Russia plans to announce this month that its civil aviation fleet will be required to carry Glonass, that nation’s GNSS, or combined Glonass/GPS units, but not GPS on its own. The mandate will be unveiled at this month’s triennial ICAO Air Navigation Conference, and it has significant cost implications for western-built corporate aircraft on the Russian register, all or most of which likely carry just GPS. Foreign-registered aircraft flying in Russian airspace would be exempt from the rule.

The prohibitive cost stems from the different technology in Glonass and GPS receivers. Glonass uses the so-called frequency division signal technology, while GPS uses code division methods and the two simply don’t understand each other. Inserting some sort of translator device sounds like a simple solution and is, loosely speaking, used in some special types of land survey satnav receivers. But aviation calls for demanding certification, and therein lies the rub, since no such equipment is available on the aviation market, and no western avionics manufacturer has shown interest in developing combined units for that niche market. In addition, such a unit would require modifications to the flight management and other onboard systems, including the need for two separate antennas.

A senior GNSS engineer at a major avionics company who wished to remain anonymous told AIN that the certification of combined Glonass/GPS units and their subsequent retrofit in, say, a GIV–several of which are on the Russian register–“would cost millions and take years” to accomplish. In turn, this raises the question of whether Russian corporate operators of western jets would swallow those costs, or transfer their aircraft to another country’s registry (if that were permitted) or buy a Glonass-only Russian aircraft. (Retrofitting a Glonass-only unit wouldn’t save much money, and could significantly reduce the aircraft’s resale value elsewhere.)

It seems unlikely that Russia will modify its upcoming mandate proposal, since it has made massive investments in Glonass–which, like GPS, is a global system–to compete in the world GNSS market, of which aviation is a minuscule part, compared to vehicles. Millions of people worldwide own Chevrolets, Fiats, Toyotas and other brands and can make just about any changes they wish, but for an aircraft owner, certification of new avionics units and their retrofit substitution for earlier or different units is a morass of cost and downtime. And with a Russian precedent, China could eventually consider the same approach with its global Compass GNSS.