Faculty of air transport engineering the department of «air navigation systems»

1.1.4 Building conventional flight patterns by instrument.
RNAV was originally introduced using build criteria based on specific sensors. An outstanding achievement in the application of RNAV was the creation of control points defined by the name, latitude and longitude. RNAV control points allow for the construction of routes with less dependence on the location of navigation aids, so that the construction of schemes can better take into account the requirements for the planning of airspace. The degree of flexibility in routing depended on the specific radio navigation system used, such as DME/VOR or GNSS. Additional advantages were the ability to store routes in the navigation database, reduced pilot workload, which leads to a more consistent maintenance of the nominal path line compared to cases where the construction of a non-RNAV scheme was based on the course, synchronization or DME arcs. Since RNAV navigation is carried out using an onboard navigation database, a radical change in the work of the developer is the increasing need for quality assurance in the process of building diagrams.

Figure 4. Construction of RNAV routes.

Despite the advantages, RNAV had a number of problematic issues and characteristics that needed to be taken into account. These were: in some cases, a wide range of differences in flight performance and in the flight paths of aircraft, as well as the inability to predict the behavior in all situations of navigation computers. This led to the creation of large obstacle assessment zones, and as a result, it was not possible to obtain significant advantages in terms of reducing the obstacle protection zone.
As experience gained during RNAV flights, other important differences and characteristics were discovered. RNAV avionics, functionality, and system configurations ranged from simple to complex. The developer had no guidance on what criteria should be applied to the fleet of aircraft for which instrument flight plans were being developed. Some features of the system behavior were the result of the development of RNAV systems, which used the schemes laid down in the database, based on the instructions of the ATC. This attempt to mimic ATC guidance has led to the emergence of a variety of methods for describing and determining the flight path of an aircraft, which has led to a marked variety of flight characteristics. Moreover, as a result of the development of aviation and navigation technology, a whole set of different types of schemes appeared, each of which required the installation of different equipment, which caused operators to incur unnecessary costs.