A new filing to the Federal Communications Commission (FCC) and commenting on the C-Band Alliance’s plan to sell off 180 MHz of satellite spectrum for 5G, has thrown up some important concerns about the scheme. In particular, the letter expresses concerns about potential extremely harmful interference from new commercial wireless applications in the 3.7-4.2 GHz band to aviation safety systems operating in the adjacent 4.2-4.4 GHz band.
The letter came from some powerful lobbyists, not least The Airline Pilots Association (ALPA), the International Air Transport Association (IATA) and many other related associations.
Key to their thoughts was potential interference in and around the 4.2-4.4 GHz bands, and “its allocated use both domestically and internationally for both the Aeronautical Radionavigation and Aeronautical Mobile Route Services (“ARNS” and “AM(R)S”, respectively), enabling both radio altimeter and Wireless Avionics Intra-Communications (“WAIC”) systems to operate within countries and across international borders. As previously explained, these two aviation systems are essential to safety of flight and may experience harmful interference by changes to the adjacent 3.7-4.2 GHz band”.
The letter to the FCC stated: “The Federal Aviation Administration (“FAA”) mandates the equipage of radio altimeters on all commercial airline and business aircraft, as well as most helicopters. Additionally, these avionics are voluntarily installed on tens of thousands of general aviation aircraft, while also being considered for Unmanned Air Systems (“UAS”) and smaller drones. Radio altimeters are a critical sensor required to automatically control aircraft landings and terrain detection/avoidance systems. Without radio altimeters as operated today, modern air travel and its excellent safety record would not be possible.”
The letter calls for the FCC to “fully address” how the aircraft spectrum allocations must be protected. “What may be adequate to protect operations immediately above 4.2 GHz may not necessarily be sufficient to also protect incumbent use of the band, and this must be further explored.”