What does the plane navigate by?

Aircraft navigation system is a set of equipment (including equipment on the plane and on the ground) that can determine the position of the aircraft and guide the aircraft to fly according to the predetermined route.

Early airplanes mainly relied on visual navigation. Instrument navigation began to develop in the 1920s. There is a simple instrument on the plane, and the position of the plane can be obtained by manual calculation. In 1930s, radio navigation appeared, and medium wave four-channel radio beacon and radio compass were used for the first time.

In the early 1940s, the development of ultrashort wave vortex navigation system and instrument landing system began (see Radio Controlled Landing). In the early 1950s, inertial navigation system was used for aircraft navigation. Doppler navigation system appeared in the late 1950s. Long-range radio Loran C navigation system was used in 1960s, with a range of 2000 kilometers.

In order to meet the military needs, Tacan navigation system was also developed, followed by Voltak navigation system and ultra-long-range Omega navigation system, and the running distance has reached 10000 km. Satellite navigation appeared in 1963, and the global positioning navigation system was developed after 1970s.

Extended data:

Navigation method:

The key of navigation is to determine the instantaneous position of the aircraft. There are three methods to determine the position of aircraft: visual positioning, geometric positioning and dead reckoning.

Visual positioning:

Visual positioning is to judge the position of the aircraft by the pilot observing the ground signs; Dead reckoning is to calculate the current position of the aircraft according to the known position at the previous moment and the measured navigation parameters. Geometric positioning is to measure the geometric relationship between the aircraft and some navigation points with completely determined positions, and finally determine the absolute position of the aircraft.

Geometric positioning:

Based on the navigation point, the position of the aircraft relative to the navigation point is determined, so as to determine the position line of the aircraft (that is, the trajectory with certain geometric parameters such as distance and angle unchanged). Then determine the position of the aircraft relative to another navigation point and determine another position line. The intersection of two position lines is the position of the plane.

Three kinds of position lines: the position line with constant relative orientation is a straight line passing through the navigation point; The position line with constant distance is a circle centered on the navigation point; The position line with constant distance difference to two navigation points is a hyperbola. Radar can also be used to determine the position of aircraft.

Dead reckoning:

According to the known position of the plane at the previous moment and the measured navigation parameters, the position of the plane at that time is calculated. For example, according to the measured real airspeed and the heading of the aircraft, at a given wind speed and direction, the ground speed is calculated by using the navigation speed triangle (see flight speed and instrument navigation), and then the ground speed is integrated with time.

Substituting the initial condition-the position of the previous moment can get the position of the aircraft at that time. Doppler radar can directly measure the ground speed and drift angle, and the position of the aircraft can also be obtained through integration.

Inertial navigation is essentially dead reckoning. Acceleration is measured by inertial components, and position information is obtained by twice integration. Dead reckoning is the main method of modern navigation. The navigation system using this method only depends on the instruments on the plane, has nothing to do with the outside world, and is not easy to be interfered by radio, so it can carry out global navigation.

Global satellite navigation system is the core of satellite navigation system. It mainly includes the global positioning system mastered by the US Department of Defense, GLONASS built by the former Soviet Union in the 1980s and now managed by the Russian Space Agency, and the navigation satellite system being built by the European Space Agency in Western Europe.

GPS is the most widely used satellite navigation system at present, but it is interfered by technology and policy in aviation application. Before NAVSAT system was put into use, users had no choice, so the combination of INS/GPS was used, which is also our most important and commonly used navigation mode.

So what we usually call GPS position is actually GPIRS, that is, the mixed position of INS/GPS.

Inertial navigation system: three accelerometers installed on the inertial platform are used to measure the acceleration of the aircraft in three directions perpendicular to each other, and the computer integrates the acceleration signal once and twice with time to obtain the speed and displacement of the aircraft in three directions, thus continuously giving the spatial position of the aircraft.

Instead of using inertial platform to measure acceleration, the accelerometer can be directly installed on the fuselage, and then the signals provided by the heading system and attitude system can be input into the computer to calculate the speed and displacement of the aircraft. This is the Strapdown Inertial Navigation System.

Astronomical navigation system: based on a celestial body (such as a star), the angle between the horizontal plane and the line of sight of this star (called the star height angle) is measured by a star tracker. The position line formed by points with equal height angles is a great circle on the earth. By measuring the height angle of two stars, two great circles can be obtained, and their intersection point is the position of the plane.

Integrated navigation system: a navigation system with more perfect performance composed of the above navigation systems.

Baidu Encyclopedia-Aircraft Navigation System