Sopwith Dolphin

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5F.1 Dolphin
Type	Fighter
Manufacturer	Sopwith Aviation Company
Designed by	Herbert Smith
Primary users	Royal Flying Corps Royal Air Force
Number built	1532

The Sopwith 5F.1 Dolphin was a British fighter aircraft manufactured by the Sopwith Aviation Company. It was used by the Royal Flying Corps, the Royal Air Force, and the Canadian Air Force during the First World War.

Contents 1 Design and development 2 Operational service 3 Survivors and reproductions 4 Variants 5 Operators 6 Specifications (Dolphin Mk I) 7 References

[edit] Design and development

In early 1917, Herbert Smith began designing a successor to the Camel. The resulting Dolphin (internal Sopwith designation 5F.1) was a large two-bay, single-seat biplane armed with twin Vickers machine guns. It was the first Sopwith design to use a water-cooled inline engine, the new 200 hp Hispano-Suiza 8B. Versions of this engine also powered the Royal Aircraft Factory S.E.5a and Spad S.XIII.

To provide an optimal view for the pilot, the Dolphin's upper wings were attached to an open steel frame above the cockpit. The pilot sat with his head raised through the frame, thereby giving excellent visibility forward and above. To maintain balance, the lower wings were positioned 13 inches forward of the upper wings, creating the Dolphin’s distinctive negative wing stagger.

The first of four prototypes flew on 23 May 1917. It was initially assessed at Martlesham Heath in late June. After modifications to the radiator, upper fuselage and vertical stabilizer, the Ministry of Munitions placed an order for 500 aircraft on 29 June. Deliveries commenced in late 1917, with 121 delivered by the end of the year.

[edit] Operational service

The Dolphin Mk I became operational with No. 19 and No. 79 Squadrons in February 1918. No. 87 and No. 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 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 frontline aircraft, though they were often retained on training aircraft. Night flying Dolphins belonging to Home Defence units had metal loops fitted over the inner bays of interplane struts.

The unreliability of the geared Hispano-Suiza 8B proved more difficult to resolve. Use of insufficiently hardened metal in the pinion gears led to numerous failures of the reduction gearing.

Despite these problems, the Dolphin proved successful and generally popular with pilots. By most accounts, the Dolphin was fast, maneuverable and easy to fly. The cockpit was warm, in part because the radiator pipes ran alongside the cockpit walls. The field of view was excellent, though some pilots were disoriented by the fact that the nose of the aircraft was not visible from the cockpit. The Dolphin performed particularly well at high altitude. For this reason, Dolphins were often deployed against German reconnaissance aircraft, such as the Rumpler C.VII, which routinely operated at altitudes above 20,000 feet.

The Dolphin could attack with its two fixed Vickers guns, or with two upward firing Lewis guns mounted next to the cockpit. In service, most pilots removed the guns. They were difficult to aim and tended to swing when the aircraft manoeuvered; removing them also reduced the aircraft's weight. Moreover, pilots feared that the Lewis guns would inflict serious head injuries in the event of a crash. Some pilots nevertheless retained one upward firing Lewis gun for use against reconnaisance aircraft. A few aircraft in No. 87 Squadron mounted two forward firing Lewis guns on the lower wing outboard of the propeller arc. These drum-fed guns could not be reloaded in flight.

Two developments of the Dolphin were planned. The French firm SACA (Société Anonyme des Constructions Aéronautiques) commenced licence production of the Dolphin Mk II in 1918. This variant, intended for the US Army Air Service, was equipped with a 300 hp direct drive Hispano-Suiza engine. The new engine was considerably larger that the 200 hp version, and required an enlarged, bulbous cowling. 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 Hispano-Suiza engine prompted development of the Dolphin Mk III, which used a direct drive version of the 200 hp Hispano-Suiza. The Mk III first flew in October 1918 and went into production just as hostilities ended.

