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Flying in tandem with 5G

Global experiences have presented both the risks of 5G rollout to the aviation sector as also the plausible solutions; India can take lessons from these as it readies herself for a network upgrade

Flying in tandem with 5G
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The rollout of 5G spectrum by the telecom industry in the United States had disrupted flight operations to, from and within that country this January, with several international airlines including Air India shutting down their operations. The aircraft belonging to all major manufacturers — Boeing, Airbus and Embraer companies — were hit. Besides, operations of helicopters, smaller aircraft flown by private operators were also affected. This major disruption was due to the new and upgraded (5G) telecom signals interfering with the functioning of the planes' radio altimeters around those airports where the fifth generation (5G) broadband cellular networks were being laid out. Radio altimeters are key safety components found on all commercial airliners, business aircraft and helicopters, which are susceptible to interference by C-Band 5G wireless systems. The altimeters also affect crucial aircraft equipment like the auto-throttle, ground proximity warning, thrust reversers and Traffic Collision Avoidance System. During an interference situation, the hazardous or misleading radio altimeter data introduces a significant level of risk to the aircraft at the worst possible times, particularly during approach and landing. It could also reduce or eliminate the functionality of terrain-avoidance systems. Altimeters operate in the 4.2-4.4 GHz range, which is very close to the 3.7-3.98 GHz range (or C-Band spectrum) that the US had auctioned to its mobile companies last year for a total of about USD 80 billion. This potential 5G interference was documented as a safety risk by the US Federal Aviation Administration (FAA) and multiple aviation safety regulators globally. "Because the proposed 5G deployment involves a new combination of power levels, frequencies, proximity to flight operations and other factors, the FAA will need to impose restrictions on flight operations using certain types of radar altimeter equipment close to antennas in 5G networks," the FAA said in a statement. It affected approximately 10,000 aircrafts across the world — those in the US and those operating to that country, and a huge number of flights were cancelled in January.

Later, the FAA said it has identified a series of steps to protect commercial air travel from disruption while also enabling the telecom firms to enhance 5G services around certain airports. FAA's Acting Administrator Billy Nolen said: "We believe we have identified a path that will continue to enable aviation and 5G C-band wireless to safely co-exist." He said "we appreciate the willingness of (telecom firms) Verizon and AT&T to continue this important and productive collaboration with the aviation industry." The FAA worked with these companies to identify airports around which their 5G service can be enhanced with the least risk of disrupting flight schedules. During their talks, the telecom companies offered to keep restrictions in place for a year so that aviation operations were not affected. A phased approach was decided upon which required operators of regional (smaller) aircraft with radio altimeters most susceptible to interference to retrofit them with radio frequency filters by the year end. The US aviation regulator told the airlines and other operators of aircraft equipped with the affected radio altimeters to install filters or other enhancements as soon as possible. The FAA directed that these filters and replacement units for the mainline commercial fleet should be available on a schedule that would permit the work to be largely completed by July 2023. After that time, the wireless companies expect to operate their networks in urban areas with minimal restrictions, the statement said. The radio-altimeter manufacturers also worked with Embraer, Boeing, Airbus and Mitsubishi Heavy Industries to develop and test filters and installation kits for these airplanes. Now, the aircraft owners have already started getting these kits and are installing them on the planes. In most cases, these kits can be installed in a few hours at airline maintenance facilities. The process is being thoroughly monitored by the American aviation regulator. With these patchwork measures, the problem in the United States seems to have been resolved for the time being. Flights from other countries to the US have also resumed and other national aviation authorities have confirmed that the issue was specific to the United States.

India's 5G rollout

India is the world's second-largest telecommunication market which is preparing to rollout 5G by the year-end. Is it likely that a similar situation will be witnessed at the aviation hubs in cities like Delhi, Mumbai, Kolkata, Chennai, Bengaluru and Hyderabad when 5G is launched? Aviation professionals clearly do not want a repeat of the chaos faced by the US this January when all American carriers and several international airlines like Air India had to cancel thousands of flights to, from and within that country. The 6,000-strong Federation of Indian Pilots recently wrote to the Civil Aviation Minister, urging him to ask the Directorate General of Civil Aviation (DGCA) and the Telecom Regulatory Authority of India (TRAI) to work in tandem to develop a plan to enable safe and efficient implementation of 5G mobile communications networks in the country. However, the Cellular Operators Association of India (COAI), which represents the telecom companies, rebuffed the suggestion, terming it an uncorroborated speculation. It said there was "enough" gap of 530 MHz (from 3,670 MHz to 4,200 MHz) in the transmission of frequencies which was safe for aviation operations. Aircraft around the world use the frequency band 4.2-4.4 GHz for radio altimeters. According to experts, there was a risk of interference to some aircraft from 5G systems being licensed in the US within the frequency band 3.7-3.9 GHz, but the frequency to be used in India is less than 3,700 GHz. "In India, there is no risk from 5G services to aircraft. We are fully safeguarded as we are only allocating 3.3-3.6 GHz, which is more than 500 MHz below the altimeter spectrum. Thus, the C-band frequencies that are being auctioned for 5G in India are completely safe and there is no risk to the civil aviation radar altimeters," said Bharat Bhatia, president of the not-for-profit telecom professionals' body ITU-APT Foundation of India (IAFI). A former Indian Air Force officer pilot, who requested anonymity, said the government has restricted "the upper-frequency band limit of 5G to an appropriate frequency in band n78, thereby ensuring minimum interference with radio altimeter of aircraft which operates in 4.2-4.4 GHz band. Since the n78 band is up to 3.8 GHz, the likelihood of interference is minimal." Also known as the 3.5 GHz band or C-band 5G, n78 is the most widely used band in 5G communication.

