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 meter (DISS), continuously determining the current values ​​of W and US and issuing them to the pointer, as well as to the navigation computer;

2) heading sensor;

3) a navigation computer (NV), which receives the current values ​​of W and DC from the DISS, and the aircraft heading from the heading system, integrates these data and leads the dead reckoning system in an orgodromic rectangular coordinate system. NV gives the crew the current position 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 solves the equation linking through the elements of the movement of the aircraft (LSD, OK, W, CSS) and the time the initial coordinates with the current coordinates of the MS, and the LSD is entered into the computer manually, OK - from the exchange rate system and RS - from Diss.

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.

Navigational calculators such as NI-50 carry out the calculation of the path for the issued DISS W and US, but can also be used when manually introducing the wind speed and direction. These calculators have a similar NI-50 two-sided counter of the x and z coordinates (the arrows "C" and "B"), the map angle adjuster and the wind controller. Navigation calculators that are part of the Doppler system, ensure the operation of the system in the mode "Memory" (remembering the parameters of the movement of the aircraft in cases of flight over calm water spaces or at large banks), when there is no arrival of Doppler frequencies in the system. In this case, while maintaining the airspeed and the direction of the flight, the calculation of the path will be carried out with permissible errors during 15-20 min.

When switching to the mode of the "Memory" system, it is advisable to switch the "DISS - L NU" switch to the "ANU" position and, if the airspeed or the flight direction change, set the wind parameters and the map angle manually on the wind tuner, since in this case the flight mode was violated (Have changed with respect to those that the navigation computer "memorized"). In this case, the values ​​of the air speed components along the coordinate axes are summed with the values ​​of the wind components along the same axes. Now, when the ZPU is changed and the new map angle is set, the wind components are 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) ensuring an accurate flight over the IPM or accurate setting on the counter of the initial coordinates relative to the LZP laid on the map;

b) MS correction without measurements on the map using a panoramic radar or a goniometric-range-measuring system;

c) accurately determining the span of the points we need (KO, PPM, KPM) without measurements on the map.

The complete set of controls and indicators Doppler system includes:

1) indicator of drift angle and ground speed;

2) card angles adjuster (given by the SDA);

3) wind generator (for setting wind speed and direction when DISS is not working);

4) counter of coordinates x (arrow "C") and z (arrow "B");

5) in-flight control panel with two signal lamps and 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 - ANU", which allows using the navigation computer (ANU, NI-50) in case of failure of DISS. In this case, it is switched from the "DISS" position to the "ANU" position and the ANU reckons the way as NI-50;

7) switch "Counter" designed to turn on and off the coordinate counter. At the moment of transferring it to the "On" position the ANU navigation computer calculates and feeds the x and z coordinates to the counter. When the switch is in the "off" position arrows "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) set the left switch on the control panel to the "Off" position, and the right switch to the "Dry" position;

2) put the "DISS - ANU" toggle switch in the "DISS" position;

3) make sure that the “Counter” switch is in the “Off” position. and the arrows of the numerator of the path are in the zero position;

4) set the specified orthodromic track angle of the first stage of the path on the map angle adjuster, then set the left switch on the control panel to the "On" position (the green warning light with the inscription "On" should light up);

5) in the air (not earlier than after 2 minutes 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?

Distances or an angular-rangefinder system. In all cases it is desirable to include the counter of coordinates with the greatest possible accuracy at the moment of the passage of the planned point; If this is impossible for some reason, then visually or by means of radio engineering means determine the MS in rectangular orthodromic coordinates x and z, place them on the counter and turn it on, setting at the same time on the card angle setter the value of the SDU and correcting the COP from The reference meridian. From the IPM to the first correction point, the flight is performed with OK = ZPU-KS, trying to hold the arrow of the counter "B" (coordinate d) 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) on the system control panel, put the left switch in the "Off" position, and the right switch in the "Dry" position;

2) put the switch on the navigator's dashboard with the inscription "DISS-ANU" in the "DISS" position;

3) put the switch with the inscription “Counter”, located near the path counter, to the “Off” position;

4) make sure that the arrow of the numerator of the path is in 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 “Counter” toggle switch is in the “Off” position, the numerator of the path does not work and its arrows will turn to zero before switching on. Indicators of the angle of demolition and ground speed are in working condition and give the value of AC.