Four Royal Air Force squadrons flew Dolphins in combat. Several other squadrons, including two Canadian Air Force squadrons, were equipped with Dolphins but did not become operational before the end of hostilities. Almost all these units disbanded after the Armistice. Only No. 79 Squadron, based at Bickendorf, Germany as part of the Army of Occupation, remained active until July 1919. The last Dolphins to see service were ten examples sent to Poland in 1920.

A total of 1,532 Dolphins were produced by Sopwith, Darracq Motor Engineering Co. and Hooper & Co.

[edit] Survivors and reproductions

A Dolphin replica, marked as serial D5329, is displayed at the Royal Air Force Museum in Cosford, England. This aircraft incorporates some original parts.

Another Dolphin replica is displayed at Old Rhinebeck Aerodrome in upstate New York. Powered by a vintage direct-drive Hispano-Suiza engine, this replica regularly flew at airshows from 1980 onward. On 27 October 1990, an engine fuel pump failure caused the aircraft to crash into a wooded area. Damage was light and the aircraft has since been restored for static display.

[edit] Variants

• Dolphin Mk I: Powered by a geared 200-hp (149-kW) Hispano-Suiza engine. Main production version.
• Dolphin Mk II: License-built in France. Powered by a direct-drive 300-hp (224-kW) Hispano-Suiza engine.
• Dolphin Mk III: Powered by a direct-drive 200-hp (149-kW) Hispano-Suiza engine.

[edit] Operators

 Canada:

• Canadian Air Force
  • No. 1 Squadron, Canadian Air Force
  • No. 2 Squadron, Canadian Air Force

 Poland:

• Polish Air Force (post-war, donated by United Kingdom, operated 1920-1923)
  • 19. Eskadra Myśliwska

 Ukraine:

• Ukrainian Air Force (post-war, donated by Poland in September 1920, returned to Poland in February 1921)
  • 1. Zaporoska Eskadra Ukraińska

 United Kingdom:

• Royal Flying Corps
• Royal Air Force
  • No. 19 Squadron RAF / RFC
  • No. 23 Squadron RAF / RFC
  • No. 79 Squadron RAF / RFC
  • No. 81 Squadron RAF / RFC
  • No. 87 Squadron RAF / RFC
  • No. 90 Squadron RAF / RFC
  • No. 91 Squadron RAF / RFC
  • No. 123 Squadron RAF / RFC
  • No. 141 Squadron RAF / RFC

[edit] Specifications (Dolphin Mk I)

General characteristics

• Crew: 1
• Length: 22 ft 3 in (6.78 m)
• Wingspan: 32 ft 6 in (9.91 m)
• Height: 8 ft 6 in (2.59 m)
• Wing area: 263 ft² (24.4 m²)
• Empty weight: 1,410lb (641 kg)
• Max takeoff weight: 1,959 lb (890 kg)
• Powerplant: 1× Hispano-Suiza 8B , 200hp (149 kW)

Performance

• Maximum speed: 136mph (219 km/h) at sea level
• Range: 195 mi (315 km)
• Service ceiling: 20,000 ft (6,100 m)
• Rate of climb: 12 min 5 sec to 10,000 ft (3048 m)
• Wing loading: 7.45 lb/ft² (36.5 kg/m²)
• Power/mass: 0.102 hp/lb (0.232 kW/kg)

Armament

• 2× 0.303 in (7.7 mm) Vickers machine guns; up to 2× 0.303 in (7.7 mm) Lewis guns
  
• Up to four 25 lb bombs.

[edit] References

• Cooksley, Peter. Sopwith Fighters In Action (Aircraft No. 110). Carrollton, Texas: Squadron/Signal Publications, 1991. ISBN 0-89747-256-X.
• Franks, Norman. Dolphin and Snipe Aces of World War I (Aircraft of the Aces). London: Osprey Publishing, 2002. ISBN 1-84176-317-9.
• Green, William and Swanborough, Gordon. The Complete Book of Fighters. London: Salamander Books, 1994. ISBN 0-83173-939-8.
• Mason, Francis K. The British Fighter Since 1912. Annapolis, Maryland: Naval Institute Press, 1992. ISBN 1-55750-082-7.