Sopwith 5F.1 Dolphin


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  FIGHTERVirtual Aircraft Museum / United Kingdom / Sopwith  

Sopwith 5F.1 Dolphin

Designed to provide the pilot with the best possible view in tactically important directions, the 5F.1 Dolphin was unusual in being a two-bay equi-span biplane with negative stagger. The pilot was seated with his head in the open framework connecting the upper mainplanes. Primarily of fabric-covered wire-braced wooden construction with an upper centre section of steel tube, the Dolphin was powered by a 200hp Hispano-Suiza geared eight-cylinder water-cooled engine in its initial production form. Armament consisted of two fixed and synchronised 7.7mm guns and either one or two guns of similar calibre mounted over the wing centre section and movable, but usually firing forwards and upwards. The prototype was flown in late May 1917, the first production contract was placed in the following month, on 29 June, and quantity deliveries to the RFC began late in the year. The first Dolphin squadron was deployed to France in February 1918, and the decision was taken to licence-build a version for the US Air Service in France. This, the Dolphin Mk II powered by a 300hp Hispano-Suiza engine, was to be manufactured by the SACA (Societe Anonyme des Constructions Aeronautiques) and the Air Service anticipated taking delivery of 2,194 by mid 1919. In the event, only a few Dolphin Mk Us were completed before the Armistice prompted cancellation of all contracts. Difficulties with the reduction gear of the original 200hp engine led to the conversion of many to direct drive, aircraft fitted with the modified power plant being designated Dolphin Mk III and some engines having their compression ratio raised to boost output to 220hp. Production of the Dolphin totalled 1,532 aircraft, of which all but 121 were built during 1918. Both Dolphin Mks I and III were finally withdrawn from RAF service mid 1919.

Sopwith 5F.1 DolphinA three-view drawing (1278 x 924)

 MODELDolphin Mk III
  Take-off weight907 kg2000 lb
  Empty weight665 kg1466 lb
  Wingspan9.90 m33 ft 6 in
  Length6.78 m22 ft 3 in
  Height2.59 m9 ft 6 in
  Wing area24.46 m2263.28 sq ft
  Max. speed206 km/h128 mph

Klaatu83, e-mail, 24.02.2011 18:49

RAF pilots were prejudiced against this fighter, partly due to the backward stagger of the wings, which reminded many of them of the much-disliked Airco DH-5 fighter. They also disliked having their heads protrude between the upper wings because they of the possible results in case of a nose-over during a bad landing. Since the Dolphin was powered by the unreliable British-built version of the Hispano-Suiza engine, the possibility of a flight ending in bad landing was not considered to be that remote.

However, in combat the Dolphin proved to be a good fighter, and is now regarded as possibly the most underrated fighter type of the First World War.


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