Infrastructure | Regulation | Spectrum Management
November 7, 2019

Spectrum for air transport and safety

By Loftur Jonasson, Technical Officer for Communications, Navigation, Surveillance and Frequency Spectrum for the International Civil Aviation Organization (ICAO)

*This article was originally published in the recent ITU News Magazine edition “Managing spectrum for evolving technologies.” Any views expressed in this article do not necessarily reflect those of ITU.

Air transport drives sustainable socioeconomic development in hundreds of nations, and for the last 45 years air traffic growth has consistently defied economic recessionary cycles, expanding twofold once every fifteen years.

These trends still hold true today and in 2018, air transport directly and indirectly supported the employment of 65.5 million people while contributing over USD 2.7 trillion to global GDP, and carrying over 4.3 billion passengers and over 60 million tonnes of cargo.

As a specialized agency of the United nations, the International Civil Aviation Organization (ICAO) was established by a number of States in 1944 to manage the administration and governance of the Convention on International Civil Aviation, also known as the Chicago Convention.

“Current and future air navigation, and air traffic management systems are highly dependent upon the avail‑ ability of sufficient, suitably protected radio spectrum.”

The ICAO Convention provides the required multilateral framework enabling commercial and civilian flights over the territories of its 193 member States.

ICAO standards and recommended practices (SARPs), as contained in 19 annexes to the Convention, provide a complete regulatory framework for aviation, including personnel licensing, technical requirements for aircraft operations, airworthiness requirements, aerodromes and communication, navigation and surveil‑ lance systems.

The safety of air operation is highly dependent on the availability of reliable communication and navigation services.

Current and future air navigation, and air traffic management systems are highly dependent upon the avail‑ ability of sufficient, suitably protected radio spectrum that can support the high integrity and availability requirements associated with aeronautical safety systems supporting truly global operations.

Fixed-satellite service (FSS) spectrum for remotely-piloted aircraft systems

The ITU World Radiocommunication Conference in 2015 (WRC‑15) took on the difficult task of developing provisions to enable the use of satellites operating under the fixed-satellite service (FSS) for the command and control (C2‑Link, known in ITU as control and non-pay‑ load communications) of remotely-piloted aircraft systems (RPAS; also known as Unmanned Aircraft Systems; or UAS). This became Resolution 155 (WRC‑15).

Developing SARPs — ICAO’s biggest task in recent decades

Since 2014, ICAO has been developing SARPs that will guide States in setting their own national regulations regarding RPAS. This is one of the largest tasks ICAO has undertaken in recent decades.

The current focus of the work is on SARPs related to airworthiness, operations, operator certification, licensing of remote pilots, air traffic management, C2‑Link, detect and avoid, and security.

Resolution 155 (WRC‑15) puts the responsibility into the hands of ICAO and aviation regulators to ensure that the C2‑Link is free from harmful interference.

As this is an unusual and untested approach, ICAO has been requested to report on the progress of developing SARPs for WRC‑19 and WRC‑23. Progress is good thus far, and the initial drafting of the first of two packages of C2‑Link SARPs was finalized in June this year, and circulated for review by States. Development of the second and more detailed technology-specific package has just begun.

Global Aeronautical Distress and Safety System (GADSS) (WRC‑19 agenda item 1.10)

One of the many reasons aviation maintains such a high level of safety is the willingness to learn important lessons — even from very rare events — such as the tragedies of Malaysia Airlines flight 370 and Air France flight 447.

These two tragedies highlighted the value of improved flight tracking and the alerting of search and rescue services, ultimately culminating in the Concept of Operations for the GADSS (see figure).

Based on the GADSS concept, the first set of new SARPs for flight tracking and autonomous distress tracking were recently introduced.

It has already been concluded that the GADSS requirements can be satisfied using existing systems operating within current frequency allocations. Hence, no action is required by WRC‑19 to modify Article 5 of the Radio Regulations.

However, some minimal amendments to Chapter VII may be useful, making reference to the GADSS and its related provisions, as contained in the ICAO regulatory framework. Sub-orbital vehicles (WRC‑19 agenda item 9.1.4)

Sub-orbital vehicles, including space planes, are being developed to reach altitudes and velocities that are much higher than those of conventional aircraft. Reusable sub-orbital vehicles that launch like traditional rockets have become routine, and re-useable space vehicles that routinely take off and land on traditional runways are close to becoming a reality.

In the not-so-distant future, we may see hypersonic travel which could cut the travelling time between the most distant points on the Earth down to 90 minutes.

The introduction of sub-orbital vehicles will pose unique challenges for spectrum and frequency management communities. While transitioning between ground and space, these vehicles must safely share airspace used by conventional aircraft.

Once they reach space, however, they no longer perform in a manner consistent with an aircraft. For that matter, even the definitions in the Radio Regulations don’t seem to apply. Hence, further studies are required within ITU–R and, based on their outcome, attention by a future WRC may be needed.

Telemetry, tracking and command in the space operation service (WRC‑19 agenda item 1.7)

While this WRC‑19 agenda item is unrelated to aviation, it is highly relevant. Some of the potential solutions to it may have a significant impact on aeronautical operations.

One of the key aeronautical concerns arises from the possible use of an existing allocation in the frequency band 137–138 MHz for the space operation service (SOS) for the satellite downlink (space-to-Earth). This would potentially have a significant impact on aviation, by changing the existing environment.

Currently, very few satellites are operating in this band, especially near the band edge of 137 MHz.

Immediately below the band edge, at 136.975 MHz, there is a common signaling channel for an ICAO standardized aeronautical VHF datalink system used for air traffic control purposes. Any spillover into this common signaling channel could disrupt the operation of that system on a global basis.

Global Maritime Distress and Safety System (GMDSS) modernization; the introduction of additional satellite systems into the GMDSS (WRC‑19 agenda item 1.8)

Civil aviation has many things in common with the marine industry. We share certain systems and frequencies for safety and distress; and in the case of a marine distress, in all likelihood there will be aircraft involved in its search and rescue.

The marine industry is currently looking at improving the GMDSS by adding a satellite service to it. The same satellite service provider also operates an aeronautical mobile satellite safety service in portions of the affected frequency band (1616–1626.5 MHz).

This operation takes place under the aeronautical mobile satellite (route) service (AMS(R)S), a safety service — afforded priority in accordance with Article 40 of the ITU Constitution.

This satellite system is used for aircraft position reporting and communications between air traffic controllers and aircraft pilots, particularly in remote, oceanic, and polar areas. Both of these services are required to ensure the safe separation of aircraft.

The radio regulatory conditions of this particular frequency band are quite complex. One current proposal to accommodate priority access to the GMDSS in this band may cause an adverse impact on the existing operation under the AMS(R)S in the band. This needs to be avoided.

Potential items for WRC‑23

Two exciting items have been identified by aviation to be potentially addressed by the World Radiocommunication Conference in 2023 (WRC‑23).

First, technology improvements have put the focus back on bands in the high frequency range (3–30 MHz) for the provision of high availability services to aviation, including digital voice and data, in remote and oceanic areas.

Second, the enabling of low Earth orbit satellite relay of certain VHF frequencies in the aeronautical mobile (route) service in some remote and oceanic areas may be a very cost effective means of improving air/ground pilot to controller communications, considering that this may not require any modification to existing equipage on-board aircraft.

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Spectrum for air transport and safety

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