Sopwith 1½ Strutter

Sopwith 1½ Strutter
Role Biplane general purpose aircraft
National origin United Kingdom
Manufacturer Sopwith Aviation Company
First flight December 1915
Introduction April 1916
Primary users Royal Naval Air Service
Royal Flying Corps
Aéronautique Militaire
Number built 4,500 France
1,439 Great Britain


The Sopwith 1½ Strutter was a British single or two-seat multi-role biplane aircraft of the First World War.[1] It was significant as the first British two-seat tractor fighter, and the first British aircraft to enter service with a synchronised machine gun. It was given the name "1½ Strutter" because of the long and short cabane struts that supported the top wing.

As well as serving with both British air services, it also saw widespread but lackluster service with the French Aéronautique Militaire.

Design and development

In December 1914, the Sopwith Aviation Company designed a small, two-seat biplane powered by an 80 hp (60 kW) Gnome rotary engine, which became known as the "Sigrist Bus" after Fred Sigrist, Sopwith's Works Manager. The Sigrist Bus first flew on 5 June 1915, and although it set a new British altitude record on the day of its first flight, only one was built, serving as a company runabout.[2][3]

The Sigrist Bus formed the basis for a new, larger, fighter aircraft, the Sopwith LCT (Land Clerget Tractor), designed by Herbert Smith and powered by a 110 hp (82 kW) Clerget engine. Like the Sigrist Bus, each of the upper wings (there was no true centre section) was connected to the fuselage by a pair of short (half) struts and a pair of longer struts, forming a "W" when viewed from the front, this giving rise to the aircraft's popular nickname of the 1½ Strutter.[1] The first prototype was ready in mid-December 1915,[3][4] undergoing official testing in January 1916.

The 1½ Strutter was of conventional wire-braced, wood and fabric construction. The pilot and gunner sat in widely separated tandem cockpits, with the pilot sitting in front, giving the gunner a good field of fire for his Lewis gun. The aircraft had a variable-incidence tailplane that could be adjusted by the pilot in flight, and airbrakes under the lower wings to reduce landing distance.[2][5]

A preserved Sopwith 1½ Strutter at the RAF Museum, London, showing the W-form pairs of "1½" struts that gave the aeroplane its name, and the centrally-mounted Vickers machine gun

The Vickers-Challenger synchronisation gear was put into production for the Royal Flying Corps in December 1915,[6] and in a few weeks, a similar order for the Scarff-Dibovski gear was placed for the RNAS.[7] Early production 1½ Strutters were fitted with one or the other of these gears for the pilot's fixed .303-in Vickers machine gun; due to a shortage of the new gears some early aircraft were built with only the observer's gun. Later aircraft were either fitted with the Ross or the Sopwith-Kauper gears.[8] None of these early mechanical synchronisation gears were very reliable and it was not uncommon for propellers to be damaged, or even entirely shot away.

The Scarff ring mounting was also new and production was at first slower than that of the aircraft requiring them. Various makeshift Lewis mountings as well as the older Nieuport ring mounting, were fitted to some early 1½ Strutters as an interim measure.[9] The two seaters could carry four 25 lb (11 kg) bombs underwing, which could be replaced by two 65 lb (30 kg) bombs for anti-submarine patrols.[10]

From the beginning, a dedicated light bomber version was planned, with the observer's cockpit eliminated to allow more fuel and bombs to be carried in the manner of the Martinsyde Elephant and the B.E.12, with an internal bomb bay capable of carrying four 65 lb (30 kg) bombs.[10][11]

Operational history

In British service

The prototype two seater flew in December 1915[4] and production deliveries started to reach the RNAS in February 1916. By the end of April, No. 5 Wing RNAS had a complete flight equipped with the new aircraft. The Sopwiths were used both for escorting the Wing's Caudron G.4 and Breguet bombers and for carrying out bombing raids themselves.[12][13] The War Office had ordered the type for the RFC in March but because Sopwith's entire production capacity was pre-contracted to the navy, the RFC orders had to be placed with Ruston Proctor and Vickers[14] and production from these manufacturers did not get into its stride until August. Since the Somme offensive was planned for the end of June and with the RFC having a shortage of up-to-date aircraft to support the planned offensive, it was agreed that a number of Sopwiths would be transferred from one service to the other, allowing No. 70 Squadron to reach the front by early July 1916, with Sopwith-built Strutters originally intended for the Navy.[15]

