Type F-1A Utility Heater The Type F-1A heater, built by the Herman Nelsen Corp., is a World War II-era portable gasoline-powered unit designed to produce a steady flow of heated air. The Army Air Forces used it in cold climates to pre-heat aircraft and motor vehicle engines for easy starting, and to heat crew compartments, tents, hangars and other shelters. A small gasoline engine powers both a combustion chamber blower and an air distribution fan. The heated air is distributed by a system of flexible, collapsible ducts. Click here to return to the World War II Gallery.