by Ing. Stefano Zaninotto
The number of people making use of air travel is on the rise, with just over four billion passengers transported by commercial airlines in 2017 alone. Consequently, air traffic is increasing as well. Conscious of this reality, the aerospace industry is taking concrete steps in order to reduce fuel consumption, as well as air and noise pollution. One of the operational areas that has been receiving specific attention is aircraft taxiing, meaning the ground movement of aircraft between the airport terminal and the runway.
In order to reduce emissions during taxiing, various electric taxiing strategies are being proposed by industry and academia. The Situation Awareness and Traffic Management for Engineless Taxiing research project, which is being coordinated by the Institute of Aerospace Technologies at the University of Malta, in collaboration with HandsOn Systems and Malta Air Traffic Services, is currently studying one of these strategies. This strategy proposes the use of autonomous, electric tow trucks to move aircraft between the terminal and the runway (and vice-versa) during taxi operations. This removes the need for aircraft to use their main engines during taxiing.
Satmet is focusing on three main challenges of electric taxiing by means of autonomous tow trucks. The first challenge is to introduce autonomous towing operations on the airfield while keeping Air Traffic Controllers aware of what is happening but without increasing their workload. For this purpose, Satmet is developing a system which will be responsible for allocating a tow truck to each taxiing aircraft; determining the optimal path to be followed by the tow trucks and aircraft and detecting and resolving any conflicts between vehicles on the taxiways.
The system will provide ATC with information regarding the movement and status of each vehicle and alert ATC about any impending conflicts. It will also enable ATC to give taxi clearances and to modify paths proposed by the system.
The second challenge is to detect obstacles around the autonomous tow trucks. For this purpose, Satmet is developing techniques to detect obstacles using multiple sensors to accurately pinpoint nearby objects so that safe passage of the tow truck to the desired runway or terminal can be determined. Potential obstacles include buildings, structures, vehicles and other aircraft. Through accurate measurements of obstacle positions, the tow truck would be able to allow enough clearance to tow an aircraft safely.
An added value of this technology is that it would contribute to eliminating ground collisions which are mostly attributed to pilot error. Unfortunately, these types of incidents and accidents still occur nowadays and, apart from possibly being fatal, tend to be costly to the airlines involved. Preliminary results obtained in Satmet demonstrate that the accuracy and confidence of obstacle information can be improved by fusing data from multiple sensors.
Additionally, this provides redundancy considering that, if a sensor fails, obstacles can still be detected by the remaining sensors. The resulting accuracy is expected to be in line with that required for autonomous taxi operations.
The third challenge is to ensure that each autonomous tow truck follows the taxiways precisely - especially when towing an aircraft - without deviating from the taxiway centre line. Otherwise, there is the possibility that the aircraft which is being towed will end up on the soil or grass outside the taxiway and get stuck. Even worse, the aircraft could collide with an obstacle situated outside the taxiway.
In order to address this challenge, Satmet is proposing a solution whereby visible and infrared cameras are mounted on the tow truck in order to detect taxiway line markings and estimate the position of the tow truck relative to the centre of the taxiway. Such a system would be able to cope with different weather and visibility conditions and would not be dependent on external systems such as the Global Positioning System.
By addressing the challenges described above, Satmet will contribute to an increase in the safety and efficiency of ground operations and a reduction of environmental impact. Furthermore, it is envisaged that the proposed solutions will facilitate various ATC tasks and improve situation awareness.
More information about the Satmet project can be obtained by visiting the Institute of Aerospace Technologies website www.um.edu.mt/iat or by sending an email to [email protected]