A coalition of 11 general aviation advocacy groups have expressed concern over the potential impact to satellite-based global positioning system (GPS) navigation capabilities from a proposed broadband cellular communications network operating within frequency bands currently used by GPS.
A prior attempt to implement a high-speed nationwide cellular network by Ligado Networks, formerly known as LightSquared, revealed signals from its cellular towers significantly disrupted aircraft navigation systems.
The Federal Communications Commission (FCC) ultimately denied LightSquared’s plans in February 2012, following a strong chorus of opposition from the aviation industry, including the industrywide Coalition to Save Our GPS.
Ligado claims it has since limited GPS signal disruptions to within a 500′ diameter around transmission towers, which the company maintains should mitigate interference concerns.
However, the aviation groups noted those assertions have not been validated through evaluation of various operational scenarios by the FCC and FAA, adding “significant safety concerns still have not been addressed,” in a letter sent to the FAA.
Heidi Williams, director for air traffic services and infrastructure for the National Business Aviation Association, emphasized the importance of GPS navigation not only for pilots, but to the entirety of FAA’s NextGen air transportation system.
Besides officials with NBAA, other advocacy groups signing the letter include the Air Line Pilots Association (ALPA), Airborne Public Safety Association (APSA), Aircraft Owners and Pilots Association (AOPA), Airlines for America (A4A), Association of Air Medical Services (AAMS), Helicopter Association International (HAI), Helicopter Safety Advisory Conference (HSAC), National Agricultural Aviation Association (NAAA), National EMS Pilots Association, and the Professional Helicopter Pilots Association (PHPA).
Look at airports that are below the level of hills that may only be to one side and not ringing that airport. Now, imagine the 100-200′ AGL towers in and around the GPS approach or approaches to that airport. Add residences and businesses that will want such a “WiFi” provider. Start thinking of the overlap between towers and that one will be below the level of the towers on the hills.
What this does is exposes your GPS antenna to direct spray from those towers instead of those towers being below the wings and fuselage so that the Satellite GPS signals will be direct to your GPS antenna — we are assuming a metal airplane. Could make an interesting glitchy day out of the GPS in VMC conditions.
But lets talk IFR and actual IMC. Here we will have clouds of unknown thickness with precipitation. IMC like this tends to cause attenuation of the desired signals when there isn’t a jamming source. Is this a recipe for failure of RAIM and GPS position(ing) to become imprecise?
These are the kinds of tests that must be run. And notice I’m talking about aircraft that are occupied. What happens to drones when they have failed RAIM and are programmed to a specific location? Those now have to be checked as well.
The other day I was in my car and was running the vehicle’s GPS system. And it was raining and we were under a canopy of several trees. The GPS system started guessing where we were. Finally we were in the clear and it was over a mile off course — that is, I was where I was, the GPS said I was more than a mile away from the intersection where I was. Will this system completely screw up non-certificated GPS receivers used in automobiles? And what will this do to autonomous vehicles?
The FAA needs to get on their A game for this. And the FCC needs to ask questions of the self-driving car manufacturers.
*Sigh* Here we go again….another bad idea. Only this time it might get through, no thanks to the current administration.
Wow. Limit to 500 feet from the towers? Gimme a break. Drones are bad enough…this should never be allowed to happen.