sopwith 1 1/2 strutter

Sopwith 1 1/2 Strutter:
This series of postings are of two aircraft. One is of the original on display at the Royal Air Force Museum and the second is an airworthy exact replica. This photographer tried to focus most of the cockpit detailing from the original while combining both aircraft on the exterior details. Most prominent differences between the two are: the burnished finished on the metal cowling on the replica. The replica uses metal for struts in place of wood. The original has the rotary engine whereas the replica has a fixed radial Warner, and the machine gun on the scarf ring set up in the rear cockpit is that of the original. -- Skyediamond

The Sopwith ​1 1⁄2 Strutter was a British single- or two-seat multi-role biplane aircraft of the First World War. 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 ​1 1⁄2 Strutter because of the long and short cabane struts that supported the top wing. The type was operated by both British air services and was in widespread but lacklustre service with the French Aéronautique Militaire.


In December 1914, the Sopwith Aviation Company designed a small, two-seat biplane powered by an 80 horsepower (60 kW) Gnome rotary engine, which became known as the "Sigrist Bus" after Fred Sigrist, the Sopwith 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. 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 horsepower (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 ​1 1⁄2 Strutter. The first prototype was ready in mid-December 1915, undergoing official testing in January 1916. 

The ​1 1⁄2 Strutter was of conventional wire-braced, wood and fabric construction. The pilot and gunner sat in widely separated tandem cockpits, with the pilot 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. 

The Vickers-Challenger synchronisation gear was put into production for the Royal Flying Corps in December 1915 and in a few weeks, a similar order for the Scarff-Dibovski gear was placed for the RNAS. Early production ​1 1⁄2 Strutters were fitted with one or the other of these gears for the 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. No early mechanical synchronisation gear was reliable and it was not uncommon for propellers to be damaged or 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 ​1 1⁄2 Strutters as an interim measure. The two seaters could carry four 25 pounds (11 kg) bombs underwing, which could be replaced by two 65 lb (29 kg) bombs for anti-submarine patrols. From the beginning, a 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 pounds (29 kg) bombs