The Flettner Fl 282 Kolibri (Hummingbird) is a single-seat intermeshing rotor helicopter, or synchropter, produced by Anton Flettner of Germany. According to Yves Le Bec, the Flettner Fl 282 was the world's first series production helicopter.
Flettner Fl 282
Flettner Fl 282 during flight trials after World War II, with US markings
Anton Flettner was a German aviation engineer and inventor. Born in Eddersheim, Flettner made important contributions to airplane, helicopter, vessel, and automobile designs.
Anton Flettner
The Flettner rotor ship Buckau
Flettner Fl 282 "Kolibri" was an early variant of helicopter using two intermeshing rotors
Letter from Dr. Hohenemser regarding his association with Anton Flettner (page 1 of 2)