The European Green Deal aims for net-zero greenhouse gas emissions by 2050, requiring smarter, environmentally friendly and sustainable mobility. In the framework of the Aviation Green Deal, Green-GEAR focusses on three research and innovation activities supporting these shifts: geometric altimetry, an evolution of separation minima, and incorporating environmental factors into the European route-charging scheme.
As airspace becomes increasingly congested with a diverse range of users, including drones, unmanned aircraft systems, vertical take-off and landing aircraft as well as high-altitude operations, the need for a unified vertical navigation reference has never been greater. Current reliance on barometric altimetry and manual pressure reference adjustments complicates operations, reduces efficiency, and carries a risk for human errors. Green-GEAR therefore aims to revolutionise vertical navigation by exploring the feasibility of adopting geometric altimetry across all flight phases. This system uses a single common reference point for aircraft altitude, enabling seamless integration between traditional and emerging airspace users.
The project focusses on traffic in the Terminal Manoeuvring Areas (TMAs) around major airports and examines two potential methods for implementing geometric altimetry for vertical navigation: (i) a defined lateral path with vertical separation provided by geometric height constraints at waypoints, with minimal changes to current airspace or instrument flight procedures; and (ii) a defined lateral and vertical path, with vertical separation assured against the geometrically-constructed flight path as a form of Vertical Required Navigation Performance (V-RNP). This would enable Instrument Flight Procedures (IFPs) to be constructed and separated much more efficiently in three dimensions than today, maximising the benefits of airspace and procedure design while constraining the aircraft’s vertical profile on the other hand. Still overall benefits are expected for safety (reducing workload and potential for human error), the environment (overall fuel savings and lower noise emissions), capacity and efficiency (maximisation of airspace use).
Geometric altimetry is also the expected enabler for reducing vertical separation minima in cruise, where the project proposes transitioning from 1000 ft to 500 ft minimum vertical separation within the so-called Reduced Vertical Separation Minima (RVSM) airspace. This would increase airspace capacity and thus contribute to avoiding increased emissions through longer routings or flight at unfavourable altitudes. This is especially beneficial when trying to avoid climate-sensitive portions of airspace, where the traffic demand in the vicinity increases.
Unlike barometric altimetry, geometric altimetry maintains high accuracy far above the altitudes that are relevant for conventional aviation, allowing an upward extension of RVSM airspace up to FL 600. The concept supports both civil and military aviation and facilitates the integration of advanced aircraft, such as Unmanned Aerial Systems (UAS) and High-Altitude Operations (HAO) aircraft, enhancing overall air traffic management efficiency and environmental sustainability. The project, however, will focus on the safety aspects, including the collision and wake turbulence risks, using the European RVSM region as a test case.
The third topic tackled by Green-GEAR is a modification of the existing en-route charging scheme, which collects charges proportional to the costs of providing en-route Air Navigation Services (ANS) from airspace users (AU). Not only does it fail to incentivise environmentally friendly practices, but practical observations actually show flight inefficiencies resulting from the route charging scheme itself (e.g. detours due to differences in local costs, so-called unit rates). The ‘Green Route Charging’ (Green RC) Solution makes use of the fact that the current regulations allow for the modulation of charges to incentivise desired behaviours; it introduces a scalable, two-step implementation process designed to modulate en-route charges. Initially, it focuses on reducing CO2 emissions and alleviating congestion by adjusting charges to promote efficient and eco-friendly flight paths. Ultimately, it aims to address the impacts of non-CO2 emissions as well.
Green RC has the potential to enhance flight environmental efficiency by encouraging sustainable trajectory planning, and by eliminating existing route inefficiencies. It maintains revenue neutrality for Air Navigation Service Providers (ANSPs) and overall cost neutrality for airspace users by recalibrating charges, and adheres to applicable ICAO guidelines.
