Aviation ministry unlikely to take hasty call on 5G altimeter's replacement

Telcos remain confident that 5G signals in C-band won't impact flights

The Ministry of Civil Aviation (MoCA) is unlikely to immediately set a deadline for airlines to replace the radio altimeters (RAs) in their aircraft because it believes that hasty decisions, without sufficient data, cannot be made in matters related to aviation safety, senior government officials have informed Business Standard.

In September, telecom service providers Reliance Jio, and Bharti Airtel, represented by the industry body Cellular Operators Association of India (COAI), requested the MoCA to establish a deadline for all airlines to replace their RAs, so that they can roll out 5G broadband services near Indian airports.

RAs furnish essential height above terrain data to various aircraft systems, ensuring safe operations. Commercial aviation RAs function within the 4.2 to 4.4 gigahertz (GHz) band, separated by 220 megahertz (MHz) from 5G C-Band transmissions situated in the 3.7-3.98 GHz band, according to the US aviation regulator Federal Aviation Administration (FAA).

Therefore, in December 2022, the Department of Telecommunications (DoT), based on recommendations from the MoCA, directed telecom operators to avoid deploying 5G base stations near India's 137 airports. A month later, the FAA requested US-based airlines to retrofit RAs by February 1, 2024. In October 2023, the FAA issued an additional notice urging all US-based operators to promptly equip their aircraft with 5G C-Band tolerant RAs.

"As the matter pertains to aviation safety, the DoT is in broad agreement with the MoCA and is not pushing to set any aforementioned deadline. We want to wait and analyse more data that comes from the US's experience with retrofitted RAs," a senior official noted.

Another official mentioned that the global aviation industry's supply chain has been affected since the COVID-19 pandemic began. "This means that the production and supply of modified RAs to Indian carriers is anyway not going to be prompt," the second official added. The DoT and the MoCA did not respond to queries sent by Business Standard on this matter.

Last year, telecom companies in India were explicitly instructed to ensure that no base station operates within 2,100 meters from both ends of the runway and 910 meters from the central line of the runway in the 3.3 GHz-3.67 GHz frequency range, also called the C-band. This measure is imperative to prevent any interference with the aircraft's RAs.

Telcos remain opposed

Sources at the two telecom service providers currently rolling out 5G said the industry has made sure 5G signals in the C-band don't interfere with flights since RAs operate in the 4200-4400 MHz band.

"We have informed the government multiple times that the situation in the US and India are different. Here, there will be a 500 MHz gap in the frequencies which will safely allow aviation without interference. We have argued that if the government wants to codify the rules, we will work with them, but there has been no forward movement on the issue," a senior industry executive said.

Case in point, US operators have used the 3.7 GHz to 3.98 GHz frequencies, which are closer to the radio altimeter frequencies inside the aircraft. Indian telcos have therefore argued the C-band 5G frequencies might not affect the altimeter readings at all owing to this safe distance between the operating frequencies.

To test this out, the COAI has told the government there should be controlled flight simulations to prove 5G signals do not interfere in controlling airborne planes. In its recent submissions to the government, it had pointed out nearly 40 countries across the world already use 5G in the C-band, with no reported impact on aviation services.

"A vast majority of the countries with 5G deployments in the C-Band have not adopted any precautionary measure regarding coexistence with aviation operations, including Europe, where more than 20 countries have deployed C-Band at power levels similar to the USA for up to three years, but without any harmful interference claims," S.P. Kochhar, Director General, COAI said.