Rotorcraft Operators Face Disruptions, Groundings as 5G Rollout Looms

Jan. 14, 2022
The Helicopter Association International is warning that the 5G wireless services rollout on Jan. 19 could result in rotorcraft groundings due to interference with aircraft radio altimeters, disrupting emergency aircraft.

With Verizon Communications and AT&T poised to begin their 5G wireless service rollout on Jan. 19, 2022, attention is being given to the disruption that 5G may have on aircraft communications. While the impact that 5G could have on commercial air service has received much of the public’s attention, the Helicopter Association International (HAI) is sounding the alarm on the impacts to rotorcraft operators.

In the wake of the Federal Aviation Administration’s (FAA) issuance of over 1,400 Notices to Air Missions (NOTAMs), HAI put out a statement warning that 5G could ground essential rotorcraft operations – such as emergency rescue and police aircraft – by interfering with radar altimeters.

During a webinar held Jan. 13, HAI’s Director of Government Affairs, John Shea; Seth Frick, radar systems engineer, Honeywell Aerospace; and Nick Kefalas, a Lockheed Martin technology fellow at Sikorsky Aircraft Corp., addressed the potential disruptions of 5G’s rollout.

Frick stated that Honeywell has been conducting “substantial testing” on all of the altimeters models they produce to discover what 5G’s impact will be.

“The behaviors we observe in the laboratory setting do vary by model to model. But generally, we’ve observed everything you can imagine,” Frick said.

Some of the behaviors recorded have been altimeters “becoming noisy,” putting out altitude misreadings of plus or minus 50 to 100 feet. Other disruptions have been more severe, with altimeters giving no reading at all or giving erroneous readings of hundreds and thousands of feet off true altitude. Compounding the issues, sometimes the altimeters do not recognize that the information they are displaying is wrong and provide no warning to pilots.

Frick noted that in real-world scenarios, they expect things to be more dynamic than can be represented in the laboratory.

“There’s going to be a range of different impacts,” he continued. “Our conclusion has been, based on our testing, that there’s not really any kind of failure mode that we could safely rule out. You could have detected faults, loss of function. You could have undetected erroneous output, which could constitute hazardously misleading information depending on how that altitude output data is used onboard the aircraft.”

There are two primary modes of interference that are of concern. Frick said they are referred to as front door and back door coupling. As he explains, 5G networks put out high-powered signals in their own frequency band, separate from the altimeter band. However, the altimeters don’t have perfect filtering for these bands built into them, meaning they pick up some of the 5G network’s signals regardless.

Frick continued that 5G networks will also leak out much lower levels of interference directly into the altimeter band. He said that the former, the high-powered signals, appear right now to be what causes the most altimeter disruptions.

One solution to the problem is to increase an altimeter’s filtering. Though it is not a quick fix. Retrofitting altimeters to filter the 5G signals is a process that can take anywhere from six months to a year. And not all altimeter models will be able to be retrofitted and will need to be replaced altogether.

It does not help, Frick added, that altimeter standards have not been updated since the 1980s – well before the introduction of cellular communications. Efforts are currently underway to update standards for the modern age, though.

In the meantime, the FAA is offering the same guidance to rotorcraft operators as they are to those of their fixed-wing brethren – guidance based on protection zones around 5G towers and airports. These zones are two nautical miles out from an airport’s runway threshold. If a 5G tower’s signal crosses into these protection zones, a pilot will need an alternative method of compliance (AMOC) to land.

Yet, this guidance is of little help to heliport operators, which do not yet have similar guidelines, or rescue operations that may be flying and landing in unconventional areas to complete their missions.

“The NOTAMs that were released today cover both airspace procedure and aerodromes. If you are, say, in the New York Metropolitan Area where you have JFK on the south of the island and LaGuardia on the north, there may be zones within that area that you may have to drop below certain altitude, or there will be an altitude of a ‘no-go’ zone,” said Kefalas. “We have seen information that shows that the lower you get, the better your performance is. So, all that will have to be weighted in the way operations are conducted going forward.”

Kefalas continued that the situation with the towers is fluid. As more and more 5G towers come online, these protection zones will shrink as towers intrude on them. To help combat this, the FAA is working on a plan with the Federal Communications Commission (FCC) to have them deliver a report every three months of where new towers are being brought online.

The FAA will use this information, along with the testing of altimeters, to build a database of where it is safe for aircraft to operate, depending on the equipment they have. This process would continue into the foreseeable future as the 5G network grows.

“That’s going to be an ongoing and dynamic process,” Kefalas said. “They are doing this [5G] rollout in phases, so every three months, we will be getting additional towers. So these assessments from the FAA against these databases will be ongoing, at least for the foreseeable future until we stabilize the number of towers popping up, which at some point, I would expect that the AMOCs to be more under control and not needing to be coming out at that frequency.”