Maintaining Aviation Safety vs. Ligado

Building a Coalition to Safeguard GPS from Interference

By Christopher Freeze, Senior Aviation Technical Writer

On April 20, the Federal Communications Commission (FCC) granted a license permitting Ligado Networks, a satellite communications company, to deploy a ground-based network to provide 5G data services. However, the radio wave frequencies that the company, formerly known as LightSquared, intends to use may not protect nearby frequencies and signals related to GPS and satellite communications from harmful interference.

The FCC order, which was issued without public or stakeholder comment, also failed to properly consider aviation safety standards when granting access to the sensitive spectrum that’s typically been reserved for GPS and other weak signals from satellites located hundreds or thousands of miles from their receivers on Earth.

Of particular concern is that the interference produced by Ligado’s signals is most dangerous for low-level aircraft—such as medevac helicopters and aircraft that are landing and departing—impeding terrain awareness and warning systems (TAWS). This vital safety system helps pilots avoid flying into the ground or obstacles, and U.S. airliners equipped with TAWS have never had a single fatality from controlled flight into terrain.

Joining the aviation industry in its concerns are the Department of Defense and many U.S. government agencies as well as dozens of private organizations representing the interests of the military, first responders, trucking, maritime, meteorology, agriculture, and construction. The only supporters of the proposal are those promoting America’s advancement toward 5G networks nationwide.

ALPA’s Government Affairs Department has been keeping U.S. legislators apprised of the Association’s concerns. On June 24, the U.S. Senate Committee on Commerce, Science, and Transportation held a hearing on FCC oversight with the FCC’s five commissioners offering testimony. Part of the hearing centered on the commission’s decision to issue Ligado a license for 5G that would interfere with the GPS spectrum.

During the hearing, Sen. Tammy Duckworth (D-IL) questioned Ajit Pai, the FCC’s chairman, as to why the commission was pushing to approve Ligado, despite it not being mentioned in any existing 5G network plans and to the objections of numerous stakeholders, and the commission’s unwillingness to reconsider the order.

“A number of conditions were imposed on this company because we wanted to balance the necessary interest and allow the company to move forward as the FCC had allowed the company to do so 17 years ago and protect GPS signals from harmful interference,” said Pai. “Based on the facts of the record, we made a decision—which was shared with federal agencies over a year and a half ago to enable them to give feedback to us based on the facts, as they saw, on the record.

“We have had a very open door,” he continued. “The process had gone on long enough, and we made a decision based solely on the facts and on the law. And I will defend this decision before any forum in this Congress or in any part of the country.”

But Jessica Rosenworcel, one of the FCC commissioners, expressed support for a stay on the decision, stating, “If the [committee] chairman was interested in circulating a decision to us staying the decision that we recently reached on the L-Band, it would certainly be something I would support because we need to iron these things out if we really want to have a big and bold 5G future.”

On July 9, the House Agriculture Committee sent a letter to Pai in which 22 representatives on the committee outlined their concerns regarding the harmful interference that would impact numerous organizations throughout the precision agriculture industry.

But many, including senators and congressmen, are looking beyond petitions to the FCC for internal reconsideration. The House and Senate version of the upcoming National Defense Authorization Act contains several provisions that would affect the FCC’s decision.

Among them would be an independent technical review of the potential impact on military systems undertaken by the National Academies of Science, Engineering, and Medicine. The review would study the different methodologies used to determine the effect of Ligado’s transmissions on GPS services and make a determination as to which is the most effective in preventing harm.

In addition, Sens. James Inhofe (R-OK) and Jack Reed (D-RI), the chair and ranking member of the Senate Armed Services Committee, respectively, also announced stand-alone legislation that will be introduced after the summer recess. The Recognizing and Ensuring Taxpayer Access to Infrastructure Necessary for GPS and Satellite Communications Act (RETAIN GPS and Satellite Communications Act) would require Ligado to modify or replace any receiver, including those used by private citizens, that would be impacted by Ligado’s signals. Furthermore, any replacements or modifications would have to be completed before any service could begin—potentially making the costs so prohibitive that it would be economically unviable for Ligado’s use of the frequency.

Representatives of ALPA’s Air Safety Organization are also continuing to press the Association’s case with the FCC, with meetings scheduled with FCC leaders in late July.

Flaws in the FCC Order on Ligado

Despite a seemingly transparent process, poor policy implementation and misinformation abound regarding the Federal Communications Commission (FCC) order allowing Ligado to operate, including the following:

 Ligado’s licensed spectrum was converted from a pure satellite license to a primarily ground-based system, fundamentally changing the environment for other nearby satellite systems.

 Despite marketing statements to the contrary, Ligado’s spectrum isn’t part of the FCC’s or National Telecommunications and Information Administration’s 5G spectrum plans.

 As modern aircraft require the use of GPS throughout flight, Ligado’s claim that it isn’t necessary when flying near its towers demonstrates a lack of understanding of the need for safety systems to work without interruption, highlighting the insufficient aviation knowledge in the company’s proposal.

  • The FCC’s decision puts the traveling public at risk, because it ignored industry and government experts, choosing instead to rely exclusively on the testing and analysis paid for by Ligado—despite extensive evidence of serious interference to GPS and satellite communications systems that the aviation industry rely on.
  • NASA and the U.S. Departments of Commerce, Transportation, Defense, and Homeland Security have each consistently raised concerns with the Ligado application and with the FCC’s order. Ligado’s proposals pose serious and completely unnecessary risks to military and civil aviation, rotorcraft, precision agriculture, and weather and maritime industries, which rely on accurate satellite navigation and timing systems to safely function.
  • The FCC order’s definition of “harmful interference”—requiring actual degradation of GPS or satellite communications to occur—isn’t compatible with either of these international radio standards, despite Ligado’s claims to the contrary.
  • Ligado’s testing of uncertified GPS devices used by general aviation was insufficient—as evidenced by a Department of Transportation report. Ligado tested only a single uncertified aviation receiver and used incomplete metrics. The performance of a single device shouldn’t be used to represent an entire category of devices.
  • The effect of Ligado interference on unmanned aircraft systems (UAS) is concerning, as the vast majority of UAS will use noncertified aviation receivers. More than 1.5 million UAS are registered in the U.S., an unknown number of which may experience a “fly-away” event in case of lost GPS due to interference. Past such UAS events have blundered onto major international airport movement areas.
  • New technologies like urban air mobility and autonomous vehicles will rely heavily on precision GPS to function safely.
  • Ligado’s network and handsets will also interfere with the only two FAA-certified satellites networks used for air traffic control messages.
  • With the exception of a single aviation operator that’s a customer of Ligado, almost the entire aviation industry is on record publicly opposing Ligado’s plans as a risk to aviation safety and efficiency. The company’s plans set up a dangerous outcome for air safety and the traveling public.
  • Ligado’s proposed change will directly impact aviation safety, put the nation’s military at risk, and harm the nation’s transportation infrastructure and the more than $1.4 trillion GPS has contributed so far to the economy.

This article was originally published in the August 2020 issue of Air Line Pilot.

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