Training courses for pilots for flights with B-RNAV area navigation system (Area Navigation)

The growth in air traffic causes a serious problem for the world civil aviation, namely the acute shortage of airspace. There was a need to search new, more rational and effective approaches to use airspace, in other words, to compact air traffic in some way. The active use of the RNAV navigation method (zone navigation) was the first step in this direction, as well as the establishment of strict requirements for navigation accuracy. It made possible to reduce significantly the lateral intervals between aircrafts.

Zone navigation or RNAV (Area Navigation) successfully replaces traditional methods of navigation using ground-based radio facilities. It very often today you can hear at the aviation frequencies the command of the dispatcher “CLEARED DIRECT TO”, which means “allow flying directly to,” while the point of the way to which the flight is allowed is usually not marked with terrestrial radio facilities, but simply set by coordinates and located several hundred kilometers away. This command can be performed using on-board equipment RNAV only. Zone navigation is used widely at the all stages of flight, including the most critical stage - landing.

Zone navigation (RNAV) is a method of navigation that allows aircrafts to fly along any desired path within the coverage area of radio beacon facilities or within the limits determined by the capabilities of the autonomous means, or a combination of them (ICAO definition).

In the previous days, the flight route had to pass strictly through the radio navigation facilities, in other words, radio navigation guidance had to be provided at the each leg of the route. Obviously, the length of the route increases by using this method of navigation, as well as the total cost of transportation.

The possibility to operate a flight without being tied to the radio navigation facilities provides a number of advantages. The first one is a significant reduction of flight time, i.e. direct savings on fuel and other costs associated with the operation of the aircraft. A wide network of ground-based radio navigation facilities is not required using RNAV equipment during operation a flight. By the way, the cost of maintenance of one VOR is about 100 thousand US dollars a year. Applying of RNAV allow more efficient use of airspace, thereby increasing its throughput as well.

The basis of any onboard RNAV system is a sensor capable to determine the coordinates of the aircraft with sufficient accuracy (usually in the WGS-84 coordinate system) and the navigation database.

For a long time, long-range navigation systems were used widely, in particular LORAN-C. Absence of satellite navigation systems, there were no other ways to determine the position of the aircraft when flying across the ocean. Long-range navigation systems based on the ground-based radio stations (also named as hyperbolic) made it possible to determine the geographical coordinates of the aircraft with relatively high accuracy (about 500 meters for LORAN-C). The distance of LORAN-C was up to 2500 kilometers.

Oddly enough, the main source of information about location in the modern onboard navigation systems is not a satellite navigation system, but an inertial navigation system. The meaning of this solution is simple. The inertial system tends to accumulate an error, but it has one indisputable advantage: it is completely autonomous. Due to the use of laser gyroscopes and accelerometers, the modern IRS (Inertial Reference System) has quite high accuracy rates as well , the maintenance is no more than 1-2 nautical miles per flight hour.

Necessary to remember, that the GPS system is controlled by the US Department of Defense. There are cases when the Pentagon excluded certain regions from the system coverage area or reduced the accuracy of determining the coordinates. However, in order to provide for the IRS the needed accuracy of determining the coordinates, it must be periodically adjusted to more precise coordinates, generally these are GPS or DME / DME ground beacons. VOR/DME and DME/DME beacons can be as independent coordinate sensors for the RNAV system.

In the future, it is planned to completely abandon the ground-based radio facilities and switch to the GNSS (Global Navigation Satellite System), which includes the already existing GPS systems, and the launch of the European GALILEO system is planned. The simultaneous use of several independent SNS will significantly improve the accuracy and reliability of navigation using the RNAV method.

Since the only heavy aircraft engaged in commercial transportation is equipped with inertial navigation system, the most widely developed systems are RNAV, in which the only coordinate sensor is GPS. Most modern commercial aircrafts are equipped with an integrated flight control system. On the aircrafts of different manufacturers it is called differently: FMC - flight management computer (Boeing), FMGS - Flight Management and Guidance System (Airbus). It is through this system and its control panel (CDU - control display unit) the capabilities of the RNAV equipment are realized, among other functions.

RNAV equipment provides a number of features specific to this method of navigation:

The zone navigation route is based on the waypoints (WPT – Waypoint).The waypoint is defined by the coordinates in the WGS-84 coordinate system. There are two types of waypoints: FLY-BY and FLY-OVER, they are flown with or without advance lead. All waypoints are of type FLY-BY, points of FLY-OVER are used mainly on the aerodrome schemes, for example, go-around points, points defining the waiting area.

RNAV equipment has certain requirements for accuracy and reliability. These requirements are formulated in the concept PBN (Performance Based Navigation). Accuracy requirements are expressed in the nautical miles of permissible lateral deviation, for example, the RNP-10 navigation specification (RNP - Required Navigation Performance) means that with a probability of 0.95, the flight should be within ± 10 nautical miles from the route axis.

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