The SPAD S.A (also called S.A.L.) was a French two-seat tractor biplane first flown in 1915. It was used by France and Russia in the early stages of the First World War in the fighter and reconnaissance roles. It was a unique aircraft that carried its observer in a nacelle ahead of wing, engine and propeller. Design and development The SPAD A.1 prototype was the first aircraft produced by SPAD following its reorganization from the pre-war Deperdussin company. The chief designer, Louis Béchereau, had been involved in designing that firm's successful monocoque racing monoplanes, and many design details were carried over from the Deperdussins. The aircraft was designed to carry not only its pilot in the normal position, but also an observer in a streamlined nacelle ahead of the propeller. This configuration was an attempt to combine the advantages of the tractor and the pusher types, giving the observer a clear field of view to the front and sides without the drag penalty of the typical pusher. However, communication between the pilot and the observer was nearly impossible. The pulpit (as it was known in English) or basket (as it was referred to in Russian) vibrated badly and, in multiple cases, parted company from the rest of the aircraft while in flight. Like many pushers, it also put the observer at risk of being crushed in even a relatively mild crash or "nose-over". A British evaluation of the type suggested "it would be expensive in observers if flown by indifferent pilots". While not originally designed explicitly as a gunner's position, early combat experience had shown a need for forward-firing machine guns. But mechanisms to allow a gun to fire through the propeller were not yet available, and the observer's nacelle on the S.A-1 represented a temporary solution. As well as the 2-seat S.A versions a single seat fighter, the SPAD S.G, was also produced with fixed forward-firing guns in the nose nacelle, without any occupant. The S.G.'s guns were not accessible to the pilot which caused problems when stoppages occurred and with cocking the guns for combat. On all but the earliest prototypes and the SPAD S.G, the nacelle was fitted with a light machine gun on a flexible tubular mount, and it incorporated air intakes on its sides and underside to redirect air toward the Le Rhône rotary engine, which was otherwise masked by the nacelle. Starting the engine