A replica Sopwith 1½ Strutter in 1916 RNAS livery, flying at a 2006 air show

At first No. 70 did very well with their new aircraft. The period of German ascendency known as the Fokker scourge was over, and the 1½ Strutter's long range, coupled with its excellent armament for the period, enabled effective offensive patrolling deep into German held territory.[16] However, by the time No. 45 Squadron reached the front in October the new Albatros fighters were appearing in the Jagdstaffeln. By January 1917, when No 43 Squadron arrived in France, the type was outclassed as a fighter. While the fitting of a more powerful 130 hp Le Clerget 9B improved performance slightly, this came too late to reverse the situation.[17] It was still a useful long-range reconnaissance aircraft when it could be provided with adequate fighter escort,[18] but was one of the types to suffer severely during "Bloody April" - No. 43 squadron alone suffering 35 casualties, from an officer establishment of 32.[19]

Like other early Sopwith types, the 1½ Strutter was very lightly built and its structure did not stand up very well to arduous war service. It was also far too stable to make a good dogfighter, and the distance between the pilot and the observer's cockpits impeded communication between them. The last operational 1½ Strutters in the RFC were replaced by Sopwith Camels in late October 1917.[18]

The type's long range and stability were good qualities for a home defence fighter and it served with three home defence squadrons, No. 37, No. 44 and No. 78 Squadrons. Most of the 1½ Strutters supplied to home defence units had been built as two-seaters but many were converted "in the field" to single-seaters to improve performance. Some of these single-seaters were similar to the bomber variant but others were of different type, known (like similarly adapted Sopwith Camels) as the Sopwith Comic. The cockpit was moved back behind the wings and one or two Lewis guns, either mounted on Foster mountings or fixed to fire upwards, outside the arc of the propeller, replaced the synchronised Vickers.

The RNAS used most of their 1½ Strutters as bombers (in the Aegean and Macedonia as well as in France) and as shipboard aircraft. In this service it was known as the Ship's Strutter and flew from aircraft carriers and other warships of the Royal Navy, as well as from HMAS Australia.

The RNAS and the RFC (and after April 1918 the RAF) used the type as a trainer after it had been withdrawn from operational service and like the Sopwith Pup, it proved a popular personal aircraft for senior officers.

In French service

French Sopwith 1B.2 Strutter in late war camouflage

The largest user of the Sopwith was the French Aéronautique Militaire. By May 1916 it was obvious that the pusher Farman and Breguet bombers and reconnaissance aircraft were obsolete, and with the failure of their tractor aircraft replacements, particularly the Nieuport 14, something was needed to fill the gap. In response, the Sopwith was ordered in large numbers from French manufacturers in three versions, the SOP. 1A.2 (two-seat reconnaissance), SOP. 1B.2 (two-seat bomber) and SOP. 1B.1 (single-seat bomber).[20][21] While in French service, they equipped a large portion of the French bomber and artillery spotting squadrons and carried out many bombing attacks against industrial and military targets, including against the German front lines. It was not as successful against fighters, suffering substantial casualties and downing fewer enemy aircraft than either the aircraft used before it or after. With the belated introduction of the Breguet 14 A.2 and B.2, the last of the Sopwiths were finally withdrawn from operational service in early 1918 although they would continue in service with training units until after the end of the war.

In other foreign service

Belgian Air Force Sopwith on display in the Brussels Military Museum

Three Belgian squadrons also flew French-built Sopwiths, and surplus French Sopwiths were used by several countries postwar.

During the war, several 1½ Strutters that were interned after landing in the Netherlands were purchased for the Dutch Luchvaart Afdeeling.

Over 100 1½ Strutters were also built in Russia by Duks and Lebedev,[22] supplemented by large numbers delivered directly from Britain and France. The 1½ Strutter remained in large scale use by both the Soviet forces and White Russians during the Russian civil war and Polish-Soviet war.[23] Three were captured during this war and used by the Poles in 1919–1920.[24] Other captured ones were used by Baltic states.

