ICAO has formulated 11 key performance parameters for the Air Transport System: access, capacity, effectiveness, efficiency, environmentally friendliness, flexibility, interoperability, predictability, safety, security and participation.
The same criteria can be applied to ATM.We need some form of management to ensure safety through separation of the traffic and warnings to traffic of potentially dangerous weather conditions. And we need to ensure that capacity in the air and on the ground can be maximized at the lowest possible cost and in a safe way. How do we avoid traffic jams, especially in the air and near/at airports?
Basic functions are navigation, separation, weather forecast and arrival/departure management.
At the start of commercial aviation the solution was to use maps and to create airways, by flying from beacon to beacon, more or less simulating ground traffic. This made navigation relative simple.
Some oversight was provided by ground based controllers who could "see " relevant traffic thanks to radio bearings and radar and could even recognize the individual aircraft thanks to transponders in the airplanes. As regulated traffic had to fly along these highways and the number of planes increased, some control was provided by the ground controller advising traffic via radio communication, based on the traffic picture provided by radar.
The system became more and more automated with tools provided to the controller. Some planning for airspace use was introduced.
Although INS provided the pilot with an alternative navigation tool, the basis for navigation and separation was still the pilot’s eyes and brain, radio beacons and the controller’s advice.
Weather information is provided to the pilot via weather information services. Some weather predictions are available at the start of the flight. Updates can be obtained by listening to other traffic and via ground information.
Landing and departure sequence is based on first come first served. Slots are given for free to customers of the airport. If there is too much inbound traffic at a given moment, the traffic is routed towards holding areas, where aircraft fly in a holding pattern.
The airspace was divided into controlled airspace and non-controlled airspace. Furthermore large parts of the airspace were allocated to the military where civil traffic cannot fly. This reduces airspace capacity substantially.
Air traffic control sectors were established according to national boundaries instead of the pattern of traffic flows.
Currently there are 36 Air Navigation Providers in Europe and 68 Area Control Centres, handling 8.9 million IFR flights per year.
The Single European Sky initiative by the European Commission tries to get commitment by Member States to restructure the airspace sectors into multinational sectors based on traffic movements and to allow joint use of civil and military airspace. This initiative is aimed at increasing airspace capacity and at reducing the cost of European ATM services, that are twice as high as in the US.
1. A need for pilots?
Based on the traditional concept for the controlled airspace, new procedures and tools are introduced. End to end planning of traffic flows is an important element. So called 4D trajectory planning is aimed at a seamless flow along airways and arrival/departure at airports. It is based on an automated control loop between the aircraft (FMS) and the Air Traffic Control computer for IFR traffic.
If such automation is the way forward, there is no need for pilots on commercial IFR flights anymore. Aircraft can be flown automatically under ground control. (There may be a need for some safety pilot to reassure the passengers and to act in case of emergencies not foreseen by the software. This safety pilot could attend to other duties like cabin service during the flight as well).
The question remains, if such a system based on automation of the traditional ATM concept is flexible enough.
How to handle unscheduled traffic? Can central computers deal with large amounts of traffic data? How to pass on control from one ground station to the other? What about intercontinental traffic planning, as international traffic is more depending on variable jet steam velocities and their 4D trajectory is difficult to predict. If flight control is fully automated, who is liable in case of an accident? Can older aircraft be upgraded to shorten the transition time into fully automated flight? Etc.
2. Free (IFR) flight?
New technologies are now available that would enable totally different concepts. Satellite based navigation, communication and surveillance enables precise navigation and broadband communication, making radar (and mode S) communication no longer needed. The aircraft has now a reliable navigation tool and thanks to advanced communication data-links can see all relevant traffic. In combination with onboard systems like collision avoidance systems (ASAS), automated weather updates, ground proximity warning systems, enhanced vision systems and wind shear/ vortex warning systems (which can be integrated into a single, easy to interpret display), the pilot can obtain total situational awareness. The function of a controller would be at best to act as safety monitor for en-route traffic and to ensure that traffic jams are avoided near airports. However, airlines may manage their own slot priorities at airports via CDM systems. So the extreme alternative is to rely totally on the pilots without a need for controllers or control centres.
3. Non controlled airspace
The air transportation system is going to change. Aeroplanes will become very silent allowing 24 hour operations at airports, even in the vicinity of big cities.
ATS may also shift from scheduled towards more unscheduled operations. There may be a variety of flying vehicles; like personal air vehicles, air taxis, business jets, charters, unmanned aircraft (flying under ground command or flying a pre-programmed track), dedicated cargo planes, and planes from regular airlines using a Hub and Spoke system as well as direct routing to both primary and secondary airports. Inter-city and intra-city traffic will be using VTOL aeroplanes, whilst civil and military aviation will share the same airspace.
Strategic 4-D planning or speed control becomes impossible as trajectories of all this traffic are unknown.
Reserving airspace for particular applications would create artificial shortage and should be avoided. In such a system the prime concern is to ensure that mid air collisions and traffic jams near airports or landing sites are avoided. Thanks to secure satellite CNS and intelligent anti collision systems, aircraft would be unable to collide in the air or with the ground. Flight control and collision avoidance would be automatic by introducing intelligent systems on board. In certain cases, manual override would still be feasible as IFR operations are like VFR operations with total situational awareness based on network-centric communication tools. Onboard navigation systems will select the best route, and ensure that flying through severe weather is avoided. Much can be learned from the route planning and navigation devices currently available for cars.
Airport shortage will be partially offset by introducing different airport layouts, the Metro liner, dedicated cargo airports, floating airports, separating take off and landing and VTOL-aircraft. Scheduled air traffic would be "depeaked" as much as possible. The restructuring of the transport system, by bringing air and ground management in one hand, will help in this respect.
If insufficient airport-slot capacity remains, slots will be sold to the highest bidder. Slots may represent a scarce commodity and thus have a price. Such an economic mechanism will stimulate operators to look for clever alternatives to offload their passengers.
4. Global ATM
By replacing traditional procedures and systems not by automation but by intelligence, a totally different air traffic control will emerge. Control will be back where it all started: inside the vehicle. We need to assure that all aircraft in the world will be equipped or retrofitted with the same standard equipment. If large production series of equipment can be realised, the equipment price will be low. Current developments in onboard equipment for air taxi aircraft are already leading the way. Human factors have to be given more attention than in the past. Certification will stay an important issue.
We need to organise a world-wide consensus on the future of air traffic control. We need to think in different concepts to cope with the future, diversified air traffic.
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