What cannon did the SPAD S.XII carry?

Short answer

A 37 mm Semi Automatique Moteur Canon (SAMC) built by Puteaux, carrying 12 rounds, rather than the old Hotchkiss cannon. The Hispano-Suiza aero engine had to be fitted with gearing so the weapon could fire through the propeller shaft, avoiding firing between the moving blades.

Published: November 5, 2026 · Updated: November 5, 2026 · Edited by Above Ten Thousand · Editorial policy

13th Aero Squadron - SPAD S XII

A 37 mm cannon through the propeller shaft

The weapon chosen for the SPAD XII was not the old Hotchkiss cannon, but a new 37 mm Semi Automatique Moteur Canon (SAMC) built by Puteaux, for which twelve rounds were carried. The Hispano-Suiza aero engine had to be given reduction gearing so that the cannon could fire through the propeller shaft, thereby avoiding the problem of firing between the moving blades.

Guynemer's idea

The aircraft was born out of the ideas of the French ace Georges Guynemer, who proposed designing a manoeuvrable single-seat fighter capable of carrying a 37 mm cannon. The aircraft he himself flew, which he called his avion magique, was armed with that 37 mm (1.46 in) piece at his express wish, with the barrel firing through the propeller shaft. In December 1916, Guynemer had written to Spad's chief designer to criticise the Spad VII as inferior to the German Halberstadt. At the time of his death he was officially credited with 54 victories.