sentences:  He became Assistant Professor of Aeronautics in 1945, Associate Professor in 1946 and Professor from 1949 to 1974.From 1974 to 1976 he was Professor of Aeronautics and Applied Physics, from 1976 to 1983 Charles Lee Powell Professor of Fluid Mechanics and Thermodynamics and 1984-85 von Kármán Professor of Aeronautics.From 1972 to 1985 Liepmann was Director of the Guggenheim Aeronautical Laboratory and Executive Officer for Aeronautics from 1976 to 1985.