Sopwith Dolphin
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| 5F.1 Dolphin | |
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| Type | Fighter |
| Manufacturer | Sopwith Aviation Company |
| Designed by | Herbert Smith |
| Maiden flight | 23 May 1917 |
| Introduced | February 1918 |
| Primary users | Royal Flying Corps Royal Air Force Canadian Air Force |
| Number built | 1,532 |
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.
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[edit] 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 200 hp Hispano-Suiza 8B. 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 center 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 Dolphin was armed with two synchronised Vickers machine guns and two Lewis guns hinged to the forward cabane crossbar. The unsynchronized Lewis guns fired forward over the propeller arc, although they could also be swung upwards to fire almost vertically.
The first of four prototypes flew on 23 May 1917. The type 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. Production commenced in late 1917, with 121 Dolphins delivered by the end of the year.
[edit] 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 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 of No. 141 Squadron, a Home Defence unit, had metal loops fitted above the inner set of interplane struts.
The unreliability of the French-built Hispano-Suiza 8B, which also dogged the early versions of the S.E.5a and most versions of the SPAD S.XIII, proved more difficult to resolve. Use of insufficiently hardened metal in the pinion gears led to numerous failures of the reduction gearing. Limited production capacity for the Hispano-Suiza engine, as well as competition with other manufacturers for the available engines, also slowed Dolphin deliveries. As many as 650 Dolphin airframes were stored awaiting engines at the time of the Armistice.
When functioning properly, the Hispano-Suiza afforded the Dolphin excellent performance 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 ft. The Dolphin could attack with its two fixed Vickers guns, or from below its quarry, with the upward firing Lewis guns. The Lewis guns proved unpopular in service, however, as they were difficult to aim and tended to swing in flight. 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 use against reconnaissance aircraft.
Pilots of No. 87 Squadron experimentally fitted some aircraft with forward firing Lewis guns on top of the lower wing, outboard of the propeller arc. These guns were actuated by a Bowden cable. 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.
No. 87 Squadron also explored the use of equipment to supply pilots with oxygen at high altitude. The experiment was abandoned after trials showed that the oxygen tanks exploded when struck by gunfire.
Despite early problems, the Dolphin proved successful and generally popular with pilots. The aircraft was fast, maneuverable, and easy to fly, though a sharp stall was noted. The cockpit was warm, in part because the radiator pipes ran alongside the cockpit walls.
Four Royal Air Force squadrons operated the Dolphin as their primary equipment, while other squadrons used it in small numbers. One Canadian Air Force squadron equipped with Dolphins but did not become operational before the Armistice.
A total of 1,532 Dolphins were produced by Sopwith, Darracq Motor Engineering Co. and Hooper & Co.
[edit] Postwar Service
In the Royal Air Force, only No. 79 Squadron continued to operate the Dolphin into the postwar period. Based at Bickendorf, Germany as part of the Army of Occupation, the squadon remained active until July 1919.
The last Dolphins to see service were 10 examples used by Polish forces in the Polish-Soviet War. From August 1920, the aircraft were primarily used for ground attack duties in the Battle of Warsaw and other actions. Two were shot down and the rest were withdrawn by 1923. In October 1920, two Polish Dolphins were loaned to the Ukrainian Air Force (1. Zaporoska Eskadra Ukraińska) for use against the Soviets. The aircraft were returned to the Poles in February 1921.[1]
[edit] Planned developments
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. This variant, intended for the US Army Air Service, was equipped with a 300 hp direct-drive Hispano-Suiza 8F. Maximum speed rose to 225 km/h (140 mph), with 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, 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.
[edit] Modern reproductions
There are no known surviving Dolphin airframes, but at least two reproductions exist. A Dolphin reproduction, marked as serial D5329, is displayed at the Royal Air Force Museum in Cosford England. This aircraft incorporates some original parts.
Another accurate Dolphin reproduction is displayed at Old Rhinebeck Aerodrome in upstate New York. Powered by a vintage direct-drive Hispano-Suiza engine, this reproduction regularly flew at Cole Palen's weekend air shows at Old Rhinebeck 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, without fabric covering.
[edit] Variants
- Dolphin Mk I
- Main production version. Powered by a geared 200 hp (149 kW) Hispano-Suiza 8B.
- Dolphin Mk II
- Manufactured under license in France. Powered by a direct-drive 300 hp (224 kW) Hispano-Suiza 8F.
- Dolphin Mk III
- Powered by a direct-drive 200 hp (149 kW) Hispano-Suiza 8B.
[edit] Operators
- Canadian Air Force
- No. 1 Fighter Squadron
- Polish Air Force (postwar, donated by United Kingdom, operated 1920-1923)
- 19. Eskadra Myśliwska
- Ukrainian Air Force (postwar, two aircraft loaned by Poland in October 1920, returned to Poland in February 1921)
- 1. Zaporoska Eskadra Ukraińska
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[edit] Specifications (Dolphin Mk I)
General characteristics
- Crew: 1
- Length: 6.78 m (22 ft 3 in)
- Wingspan: 9.91 m (32 ft 6 in)
- Height: 2.59 m (8 ft 6 in)
- Wing area: 24.4 m² (263 ft²)
- Empty weight: 641 kg (1,410 lb)
- Max takeoff weight: 890 kg (1,959 lb)
- Powerplant: 1× Hispano-Suiza 8B, 149 kW (200 hp)
Performance
- Maximum speed: 211 km/h (131 mph) at sea level
- Range: 315 km (195 mi)
- Service ceiling 6,100 m (20,000 ft)
- Rate of climb: 12 min 5 sec to 3,048 m (10,000 ft)
- Wing loading: 36.5 kg/m² (7.45 lb/ft²)
- Power/mass: 0.232 kW/kg (0.102 hp/lb)
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] See also
Related lists
[edit] References
[edit] Notes
- ^ Kopañski 2001, pp. 11–40.
[edit] Bibliography
- Bruce, J.M. "The Sopwith Dolphin." Aircraft in Profile, Volume 8. New York: Doubleday & Company, Inc., 1970. ISBN 3-910192-52-1.
- 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.
- Kopañski, Tomasz Jan. Samoloty brytyjskie w lotnictwie polskim 1918-1930 (British Aircraft in the Polish Air Force 1918-1930) (in Polish). Warsaw: Bellona, 2001. ISBN 83-11-09315-6.
- Mason, Francis K. The British Fighter Since 1912. Annapolis, Maryland: Naval Institute Press, 1992. ISBN 1-55750-082-7.
[edit] External links
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