The helicopter is mainly composed of the fuselage and three major systems of lift (including rotor and tail rotor), power and transmission, as well as on-board flight equipment. The rotor is generally driven by a turboshaft engine or a piston engine through a mechanical transmission system consisting of a drive shaft and a reduction gear, or it can be driven by the reaction force generated by the jet from the tip of the paddle. The current practical application is mechanically driven single-rotor helicopters and dual-rotor helicopters, of which the number of single-rotor helicopters is the largest.
The maximum speed of the helicopter can reach more than 300 km / h, swooping limit speed of nearly 400 km / h, the use of the ceiling can reach 6,000 meters (the world record is 12,450 meters), the general range of up to 600 to 800 km or so. Carrying in-flight and external sub-tank transit range of up to 2,000 kilometers or more.
Based on the different needs of the helicopter has a different takeoff weight. Currently the world's largest heavy helicopter in use is the Russian Mi-26 (maximum takeoff weight of 56 tons, payload 20 tons).
The helicopter's outstanding feature is that it can do low altitude (a few meters above the ground), low speed (from hover) and nose direction of the constant maneuvering flight, especially in a small area of the site can be vertical takeoff and landing. Because of these characteristics make it has a wide range of uses and development prospects.
In the military has been widely used in ground attack, landing, weapons delivery, logistical support, battlefield rescue, reconnaissance and patrol, command and control, communications, anti-submarine mine clearance, electronic countermeasures. In civilian use, it has been applied to short-distance transportation, medical care, disaster relief, emergency rescue, lifting equipment, geological exploration, forest protection and fire-fighting, and aerial photography. The transportation of personnel and materials between oil wells and bases at sea is an important aspect of civil use.
Current helicopters relative to the aircraft, vibration and noise level is higher, maintenance and repair workload is larger, the use of higher costs, lower speed, shorter range. The future direction of helicopter development is to improve on these aspects. Modern helicopter
The 1990s is the fourth stage of helicopter development, the emergence of visual, acoustic, infrared and radar integrated stealth design of armed reconnaissance helicopters. Typical models are: the United States of America's RAH-66 and S-92, international cooperation "Tiger", NH90 and EH101, etc., known as the fourth generation of helicopters.
This stage of the helicopter has the following characteristics: the use of the 3rd generation of turboshaft engine, this engine is still free turboshaft structure, but the use of advanced engine full digital control system and automatic monitoring system, and with the on-board computer management system integrated together with a significant technological advances and comprehensive features.
The fuel consumption rate of the third generation turboshaft engine is only 0.28 kg/kWh, which is lower than that of the piston engine. Its representative engines are T800, RTM322 and RTM390. the paddles are made of carbon fiber, Kevlar and other advanced composite materials, and the life of the paddles reaches infinite. The new propeller tips come in a wide variety of shapes, with the more prominent ones being the parabolic swept-back shape and the swept-forward and then swept-back BERP tips.
The ****same feature of these new tips is that they can weaken the compressive effect of the tips, improve the aerodynamic load distribution of the paddles, reduce the vibration and noise of the rotor, and improve the aerodynamic efficiency of the rotor. Ball flexible and bearingless paddle hubs have been widely used, and the connecting parts of the paddle hub shell and the paddle blade are made of composite materials, which make the structure more compact, the weight greatly reduced, and the resistance greatly reduced.
The rotor lift-to-drag ratio reached 10.5, and the rotor efficiency was 0.8. At this stage, the tail rotor counter torque system was applied, which has the advantages of good maneuvering response characteristics, low vibration, low noise, and does not need tail drive shaft and tail reduction, so the number of parts is greatly reduced, thus improving the maintainability.
Composites have been used in helicopters on an unprecedented scale. Helicopters began to use composite main structure, the proportion of composite material application has risen dramatically, usually accounted for 30~50% of the weight of the body structure. The air weight/gross weight ratio of civil helicopters in this period was about 0.37. Highly integrated electronic equipment. Computer technology, information technology and intelligent technology in the helicopter to obtain the application of helicopter electronic equipment toward the direction of highly integrated development.
The helicopters in this period adopted advanced stabilizing and increasing control devices, replaced the conventional manipulation system with electric and optical transmission manipulation, adopted advanced Jetlink inertial guidance, satellite navigation equipment and combined navigation technology, advanced communication, identification and information transmission equipment, advanced target identification, targeting, weapons launching and other fire control equipment and advanced electronic countermeasures, adopted bus information transmission and data fusion technology, and is moving towards sensor technology, which is the first time in the history of helicopter electronic equipment development. data fusion technology, and is developing in the direction of sensor fusion. On-board electronics, fire control and flight control systems are interconnected through redundant digital data buses, realizing information **** enjoyment.
Adopted multi-functional integrated display technology, with a small number of multi-functional displays instead of a large number of individual instruments, through the keyboard control display helicopter flight information, the use of the central computer for communication, navigation, flight control, enemy identification, electronic countermeasures, system monitoring, weapons and fire control information integrated processing and thus integrated control.
The use of such advanced integrated electronic equipment, greatly simplified the helicopter cockpit layout and instrument panel layout, system components have been simplified, the weight is greatly reduced. More importantly, it greatly reduces the pilot's workload and improves the helicopter's aircraft quality and performance. The helicopter's lift-to-drag ratio reaches 6.6, the vibration level is reduced to 0.05g, the noise level is less than 90 decibels, and the maximum speed can reach 350 kilometers per hour.