FAA Issues Flight Restrictions As 5G Signals May Interfere With Aircraft Instrumentation

The Federal Aviation Administration (FAA) has issued an Airworthiness Directive for pilots in response to concerns that mid-band 5G wireless signals may interfere with aviation electronics. Under the new rule, pilots are forbidden from using auto-landing or certain other flight systems at low altitudes. The worry lies in possible interference with radio altimeters from 5G wireless signals.

More than 6,800 airplanes and helicopters in the US are affected, along with dozens of aircraft manufacturers. Under low-visibility conditions, where the use of radio altimeters is almost a necessity, flight delays or diversions might occur.

Understanding the Threat of 5G for Aviation

A radio altimeter measures the distance between the aircraft and the ground or water. It’s much more accurate than a barometric altimeter, making it an essential piece of equipment when pilots are landing and cannot see the ground.

This equipment operates on a radio frequency near that of 5G mid-band transmitters. Specifically, radio altimeters use the 4.2-4.4GHz band, while mid-band 5G uses the 3.7-3.98GHz portion of the spectrum. The 220MHz separation, experts believe, isn’t enough to avoid interference during low-altitude flying.

The rollout of mid-band 5G is crucial for both AT&T and Verizon. Both carriers are currently relying mainly on mmWave 5G equipment. These transmitters are capable of the highest speeds, but lack the ability to penetrate obstacles or cover larger areas. Mid-band 5G transmitters maintain a more happy medium of coverage strength and transfer speeds.

Ongoing Cooperation Between Aviation and Telecommunications

The rules may only be temporary, however. The FAA is gathering more information, and telecommunications carriers are cooperating to reduce the risk to safety and normal flight operations. AT&T and Verizon, two major carriers rolling out mid-band 5G transmitters, are in close talks with regulators.

Initially, the two cellular providers were to begin expanding their 5G network in December 2021. They delayed those plans until January 2022, and agreed to limit broadcast power near flight paths.

CTIA, a major wireless trade group, pointed out other countries safely using C-Band airwaves for 5G without any impact to aviation. US experts point out, though, that many of those countries continue to limit transmission strength while aviation authorities finish safety assessments.

In its rulings, the FAA points out the Airworthiness Directives are interim rulings. The agency “believes the expansion of 5G and aviation will safely co-exist”.