Flettner

Anton Flettner, Flugzeugbau GmbH was a German helicopter and autogyro manufacturer during World War II, founded by Anton Flettner.
Flettner aircraft included:

Flettner Fl 184 - Reconnaissance autogyro, prototype
Flettner Fl 185 - Reconnaissance helicopter, prototype
Flettner Fl 265 - Reconnaissance helicopter, prototype
Flettner Fl 282 Kolibri - Reconnaissance helicopter
Flettner Fl 339 - Reconnaissance helicopter, project
Flettner Gigant - Experimental helicopter

Anton Flettner's interest in aerodynamics also led him to invent the Flettner rotor which he used to power a Flettner ship which crossed the Atlantic, and the Flettner ventilator which is still widely used as a cooling device for buses, vans and other commercial vehicles and which is based upon the Savonius principle.