For the provision of navigation services BULATSA maintains radio navigation infrastructure, including en-route navigation systems as well as approach and landing systems, ensuring the approach and landing of aircraft at the international civil airports in the Republic of Bulgaria. By processing the received radio signals emitted from the navigation systems, the aircraft establish their exact location and heading within the delegated to the Republic of Bulgaria airspace.
BULATSA implements continuous program for modernization of the communication infrastructure in view of providing high quality navigation service with high level of safety and reliability. A significant part of the existing navigation systems are already modernized by integration of latest generation equipment delivered by leading manufacturers. For some other navigation systems the modernization is lying ahead.
BULATSA maintains Instrument Landing Systems (ILSs), used by the aircraft in the phase of final approach and landing on runway. All systems of this type meet the requirements for use under the conditions of ICAO CAT I, and one of the systems located at Sofia Airport, allows its use in conditions of low visibility ICAO CAT IIIB.
Another type of radio navigation systems maintained by BULATSA are VOR/DME, which can be used equally for en-route flights and flights in the controlled are of the airports. Based on the radio signals emitted by these systems, the air crews determine the distance and heading of the aircraft compared to the location of the VOR/DME system.
At certain points throughout the country, DMEs are installed individually and are used to determine the distance between the aircraft and the equipment. These radio navigation systems are used together with DMEs collocated with VORs, in a reserved DME/DME network for the needs of the area navigation (RNAV).
The proper assessment of the weather conditions is a key factor to ensuring safety at every stage of the flight.
In this regard, all international airports in the Republic of Bulgaria are equipped with automated weather observation systems (AWOS) measuring and calculating the main meteorological parameters as required by ICAO Annex 3. The AWOS system located at Sofia airport is configured to fully perform the necessary measurements for low visibility conditions ICAO CAT IIIB.