The American Expeditionary Force purchased 384 two-seat Strutter observation aircraft and 130 single-seat bombers from France in 1917-18.[25] While mainly used for training, they were used operationally by the 90th Aero Squadron as an interim measure, due to a shortage of later types.[21] The U.S.Navy used a number of the two-seat Sopwiths, along with Nieuport 28s and Hanriot HD.1s and 2s as ships' aircraft in the early postwar years, testing the use of aircraft from platforms mounted on the turrets of battleships.

The 1½ Strutter also served with the Imperial Japanese Army Air Force - some examples serving in the Japanese expeditionary force in Siberia during 1918.

Around 1,500 1½ Strutters were built for the Royal Flying Corps and the Royal Naval Air Service and between 4,200 and 4,500 were built in France.

Variants and designations

Sopwith Land Clerget Tractor (or Sopwith LCT)
Sopwith company designation.
Sopwith Type 9400
Admiralty designation for two seater, number from serial of last aircraft in first batch ordered.
Sopwith Type 9700
Admiralty designation for single- seater bomber, number likewise assigned.
Sopwith Two seater
RFC designation.
Sopwith 1½ Strutter
Unofficial name due to configuration of struts, also used by US Navy.
Sopwith Comic
Single seat home defence fighter
Ship(s) Strutter
Shipboard version
SOP. 1
French built version.
SOP. 1A.2 two-seat reconnaissance aircraft[20][21]
SOP. 1B.1 single-seat bomber[20][21]
SOP. 1B.2 two-seat bomber[20][21]
LeO 1
Lioré et Olivier licence-built version.
So-shiki Model 1
Japanese licence-built bomber version.[26]
So-Shiki Model 2
Japanese licence-built LeO 1 reconnaissance version.[26]

Survivors

Sopwith No. 556 on display in the Musée de l'Air et de l'Espace at Paris le Bourget

Original Sopwith 1½ Strutter aircraft are preserved at the following locations.[27]

Belgium
S85, Koninklijk Legermuseum/Musée Royal de l'Armée, Brussels.
France
No. 556, Sop.1A.2 at Musée de l'Air et de l'Espace, Paris Le Bourget airport.
France
No. 2897, Sop.1B.2 at the Association Memorial Flight, La Ferté-Alais near Paris (under restoration 2009).
New Zealand
former Argentinian machine formerly in the possession of Kermit Weeks' Fantasy of Flight museum at Polk City, Florida is under restoration with Peter Jackson's firm, The Vintage Aviator Limited in New Zealand.[28]

A number of reproductions of this popular machine now exist. Visitors to the Scottish National Museum of Flight in April/May 2013 can see a Sopwith 1½ Strutter being built in the Concorde hangar. This machine differs from originals in being powered by a radial engine instead of a rotary.

Operators

Military

1½ Strutter operators.
 Afghanistan
 Australia
 Belgium
 Brazil
 Czechoslovakia
Czechoslovak Legion used four SOP 1 A.2 delivered by the French Aviation Mission in Russia, and at least one Strutter captured from bolsheviks.[30]
 Estonia
 France
 Greece
 Japan[21]
 Latvia
 Lithuania

 Mexico

 Netherlands
 Poland
 Romania[21]
 Russia
 Soviet Union
 Ukraine

A single aircraft acquired from Russia in 1918.[23]

 United Kingdom
 United States

Civil

 Argentina

Two aircraft registered in 1928. R-105 (later LV-BAA) and R-106 (later LV-CAA). One of these two preserved in Florida.[22]

 France

55 aircraft on French civil register in 1922.[22]

 Japan

At least seven aircraft registered.[22]

 Sweden

Possibly one aircraft from Switzerland in 1926.[22]

  Switzerland

Two aircraft, CH-53 registered 9 April 1921, cancelled 9 October 1923. CH-67 registered 5 December 1923, cancelled December 1926 as sold to Sweden.[22]

 United Kingdom

One civil registered aircraft, G-EAVB.[22]

Specifications (1½ Strutter - two seater, 130 hp Clerget)

Sopwith 1½ Strutter drawing

Data from British Aeroplanes 1914-18[39]

General characteristics

Performance

Armament

See also

Related development
Aircraft of comparable role, configuration and era
Related lists

