Doppler radar system Samoletnaya
Samoletnaya Doppler radar system is an autonomous system of piloting. Doppler system is largely free from such defects panoramic radar as a small their effectiveness when flying over smooth terrain, time-consuming to determine the navigational elements (ground speed and drift angle) and low accuracy of these measurements.
Samoletnaya Doppler system solves the problem of determining the elements of navigation and dead reckoning.
Doppler piloting system used in civil aviation in different countries, the travel speed is measured from the 130 1800 to km / h, and the angles of the demolition - of 0 45 ° up to altitudes of up to 15 000 m and above. At the same mistakes of the ground speed range from 0,2 to 0,9% 'and the angle of drift in the range of 0,2 to 0,6, and the accuracy of dead reckoning in range and lateral deviation in the accuracy of compass heading ± 0 °, 5 is 1% of the distance.
Operating principle. If moving the aircraft with the help of a radio transmitter to emit electromagnetic waves at an angle to the surface 0, between the frequency of oscillation and the frequency of the received radio airplane reflected from the earth's surface vibrations found to shift. The phenomenon of the oscillation frequency shift is called the Doppler effect, a frequency difference between the emitted and received oscillations, called the Doppler frequency. This frequency, in relation to the moving plane is defined as follows:
Ground speed in Doppler system schematically defined as follows:
the aircraft through the radio antenna in the direction coinciding with the longitudinal axis of the aircraft to the ground surface emits a radio wave with an angle unchanged oscillation frequency;
radio waves, falling on the ground, changing its frequency proportional to the ground speed of the aircraft and reflected partially back on the plane again changing its frequency; Thus, the radio waves are returned to the aircraft with a frequency change is proportional to twice the longitudinal component of the ground speed;
automatically measured by the difference between the transmitted and received frequency of radio waves using a special device issuing this value to a digital device.
Determining drift angle takes on a similar principle, but an antenna directed perpendicular to the longitudinal axis of the aircraft.
Doppler system can have single-line, double-beam, three-beam antenna and a four. Now, however, the most widely used four-beam antennas, since they exclude a number of errors and improve the accuracy of measurement of ground speed and drift angle.
Typically, Doppler systems include three basic devices, placed on the plane:
1) Doppler ground speed and drift angle (Diss) continuously determines the current values of W and CD and provides them to a pointer, as well as the navigation computer;
2) heading sensor;
3) navigation computer (HB), gets the current value of the W and CSS from Diss and the course of the aircraft - the foreign exchange system, integrating the data and lead reckoning orgodromicheskoy in a rectangular coordinate system. HB gives the crew the current location of the aircraft.
Coordinates x (path traveled by plane along a given great circle) and z (linear lateral deviation from the Great Circle) served on the instrument dial and a digital counter.
IIB solve an equation that relates the terms of the elements of the aircraft (TAL, OK, W, FF), and the initial coordinates from the current coordinates MS, LSD and entered into the computer by hand, OK - Foreign exchange system and CSS - fromDiss.
The greatest error, determining the accuracy of HB is the error rate sensors - exchange systems. Equally important are the measurement error and the installation OK, and error in determining the W and CSS Diss.
Navigation computer type NOR-50 perform reckoning of issued Diss W and CSS, but can also be used for manual introduction of wind speed and direction. These calculators have similar NI-50 dvuhstrelochny counter coordinates x and z (arrow "C" and "B"), dial angles cards and dial the wind. Navigational calculators included in the Doppler system, ensure the system is in "Memory" (storage of motion parameters of the aircraft in case of a flight over the calm water areas or for large banks), when there is no flow in the Doppler frequency. In this case, while maintaining the airspeed and direction of flight reckoning will be performed with acceptable errors during 15-20 min.
When switching to the system mode "Memory" it is advisable to switch "DISS - L OU" put to "ANU" and a change in airspeed or flight path set adjuster wind manually wind parameters and corner of the map, as in this case, the flight mode was broken (unchanged with respect to those who "remember" navigation computer). The values of the components of the air speed of the axes are added together with the values of components of the wind on the same axis. When you change the TAL and the installation of a new wind angle of the card is automatically redistributed.
Navigational training to fly with the Doppler system is carried out in accordance with the requirements of the Manual on the navigation service for a flight to travel great circle angles. Keep in mind that the accuracy of the calculation set orthodromic travel angles and races
distance depends on the accuracy of piloting. Therefore, in preparation for the flight is best that data to calculate analytically, without resorting to the measurements on the map. The formulas for calculating the great circle track angle and great circle distance given in "Aviation cartography."
In addition to preliminary calculations, the income statement and 5ort, in the preparation of flight maps should:
outline the route control radar guidance through 150-200 km depending on the length of the route and the speed of the aircraft, calculated analytically or measured rectangular coordinates x and z of these guidelines, write them on the map and connect benchmark with LZP straight line perpendicular to the desired course (or its continuation );
It does the same for the installation points of land beacon azimuth-distance-measuring system;
each MRP record the angle of rotation (SD) to enter the desired course of the next stage of the way.
