[Editorial] The distress over 5G and flight safety

What is the Context?

Almost 11 months after the United States’ leading telecommunications companies won bids for
$81 billion worth of C-band radio spectrum to roll out 5G services, the much-awaited introduction
hit a major snag after the country’s leading airlines warned of massive flight disruptions if the
wireless technology was put into operation, especially around the nation’s airports.

Flights to the United States from India were briefly suspended after the Federal Aviation Administration warned that the rollout of new 5G technology could potentially lead to interference with onboard instruments.

How do flight radar altimeters help in safe flight operations?

For all airborne vehicles — an aircraft, spacecraft, or even a missile — an altimeter is crucial to gauge the altitude and the distance covered.

Altimeters are of three main kinds: barometric, laser, and radio or radar altimeters. Most commercial passenger and cargo aircraft use a combination of all these altimeters along with a global positioning system (GPS) to determine their path, as well as factors such as height above sea level, presence of high-rises, mountains, and other obstacles, and the likely flying time.

The radio or radar altimeter is a very small, low-power radar system that operates in the 4.2-4.4 GHz frequency microwave C-band. The high frequency of these altimeters enables aircraft makers to install small antennae that produce powerful signals that can be relayed quickly and accurately.

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How is the functioning of radar altimeters may be affected by the 5G radio frequencies?

The altimeters provide information on an aircraft’s altitude and are a crucial part of flight operations for pilots, particularly while seeking to make low-visibility landings in inclement weather. At the heart of the impasse lies the fact that both the 5G services and some flight equipment operate on the same C-band radio spectrum, with only the frequencies varying. The FAA has said it is working with altimeter manufacturers to evaluate data from the wireless companies to determine how robust each model is, and, if required, have the devices retrofitted or replaced.

In a compromise on the eve of the planned roll-out, AT&T and Verizon agreed to delay the introduction of the new wireless service near key airports.

Why is there a concern about radar altimeter interference specifically in the US?

Although the rollout of 5G by telecom service providers has been a cause of concern for aviation everywhere, the situation is critical in the US, which auctioned 5G bandwidth in 2021 in the 3.7-3.98 GHz on the C-band spectrum range. This band is very close to the 4.2-4.4 GHz range in which radio or radar altimeters operate, airline companies have complained.

According to industry experts, there are chances of interference of the two bands as telecom service operators, in order to extract the full value of 5G and give customers the best experience, push operations to the highest band possible. Altimeters too need to operate at higher frequencies in order to get the most accurate readings possible.

How big is the concern?

The fact that the world’s largest economy is now faced with the risk of large-scale domestic and international air travel disruptions as a result of the relatively belated roll-out of 5G telecom services points to the peculiar problems of the U.S. market, including the particular frequencies allotted there for 5G.

South Korea, China, Japan and several European nations have already successfully rolled out 5G services and the U.S. telcos have cited the lack of problems in these jurisdictions as evidence that the FAA and airlines need to do more to find solutions to the deployment of the wireless technology near airports.

The FAA on its website has pointed to the specifics of the proposed 5G roll-out in the U.S. with a comparison to the situation in France and asserted that some key differences pose challenges. For one, the aviation regulator contends planned buffer zones for U.S. airports only protect the last 20 seconds of flight, while in France the last 96 seconds of flight are protected from any interruption from 5G signals. Also, 5G power levels are lower in France, with even the planned temporary nationwide lower power levels in the U.S. still expected to be 2.5 times more powerful.

What is the situation in India?

In India, where 5G is yet to be rolled out, the frequency range for 5G telecoms operations is pegged around 3.3-3.68 GHz. It is learnt that the Federation of Indian Pilots has, in its meetings with the Department of Telecommunications (DoT), expressed concern about the frequencies being close together.

The DoT, however, assured them that there would be no interference as the frequencies for commercial 5G services were at least 530 MHz away from those used by altimeters.

What can be a way forward for the US?

The US will have to find a long-term solution to this impasse so as to minimise any further disruption to the already pandemic-hit global travel and trade sectors.

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