Engine problems . The scarcity and unreliability of the French - built Hispano - Suiza 8B engine proved to be the most serious problem in the deployment and use of the Dolphin . Use of insufficiently hardened metal in the pinion gears led to numerous failures of the reduction gearing , particularly in engines built by the French firm Brasier . The engine also suffered persistent lubrication problems . Limited production capacity for the Hispano - Suiza engine , and the priority afforded to French aircraft like the SPAD S . XIII slowed Dolphin deliveries . Availability of the Hispano - Suiza improved in early 1918 as the French firm Emile Mayen began deliveries on an order placed by the British Admiralty . Use of the Lewis guns . The official armament of the Dolphin was two fixed , synchronized Vickers machine gun s and two Lewis gun s mounted on the forward cabane crossbar , firing at an upward angle to avoid the airscrew disc . The mounting provided three positions in elevation and limited sideways movement . In service , however , the Lewis guns proved unpopular , as they were difficult to aim and tended to swing into the pilot ' s face . Pilots also feared that the gun butts would inflict serious head injuries in the event of a crash . Most pilots therefore discarded the Lewis guns , though a minority retained one or both guns specifically for attacking high altitude reconnaissance aircraft from below . Pilots of No . 87 Squadron experimentally fitted some aircraft with two forward firing Lewis guns mounted on top of the lower wing , outboard of the propeller arc . These guns could fire incendiary ammunition , which could not be used with the synchronized Vickers guns . However , the 97 - round ammunition drums could not be changed once empty , nor could the pilot clear gun jams . This field modification did not become standard . Postwar service . Dolphins were quickly retired after the war . Nos . 19 and 87 Squadrons demobilized in February 1919 , followed by No . 23 Squadron in March . The last RAF unit to operate Dolphins was No . 79 Squadron , based at Bickendorf , Germany , as part of the Army of Occupation . The squadron demobilized in July 1919 . The Dolphin was declared obsolete on 1 September 1921 . No . 1 ( Fighter ) Squadron of the Canadian Air Force , which operated Dolphins and S . E . 5a s , Sopwith Snipe s and captured Fokker D . VII s , was disbanded on 28 January 1920 . Although retired from Canadian Air Force service , a small number of Dolphins were sent back to Canada . One Dolphin was converted for civilian use . In 1920 , Handley Page Ltd . obtained D5369 and operated it as a demonstrator under the civil registration G - EATC . This aircraft was sold in 1923 . The Polish Air Force operated 10 Dolphins during the Polish - Soviet War . From August 1920 , these aircraft were primarily used for ground attack duties in the Battle of Warsaw and other actions . They were soon grounded due to lack of spare parts . In October 1920 , two Polish Dolphins were loaned to the Ukrainian Air Force ( 1 . " Zaporoska Eskadra Ukraińska " ) for use against the Soviets . Both aircraft were returned to the Poles in February 1921 . Production and planned developments . A total of 2 , 072 Dolphin Mk I aircraft were produced by Sopwith , Darracq Motor Engineering Co . and Hooper & Co . Approximately 1 , 500 Dolphins were stored awaiting engines at the time of the Armistice . These incomplete airframes were eventually scrapped . Two developments of the Dolphin were planned . The French firm SACA ( " Société Anonyme des Constructions Aéronautiques " ) commenced licensed production of the Dolphin Mk II in 1918 . The RAF expressed no interest in this variant , which was intended for the French " Aéronautique Militaire " and the US Army Air Service . The Mk II ' s 300 hp direct - drive Hispano - Suiza 8F gave a maximum speed of 225 km / h ( 140 mph ) and a ceiling of 8 , 047 m ( 24 , 600 ft ) . The new engine was considerably larger than the 200 hp version and required an enlarged , bulbous cowling that fully enclosed the guns . The Mk II also featured an additional fuel tank , a variable incidence tailplane , strengthened airframe and longer exhaust pipes . The Air Service anticipated delivery of over 2 , 000 Mk II aircraft by the summer of 1919 , but only a few were delivered before the Armistice . Meanwhile , persistent difficulties with the geared 200 hp Hispano - Suiza 8B prompted development of the Dolphin Mk III , which used a direct - drive version of the 200 hp engine . The Mk III first flew in October 1918 and went into production just as hostilities ended . Many existing Dolphins were also converted to Mk III standard at aircraft repair depots by removing the reduction gearing and fitting a modified cowling to accommodate the resultant lowered thrustline . Survivors and reproductions . No complete Dolphin is known to have survived to the present . However , a composite Dolphin Mk I was rebuilt at the Michael Beetham Conservation Centre , part of the Royal Air Force Museum Cosford . The airframe is based on an original 6 ft length of rear fuselage from serial no . C3988 . It includes many other original parts , including a fuel tank , wheels , radiators , tailplane , and elevators from serial nos . D5329 and C4033 . In March 2012 , the Dolphin went on display in the Grahame White Hangar , at the Royal Air Force Museum London . In 1977 , Cole Palen built an accurate Dolphin reproduction for his Old Rhinebeck Aerodrome living aviation museum , in upstate New York . It flew regularly at Old Rhinebeck ' s weekend airshows until September 1990 , when its direct - drive Hispano - Suiza 8 engine suffered a fuel pump failure . The aircraft is presently under restoration to flying condition .