This additional work is needed to:
a) ensure accurate overflight IPM or accurate setting of the counter starting positions relatively laid LZP on the map;
b) correction of MS without measurement on the map with a panoramic radar and long-range-azimuth numbering system;
c) The precise definition of the passage of the necessary points to us (KO, MRP, PCF) no measurements on the map.
The complete set of controls and indicators Doppler system includes:
1) pointer drift angle and ground speed;
2) setpoint angle map (given the income statement);
3) dial the wind (to set the speed and direction of wind, Diss when not working);
4) coordinates x meter (arrow "C") and z (arrow "B");
5) flap control system in flight, having two signal lamps n two switches.
The first switch has four positions:
"Off". - Low-voltage power supply is turned off;
"On." - Low-voltage power supply is turned on and lights green (left) warning lamp with the inscription "On.";
"Pam." - Switches the system to operating mode "Memory".
"Hi." - High voltage power is on and lights up red (right) warning light.
The second switch also has four positions:
"Land" - position when flying over land;
"Sea" - the situation in flight over the sea;
"Counter. 1 »and« Contra. 2 »- the position in the control system calibration;
6) switch "Diss - ANB" allows you to use the navigation computer (ANU NOR-50) in the event of Diss. In this case, it is switched from the "Diss" to "ANU" and ANB is reckoning like no-50;
7) switch "Counter" is designed to turn on and turn off the meter origin. At the time of his transfer to "On." Navigation computer ANU is numbered and supplied to the counter coordinates x and z. When the switch to "Off." Arrow "C" and "B" do not move.
If the flight is expected to use the Doppler system, the co-driver is required before take-off:
1) control panel installed on the left switch to "Off." And the right - to the "Land";
2) switch "Diss - ANB" put to "Diss";
3) make sure that the switch is "counter" is set to "Off." Schislitelya path and arrows are in the zero position;
4) adjuster corner of the map to set a given great circle track angle of the first stage of the path, after which the control panel on the left side be set to "On." (Green indicator light marked "ON." Should light);
5) in the air (not earlier than2minutes after switching on) the left switch on the control panel Charter; novit to "high." (should light up red light).
3 minutes later, you can use the Doppler system, given that the arrow schislitelya way will be in the zero position as long as the switch is "counter" is to "Off.", While the index of ground speed and drift angle is in the working position.
Despite the fact that the Doppler system essentially provides that full control of the way, but due to its inherent errors are mainly due to the low accuracy of the determination of the course, the crew during the flight should be possible to more accurately put the initial coordinates of the MS, in a timely manner on the navigator's flight plan to correct readings of using other radio equipment and promptly make the transition to a new stage of the route.
The initial coordinates of the MS can be considered a point of departure coordinates, if performed after takeoff circle over the airfield, or the coordinates of the IPM - anywhere at some distance from the airport, the exact flight that easily "detect" with the on-board radar drive?
Distance or azimuth, rangefinder system. In all cases, preferably with the greatest possible precision at the time of flight of the target point coordinates include the counter; If this is for some reason not possible, either visually or by means of radio equipment to determine MS orthodromic rectangular coordinates x and z, put them on the counter and turn it on by setting the same time adjuster corner of the map and adjust the value of the income statement from the COP the reference meridian. From the IPM to the first point to carry out a correction flight OK = TAL-US, seeking to keep the counter arrow "B" (coordinate z) in the zero position.
Active correction of indications in flight navigation calculator carried out by the aircraft radar or pan-azimuth rangefinder system. For correction is necessary to determine the actual location of the aircraft in the great circle of rectangular coordinates.
Formula for determining the actual S \ C by radar and azimuth-distance-measuring system are substantially the same.
On and Getting Started. By plane Doppler equipment included a navigator. To activate equipment you need:
1) in the left panel system control switch is set to "Off.", And the right switch to "Land";
2) switch on the dashboard navigator with the inscription "Diss-ANB" put to "Diss";
3) switch labeled "Counter", located near schisli- telya way, to put to "Off.";
4) make sure that the arrow is in the numerator of the way the zero position.
After checking that all the tumblers and switches are in this position adjuster corner of the map to set a given great circle track angle of the first stage of the route and the left switch on the control board be set to "On" (on the label control should light green indicator light marked "ON . ").
Through 1-2 minutes after turning on the system (after launch) the left side should be moved to the "High" on the control panel, and the indicator light will turn red with a sign.
After switching on the high voltage no earlier than 3 minutes
the system is in working order and can be used for piloting.
Since the switch "counter" is set to "Off", the numerator is not the way it works and the arrow to turn on will stand at zero. Pointers drift angle and ground speed are in working order and give the value FF.
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