What is the difference between Russian avionics and Western Airbus & Boeing avionics? The Former USSR had their own Pizhma 1 Navigation Systems and GLONASS (Russian GPS.) Until some time in the 1980s Russian aircraft could not fly outside the USSR. Until the production of the Illyushin IL-86 and the development of the high standards of Category III ICAO there were no Russian aircraft that could be given clearance to land. The reason is: Russian aircraft had a different method of approaching an airport. Outside the USSR, The ICAO (International Callsign of Airports) had a reliable system that uses navigational equipment and automated systems onboard the aircraft to set up an aircraft for the approach to a runway. This is called the ILS (Instrument Landing System.)
Russian airliners had their own system but it was not compatable with systems outside the USSR. Their system used GLONASS. GLONASS was developed by the USSR, launched from their own satellites and from there they developed their own GPS system. GLONASS is still in use today for marine navigation and with the Russian Space Agency.