NAS-1

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NAS-1 as well as NV-PB1 and NVU are Russian navigation systems in aircraft that operate independently of ground stations .

Working principle

The flight path of the aircraft is determined by measuring the distance, determining the drift and entering the direction.

The distance passed during the flight from one waypoint to the next waypoint and the drift (lateral deviation e.g. due to the influence of wind) are determined by means of a Doppler radar (the Russian "DISS" type is common in Russian aircraft). The Doppler radar ( Doppler effect ) emits 3 beams that are reflected from the earth's surface. If the aircraft moves towards the point of reflection, the received frequency of the reflection signal increases (Doppler shift).

Without drift , the other two radar beams show no Doppler shift. However, they are different in the case of drift. By rotating the radar antenna by the opposite drift angle, this difference is compensated for and can thus be read (lateral deviation).

Operating principle

The distance measured since the previous waypoint (leg) can be read on a counter (a kind of flight mileage counter - determined by the Doppler radar). When the next waypoint is reached, this counter is set to zero by means of a kind of reset button and the next course angle required from here is set. You can also set the distance on the counter according to the flight plan or map and let it run back to zero. At zero the new waypoint would be reached. This means that you know exactly when a necessary course change can be made according to the flight plan.

The course angle map angle for determining the new flight direction is set similar to the course selector of a gyro compass . If the NAS-1 system is switched to the autopilot, the aircraft follows the course set in this way according to the map or the calculated flight path (the orthodromic course is used , based on the geographic North Pole, true course , true course ).

The navigation system type NV-PB1, which is used, for example, in the Ilyushin Il-62 , has a higher level of operating comfort and the possibility of programming approaches and holding patterns. Like the navigation system NVU (for example in the Tupolev Tu-154 ), it can receive correction data by means of RSBN radio navigation.

Web links

detailed and competent explanation with pictures of navigation procedures Russian type, for the purpose of realistic flight simulation free software: