Antoinette military monoplane

Designed by Léon Levavasseur and Jules Gastambide, and baptized with the name "Monobloc", the aircraft featured a number of innovative aerodynamic refinements for its time. The design was characterized by an enclosed and streamlined body and wings. The design reduced air resistance by the absence of any external bracing wires, and by having its control cables totally enclosed within its quadrangular-section fuselage and large wooden cantilever wings.[1]

The wooden wings were 70 cm thick at the base and 25 cm at the ends, with internal bracing and built around four square steel spars. The main spar was 70 cm high and fixed at the front third of the wing; the others (i fore, 2 aft) hinged in the middle of their axes, allowing the wings to 'warp' to provide lateral control of the machine. These were controlled by the pilot by a distortable frame which could be pushed for-and-aft or side-to-side for controlling the wing warping.[1][2]

The spars were supported by ribs spaced 40 cm apart; the wings, fully loaded, were designed to bear about 25 kg per m² — when the current aircraft of the time only were designed to bear 15 kg/m². The chord of each wing was 4 metres at the junction with the fuselage, and decreased to 3 metres at the wing tip. The upper side of the wing's airfoil was cambered, while the under side was very flat, with the leading and trailing edges being quite sharp.[2][3][4] The tailplane included a long, low fin and a large rectangular rudder that could be enlarged by an extension.[5]

Antoinette Monobloc aircraft at Le Grand Concours d'Aviation Militaire at Reims in September 1911

The streamlined fuselage was decked over with wood frames and tight canvas, with only the cylinder-head of the engine exposed. The fuselage terminated at the front by a bow shaped like that of a boat. The crew compartment had three seats lined up and was closed, so access was through a door under the fuselage. Seated at the front was the mechanic, who had easy direct access to the engine at the front. Behind him, the pilot had a good range of vision, with windows in the floor enabling him to see beneath him. An observer sat behind the pilot in the rear.[2][4][5][6]

The enclosure of the aircraft's fixed landing gear by streamlined fairings or "spats" was viewed as a remarkable innovation in 1911.[7] Each fairing consisted of a canvas-covered structure containing a large double main wheel on a flexibly sprung axle, and a smaller wheel placed forward to avoid nose-overs on landing.[1][3][5][7] A similar arrangement was used by the Coandă 1911 twin-Gnôme engine monoplane.[7]

Acting as a radiator, a network of copper tubes running along the fuselage cooled the Antoinette 8V engine of 50 to 60 hp (according to different sources).[3][5][6] For the 1911 military contest at Reims in September-October 1911 a larger V12 engine of 100 hp was fitted. This was cooled by steam — heated water evaporated in the cylinder jackets and then condensed in copper tubing attached to the outside of the aircraft. The engine had two valves per cylinder, a mechanically operated exhaust valve and an automatic inlet valve. Instead of a carburetor, two fuel pumps delivered fuel to the inlet valve chambers.[8]

A larger engine of V16 configuration and 120 hp was planned,[2] but this may not have been possible due to limited space between the engine and the crew's entry hatch located underneath the fuselage.[9]