Picture: Sopwith 5F.1 Dolphin Third Prototype

Role - Fighter
Manufacturer - Sopwith Aviation Company
Designed by - Herbert Smith
First flight - 23 May 1917
Introduced - February 1918
Primary users - Royal Flying Corps
Royal Air Force
Number built - 2,072[1]

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

Picture: Sopwith 5F.1 Dolphin Third prototype at Brooklands Airfield

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.[2] 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.[2][3] 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.[4] The cockpit was nevertheless warm and comfortable,[3] in part because the radiator pipes ran alongside the cockpit walls.

The first Dolphin prototype was powered by a geared 150 hp Hispano-Suiza 8 and featured a deep "car-type" frontal radiator.[5][6][7][8] Test pilot Harry Hawker carried out the maiden flight on 23 May 1917.[4][6] In early June, the prototype was sent to Martlesham Heath for official trials. On 13 June, the prototype flew to St. Omer, France, where the aircraft's unfamiliar shape prompted Allied anti-aircraft gunners to fire on it.[6] Several pilots, including Billy Bishop of No. 60 Squadron, evaluated the prototype and reported favorably on it.[9] On 28 June 1917, the Ministry of Munitions ordered 200 Dolphins from Hooper & Co.[10] Shortly thereafter, the Ministry ordered a further 500 aircraft from Sopwith and 200 aircraft from Darracq Motor Engineering Co.[10]

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.[10] These features proved unsuccessful and were omitted from subsequent aircraft.[8][11] The third and fourth prototypes incorporated numerous modifications to the radiator, upper fuselage decking, vertical stabilizer, and rudder.[4][11] The fourth prototype was selected as the production standard.[11][12] Series production commenced in October 1917, with 121 Dolphins delivered by the end of the year.[1][8]

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.[13] For the next few weeks, Dolphin pilots accordingly exercised caution near other Allied aircraft.

Picture: Sopwith Dolphin of No. 87 Squadron, showing Lewis gun mounted atop the lower right wing

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.[14] 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.[15]

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.[14] 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.[14]

Picture: Sopwith Dolphin cockpit

The highest-scoring Dolphin unit was No. 87 Squadron, which shot down 89 enemy aircraft in the type.[16] Pilots of No. 79 Squadron shot down 64 enemy aircraft in the eight and one half months that the aircraft was at the front.[17] The top two Dolphin aces served in No. 79 Squadron. Captain Francis W. Gillet, an American, scored 20 victories with the type.[18] Lieutenant Ronald Burns Bannerman, a New Zealander, scored 17 victories.[19] Another notable ace, Major Albert Desbrisay Carter of No. 19 Squadron, obtained approximately 13 of his 29 confirmed victories in the Dolphin.[20]

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.[21] The unit became operational shortly after the Armistice.[16]

In October 1918, the American Expeditionary Force purchased five standard Mk Is for evaluation, sending four back to the United States.[22]

Engine problems

Picture: Sopwith Dolphin fitted with two upward firing Lewis guns and Norman vane sights

The scarcity and unreliability of the French-built Hispano-Suiza 8B engine proved to be the Dolphin's most serious shortcoming. Use of insufficiently hardened metal in the pinion gears led to numerous failures of the reduction gearing,[1] particularly in engines built by the French firm Brasier.[23] The engine also suffered persistent lubrication problems.[24] Limited production capacity for the Hispano-Suiza engine, and the priority afforded to French aircraft, 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 Dolphin was armed with two fixed, synchronized Vickers machine guns and one or two unsynchronized Lewis guns flexibly mounted to the forward cabane crossbar. The mounting provided three positions in elevation and limited sideways movement.[11][25] The Lewis guns proved unpopular in service, however, as they were difficult to aim and tended to swing into the pilot's face.[1] 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,[1] 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.[1] These guns could fire incendiary ammunition, which could not be used with the synchronized Vickers guns.[25] 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

Picture: Canadian Air Force Dolphins of No. 1 (Fighter) Squadron at RAF Upper Heyford, December 1918

Dolphins were rapidly phased out of the postwar inventory. Nos. 19 and 87 Squadrons demobilized in February 1919, followed by No. 23 Squadron in March.[26] 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.[26][27]

No. 1 (Fighter) Squadron, which operated Dolphins alongside a mix of S.E.5as, Sopwith Snipes and captured Fokker D.VIIs,[28] was disbanded on 28 January 1920.[29] Although retired from Canadian service, a small number of the Dolphins were sent back to Canada.[30]

In 1920, Handley Page Ltd. obtained D5369 and operated it as a demonstrator under a civilian (G-EATC) registration.[22][30]

The last Dolphins to see combat service were 10 examples used by Polish forces in 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.[26]

In October 1920, two Polish Dolphins were loaned to the Ukrainian Air Force (1. Zaporoska Eskadra Ukrai?ska) for use against the Soviets. Both aircraft were returned to the Poles in February 1921.[31]

Production and planned developments

A total of 2,072 Dolphin Mk I aircraft were produced by Sopwith, Darracq Motor Engineering Co. and Hooper & Co.[1] Approximately 1,500 Dolphins were stored awaiting engines at the time of the Armistice. These incomplete airframes were eventually scrapped.[32]

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.[33][34] 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.[22] The Mk II also featured an additional fuel tank, a variable incidence tailplane, strengthened airframe and longer exhaust pipes.[33] 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.[3] The Mk III first flew in October 1918 and went into production just as hostilities ended.[3] Many existing Dolphins were also converted to Mk III standard at aircraft repair depots by removing the reduction gearing and fitting a modified cowling.[26]

Modern reproductions

There are no known complete surviving Dolphin airframes, but at least two reproductions exist. A Dolphin is under construction at the Royal Air Force Museum in Cosford, England, which incorporates some original parts from serial nos. D5329 and C3988.

