Flying a Fw 44 Stieglitz, Achgelis was placed third in the 1934 World Aerobatic Championships in Paris, and was 5th at the 1936 event in Berlin. From April 1932, he also worked as a flying instructor at the Technikum Weimar, and in 1933 became chief test pilot for the Focke-Wulf company in Bremen. On 26 June 1936 he flew the Focke-Wulf Fw 61, considered the first practical helicopter, on its maiden flight.
On 27 April 1937, together with Henrich Focke, he founded the company Focke-Achgelis to develop and manufacture helicopters at Hoykenkamp.
In 1933 Hermann Goering proposed that Achgelis take a post as an instructor at the Deutsche Verkehrsfliegerschule ("German Air Transport School"), to establish and train an aerobatic team Achgelis turned down the offer, and he also refused Goering"s request to take the position of Generalluftzeugmeister ("Luftwaffe Director-General of Equipment") after the death of Ernst Udet in November 1941.
He worked as a test pilot at an aircraft factory in Graudenz until the end of World World War World War II After the war, Achgelis retired to his family farm, and from 1952 had commercial interests in Hude. However he remained connected to flying.
He also donated the Kavalier der Lüfte trophy, which is presented annually every November.
Achgelis died at his home in Hude in 1991.