کتاب helicopter aerodynamic (second volume) نشر کنکاش

One may doubt whether Lilienthal, the pioneer par excellence of gliding flight, had the helicopter in mind when he wrote the above but his words could not have been more appropriate to our subject. To take the quotation line by line, the concept of a lifting rotor constitutes the essential invention. Making it large is simply taking advantage of Newton’s Second and Third Laws, which guarantee that blowing a large quantity of air at low speed is an efficient way of producing a thrust.