/kloc-at the end of 0/9, a helicopter about Leonardo da Vinci painted by 1475 was found in Milan Library, Italy? An imaginary map of a helicopter. This is a huge spiral body, made of pulped linen, which looks like a huge screw. This aircraft is operated by four people. The spinning toys popular in Leonardo da Vinci's time may have inspired the great inventor's design. He proposed that vertical flight can be achieved by rotating the helicoid around the vertical axis. It is powered by a spring, and when it reaches a certain speed, it will take the body into the air. The driver stands on the chassis and pulls the wire rope to change the flight direction. In fact, Leonardo da Vinci said that his invention only provided a helicopter power, not a real working plane. Westerners say this is the earliest blueprint for helicopter design.
Although modern scientists think that the "helicopter" designed by Leonardo da Vinci may never take off, this design is still one of his most famous inventions. Today, Leonardo da Vinci is still regarded as the originator of the concept of twin-rotor helicopter.
Early folding stage
From the 1940s to the mid-1950s, it was the first stage of the development of practical helicopters. Typical aircraft types in this period are: S-5 1, S-55/H- 19, Bell 47; Soviet Mi -4 and Ka-18; Bristol, England-171; Czech HC-2 and so on. Helicopters in this period can be called the first generation helicopters. Bell 47 is a single-engine light helicopter developed by American Bell Helicopter Company. The development work started at 194 1, and the testing machine bell 30 started at 1943. It was renamed as Bell 47, 1945, and obtained the airworthiness certificate of CAA on March 8, 2006. The machine is a seesaw rotor, single rotor and tail rotor layout, with two blades. There is a stabilizer bar under the rotor, which is at right angles to the blades. Ordinary automatic turning machine can operate the change of total pitch and periodic pitch. All-metal tail rotor with two blades at the back of the tail beam. Ka-18 is located in kamov, Soviet Union, and is enjoyed by helicopters from various countries. The single-engine dual-rotor coaxial light multi-purpose helicopter designed by the bureau made its first flight in the middle of 1957, and it was put into mass production shortly thereafter. Two groups of three-blade coaxial rotors with opposite rotation directions are adopted, and the blades are made of wood. Install 1 9-cylinder star piston engine with 275 horsepower. The fuselage is welded steel pipe structure, light metal skin and hard shell tail beam. The cockpit can accommodate 1 pilot and 3 passengers. With four-wheel landing gear, the front landing gear wheel can rotate freely. The helicopter at this stage has the following characteristics: the power source is a piston engine, with low power, low specific power (about 1.3 kW/kg) and low specific capacity (about 247.5 kW/m3). The life of rotor blades with wood or steel-wood mixed structure is short, about 600 flight hours. The airfoil of the blade is symmetrical, the tip is rectangular, and the aerodynamic efficiency is low. The rotor lift-drag ratio is about 6.8, and the rotor efficiency is usually 0.6. The machine body structure adopts all-metal frame type, and the empty weight accounts for a large proportion of the total weight, about 0.65. There is no necessary navigation equipment, only a single-function visual flight instrument, and the communication equipment is electronic tube equipment. Poor dynamic performance, low maximum flight speed (about 200 km/h), vibration level of about 0.25g, noise level of about 1 10 dB, and poor ride comfort.