The genesis of the Sopwith 1½ Strutter may be traced back to a small two-seat biplane designed by Harry Hawker in late 1914.
It featured a novel wing strut arrangement in which the two halves of the top wing were braced by a W-form strut system rising from the cockpit area of the fuselage. The outer struts which reached so far outboard that they were regarded as 'half-struts'. When these were added to the conventional outboard interplane struts, the unofficial name 1½ Strutter was coined and subsequently and stuck.
The prototype of the new aircraft was originally known as 'Sigrist’s Bus' after Sopwith Aviation Company's Chief Engineer Fred Sigrist and it set a new British altitude record of 18,393 ft in the hands of Harry Hawker on 6th June 1915.
A slightly larger machine (serial 3686) was built on the same principles (but finessed by Chief Designer Herbert Smith) and on completion it was first flown in December 1915. Initially designated the LCT (Land Clerget Tractor), the new aircraft was powered by a 110hp Clerget 9Z rotary engine and introduced several innovations.
These innovations included a variable-incidence tailplane controlled from the cockpit to balance the aircraft over a wide range of load distributions. It also featured air brakes (essentially flaps) fitted in the centre section of the lower wing to reduce the landing speed and a synchronising gear for the fixed forward-firing machine-gun. This enabled the latter to be fired through the revolving propeller blades without causing damage.
The prototype was tested by the Royal Flying Corps’ Central Flying School in January 1916 and it showed remarkable promise as a fully-loaded, two-seat fighter some 12mph (20km/h) faster than the German Fokker Eindecker monoplane. It terrorised the Western Front with its four-hour flight duration, significantly exceeding that of any other fighter as well most reconnaissance types.
A second prototype (serial 9376) was built although there was still with no formal contract from the government. It was used for trials by the Royal Naval Air Service the following month and it impressed the RNAS so much that they placed an order for the type almost immediately.
The RFC also did the same in March although their examples were built by Lincoln-based engineering company Ruston, Proctor Ltd. (and later by a number of other companies) as factory space at The Sopwith Works was at a premium.
In addition to Sopwith, contractors producing the 1½ Strutter included Fairey Aviation Co Ltd, Hooper & Co Ltd, Mann, Egerton & Co Ltd, Morgan & Co, Ruston Proctor & Co Ltd, Vickers Ltd, Wells Aviation Co Ltd and the Westland Aircraft Works of Petters Ltd.
The 1½ Strutter entered operational service with the RNAS in April 1916, being deployed to France during the same month. The Senior Service used two distinct variants of the aircraft. One was a standard two-seater fighter with fixed forward-firing armament and a machine-gun on a flexible mount operated by the second crew member. The other was a single-seat bomber variant in which bombs, stowed in the faired-over rear cockpit, fell through a trapdoor in the underside of the fuselage.
The RNAS also used the 1½ Strutter for anti-submarine patrols, both in home waters and in the Mediterranean from the spring of 1917.
When flying from ships, the type was known as the 'Ship’s Strutter' and used either a standard wheeled undercarriage or a specially designed skid. It was launched off a platform fitted to the forward end of the ship or sometime later, a gun turret.
Numerous experiments in deck-flying were undertaken with 1½ Strutters including the use of skids on a deck fitted with rails for take-off and the first successful deck landings used cable arrester equipment.
The RFC meanwhile introduced the type into service in the spring of 1916 when No 70 Squadron received its first examples, all of which had been transferred from RNAS orders to strengthen RFC resources in France in preparation for the Somme offensive that July.
The 1½ Strutters ordered by the RFC began arriving at their units from July 1916 and the type was used extensively as a fighter-reconnaissance aircraft in France.
However, such was the pace of aircraft development during this period the First World War and despite the fitting of a more powerful 130hp Clerget engine, the 1½ Strutter struggled to retain its superiority. It was quickly outclassed in combat by more modern types although it nevertheless continued to show its claws by virtue of its extensive offensive firepower.
The RFC explored using the 1½ Strutter as a single-seat bomber although it was little used in such operations. The RFC also developed a Home Defence variant in which the front cockpit was faired over and the pilot moved to the rear cockpit, From there he could fire a machine-gun over the upper wing and rather unfairly these were dubbed 'Sopwith Comics'.
