The Sopwith 1½ Strutter was a British one or two-seat biplane multi-role aircraft of the First World War. It is significant as the first British aircraft to be designed with an interrupted machine gun and, along with the DH.2 and F.E.2, contributed to the ending of the German period of dominance on the Western Front known as the Fokker Scourge.

Designed by the Sopwith Aviation Company, the 1½ Strutter was so nicknamed because the upper and lower wings on each side of the aircraft were connected by a pair of full struts near the tip while a pair of half struts connected the upper wing to the fuselage fore and aft of the pilot's cockpit. The aircraft also featured airbrakes on the lower wings. It was powered by a 130-hp (97 kW) Clerget rotary engine.

The main armament was a .303-in Vickers machine gun and up to four 56 lb (25 kg) bombs could be carried. The observer was also armed with a Lewis gun. The Ross interrupter gear used by the forward-firing gun was unreliable and many aircraft flew with the non-interrupted trigger still fitted so that, if necessary, the pilot could trust to luck and the Strutter's good glide performance, and fire uninterrupted through the propeller. Consequently 1½ Strutter squadrons were known to go through a few propellers.

The prototype two-seater flew in December 1915 and the first aircraft entered service in April 1916. A single-seat bomber version was also built. Large numbers — in excess of 4000 — of the 1½ Strutter were built in France. Another variant, known as the Ship Strutter, was built for service from aircraft carriers and other warships of the Royal Navy.

The first great British dog fighter of the war, the Sopwith Pup, was essentially a scaled-down, single-seat version of the 1½ Strutter.

Specifications

General Characteristics

• Crew: two, pilot & observer
• Length: 25 ft 3 in (7.7 m)
• Wingspan: 33 ft 6 in (10.21 m)
• Height: 10 ft 3 in (3.12 m)
• Wing area: 346 ft² (32.14 m²)
• Empty: 1,260 lb (570 kg)
• Loaded: lb ( kg)
• Maximum takeoff: 2,149 lb (975 kg)
• Powerplant: 1x Clerget rotary engine, 130-hp (97 kW)

Performance

• Maximum speed: 102 mph (164 km/h)
• Range: 350 miles (565 km)
• Service ceiling: 13,000 ft (3,960 m)
• Rate of climb: ft/min ( m/min)
• Wing loading: lb/ft² ( kg/m²)

Armament

• 1x .303 in (7.7 mm) forward-firing Vickers machine gun with Ross interrupter gear
• 1x .303 in (7.7 mm) Lewis gun in observer's cockpit
• up to 224 kb (100 kg) bombs

Related content

Related development: Sopwith Pup

Comparable aircraft: Bristol F.2 Fighter

Designation sequence: Tabloid - Baby - 1½ Strutter - Pup - Triplane