Sopwith 5F.1 Dolphin
Designed as a progressive successor to the Sopwith F.1 Camel, the first prototype Dolphin passed out of the Sopwith experimental department on May 23, 1917. A two bay biplane, with equi-span backward staggered wings, the Dolphin was designed to carry two fixed and synchronised 7.7mm Vickers guns either one or two guns of similar calibre mounted over the wing centre section and movable, but usually firing forwards and upwards. Ailerons were fitted to all four wings. The pilot was seated with his head in the open framework connecting the upper mainplanes. The back staggered wing arrangement gave its pilots a superb view, but was less satisfactory in the event of crash landing. 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. The prototype had a car type radiator which was changed for side radiators on production aircraft.
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. 19 Squadron, the first operational unit to be fully equipped, received replacements for its former French Spad S7s; 19 Squadron's official badge still has a dolphin motif.
Only three more RFC/RAF units were wholly Dolphin-equipped. In England, 79 Squadron began receiving Dolphins on December 15, 1917; then proceeded to France in February 1918, and began operations in the following month. In France, 23 squadron replaced its Spads in April 1918; while later in the same month 87 Squadron arrived from England fully equipped. Several other units were initially intended to use Dolphins, but in the event used other types of aircraft.
A small number of Dolphins were issued to home defence units, and 141 Squadron operated one flight for a period; while large-scale production of the type was plan-ned in France with a view to equipping both French and American units. At least five examples were bought and evaluated by the US Air Service in late 1918. 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 IIs 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.
In operational service over the Western Front, the Dolphin proved highly successful, having the distinct advantage of a higher fighting ceiling than most of its contemporaries. Although ostensibly a four-gun fighter, in practice most pilots discarded the upper Lewis guns in favour of less weight and thereby improved performance. Nevertheless, in 87 Squadron at least, several Dolphins experimented with fixed Lewis guns on the lower wings. When employed on ground-strafing duties, Dolphins were fitted with under-fuselage racks to carry four 11.3-kg (25-1b) Cooper bombs. In combat, many of the Dolphin pilots ran up appreciable victory tallies, such as F W Gillet, DFC, of 79 Squadron (17), R B Bannerman of 79 Squadron (16) and A D Carter of 19 Squadron (at least nine victories in Dolphins). A further indication of the machine's fighting ability was 87 Squadron's claims for a total of 89 combat victories - all claimed by Dolphin pilots, in only seven months of fighting.
Just before the Armistice a further Dolphin unit came into being - No.1 Squadron, Canadian Air Force - but this unit saw no operational service. By mid-1919, all other Dolphin squadrons had been disbanded within the Royal Air Force.
A total of 1,532 Dolphins were built, of which all but 121 were built during 1918.
Dolphin Mk I
Engine Hispano Suiza, 200 hp
Span: 9.9 m (32 ft 6 in)
Length: 6.8 m (22 ft 3 in)
Height: 2.6 m (8 ft 6 in)
Wing area: 263.25 sq.ft
Maximum speed: 205 km/h (127.5 mph) at 10,000 ft
Service ceiling: 6400 m (21000 ft)
Weight empty 1,406 lb. (638 kg)
MTOW: 2008 lb
Fuel capacity: 27 gal
Armament: 2-3 7.7mm Vickers mg
Bomb load: 100 lb. (45 kg.)
Endurance: 1.75 hours
Dolphin Mk III
Engine: 220-hp Hispano-Suiza
Max take-off weight: 907 kg / 2000 lb
Empty weight: 665 kg / 1466 lb
Wingspan: 9.90 m / 33 ft 6 in
Length: 6.78 m / 22 ft 3 in
Height: 2.59 m / 9 ft 6 in
Wing area: 24.46 sq.m / 263.28 sq ft
Max. speed: 206 km/h / 128 mph
Sopwith 5F.1 Dolphin