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Aviation’s 5G problem


Concerns about 5G wireless technology affect both fixed-wing and vertical-lift business aircraft operations.

By Owen Davies
Contributing Writer

GA has been left out of FAA’s ongoing scramble to keep airlines flying. For low-visibility landings, 124 runways at major US airports remain closed to around 65% of airliners.
This March, a reporter in Traverse City MI gave his readers happy news. “5G is here, but not the anticipated chaos,” he said. “Seems it was much ado about nothing.” The local airport manager had said that fliers in the region were having no trouble with 5G.

He added that there was only one 5G tower in southeast Michigan, “and it’s not even by airports.” The significance of this apparently went over the reporter’s head.

After the usual telecom talking points about FAA clearances and 40 countries where 5G has not affected aviation, the writer moved to a more important issue – consumers with 3G phones about to go out of service. Somehow, it seems time for a clearer look at aviation’s 5G problem.

A brief recap

It surprised no one in aviation. Speculation about future conflicts between cellphones and avionics reportedly began as early as 2006.

Three years later, Turkish Airlines Flight 1951, a Boeing 737-800, showed what can happen when radar altimeters go wrong. On approach to Rwy 18R at AMS (Schiphol, Amsterdam, Netherlands), radar altitude dropped abruptly from 2000 ft to –8. The autothrottle then cut power to idle, and the airplane stalled and crashed 1.5 km (approx 1 mile) from the runway, killing 9.

Investigation found the accident had resulted from mistakes by an inexperienced first officer. Today, it seems clear that 5G interference could have much the same result. We all know the recent story. In 2019, then-FCC Administrator Ajit Pai announced plans to sell rights to the C band spectrum from 3.70 to 3.98 GHz. More than 2 years of bureaucratic infighting followed.

Studies by groups advising FAA predicted that broadcasts high in the C band could interfere with radar altimeters. A goal-oriented report from FCC’s advisors rejected that conclusion. Pai’s successor, Jessica Rosenworcel, discounted FAA’s concerns. On December 7, 2020, Chairman Peter DeFazio of the House Committee on Transportation and Infrastructure, urged FCC to delay the sale pending further study.

The auction began the next day. A year later, the action had moved to FAA and the telecom industry. After negotiation, Verizon and AT&T agreed to delay their 5G rollout for a month, then for 2 weeks more. They also reduced the power of 5G signals near certain airports and helipads, and set a 1.5-mile buffer zone around some.

When foreign airlines began canceling flights to the US, the telecoms agreed not to turn on 5G towers around some airports.

Helo ops remain in 5G limbo. They use about 12,200 heliports and helipads in the US, as well as 8500 designated sites for medical emergencies. At nearly all of them, FAA has no authority.

State of play

Concerns about 5G proved justified. Two weeks after towers went into operation, FAA had received more than 100 Pireps of possible interference problems.

It has found other explanations for many, but not nearly all. There should be fewer incidents now that FAA has approved 20 radar altimeters for use in 5G environments. This provisionally clears 89% of airliners for IFR near 5G towers, and warns vulnerable operators to stay away.

Up to this article’s publication, no more clearances had been announced since the end of January. Instead, FAA is evaluating 510 individual 5G towers located near runways – some 500 owned by Verizon.

The company has agreed to put them into service individually once FAA clears them for use. A map of 87 airports shows only 8 restricted for use by fewer than 90% of aircraft.

The remainder are approved for 90–100% of aircraft models. Yet, there are qualifiers, as readers will be too aware. Airports are approved to handle 100% of aircraft, even if only 1 runway accommodates them. LGA (LaGuardia, New York NY) is closed to 1/5 of airliners for low-visibility operations. And at ORD (O’Hare, Chicago IL), 4 of 8 runways are restricted.

Approvals apply only to airliners. They expire every 30 days to account for new 5G towers and other changes. Business aircraft fly under Alternative Means Of Compliance (AMOC) forwarded by aircraft manufacturers. They also expire at the end of each month.

Advisories come out daily, making it impossible to plan a flight without checking for new developments. As early as January 19, FAA had issued more than 1400 aerodrome Notams and IAP Notams for more than 100 airports. Vertical-lift operators have it even worse, as no helicopters are approved for flight near 5G towers and no heliports have been cleared.

AMOCs for helicopter operators appear to give them tacit approval to fly without radar altimeters wherever they usually go, and on their own heads be it. The situation is not entirely clear.

Under the telecom-friendly rules set by FCC, 5G towers near US runways are much more likely to interfere with low-viz ops than in the 40 lands telecoms cite as proof that FAA has bungled the intro of 5G communications.

Looking ahead

It will be a long time before the 5G mess is behind us. Here is some of what lies ahead: • Congress will not avert future problems by adding public safety to FCC’s mandate or requiring the commission to share decision-making with affected agencies. Politicians with oversight authority see any such change as diluting their own power.

Only a disaster could force them to accept it. • A key decision will come this June, when 2 agreements expire. FAA expects Verizon and AT&T to continue “responsible cooperation” to keep aircraft safe. Yet, if airport buffers disappear next month and 5G towers near runways come online without FAA approval, we will know that cooperation has ended.

• Business aircraft will continue to operate under short-lived AMOCs. • Vertical-lift specialists have even less joy ahead. Few heliports can ever be approved for operation near 5G towers. FAA counts 8712 in the country, with probably 3500 hospital helipads untallied. Yet, it has no authority over private-use facilities.

This leaves FAA with full oversight power for exactly 3. Unfortunately, this leaves a big bill to be paid. One estimate puts the cost of new radar altimeters for airlines alone around $3 billion. It could be more.

Unless Congress unexpectedly offers help, GA and commercial aviation alike have a painful expense in their future. Worse may be coming. In December 2023, FCC is scheduled to auction frequencies up to the low end of radar-altimeter operations at 4.2 GHz.

Commissioner Rosenworcel says the auction will omit a 200-MHz band at the top to provide a safety margin for aviation. “Razor thin” hardly covers it. Whether out of devotion to the priorities that led her here or as a form of bureaucratic duck-and-cover, Rosenworcel has adopted a time-tested strategy for dealing with institutional bungling – blame the victims, and hit them with more regulation.

FCC’s party line now is that radio altimeters are poorly designed, and receivers must be reworked to prevent interference. Avionics companies are already on it. FreeFlight, for example, will soon introduce its Terrain series radar altimeters, which are designed to resist 5G interference.

Its competitors will bring out similar products. They may meet FCC’s demands. Or not. For a silver lining in all this, we can praise FAA for its diligence in trying to prevent, and now to deal with, a serious problem. We can aknowledge the telecoms for responsible cooperation in a potential emergency. And we can recognize FCC for… well, that may be too big a stretch.

OwenOwen Davies is a veteran freelance writer specializing in technology. He has been a futurist at Forecasting International and TechCast Global.