Since India is yet to launch 5G services, it could take lessons from the US authorities to rule out any possibility of signal interference of the spectrum with the aircraft altimeters and other equipment. To begin with, the Indian telecom companies must sit with the civil and defense aviation agencies and professionals and aviation regulator DGCA to work things out. The experts stress that aviation safety must be foolproof when 5G technology is introduced in one of the fastest-growing aviation markets in the world like India. They said that lessons should be learnt from the ongoing safety measures for aircraft operations in the US, particularly during low visibility operations. Steps must also be taken by the regulatory agencies, both TRAI and DGCA, to conduct adequate trials to rule out all safety concerns before rolling out 5G services in India. These experts noted that the crisis in the United States could have been avoided through timely intervention. Equipment upgrade or changes in technologies could have been carried out several months before 5G introduction, as was done in Europe, Japan and some other nations.

Even though the Indian authorities now say 5G deployment in India would not impact civil aviation, it is possible that Indian airlines might raise similar concerns as the US ones in the long run when further developments in the field of telecom take place. Companies such as Vodafone, Airtel and Jio are currently working on testing 5G across the country and the service is expected to roll out this year. The government plans to auction 5G airwaves in the 3.2 to 3.6 GHz band, a lower frequency than the US, providing for greater elbow room when it comes to dealing with aviation safety. Many Indian telecom operators are using lower bands at the moment for offering 4G. However, it must be noted that some mobile manufacturers are bringing out products capable of supporting 5G up to 4.2 GHz. This may cause similar problems in India in the future, should the government decide to raise the 5G spectrum band to the US standard of 3.7-3.98 GHz range then.

The US-based Air Line Pilots Association International (ALPA) has also called on the mobile wireless industry to work in cooperation with the aviation community on implementing the mitigation practices that will ensure an equivalent level of safety by protecting against radio altimeter interference. "There are ways that 5G can be deployed while maintaining our high level of aviation safety, and time is running out for the wireless industry and the broader aviation community to work together on implementing mitigations that will ensure that every passenger and cargo flight arrives safely without severe disruptions to aviation operations," Capt. Joe DePete, ALPA president, said in a statement. Even though the armed forces have not openly come out with any measures pertaining to 5G, attention must be given by them to testing the impact of the spectrum on communication on the bands they use. Aviation markets where 5G telecommunications services have been successfully implemented with little or no impact on airline operations include Canada, France, Thailand, the United Kingdom, Japan, South Korea and Australia.

Hence, it is imperative for the aviation regulator DGCA to work closely with TRAI and Department of Telecom to ensure that long-term solutions are implemented in India for 5G and aviation safety to coexist. As demanded by the Air Line Pilots' Association (ALPA), a detailed evidence-based study needs to be carried out to ascertain the 5G interference and aviation safety issue. The absence of such a study was acknowledged by Minister of State for Communications, Devusinh Chauhan, in the Lok Sabha recently. Consultations among all stakeholders must be held to evolve a long-term approach in India for safe and timely rollout of 5G, so that such aviation safety concerns and chaos are prevented. Lessons also need to be learnt for harmonising other vulnerable sectors with further developments in telecommunication technology such as the next stage of 6G. Not just this, but at the world level, governments and their agencies should also work closely to ensure that aviation and its safety systems can co-exist with 5G. "We must not repeat the recent experience in the United States, where the rollout of C-band spectrum 5G services created enormous disruption to aviation, owing to the potential risk of interference with radio altimeters that are critical to aircraft landing and safety systems. In fact, many countries have successfully managed to facilitate the requirements of 5G service providers, while including necessary mitigations to preserve aviation safety and uninterrupted services. These include, for example, Brazil, Canada, France and Thailand," said Willie Walsh, Director General of International Air Transport Association (IATA). Hence, the governments must ensure that every frequency is comprehensively examined before it is allocated or auctioned so that it does not adversely impact aviation safety. In addition, aircraft and avionics manufacturers should carefully review their designs and engineering methodology to ensure that a single point of failure due to electromagnetic interference will not negatively impact safety of flight operations and performance of aircraft, the global airlines body IATA said.

Views expressed are personal

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