37mm Aircraft Cannon This Model 1918 Type M1 Cannon was manufactured at the Watervliet Arsenal, N.Y., during World War I. Mounted on a swivel, it was designed to be fired one shot at a time. Tests indicated that single-shot cannon of this type required too much attention by the pilot or observer during actual combat, recoil was too great, the blast effect often was detrimental to the fabric-covered airplanes in or on which they were mounted, and they were not sufficiently effective to replace the automatic machine gun. The French Air Service installed a similar type cannon in some SPAD XII fighters during WWI. One of those planes was provided to the U.S. Air Service ace Lt. David Putnam of the 139th Aero Squadron, but he never had an opportunity to use it in combat prior to being killed in action. During the World War II period, the airborne cannon became an effective weapon. Click here to return to the Early Years Gallery.