August Euler (1868-1957) was a pioneer pilot/builder, active in 1909-1910. In 1910 he patented a machine gun installation for aircraft, and at the request of the German War Department some sort of presentation of it was withdrawn from the Berlin Aeronautical Exhibition of 1912. Euler acquired a license for Voisin aircraft, and Prince Heinrich of Prussia took his pilot's certificate on an extensively modified example of the type. At least 30 other Germans learned to fly on this aircraft. An early wartime reconnaissance type was the BII tractor biplane (built at Frankfurt in late 1914), an early version of which had tricycle landing gear; B III was a license-built LVG; Type C a pusher of 1916; Dr 1-Dr 4 were triplanes. A quadruplane was also built (though top surfaces were really full-span ailerons), but Euler types achieved little distinction after 1916.