of maintaining formation and using the crossfire of the observers' guns to counter enemy fighter aircraft. Pilots soon realised that the Bristol Fighter was a strong and agile aircraft, capable of manoeuvring with single-seat fighters, despite some rumours that the type lacked the structural strength to be flown as a fighter. While its fixed forward-firing machine gun could be used as the primary weapon, the observer could use his flexible, rear-mounted gun to provide protection from attacks from the rear. Flown in this manner, the Bristol Fighter achieved a 'remarkable' level of success and proved to be a formidable opponent for German fighters. From May 1917 onwards, the definitive F.2B Fighter quickly supplanted the earlier F.2A model. In July 1917, the War Office decided to adopt the F.2B Fighter as the equipment of all fighter-reconnaissance squadrons, leading to a significant increase in production. Despite the issuing of contracts for further large batches of aircraft, it was apparent that the rate of production could not keep up with demand for the type. Perhaps one of the best known flying aces to use the type was Canadian Andrew McKeever, and his regular observer L. F. Powell. By the end of 1917 McKeever had accumulated 30 victories and Powell had achieved eight, while operating the Fighter. McKeever later became a flying instructor stationed in England before becoming the commanding officer of 1 Squadron of the new Royal Canadian Air Force (RCAF), where he continued to use the Fighter as his personal aircraft, which was later transferred to Canada. Near the end of the war, the Bristol Fighter was used in a pioneering new capability in the form of radio communications; 11 Squadron was the first such squadron to be equipped. Only the flight commander's Fighter would be equipped with a transmitter while others were outfitted with receivers, allowing for one-way communication of orders; as the trailing aerials employed needed to be wound in prior to aerial combat, this requirement reduced the usefulness of the system. The Fighter also participated in experiments held by the Royal Aircraft Establishment (RAE) into the use of parachutes, resulting in several aircraft being modified to carry static-line parachutes within the underside of the fuselage; these trials continued following the signing of the Armistice. In September and October 1917, orders for 1,600 F.2B Fighters were placed; by the end of the First World War, the Royal Air Force (RAF)