References

Notes

  1. 1 2 Lake 2002, p. 40.
  2. 1 2 Bruce 1982, p. 499.
  3. 1 2 Jarrett 2009, p. 56.
  4. 1 2 Bruce 28 September 1956, p. 544.
  5. ↑ Jarrett 2009, pp. 56, 8.
  6. ↑ Bruce 28 September 1956, p. 543.
  7. ↑ Bruce 5 October 1956, p. 586.
  8. ↑ Bruce 1957, p. 542.
  9. ↑ Bruce 1957, pp. 542—543.
  10. 1 2 Jarrett 2009, p. 59.
  11. ↑ Bruce 2000, p. 6.
  12. ↑ Bruce 28 September 1956, p. 545.
  13. ↑ Thetford 1978, p. 292.
  14. ↑ Bruce 1982, p. 500.
  15. ↑ Bruce 1982, pp. 501, 503.
  16. ↑ Bruce 5 October 1956, p. 587.
  17. ↑ Bruce 1982, p. 504.
  18. 1 2 Bruce 5 October 1956, p. 588.
  19. ↑ Herris and Pearson 2010, p. 51.
  20. 1 2 3 4 Bruce 2000, pp. 10–11.
  21. 1 2 3 4 5 6 7 Bruce 5 October 1956, p. 590.
  22. 1 2 3 4 5 6 7 Jarrett 2009, p. 60.
  23. 1 2 3 4 Jarrett 2009, p. 66.
  24. 1 2 Kopański 2001, pp. 73–78.
  25. ↑ Swanborough and Bowers 1963, p. 560.
  26. 1 2 3 4 5 Jarrett 2009, p. 65.
  27. ↑ Jarrett 2009, p.70.
  28. ↑ "Rare Sopwith for New Zealand." Aeroplance Monthly, April 2011, p. 6.
  29. ↑ Andersson Air Enthusiast May/June 2003, p. 26.
  30. ↑ Čejka, Zdeněk (November 1999). "Českoslovenští letci a Sopwith 1 1/2 Strutter". Historie a plastikové modelářství. IX (11): 18–20. ISSN 1210-1427.
  31. ↑ Gerdessen 1982, pp. 64, 76.
  32. ↑ Jarrett 2009, p. 64.
  33. ↑ Jarrett 2009, pp. 65–66.
  34. ↑ Humberstone, Richard. Latvian Air Force 1918–1940. London: Blue Rider Publishing, 2000, ISBN 1-902851-04-8.
  35. ↑ Vistakas 1985, p. 61.
  36. ↑ Flores Aeroplane, May 2010, p. 94.
  37. ↑ Bruce 1982, p. 508.
  38. ↑ Swanborough and Bowers 1976, p. 495.
  39. ↑ Bruce 1957, pp. 549—550.

Bibliography

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  • Bruce, J.M. "The Sopwith 1½ Strutter: Historic Military Aircraft No. 14 Part I." Flight, 28 September 1956, pp. 542–546.
  • Bruce, J.M. "The Sopwith 1½ Strutter: Historic Military Aircraft No. 14 Part II." Flight, 5 October 1956, pp. 586–591.
  • Bruce J.M. British Aeroplanes 1914-18. London: Putnam, 1957.
  • Bruce, J.M. The Aeroplanes of the Royal Flying Corps (Military Wing). London: Putnam, 1982. ISBN 0-370-30084-X.
  • Bruce, J.M. Sopwith 1½ Strutter: Windsock Datafile 34. Berkhampstead, UK: Albatros Productions, Second edition, 1998. ISBN 0-948414-42-1.
  • Bruce, J.M. Sopwith 1½ Strutter: Volume 2: Windsock Datafile 80. Berkhampstead, UK: Albatros Productions, 2000. ISBN 1-902207-22-X.
  • Flores, Santiago A. "Skywriters: Mexican Strutter". Aeroplane, Vol. 38, No. 5, Issue No 445, May 2009, p. 94.

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  • Gerdessen, F. "Estonian Air Power 1918–1945". Air Enthusiast No 18, April - July 1982, pp. 61–76. ISSN 0143-5450.
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  • Kopański, 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.
  • Lake, Jon. The Great Book of Bombers: The World's Most Important Bombers from World War I to the Present Day. St. Paul, Minnesota: MBI Publishing Company, 2002. ISBN 0-7603-1347-4.
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