Industry Awaiting Notam on 5G Ops Limits

 - December 16, 2021, 11:26 AM

Aviation leaders are bracing for a wave of restrictions and potential disruption of air traffic operations at airports in a number of major metropolitan areas as the FAA crafts a notam to implement safety measures surrounding the rollout of 5G in the C-Band. The notam is anticipated to provide specifics of restrictions contained within two airworthiness directives the FAA released earlier this month covering transport- and commuter-category airplanes and another directed at helicopters to address the threat of potential radar altimeter interference from 5G cellular in the 3.7 to 3.98-GHz frequencies.

Those ADs called for operational limits when aircraft are at risk of such interference, including prohibitions on CAT II/III operations; special authorization (SA) CAT I and SA CAT II; autoland; manual flight control guidance system operations to landing/HUD to touchdown; and use of enhanced flight vision systems (EFVS) to touchdown under FAR 91.176(a). Certain RNP and other procedures dependent on radar altimeter use would also be disrupted.

Aviation industry groups point out that the limitations essentially affect systems and operations to enable safe approaches in poor weather or reduced visibility.

Telecom providers AT&T and Verizon have indicated plans to implement their 5G signals on January 5—initially at a reduced power level—in certain areas of the country, including much of California and Florida and other major metropolitan areas that include Seattle, Chicago, Houston, Dallas/Fort Worth, and the Northeast.

The telecom providers have indicated they would share data with the FAA regarding what power levels they plan to use and how it will be directed. This information could help the FAA tailor notams specific to airports and even approaches at airports rather than necessitate a blanket notam that affects all airports within the regions where 5G is emitted in C-Band.

However, much uncertainty still exists on the available data and how expansive these restrictions will be, leading a coalition of aviation organizations to reiterate: “Time is running out before millions of air travelers and the shipping public experience significant disruptions such as flight delays, flight cancelations, and backups to the already-stressed supply chain.”

The joint statement—by the Airline Pilots Association, Airlines for America, Aircraft Owners and Pilots Association, Experimental Aircraft Association, Helicopter Association International, International Air Transport Association, NBAA, and the Regional Airline Association—added, “We implore the Federal Communications Commission (FCC), FAA, and National Economic Council (NEC) to continue meaningful discussions in good faith and to identify mitigations and reach a successful implementation plan that will ensure new 5G technologies can safely coexist with the aviation industry.”

Walter Desrosier, v-p of maintenance and engineering for the General Aviation Manufacturers Association, which also has remained closely involved in the deliberations surrounding the 5G rollout, reiterated concerns that a ban on Cat II/Cat III operations and major cities could have a crippling effect throughout the national air transportation system.

While he believes that the situation will not be permanent—noting that once the industry gets the requisite data then it could develop appropriate safeguards to affected equipment—he also expressed a key human factors concern as a result of the situation: pilots will stop trusting their instruments on landing.

Desrosier also raised the concern that this first phase only involves lower power transmissions, which is more possible in major metropolitan areas where there already are significant signal outputs. But once 5G in C-Band goes nationwide, towers in rural areas will require a much higher output, possibly creating greater threats.

The FCC had awarded radio spectrum in the C-Band for 5G transmissions to telecom providers earlier this year despite objections of the industry and concerns raised by the FAA and Department of Transportation and Congress. Canada similarly has approved 5G in the C-Band but restricts its use near 26 airports and has implemented other measures to ensure aviation safety.

“It’s very frustrating and disappointing that a level of coordination just wasn’t there” as the approvals were being made, Desrosier said.

In a recent article, aviation operations specialists OpsGroup, wrote: “The big problem in all of this is the lack of information on how much interference will actually occur. It is not clear which airports will be impacted or to what degree equipment might be disrupted because it depends on the location and the strength of signals.”

RTCA measurements have found high levels of inaccuracy to “outright failure” of radio altimeters can be anticipated as a result of the 5G output. Until the towers are turned on, it added, “it is hard to know.” And while the focus has been on radar altimeters, “it is unknown what else may be impacted, so crew are going to have to be extra vigilant of their instruments.”

OpsGroup advised operators to check notams and to remain aware of potential instrument interference.

The aviation organizations have submitted suggested preventative measures and mitigations to ensure safety but limit the impact on operations. “We strongly believe that by working together these groups can create a win-win situation for all stakeholders—the telecommunications industry, the aviation industry, and most importantly the millions of customers who depend on our services every day across the country,” they said.