In 1917 his old mentor, Bertram Hopkinson, who was now Technical Director at the Air Ministry, invited him to join the new engine research facility at the Department of Military Aeronautics, later to become the RAE. In 1918 Hopkinson was killed while flying a Bristol Fighter, and Ricardo took over his position. From that point on the department produced a string of experimental engines and research reports that constantly drove the British, and world, engine industry.[7]