We saw so many gold sculptures, and saw that there was a large empty space in front of the underground secret room, so everyone couldn't wait to continue to walk inside with great interest, only to see a glittering helicopter inside, it was really a piece of gold, as if the city was actually a golden armor inside the eye-catching, brilliant bright gold color, and very large, like the size of a real helicopter, from the appearance looks exactly the same, except for the difference in color, the general is a silver-white metal fuselage, but is this a giant sculpture？

It's really well-built, ingenuity, this gold helicopter is like a huge golden dragonfly, parked steadily in the open space, such an expensive gold helicopter, if we can be lucky enough to carry it back, oh my God, so much gold can buy how many luxury cars, how many mansions, a lifetime of inexhaustible, really think about it is comfortable, comfortable, what a pity, such a large gold sculpture, we can only look at each other with dry eyes, and there is nothing we can do.

However, in addition to me and Xiaofei, two modern people who have crossed over, are not surprised by the helicopter and are accustomed to it, this group of ancient people is really dumbfounded, dumbfounded, dumbfounded, although they were fortunate to take a Boeing plane last time, but they have never seen such a beautiful, beautiful helicopter, can't help but concentrate on the study, stop and watch, they talk one after another, I don't know what it is, they are all inconsistent.

Hu Jiaojiao couldn't help but say: "Isn't this the bamboo dragonfly we have here, it's just many times bigger than it." Zeng Lu couldn't help but say: "Yes, this is an enlarged version of the bamboo dragonfly," Xiao Fei said disapprovingly: "Yes and no." The bamboo dragonfly, also known as the flying spiral and the Chinese spinning top, is a peculiar invention of our ancestors. Some people believe that China had bamboo dragonflies in 400 B.C., but in fact, the Qihui Flying Car 1,500 A.D. was an unpowered enlarged bamboo dragonfly. This folk toy called bamboo dragonfly has been handed down to the present. And now this thing in front of us is actually called a helicopter, don't ask me why I am so knowledgeable, in fact, I also happened to see this thing in an ancient book, that is, a detailed introduction to the helicopter, although its internal composition is ten million times more complex than the bamboo dragonfly, but its flight principle is similar to the bamboo dragonfly. The rotor of the helicopter is like the blades of a bamboo dragonfly, the rotor shaft is like the thin bamboo stick of a bamboo dragonfly, and the engine that drives the rotor is like the hands of a bamboo stick that we rub together. The blades of the bamboo dragonfly are round and blunt in front and sharp in the back, with the upper surface relatively round and the lower surface relatively straight. When the air flow passes over the upper surface of the arch, it flows at a fast rate and with low pressure, and when the air flow passes through the straight lower surface, it flows slowly and with high pressure. As a result, a pressure difference is formed between the upper and lower surfaces, and an upward lift is generated. When the lift force is greater than its own weight, the bamboo dragonfly will take off into the air. The principle of helicopter rotor rotor generating lift is the same as that of bamboo dragonflies. Another characteristic of the bamboo dragonfly is that it can also rise when it is inserted in the bamboo tube and is rotated by the crosswind. This characteristic allowed the 3,500-year-old Qihui people to fly a distance of 1,000 kilometers with the help of natural winds. The Encyclopædia Britannica records: This is called

"The Chinese gyroscope helicopter toy was introduced to Europe before Leonardo da Vinci drew the design of a helicopter with screw rotors. Volume 9 of the Concise Encyclopædia Britannica reads: Helicopters are one of the earliest flying ideas of mankind, and for many years it has been believed that Leonardo da Vinci was the first to propose this idea, and the Italian Leonardo da Vinci proposed the idea of the helicopter and sketched it. An imaginary drawing of a helicopter by Leonardo da Vinci was found in the Milan Library in Italy. It is a huge spiral made of sizing linen that looks like a giant screw. It rotates with a spring as the power force, and when it reaches a certain speed, it carries the body into the air. The driver stands on the chassis and pulls the wire rope to change the direction of flight. Westerners say that this is the earliest blueprint for helicopter design. But we all know by now that the Chinese made helicopter toys earlier than the Europeans in the Middle Ages. So it is no exaggeration to say that in fact, China is still the birthplace of helicopters. Zeng Meinu deflated her good-looking cherry mouth, and said impatiently: "That little flying brother, you tell us what a helicopter is, I didn't hear it clearly for a long time, I understood it." Xiao Fei took the trouble to say: "How to say it, in fact, the ancient book says that the helicopter is a kind of aircraft, and the lift that supports its flight in the air completely depends on the reaction force generated by one or more rotors rotating around the vertical axis to repel the air flow downward, and the helicopter is mainly composed of the fuselage and lift (including rotor and tail rotor), power, transmission three major systems and airborne flight equipment. The rotor is generally driven by a turboshaft engine or piston engine through a mechanical transmission system composed of a propeller shaft and a reducer, and can also be driven by the reaction force generated by the jet at the tip of the propeller. The maximum speed of the helicopter can reach more than 300km/h, the ultimate speed of the dive is nearly 400km/h, the practical ceiling can reach 6000 meters (the world record is 12450m), and the general range can reach about 600~800km. The transfer range of the internal and external auxiliary fuel tanks of the aircraft can reach more than 2000km. Depending on the need, the helicopter has different take-off weights. The largest heavy helicopter currently in service in the world is the Russian Mi-26 (with a maximum take-off weight of 56 tons and a payload of 20 tons). Mechanically driven single-rotor and twin-rotor helicopters are currently in practical use. The helicopter is mainly composed of four major systems: fuselage and lift (including rotor and tail rotor), power, rotation and airborne flight equipment. The rotor is generally driven by a turboshaft engine or piston engine through a mechanical transmission system composed of a propeller shaft and a reducer, and can also be driven by the reaction force generated by the jet at the tip of the propeller. The Chinese bamboo dragonfly and the Italian Leonardo da Vinci's helicopter sketches provided inspiration for the invention of modern helicopters and pointed out the correct direction of thinking, and they are recognized as the starting point of the history of helicopter development. Hu Jiaojiao said with an ignorant face: "Oh, Xiaofei, can you speak slowly, I don't understand it at all." Xiao Fei smiled and said: "Then I will be simple, in a word, straightforward talk about the flight principle of the helicopter, that is, the helicopter has a large propeller at the head, and a small propeller at the tail, and the small propeller is in order to counteract the reaction force generated by the large propeller." The helicopter engine drives the rotors to provide lift and lift the helicopter in the air, and the rotors can also tilt the helicopter to change direction. The propeller speed affects the helicopter's lift, allowing the helicopter to take off and land vertically. ”