450 ft
Low-Altitude Aviation at Risk from Ligado Networks Interference. Many helicopter missions are performed at low altitudes or require pilots to land without airport navigation aids. Proximity to Ligado Networks towers and handsets dramatically increases interference with GPS and some air-to-ground communications, a particular concern during takeoff and landing phases of flight.
Beyond safety concerns, are there other costs to harmful spectrum interference?
GPS and satellite communications make up an expansive array of technologies and platforms that daily benefit users across the United States and, indeed, contribute to the US economy as a whole. In fact, the Department of Transportation (DOT)—and multi- ple users and industries—has noted that the types of GPS uses that would experience interference from the Ligado network include emergency response, commercial trucking, general naviga- tion, high-precision instruments for surveying, machine control, scientific applications, precision agriculture, and timing signals. Many GPS receivers have integrated antennas, and fitting them
with new antennas could be extremely expensive. And because many receivers are integrated directly into the platforms without the ability to be accessed for replacement, retrofitting them is vir- tually impossible.
Why should rotorcraft owners and operators care about spectrum policy? The Ligado issue is one use case that demonstrates a broader issue: spectrum policy is sometimes generated in a vacuum, and there’s often not enough interagency coordination, particularly with the agencies and entities charged with public safety. The FCC is an expert agency that deals primarily with commu- nications—cellular towers and services, Internet access, wireline broadband equipment. As a result, the agency tends to treat all spectrum uses as just another communications tool. But issues
like the interference caused by the Ligado network are actually about the compatibility between a communications network and a positioning, navigation, and timing (PNT) network, such as GPS. The FCC doesn’t historically have this in-house expertise; this
expertise lives at the Department of Defense, DOT, and the FAA, among others—which is fine. But the FCC shouldn’t treat spec- trum use as solely a communications issue and not consult with other agencies, which is what happened in the Ligado Networks case. Fourteen other federal agencies went on record opposing this deal, but the FCC went ahead with it anyway.
What’s next on this issue? What’s next for spectrum policy generally?
On the Ligado issue, specifically, a bipartisan group of senators has introduced legislation that would address the costs to the pri- vate sector that would result from harmful interference with GPS and satellite communications. And the new FCC leadership will soon have the opportunity to address petitions to reconsider its decision. Bottom line: spectrum is a resource that’s taken for granted—
until you no longer have access to it or it no longer works as it should. This is a lesson as to what we can expect when spectrum policy and aviation safety aren’t aligned. And what we see here is that a well-informed spectrum management framework matters. Input from all the relevant stakeholders needs to be solicited and considered.
JUNE 2021 ROTOR 19
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