GS-3: Infrastructure; Science and Technology - developments and their applications and effects in everyday life; Awareness in the fields of IT.

Key Phrases: Airworthiness, Potential effects of 5G, Aviation Safety, Radio Altimeters, Flight Operations, landing and navigation systems, Transmissions in C-Band, 5G Frequency Bands, automatic landing approaches, Precautionary principle.

Why in News?

• On December 7, 2021, the U.S. Federal Aviation Administration (FAA) issued two airworthiness directives (with effect from December 9, 2021) that are to create a framework as well as gather more information about the potential effects of 5G on crucial aviation safety equipment.

Key Points:

• The directives affect two categories of air transportation, the first being transport and commuter-category aircraft and the second, helicopters.
  • It is estimated that over 6,800 aircraft equipped with radio altimeters will be affected; they include aircraft made by Airbus, Boeing, Embraer and Gulfstream to name a few.
• The directives will also require highlights in flight/flight operation manuals that will limit flight operations when such interference is experienced.
• Operations by aircraft including large jets could be limited or prohibited from using certain landing and navigation systems in places where there is scope for potential interference from new 5G cellular networks.
• These could result in flight cancellations, delays or diversions in 46 places where these towers are, according to an aviation report.
• It is significant as American wireless communications companies get ready in early January 2022 to begin transmission in the “C-Band” (in 46 places), which is a range that is close to the one used by certain aircraft equipment.
  • This will be in addition to other frequencies already in use for 5G.
• There is a “threat of potential radar altimeter interference” from 5G cellular in the 3700 MHz-3800 MHz frequency, or the C-band — another report gives it as between 3700-4200 MHz — which is close to the 4200 MHz-4400 MHz range used by aircraft radio altimeters.
• In November 2021, telecom firms had announced voluntarily restricting power output at cell towers (using these frequencies) in locations near an estimated 46 airports and other strategic locations for about six months.
• The FAA has also sought specific data about the locations of 5G towers, their power supply and angles to study how they can interfere with aircraft approaches.
• The FAA is also working with the Federal Communications Commission and wireless companies to ensure that the expansion of 5G and aviation can co-exist in a safe manner.
  The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic management, certification of personnel and aircraft, setting standards for airports, and protection of U.S. assets during the launch or re-entry of commercial space vehicles.

The Federal Communications Commission is an independent U.S. government agency overseen by Congress that regulates “interstate and international communications by radio, television, wire, satellite and cable in all 50 states, the District of Columbia and U.S. territories”. It is the primary authority for communications law, regulation and technological innovation.

What is the affected Instrument?

All medium and large commercial aircraft have two types of altimeters — pressure altimeter and radio altimeter.

• The pressure altimeter displays the altitude of the aircraft in relation to mean sea level and uses the ambient pressure to measure the altitude.
  • It is prone to various errors and requires certain corrections but has the advantage of giving altitude measurements all the way up to the aircraft’s cruise level.
• The radio altimeter, is a misnomer as it measures height (not altitude) of the aircraft above the surface immediately below the plane.
  • For this purpose, it transmits a radio signal directly below.
  • While older systems calculated height based on the time between transmission and reception of the reflected signal, the more modern radio altimeters use more refined techniques such as “measuring the phase shift of the reflected signal”.
• For all modern commercial aircraft, radio altimeter is a very important tool used for precision approaches and landing.
• There are various other systems that depend on inputs from the radio altimeter — for example, predictive windshear, ground proximity warning system, traffic collision avoidance system, and auto land.
• These effects are only when the aircraft is close to the ground, i.e., up to 2,500 ft above ground level (depending on the aircraft make).
• The non-availability of the radio altimeter can be crucial during approach and landing for most modern aircraft and any disturbance to internal radio altimeter readings caused by 5G or other equipment transmitting in frequency bands close to it, can result in disastrous effects on crucial systems during approach/landing.

Key Takeaways from the Directives:

• Prohibited operations include instrument landing system approaches (ILS), required navigation performance (RNP) operations, automatic landing operations and some use of enhanced flight vision systems and other flight control systems.
• If ILS, RNP operations and auto-land are prohibited, the entire operations come under what is called a non-precision approach category which will require increased visibility and obstacle clearance limit requirements. For airports and passengers, this will result in additional flight times and also more fuel requirement for each flight. The effect could be compounded in areas that experience adverse weather conditions.
• The FAA’s separate order for helicopters likewise prohibits automated flight that requires use of radio altimeter data in 5G-affected areas. Those operations include auto-hovering. This means that helicopter flying in all areas within the vicinity of a city or town will become impossible unless they revert to manual flights.
• There is a warning of potential interference from both transmissions from 5G base stations and from the handheld phones of passengers, as a majority of passengers do not switch off cell phones. This could pose extreme danger when flying in the vicinity of major airports.
  • Even if 5G towers are prohibited within a certain radius, any passenger switching on and using the (5G) phone while the aircraft is at lower altitudes and hovering due to delays, can be in danger.
• For large commercial aircraft, the risk is limited to “specific scenarios”, but can cause “extreme” consequences in some circumstances, such as when aircraft are performing reduced-visibility instrument approaches.
• Reduced visibility approaches, pose a big danger as the aircraft is close to the ground and a false input to the autopilot system due to erroneous signals can result in a crash.

Way Forward:

• There needs to be a lot more research to realise the full implications of 5G on the radio altimeter and other aircraft systems. There could also be expensive protective countermeasures or mitigating procedures. But till then, precautionary measures while rolling out 5G seems to be the safest option.
• Wireless carriers could also operate in certain frequencies within the C-band, leaving what is called a buffer between 5G signals and frequencies used in aviation.
  • In India, 5G could be rolled out in the 3.2 GHz-3.6 GHz band, which may not have the potential to interfere with aircraft operations
• DGCA could order a ban on 5G towers within 15 nautical mile radius of any airfield with precision approaches such as ILS.

With densely built-up areas in many cities coming up or that are close to airports, interference to navigation signals can be catastrophic. Hence, Stringent rules and punishment criteria are required to enforce safety.

Source: The Hindu

Mains Question:

Q. Unless sufficient studies establishing impact of 5G are available, staying away from 5G seems to be the easiest and safest option. Analyse Critically.