Russia 🇷🇺 @Russia
🚁 #OTD in 1952 the Kamov Ka-15 #helicopter (aka 'Hen') took its first flight. It was the world's first mass-produced helicopter featuring two rotors mounted one above the other but turning in opposite directions. 💡 The idea of coaxial rotors originates with Mikhail #Lomonosov. https://t.co/aXYTdDKTXn — PolitiTweet.org