NLR develops virtual traffic lights for taxiing aircraft

NLR recently tested and validated a so-called ‘Virtual Stop Bar Guidance Concept’ in its air traffic control simulator NARSIM (NLR ATC Research Simulator). This involved making several changes to the working position for the traffic controller in the tower to allow the status of a virtual ‘stop bar’ to be displayed for each aircraft selected on the radar screen. Stop bars work like traffic lights on the airport indicating whether aircraft can proceed taxiing or need to stop. Virtual stop bars are only shown on the displays of air traffic controllers or pilots and do not exist as physical objects on taxiways or on the platform. In addition, the new working concept allows air traffic controllers to select the taxi route to a virtual stop bar for each aircraft. Information is exchanged between the control tower and pilots via data communication, the so-called data link. The data link ensures that both the status of a virtual stop bar and the route to the virtual stop bar are shown on the navigation display in the cockpit.

Using this new technology, more aircraft will be able to use the available space on the platform and taxiways simultaneously during low visibility conditions. Although it would be possible to install more ‘real’ stop bars on the airport, it would be a costly solution, adapting the installations to changing circumstances would be difficult, and these stop bars would show the same status for each aircraft.

In the old situation, the so-called ‘clearance limits’ for an aircraft were restricted to the position of the aircraft taxiing in front. With virtual stop bars, the clearance limit of each individual aircraft can be expanded. In practice, this would mean that aircraft can keep moving, thereby increasing the capacity of the taxiways. Another advantage of this technology is that pilots can see the correct route to the position of the virtual stop bar on their navigation screen.

Detail - Virtual Stop Bar Guidance Concept

NLR developed the concept in co-operation with Italian air traffic controllers from ENAV SpA, the Italian ANSP. A touch-pen display was used to integrate radar information, the switching of stop bars, the assignment of clearance limits and the route, and other relevant flight information (so-called Electronic Flight Strips). The real-time simulations with air traffic controllers and pilots as well as the validation of the new technology were carried out on NARSIM. The tests focused on optimising communication between control tower and cockpit as well as the working environment of air traffic controllers at Malpensa Airport, which is located northwest of Milan. Low visibility operations are carried out frequently at this airport which is characterised by a large movement area.

The NLR real-time simulation tests were part of the Integrated Surface Management (SUMO) project under the European SESAR 2020 programme. The SESAR 2020 programme aims to increase the safety and efficiency of air traffic control in Europe. In the development and validation of the concept, NLR collaborated closely with Italian air traffic controllers from ENAV and flight simulation experts from the Turin-based company Leonardo. The project incorporated creating a connection between the GRA flight simulator in Turin and NLR’s NARSIM control tower simulator in Amsterdam. The cockpit navigation display was supplied by Thales Avionics.

The ENAV air traffic controllers are convinced of the advantages of the concept and assessed NLR’s simulation environment as realistic and reliable. ENAV is further studying both concept and interface in an adaptation for future operations in Italy. Based on this new development, NLR can support air traffic control organisations across Europe that want to be able to guide aircraft to runways or gates with greater efficiency, safety and predictability.