The schoolteacher inventor

Anton Flettner was born in 1885 in Eddersheim, near Frankfurt, and began as a village schoolteacher, then taught mathematics and physics in Frankfurt. In the First World War he worked on remote control for the War Ministry, proposing a steerable torpedo and a remote-controlled combat car, both rejected as impractical. His lasting gift was smaller: the servo tab, patented in 1918, which evolved into the trim tab found on virtually every aeroplane and many large ships.

A ship driven by spinning towers

Then came his strangest invention. Watching sand flow over his spinning hand on a beach, the story goes, he grasped the Magnus effect, and with help from Ludwig Prandtl, Albert Betz and others he refitted the schooner Buckau with two tall rotating cylinders in 1924. Renamed Baden-Baden, the rotor ship crossed the Atlantic in 1926. A partner, Sigurd Savonius, turned the idea into a wind turbine, and Flettner’s ventilator company, built on that patent, paid for his later work on helicopters.

Rotors instead of wings

Flettner Flugzeugbau, based at Berlin-Johannisthal, spent years chasing rotary-wing flight. The Fl 184 autogyro and the Fl 185 gyrodyne of the mid-1930s were steps on the way. With Kurt Hohenemser and Gerd Sissingh, Flettner then built the Fl 265 of 1939, with two intermeshing, contra-rotating rotors whose torques cancelled out. This synchropter layout, the Flettner double rotor, could switch from powered flight to autorotation and back, making it the safest helicopter of its day.

The Kolibri

Its refinement was the Fl 282 Kolibri, a small open-cockpit synchropter first flown in 1941. It took off repeatedly from a platform on the cruiser Köln and was tested in the Baltic, Mediterranean and Aegean. The French historian Yves Le Bec calls it the world’s first series-production helicopter. In 1944 the air ministry ordered 1,000 from BMW, but bombing destroyed the Munich plant after only 24 were built. The last served as artillery spotters near Berlin, falling to Soviet fighters and flak.

Paperclip and the synchropter legacy

Flettner’s Jewish wife and family spent the war in Sweden. Interned at Kransberg Castle in 1945, he was taken to the United States under Operation Paperclip and founded the Flettner Aircraft Corporation in New York, which was not commercially successful. He researched for the US Army, Air Force and Navy until his death in New York in 1961. Intermeshing rotors reappeared after the war in Kaman’s helicopters, though accounts differ on whether Flettner himself ever worked for Kaman.

Továrny

• Johannisthal works · Berlin-Johannisthal — Company base 1935–1945

Lidé

• Anton Flettner · founder — 1885–1961; inventor of the servo tab and the Flettner rotor ship
• Kurt Hohenemser · engineer — Partner who worked out the detail of Flettner’s helicopters; emigrated to the US
• Richard Perlia · test pilot — Tested the Fl 265 in 1939

Rekordy a prvenství

• Fl 265 (1939): first helicopter with intermeshing rotors, able to switch between powered flight and autorotation
• Fl 282 Kolibri: described by Yves Le Bec as the world’s first series-production helicopter