What year did Igor Sikorsky invent the snowmobile?

Sikorsky was an aircraft engineer and only peripherally involved with snow vehicles. the famous S-l7 which was in effect a long-range patrol bomber and could be used and was, as a spy plane had various types of landing gear, for different missions, wheels, skids and runners for snow ops ( this may be what you are thinking of) and pontoons for naval operations. The most advanced version the Type V Ilya Mourometz- or Russian Knight- named after a medieval Russian soldier- hence the name- was a big hit. about 8l were deployed, only two were knocked out from enemy action, many survived the war, some, we don:t know how many- may be museum pieces in US and in Russia!