Looming deadlines in the ongoing dilemma surrounding 5G implementation in the United States threaten to disrupt global aviation.

Time is running out for airlines to meet proposed regulatory deadlines in the United States to retrofit or modify aircraft radar altimeters (RadAlts) to ensure that they won’t suffer interference from 5G C-band transmissions from towers located near US airports and approach paths.

RadAlts not only tell an aircraft its height from the ground but also feed into other safety-critical systems that are vital for landing, particularly in poor weather.

An eleventh-hour compromise between the US Federal Aviation Administration (FAA) and 5G telecom providers avoided massive flight disruptions in 2022. Under the deal, the telecom providers—AT&T and Verizon—agreed to restrict power levels of their 5G C-band towers near airports and approach paths.

That compromise is set to expire in July 2023, however. In the same month, up to 19 additional telecom providers are expected to introduce 5G services in the C-band and they are not part of the existing, voluntary deal.

Aviation interests including the FAA, airlines, and manufacturers have warned of 5G interference risks since 2018, when the US Federal Communications Commission (FCC) proposed auctioning off the bandwidth to telecom providers. The industry continued to raise these concerns during and following the auctions, which raised billions of dollars for the US government.

Unfortunately, industry concerns went unheeded until late 2022, when they reached the White House, leading to the last-minute compromise. Since then, airlines have borne the cost of modifying thousands of aircraft to enable them to operate in CAT 2 and CAT 3 landing conditions in the presence of 5G transmissions. The FAA, meanwhile, has logged about 100 instances of possible interference with RadAlts, although none has resulted in an incident or accident.


Operational ban

Adding new urgency to this race to modify aircraft is the FAA’s proposed Airworthiness Directive (AD), issued in January 2023, which gives airlines until 1 July 2023 to install new RadAlts or upgrade existing ones with new filters to utilize instrument landing systems at affected US airports. Furthermore, from 1 February 2024, aircraft that have not been retrofitted with filters or new RadAlts will be banned from operating in US airspace.

Although the 2024 deadline specifically applies only to US airlines, under Annex 8 of the Chicago Convention, other Contracting States must take steps to bring the requirements of an FAA-issued AD into effect with respect to aircraft on their registries.

The FAA estimates the cost of compliance at $26 million based on $26,000 per retrofit for approximately 1,000 aircraft. IATA calculations put the cost at twice that—based on a real-world example—and if the 6,000 US aircraft that have already been retrofitted to follow FAA recommendations are included the price soars to more than $450 million. Add in the cost of non-US carriers and the industry outgoing will be close to $640 million.

“The unfairness of this outcome cannot be overstated,” says Doug Lavin, IATA’s Vice President, Member and External Relations – North America. “Airlines are having to find and pay for a solution to a problem of somebody else’s making. They are blameless yet suffering the consequences. But we want to move forward. We are working hard to find a rational solution.”

Putting aside the injustice of the situation, the FAA deadlines are simply not achievable. IATA Director General Willie Walsh made that point in a letter to US Secretary of Transportation Pete Buttigieg and Acting FAA Administrator Bill Nolen: “It is now clear to everyone (the FAA, the aircraft manufactures, the radio altimeter manufacturers, and airlines serving the United States) that many operators will not make the proposed July 2023 … retrofit deadline owing to supply chain issues, certification delays, and unavoidable logistical challenges,” Walsh wrote.

Further complicating the situation for airlines is the fact that the proposed FAA compliance deadlines for airlines to have “radio altimeter tolerant” aircraft are based on AT&T and Verizon maintaining their voluntary limits on transmitting power beyond the 1 July expiration date. Although AT&T and Verizon have indicated a willingness to extend the informal agreement, as yet there is no such deal with the remainder of the telecom industry. In any case, asking airlines to quickly sign off huge amounts of money on the basis of an informal agreement is an inappropriate way forward.

Moreover, the FAA has not stated which radio altimeters and filters will meet its requirements. Rather, it is redirecting airlines to the airframe and radio altimeter manufacturers and airlines must hope for a solution that will pass muster. Alternative Methods of Compliance (AMOCs)—used until now to allow aircraft to operate at airports with nearby 5G towers—will no longer be issued post-July 2023 and aircraft equipment must be “5G tolerant”.

“The FAA needs to provide an updated list of 5G-tolerant radio altimeters by make, model, part number, and, as appropriate, dash number,” says Lavin. “This list should be updated on a timely basis as additional radio altimeters are deemed compliant by the FAA.”


Foreign carriers

Perhaps the greatest failing of the FAA process is not including foreign carriers in their 5G industry roundtables where these policies were debated. Often, these carriers need an official directive before they can proceed with a retrofit, but the FAA is technically only dealing with US carriers through the AD. To compound matters, US carriers are being prioritized by RadAlt manufacturers. The chances of all foreign carriers meeting the July 2023 deadline are therefore remote.

“Foreign carriers are at a particular disadvantage in this retrofit process,” agrees Lavin. “Think again about the operating restrictions resulting from the 1 July deadline. If you’re flying from New York to Chicago, you would be aware of the weather and potential ILS conditions. But what if you took off from Singapore 19 hours previously?”


The rest of the world

To date, only Laos has joined the United States as being of high concern, though the country is at the early stages of 5G development and there is every reason to believe that it will listen to IATA advice on keeping 5G away from the aviation spectrum, according to Stuart Fox, IATA’s Director, Flight and Technical Operations.

There is a minor issue in India with carriers unnecessarily advised to contact RadAlt manufacturers about upgrading but there are no safety issues, he says.

At present, Canada has limited 5G C-band transmission power, introduced exclusion zones on an interim basis, and antennas have a national down-tilt requirement. Australia, China, and Japan have all taken sensible precautions. In Japan, for example, the macro cell power levels are only 4% of that permitted in the United States and the small cell power levels are less than 1%.

In Europe, the dedicated 5G spectrum is in the 3.4GHz to 3.8GHz range, far enough away from that used by radio altimeters. The power levels are generally far lower too. French transmission power, for example, is ten times lower than that licensed in the United States.


Potential solutions

In his letter to DOT and FAA, Walsh urged the FAA to develop a project plan that includes milestones agreed to by all involved in the retrofit implementation. “A well-crafted implementation project plan clearly offers greater opportunities for success than today’s decentralized approach. It will also give the telcos a realistic picture as to progress to date and an expectation as to when they can take full advantage of their 5G investment. Finally, it will inform the US Government as a whole as to what steps may need to be taken if the current deadlines prove unachievable.”

Fox says the US situation highlights a more general point. “The spectrum is a scarce resource,” he emphasizes. “There are only so many frequencies available and there is increasing demand. Unmanned aviation will doubtless be looking to exploit bandwidth in future, for example.”

The International Telecommunication Union (ITU) meets every three years to discuss frequencies with the next gathering in October 2023 in Dubai. “They need to change guidance at that meeting to consider the impact on aviation and we are working hard to that effect,” says Fox. “We need to know avionics’ tolerance levels to nearby spectrum and there should be time for extensive testing to ensure aircraft safety and the correct allocation of cost for doing these tests.

“With 5G in the United States, the cost is falling entirely on the airlines. Not only are they being forced to pay but also they are being forced to make extremely costly decisions based on a voluntary agreement to keep power levels at reduced levels. What happens if the power ramps up? The very least that should happen is the continued use of AMOCs.”


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