Analysis of the Environmental Benefit of RVSM

Author: Frank Jelinek, Analysis and Scientific Centre of Expertise for Business Area Society, Environment & Economy

Following the implementation of RVSM in the EUR RVSM airspace in January 2002, the "Environmental Studies" Business Area of the EUROCONTROL Experimental Centre performed an additional analysis focusing on the environmental aspects for the EUROCONTROL RVSM programme office.

The objective of this study was to test the hypothesis that the implementation of RVSM leads to reduced aviation emissions and fuel burn, since RVSM offers the possibility to optimise flight profiles due to the availability of six additional flight levels.

For this purpose, the Advanced Emission Model (AEM3), developed at the EUROCONTROL Experimental Centre was used to estimate fuel consumption and emissions for a series of air traffic scenarios. AEM incorporates the EUROCONTROL modified Boeing Method 2 (EEC-BM2), which added improved realism to the estimation of in-flight Oxides of Nitrogen (NO_x) emissions.

Traffic from 3 days just before RVSM implementation was compared with 3 traffic days just after implementation of RVSM. An additional 3 days from July 2002 were compared with the January traffic data.

The traffic data used in the study was Correlated Position Report (CPR) radar data provided by the EUROCONTROL Central Flow Management Unit (CFMU).

The results obtained from this study support the initial hypothesis that RVSM lead to environmental benefits. From the very first days of RVSM implementation a clear trend develops with increasing environmental benefit until July. From July the results are stable and it can be concluded that RVSM implementation led to significant environmental benefit. Total NO_x emissions are reduced by 0.7 – 1%. This represents about 3500 tons per year less NOx emitted by aviation into the atmosphere. Sulphur oxide emissions have been reduce as a result of the introduction of RVSM by around 260 tons per year.

Total fuel burn, CO₂ and H₂O emissions are reduced by 1.6 –2.3%.

This above qualitative figure of about 2% reduced fuel burn translates into reduced cost for airlines operating in the EUR RVSM area for up to 310.000 tons of fuel on a yearly base.

The environmental benefit is even more positive for the high altitude band along and above the Tropopause between 8 and 10 kilometres. Whereas in the Troposphere (below the Tropopause) a negative temperature gradient assures dispersion and mixing processes, the Stratophere above the Tropopause is characterised in its lower parts by a constant temperature. Mixing processes and dispersion are less important. Emitted pollutants stay longer and chemical reaction processes have longer time to impact the atmosphere.

At these flight levels NO_x emissions are reduced by as much as 2.3 - 4.4%, fuel burn and directly proportional emissions like CO₂, SO_x and especially H₂O are reduced by 3.5 – 5.0%.

This is an important benefit for the environment, since these atmospheric layers are most sensitive to aviation NO_x and H₂O emissions.

A complete version of the study report will be made available during April 2003 on the EUR RVSM airspace programme site.

Future

After the work on RVSM and the Free Route Airspace project (FRAP), further studies on the potential environmental benefit of the Meditereanean Free Flight project (MFF) and the Flexible Use of Airspace (FUA) are planned for 2003 to further consolidate the potential contribution of ATM to the goals defined by the Kyoto protocol.

A validation campaign with operational airline data aims to further consolidate the AEM3 model on fuel burn and emission results.

Integration of a Meteorology model and atmospheric reaction models will complete the AEM3 to evolve into the Toolset for Emission analysis (TEA).