What is the difference between a helicopter and a fixed-wing aircraft

The rotor blades are generally driven by turboshaft engines or piston engines through a mechanical transmission system consisting of drive shafts and speed reducers, etc. They can also be driven by the reaction force generated by the jet from the tip of the paddle. The outstanding features of helicopters are that they can do maneuvering flights at low altitude (several meters above the ground), low speed (from hover) and constant nose direction, especially vertical takeoffs and landings in small sites. Because of these characteristics, it has a wide range of uses and development prospects. In the military aspect, it has been widely used in ground attack, airborne landing, weapon transportation, logistic support, battlefield rescue, reconnaissance patrol, command and control, communication, anti-submarine minesweeping, electronic countermeasures and so on. 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 offshore oil wells and bases is an important aspect of civil use. Principle of the helicopter engine driven rotor to provide lift, the helicopter lifted in the air, the main engine also output power to the tail of the small propeller, the onboard gyroscope can detect the helicopter slewing angle and feedback to the tail rotor paddles, by adjusting the pitch of the small propellers can be counteracted by the large propellers produced by the different speed of the reaction force. Through the so-called "tilt disk" mechanism can change the helicopter rotor blade angle, so as to realize the rotor cycle pitch, so as to change the rotor rotating plane of the different positions of the lift to achieve changes in the helicopter's flight attitude, and then the direction of the change in the direction of lift to change the direction of flight. At the same time, after the helicopter lifts off, the engine is kept at a relatively stable rotational speed, to control the helicopter's ascent and descent by adjusting the rotor's total pitch to get different total lift, so the helicopter realizes vertical takeoff and landing fixed-wing aircraft refers to the aircraft's wing position, swept back angle and other parameters are fixed; relative to the modern supersonic aircraft, in order to get a larger lift at a low speed, the wing is stretched out, and the wing is extended by the wing's rotor. Relatively modern supersonic aircraft at low speeds, in order to get a larger lift, the wing extension is larger (smaller swept back angle), in flight with the increase in aircraft speed, swept back angle can be changed to increase, this is no longer a fixed-wing aircraft, typically helicopters, which is also called rotorcraft, there is no fixed wing; shipboard aircraft in order to reduce the parking area, the wings will be folded; but the wings can not be seen in the flight of the folding action, or to change the angle of the aircraft, is still a fixed-wing aircraft. At present, civil aviation airliners are all fixed-wing aircraft. Today's world aircraft, the main fixed-wing aircraft: the wings extend flat on both sides of the fuselage, the main generation of lift, the wings are relatively fixed. There is another kind of variable swept wing aircraft, that is, the wing swept back angle can be changed in flight aircraft, also belongs to the fixed-wing aircraft. Modern supersonic airplanes widely used in small chord ratio large swept back wing, supersonic drag is smaller, but low speed aerodynamic efficiency, lift characteristics are not good. A large-sweep wing with a small swept-back angle with good low-speed performance will in turn deteriorate supersonic performance. Variable-sweep wing airplane can solve the contradiction between high and low speed performance requirements through the change of wing swept back angle. Aircraft in the takeoff and landing and low-speed flight with a smaller swept-back angle, when the wing chord ratio is the largest, and thus has a higher low-speed cruise efficiency and greater takeoff and landing lift. In supersonic flight with a larger swept-back angle, the wing chord ratio and the relative thickness of the wing is reduced, which is very favorable to reduce the drag of supersonic flight. In addition, the supersonic bomber and the strong attack aircraft for ultra-low altitude and high-speed flight, in order to reduce the bumps caused by the unsteady airflow, also requires a large angle of wing swept back, the chord ratio is small.