Future Air Ground Integration: A scalable concept to start with green approaches today

Kurzfassung

Today, the usage of highly efficient flight procedures often lacks on the missing integration between air and ground based tools. Typically, modifications on both airborne and ground side are necessary to fully benefit from new technologies. Furthermore, modifications are usually expensive and therefore only implemented if the counterpart also invests in the corresponding work. In the past ten years, the Institute of Flight Guidance in Braunschweig performed extensive investigations on how airborne capabilities can be improved. Studies with the A330 Full Flight Simulator of ZFB Berlin and DLR’s testing aircraft ATTAS both using DLR’s Advanced Flight Management System onboard proved a highly accurate predictability of 4D-trajectories. Based on aircraft model and actual weather forecast, the 4D-FMS enables fuel efficient and noise optimized continuous descent approaches. With a planning horizon of about 20 minutes, threshold times were anticipated with deviations of highly accurate +/-5s and +/-150ft during the whole approach. Having a look at today’s traffic mixture and its equipage level, about 11% of all aircraft flying in Europe are capable of reaching time constraints of +/-6s. At least in high traffic situations, current terminal manoeuvring area concepts do not support 4D-capable aircraft in flying fuel efficient and noise abating profiles. In contrast, equipped aircraft are all forced to early join the same lateral flight path flying at normalized speeds to ensure separation at all times and avoid a break-in of capacity. Thus, fuel and noise efficient approaches are currently performed in low traffic scenarios only. In 2007, DLR launched the project “Future Air Ground Integration (FAGI)” that tries to solve today’s trade-off between capacity and environmental sustainability. The major concept element (see Figure 1) is usage of trajectory based TMA operations to combine aircraft optimized flight profiles with a high airport throughput. A time based late merging allows aircraft to fly their preferred trajectories by staggering them laterally in an extended terminal manoeuvring area with a time constraint to be fulfilled at a late merging point. Due to their high navigation accuracy 4D-capable aircraft are able to follow their predicted flight path on their own. Unequipped aircraft are supposed to be integrated by means of a ground based 4D-guidance module. The proposed concept integrates 4D-equipped aircraft in the normal traffic flow without losing aircraft throughput. The generic concept is fully scalable based on the equipage degree and leaves high flexibility for short term departures, reaction on contract violations (e.g. equipped aircraft not meeting their constraints) and emergency situations. Since the concept does not penalize FMS-unequipped aircraft (compared to today’s operation) the overall system performance benefits from every single aircraft flying advanced approach procedures. Thus, even with a small percentage of 4D-capable aircraft traffic is handled more efficiently and environmentally friendly. This paper also presents results from the real time simulations performed in the final validation campaign. The human-in-the-loop simulations were performed using a generic airport layout with one runway. The FAGI route structure had four static entries, with one of them being aligned to the landing direction. The simulated scenarios contain 33-36 aircraft with 10%-70% of them being FMS equipped; simulation time was one hour. The main task of the participating air traffic controllers was to separate the more flexible unequipped aircraft from the 4D-capable aircraft that had a rather fixed trajectory from top of descent at latest. They were assisted by means of a timeline providing the arrival sequence and times, an advisory stack providing advises on how to guide the unequipped aircraft, and ghosting/targeting of traffic onto the centreline.