Complete works of helicopter traditional tail rotor

Helicopters belong to rotorcraft. Different from ordinary aircraft, the upward lift of helicopter is produced by the rotation of propeller. If you have played with bamboo dragonflies, you can understand how helicopters fly. Our common ordinary helicopter has a big propeller and a small propeller behind it, but some helicopters have two propellers of the same size and rotate in opposite directions. Why?

According to the third law, "the acting force and reaction force between two interacting objects are always equal in size and opposite in direction, and act on the same straight line", we can know that when the helicopter drives the propeller to rotate, the propeller will inevitably produce opposite acting force on the helicopter. This force will drive the helicopter's body to rotate in the opposite direction. If there are no other measures to counteract this reaction, the helicopter will enter the "involuntary" rotation mode. If the driver follows this, let alone fly the plane, he can spit out the food overnight. Therefore, in order to counteract the rotation of the fuselage, the helicopter needs to introduce an extra force to eliminate this reaction force and ensure that the fuselage will not rotate.

The most common is a helicopter with a tail rotor. The force generated when the tail rotor rotates counteracts the reaction force acting on the fuselage, so that the helicopter can take off safely driven by the propeller. The helicopter using tail rotor accounts for the vast majority in the world, including military and civilian. The advantages of this helicopter are simple structure, mature technology, reliable performance and balanced performance in all aspects. Interestingly, helicopter propellers in the United States, Britain, Germany, Italy and Japan all rotate counterclockwise, while those in France, Russia, China and India all rotate clockwise.

Russian Mi -24 helicopter with tail rotor.

Knowing the basic principle, we can know that the helicopter will take off and land normally as long as the reaction force acting on the body can be eliminated. So there are many other ways to make a helicopter fly besides using the tail rotor.

1.*** axis twin-rotor helicopter

There are two propellers above the helicopter body, which rotate in opposite directions around the same axis. In this technology, because the propellers turn in opposite directions, the forces generated by the two propellers cancel each other, thus ensuring that the lower body will not rotate. Compared with ordinary helicopters, the twin-rotor helicopter with * * axis has shorter fuselage, higher lift and higher flying efficiency, but it requires higher technical level. At the same time, when the two rotors get too close and maneuver violently, they may collide with each other, resulting in accidents such as plane crash and death.

* * * axis twin-rotor anti-submarine helicopter imported from Russia.

2. Twin-rotor tandem helicopter

Two propellers, one left and one right, of a twin-rotor tandem helicopter are respectively installed on the supports on both sides of the fuselage. When taking off, the propellers rotate in opposite directions, and the mutual forces cancel each other out. The technology of twin-rotor tandem helicopter has been abandoned because of too many shortcomings. Only the Soviet Union made several Mi-12 twin-rotor tandem helicopters, but there is no development at present.

The former Soviet Union Mi 12 helicopter

3. Twin-rotor tandem helicopter

The two propellers of twin-rotor tandem helicopter are arranged at the front and rear of the fuselage. According to the flight principle, the reverse rotation of two propellers is used to counteract the generated torque. In some helicopters, in order to keep the whole compact, the two propellers are one high and one low, so that the propellers will not interfere with each other when flying. This kind of helicopter has a large load and a large space, because it has no tail structure of ordinary helicopters, and it is like a flying carriage. The most typical twin-rotor tandem helicopter is CH-47 nicknamed "Air Carriage".

CH-47 "Air Carriage" in Flight

4. Twin-rotor cross helicopter

The two propellers of this helicopter rotate in opposite directions, and the propeller base is installed obliquely, and the two propellers cross when rotating. In order to prevent rotor collision, flight coordination devices are used to ensure safety. Strapdown helicopter has good flight stability, but it is technically difficult. Basically, it is for civilian use and rarely appears in public view.

5. Deflection wing aircraft

Deflection wing aircraft is a new type of aircraft which combines the characteristics of helicopter and aircraft. Deflection wing aircraft take off like a tandem helicopter with two rotors. After take-off, the propeller and engine compartment rotate 90 degrees forward, which looks like an ordinary propeller plane. Deflection wing aircraft combines the characteristics of two kinds of aircraft, which can not only reach the speed and range of fixed-wing aircraft, but also take off and land without airport like a helicopter. However, the design of this kind of deflection wing aircraft is difficult and the technical level is high. Even the MV-22 deflection wing aircraft in the United States had many accidents during the test, resulting in dozens of people being killed.

American MV-22 Osprey Deflection Wing Aircraft

6. Jet tail rotor

In a conventional tail rotor helicopter, a small propeller is generally used on the tail beam to rotate and generate reaction force. There are also some small helicopters, which find another way. These helicopters are equipped with fans in the thick tail beam, and the end side of the tail beam is provided with air jets. When the helicopter takes off, the wind blown by the fan is ejected from the air nozzle to form a reaction force to offset the deflection of the helicopter body and ensure that the helicopter body will not rotate during take-off. The biggest advantage of this helicopter is that it has no tail rotor, which greatly reduces the noise and improves the safety performance. Of course, the disadvantage is that the tail beam is enlarged and the weight is increased, which is only suitable for small helicopters.

MD-600 helicopter