Green-GEAR is an Exploratory Research Project and has worked on three Solutions aiming to enable and incentivise optimum green trajectories and airspace use through new ATM procedures.
Green-GEAR’s Geometric Altimetry Solution aims to mitigate inefficiencies in current flight operations and airspace use resulting from the limited accuracy of barometric altimetry. The project conducted fast-time flight simulations using geometric instead of barometric altimetry and vertical containment assumptions for the Northern London TMA. Potential operational benefits through reduced airspace design complexity were assessed in terms of fuel consumption for both arrivals and departures, controller workload and safety.
The TMA-level validation is complemented with more detailed aircraft-level simulations for selected procedures, as well as an aircraft-level feasibility assessment, and a study of the potential use of geometric cruise, which does not seem suitable on its own but may offer benefits as an enabler for other operational improvements.
Indeed, the Separation Minima Solution investigated the feasibility of reducing the minimum vertical separation from 1,000 ft to 500 ft in upwards extended reduced vertical separation minimum (RVSM) airspace, enabled by improved altitude-keeping performance through the use of geometric altimetry (RVSM 2 concept).
The feasibility was assessed from a collision-risk perspective, both under nominal and non-nominal operating conditions, and regarding the wake vortex encounter risk. Several key challenges have been identified that would need to be addressed – on the other hand, the finer granularity of available flight levels and the potential capacity increase both would allow flights to operate closer to their optimum cruising altitude, improving flight efficiency and potentially outweighing the drawbacks of foregoing the barometric reference.
Last but not least, the Green Route Charging Solution studied a two-step approach to rewarding more eco-friendly choices in flight planning through the so-called modulation of en-route charges, which are collected from airspace users to cover the costs of provision of air navigation services. The best trade-off was sought between the reduction of overall environmental impact and keeping the economic and capacity impacts stable. The initial step of the solution looked at reducing CO2 emissions and demand-capacity imbalance, while the full Green Route Charging solution additionally addressed non-CO2 effects, which account for roughly two-thirds of aviation’s environmental footprint.
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