Biplane-bladed Helicopter

n 1921, Argentinian inventor Raúl Pateras Pescara created this advanced helicopter with counter-rotating props–each made of SIX small biplane wings! The 1931 version looked considerably more modern (Popular Mechanics, April 1921).

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By Bundesarchiv, Bild 102-12592 / CC-BY-SA 3.0, CC BY-SA 3.0 de, https://commons.wikimedia.org/w/index.php?curid=5480596