Implementing enhanced arrival procedures enabled by a ground-based augmentation system (GBAS) can significantly reduce noise impact of arriving aircraft at airports. This was the main conclusion of a series of validation exercises that took place in a number of European airports within the framework of a SESAR project (ref P06.08.08). The findings of these exercises were presented by SESAR members at a workshop in Rome on 18 and 19 October.
GBAS is a satellite-based technology which uses digitally-coded broadcasts loaded into the aircraft’s navigation and guidance capabilities to allow for more precision approach and landing. Using GBAS, SESAR members have developed advanced approach procedures and more efficient flight trajectories with a view to reducing noise impact and improving fuel efficiency without impacting runway throughput. Specifically, SESAR members focused on GBAS-enabled approach procedures with various characteristics, including increased glide slopes, adaptive increased slopes, multiple runway aiming points, double slope approaches and approaches integrating curved transitions from required navigation performance (RNP) segments to GBAS landing system (GLS).
To allow for a comparative assessment, a common tool (IMPACT tool) was used to calculate the noise impact of the GBAS procedures when implemented at the different airports using different types of aircraft. The tool uses an EU recommended metric, which takes an average of the noise and weights it according to the period of the day and density of traffic. Extensive safety and human factor assessments were also conducted of the new procedures, which identified a number of requirements which must be put in place for each of the procedures, including additional training for controllers.
The procedures were matured during a series of simulations and flight trials at Frankfurt, Milan Malpensa, Amsterdam Schiphol and Stockholm Arlanda airports with a slightly steeper approach trial using area navigation (RNAV) global navigation satellite system (GNSS) procedures at Heathrow. These validations showed how the procedures need to be developed according to the specific airport, its layout and traffic, surrounding communities and environmental context. SESAR members showed that while noise impact could be considerably reduced with the various procedures, they indicated the need for trade-offs with other performance areas such as capacity and predictability.
In the case of Stockholm Arlanda, a court ruling from 2008 prohibited straight-in approaches to one of the airport’s runway to avoid flying over densely populated areas. Using curved approaches and increased glide slopes (IGS), SESAR members were able to show how GBAS-enabled procedures can completely avoid such areas and lower the noise impact.
The situation at Frankfurt is more challenging given the density of the population surrounding the airport. The validations here compared the performance of traffic using RNP to GBAS procedures with traffic using the conventional straight-in instrument landing system (ILS). The results show that if carefully designed, the new procedures can reduce the areas and number of people severely impacted by aircraft noise. However, it was noted that to achieve this reduction in noise and shorter arrival routes and fuel consumption, changes would need to be made to the ICAO regulation to allow independent parallel approaches using curved RNP transition to GBAS precision approaches.
Heathrow operates at near full capacity, but, due to the compact and busy airspace above London, it also has less room to manoeuvre aircraft in the skies. Like all airports, Heathrow is working with local communities to develop quieter procedures. Although the airport does not currently have GBAS, it was able to trial over six months the use of steep approaches using RNAV GNSS procedures. The SESAR team found that the procedures improve the noise footprint of the airport and did not impact on the runway throughput. Going further, they found the application of the procedures could also result in lower fuel consumption. The airport is aiming to run more trials to gather further data on these procedures during the summer period.
Like its other European counterparts, Milan Malpensa airport also has to cope with noise issues for local communities in addition to the mounting capacity constraints. In this context, the SESAR team was able to prove significant noise reduction by simulating several types of approaches. The integration of these procedures within the real operational environment was confirmed through live trials which showed that noise reduction is possible as well as improved fuel efficiency without impacting runway throughput. Human performance and safety assessments complemented the outcomes of these trials to support the feasibility and acceptability of the procedures. Finally the SESAR team found noise benefits at Amsterdam Schiphol airport thanks to increased glide slope and multiple runway-aiming points and investigated the acceptability and feasibility of these procedures for flight crew through pilot-in-the-loop real-time simulations.
Significant progress has been made on these procedures. With SESAR 2020, further work is planned to prepare these procedures for implementation, while research will also be carried out on the visual aids and tools needed to support controllers and flight crew when using these enhanced procedures.
The project (P06.08.08), led by ENAV, brought together SESAR members Airbus, DFS Deutsche Flugsicherung, ENAV, Eurocontrol, Honeywell, Leonardo, NATS, Noracon, SEAC and Thales.
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