The full launch of the world's first helicopter, albeit a military one, can be considered an event on January 13, 1942, when a Sikorsky helicopter intended for military purposes was lifted into the air. The aircraft scientist began developing helicopters in pre-revolutionary Russia, continuing their emigration to the United States. Since then, a lot of time has passed, the device of helicopters has undergone significant changes, but the purpose of the application of technology has remained the same.
Helicopter construction
In all helicopter circuits, the same main parts are distinguished:
- Main rotor. Creates propulsive and lifting forces and controls a helicopter. Structurally, it consists of blades and a sleeve that transmits torque from the main gearbox shaft to the blades.
- Steering screw Compensates the reactive torque of the rotor for the directional control of a single-rotor helicopter. Its design includes a sleeve and blades fixed to the shaft of the tail gear.
- Swashplate. It controls the cyclic and common pitch of the rotor, transmits signals from the control circuit to the axial joint of the sleeve, and then to the blades.
- Control system. Helicopters are equipped with three independent control systems: track, longitudinal and transverse and controlling the total pitch of the propeller. Such systems include levers in the cab, force gradient mechanisms, rocking and traction, swash plate and power steering.
- Transmission. It transfers power to the propellers and auxiliary units from the engines. The number and placement of engines, as well as the layout of the helicopter determine the design of the transmission.
- Fuselage. The main components of the helicopter are attached to it. Designed to accommodate passengers and goods, fuel, equipment.
- Wing. It forms additional lifting force, reducing the load on the main rotor and increasing the speed of the helicopter. The wings can also house equipment, fuel tanks, and niches to hide the chassis. The rotors in cross-section helicopters are supported by the wing.
- Plumage. Provides balancing, stability and controllability of the helicopter. It is divided into two types - vertical, or keel, and horizontal, or stabilizer.
- Helicopter take-off and landing parts. Designed for helicopter parking, quenching of kinetic energy during landing and movement on the ground. Many helicopters retract the landing gear in flight.
- Helicopter engine. Creates the power necessary to power the auxiliary units, the main drive and the steering screws. The power plant combines several engines with systems that ensure their stable operation in different modes.
Types of Helicopters
Helicopters are divided into several types. Each of the types has its own characteristics, strengths and weaknesses.
Single-rotor helicopters
The most common type of helicopter device is a single-rotor tail rotor machine. The advantage of this design lies in simplicity - one transmission, one screw, easy operation. About 8-10% of the engine power goes to the operation of the tail rotor when it hangs in the air, about 3-4% - during translational flight. The relatively light weight and simplicity of the design covers such power losses. The disadvantage of such a helicopter arrangement is the danger that threatens ground personnel from the tail rotor.
Zhirodin
The rotor axis of such helicopters, which compensates for the torque, is directed along the flight. This design allows you to create traction without resorting to the use of a rotor. This increases its efficiency, since there is no need for it to lean forward. The rotor compensating rotor torque is positioned so as not to form drag and increase the power supplied to the rotor.
Jet helicopter
The device of such a model is an easy way to eliminate the problem of torque. It is created by engines located at the end of the blades, but is not transmitted through the shaft. Only the moment of friction of the bearings is transmitted to the fuselage.
Jet engines create jet thrust. This type of rotor has a simple design, which is its advantage; Among the shortcomings are high fuel consumption.
Coaxial helicopter
Two coaxial helicopter screws located one above the other and rotating in opposite directions extinguish the moment transmitted to the fuselage. The only requirement for screws is the same torque.
Coaxial helicopters are inferior to single-rotor in size, but at the same time the torque is not compensated by power, which is possible due to the arrangement of helicopters.
Helicopters with transverse rotor
The advantage of such a helicopter lies in reducing the power required for translational motion. This is especially important in multi-engine helicopters, which must continue to move in the horizontal direction with the engine stopped.
The disadvantage of such machines is their high resistance due to the drag of the structure on which the rotors are supported. Streamlining and reducing the size of the structure increases the weight of the helicopter.
A helicopter with transverse propellers is equipped with a more complex transmission and has large dimensions, although they are affected by the degree of overlap of the rotor. One of the largest and heaviest helicopters of this design is the Mi-12.
Helicopter
A capacious fuselage and the possibility of shifting the center of gravity are the advantages of such a helicopter design. The payload is distributed between the rotors. The complicated transmission and its heavy weight are the main disadvantages characteristic of helicopters with transverse propellers.
The second drawback is the reduced efficiency of the screws, as the jets of their work intersect. During forward flight, loss of quality is reduced due to the fact that the rear propeller is located above the front. How many blades do helicopters of this design have? The diameter of the screws and the number of blades can vary to improve the handling and stability of the machine.
Multi-rotor helicopters
Multi-rotor helicopter projects developed by aircraft designers involved the creation of heavy machine models. Thanks to several rotors, control is simplified, since the helicopter can rotate relative to any of the three axes by increasing the thrust of a particular rotor. The multi-rotor scheme of heavy helicopters allows you to save the diameter of the propellers within certain limits.