The RFC and RNAS careers of the 1½ Strutter were relatively short, the type having been withdrawn from front-line service by the end of 1917. It did however continue to serve both organisations in training roles.
The 1½ Strutter saw service with numerous foreign services, most notably in France, where some 4,200 were built in two-seat and single-seat versions and used by the Aéronautique Militaire.
The type was also built under licence in Russia where it was used extensively in regional conflicts after the Great War.
The American Expeditionary Force and the US Navy acquired French-built two-seat and single-seat examples of the type, using them for training and as ships aircraft respectively during 1917–18.
The Imperial Japanese Army Air Force also used the 1½ Strutter both as a bomber and as a reconnaissance aircraft.
Although quickly losing its advantage as a front-line fighter, the 1½ Strutter nevertheless proved invaluable as an innovative and prescient multi-role combat aircraft and it set the scene for the advent of the next generation of British fighters, including its own progeny, the world-class Sopwith Pup.
Variants & Numbers
|Land Clerget Tractor (LCT)||Initial Sopwith designation|
|Type 9400S||RNAS two-seat fighter/reconnaissance aircraft|
|Type 9700S||RNAS single-seat bomber|
|1½ Strutter||Semi-official RFC designation (also “Sopwith Two-Seater”)|
|“Sopwith Comic”||Modified two-seater into single-seat Home Defence variant|
|Ships’ Strutter||Shipboard version|
|SOP.1A2||French-built two-seat reconnaissance variant|
|SOP.1B1||French-built single-seat bomber|
|SOP.1B2||French-built two-seat bomber|
|LeO 1||Licence-built by Lioré et Olivier in France|
|So-shiki Model 1||Japanese-built bomber variant|
|So-shiki Model 2||Japanese-built reconnaissance variant|
|Number built||Approx 1,500 in UK + 4,200 in France, more than 100 in Russia|
|Powerplant||One 110hp Clerget or 110hp Le Rhone or 130hp Clerget rotary engine|
|Maximum weight||110hp Le Rhone engine: 2,205lb; 130hp Clerget: 2,342lb|
|Capacity||One pilot and one gunner/observer (two-seat fighter and reconnaissance aircraft); one pilot (single-seat bomber and Home Defence fighter variants)|
|Maximum speed||107 mph (130hp Clerget)|
|Range||Approx. 230 miles|
Survivors & Replicas
|Belgium S-88||Belgian serial S-88 on display (as S-85) at the Royal Museum of the Armed Forces and Military History, Brussels http://www.klm-mra.be|
|Canada C-FSOP||Airworthy replica C-FSOP at the Great War Flying Museum, Brampton-Caledon Airport, Canada https://greatwarflyingmuseum.org/|
|France ‘556’||French-built SOP.1A2 two-seater serial “556” is preserved at the Musée de l’Air et l’Espace at Le Bourget, Paris, painted in colours representative of machines that served with the Aéronautique Militaire. https://www.museeairespace.fr/le-musee/|
|France ‘2897’||SOP.1B2 two-seat bomber serial “2897” is an airworthy survivor restored by the Memorial Flight Association at La Ferté-Alais, Ile-de-France. http://memorial.flight.free.fr/Strutteruk.html|
|New Zealand||Possibly French-built example that later went to Argentina under restoration at The Vintage Aviator Ltd http://thevintageaviator.co.nz/|
|UK G-BIDW||Replica two-seater G-BIDW, painted as “A8226” at Royal Air Force Museum Cosford. https://www.rafmuseum.org.uk/cosford/|
|UK Replica||Replica under construction by the Aviation Preservation Society of Scotland at the National Museum of Flight, East Fortune, Scotland. Moved in 2018 to a workshop at Congalton Gardens, in North Berwick for completion. https://warbirdtails.net/2018/11/01/warbird-people-scottish-strutter-ww1-replica-nears-completion/|
Hawker Association: www.hawkerassociation.org.uk
Brooklands Museum: www.brooklandsmuseum.com