Another accurate Dolphin reproduction was built by Cole Palen for Old Rhinebeck Aerodrome in upstate New York. Powered by a vintage direct-drive Hispano-Suiza engine, this aircraft regularly flew at Palen's weekend air shows from 1980 onward. The Dolphin was placed on static display after suffering minor damage in a September 1990 crash landing. In November 2007, Old Rhinebeck Aerodrome began restoring the aircraft to flying condition. When completed, it will be painted in the markings of No. 19 Squadron.

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.

Operators

Canada

- Canadian Air Force
- No. 1 (Fighter) Squadron

Poland

- Polish Air Force (postwar, donated by United Kingdom, operated 1920-1923)
- 19. Eskadra My?liwska

Ukraine1918.png Ukraine

- Ukrainian Air Force (postwar, two aircraft loaned by Poland in October 1920, returned to Poland in February 1921)
- 1. Zaporoska Eskadra Ukrai?ska

United Kingdom

- Royal Flying Corps/Royal Air Force
- No. 19 Squadron
- No. 23 Squadron
- No. 56 Squadron (operational trials only)
- No. 79 Squadron
- No. 85 Squadron
- No. 87 Squadron
- No. 90 Squadron
- No. 91 Squadron
- No. 141 Squadron

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.

References

Notes

1. a b c d e f g Mason 1992, p. 105.
2. a b Franks 2002, p. 7.
3. a b c d Cooksley 1991, p. 34.
4. a b c Franks 2002, p. 8.
5. Mason 1992, p.104.
6. a b c Robertson 1970, p. 102.
7. Davis 1999, p. 126.
8. a b c Bruce 1969, p. 15.
9. Davis 1999, pp. 126-127.
10. a b c Davis 1999, p. 127.
11. a b c d Davis 1999, p. 128.
12. Bruce 1961, p. 134.
13. Franks 2002, p. 11.
14. a b c Franks 2002, p. 21.
15. Lamberton 1960, p. 62.
16. a b Robertson 1970, p. 106.
17. Bruce 1961, p. 135.
18. Franks 2002, p. 31.
19. Franks 2002, p. 32.
20. Franks 2002, p. 24.
21. Milberry 1984, p. 16.
22. a b c Bruce 1961, p. 150.
23. Davis 1999, p. 125.
24. Davis 1999, p. 129.
25. a b Robertson 1970, p. 105.
26. a b c d Davis 1999, p. 135.
27. Franks 2002, p. 18.
28. Milberry 2008, p. 160.
29. Payne 2006, p. 47.
30. a b Connors 1976, p. 12.
31. Kopañski 2001, pp. 11–40.
32. Mason 1992, p. 106.
33. a b Davis 1999, p. 134.
34. Bruce 1969, p. 20.

Bibliography

- Bruce, J.M. "The Sopwith Dolphin." Aircraft in Profile, Volume 8. New York: Doubleday & Company, Inc., 1970. ISBN 0-85383-016-9.
- Bruce, J.M. "The Sopwith 5F.1 Dolphin." Air Pictorial. Vol. 23, No. 5, May 1961.
- Bruce, J,M. War Planes of the First World War: Volume Three: Fighters. London: Macdonald, 1969, ISBN 0-35601-490-8.
- Connors, John F. "The 11th Hour Sopwiths." Wings, Volume 6, No. 1, February 1976.
- Cooksley, Peter. Sopwith Fighters in Action (Aircraft No. 110). Carrollton, Texas: Squadron/Signal Publications, 1991. ISBN 0-89747-256-X.
- Davis, Mick. Sopwith Aircraft. Ramsbury, Marlborough, Wiltshire: Crowood Press, 1999. ISBN 1-86126-217-5.
- Franks, Norman. Dolphin and Snipe Aces of World War I (Aircraft of the Aces No. 48). Oxford: Osprey Publishing, 2002. ISBN 1-84176-317-9.
- Green, William and Gordon Swanborough. 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 8-31109-315-6.
- Lamberton, W.M., and E.F. Cheesman. Fighter Aircraft of the 1914-1918 War. Letchworth, UK: Harleyford, 1960. ISBN 0-90043-501-1.
- Mason, Francis K. The British Fighter Since 1912. Annapolis, Maryland: Naval Institute Press, 1992. ISBN 1-55750-082-7.
- Milberry, Larry. Aviation in Canada: The Pioneer Decades. Toronto: CANAV Books, 2008. ISBN 0-921022-19-0.
- Milberry, Larry. Sixty Years: The RCAF and Air Command 1924-1984. Toronto: CANAV Books, 1984. ISBN 0-9690703-4-9.
- Payne, Stephen, ed. Canadian Wings: A Remarkable Century of Flight. Vancouver: Douglas & McIntyre, 2006. ISBN 1-55365-167-7.
- Robertson, Bruce. Sopwith – The Man and His Aircraft. London: Harleyford, 1970. ISBN 0-90043-515-1.

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