Advanced emission model

The advanced emission model (AEM) is a stand­alone application, developed and maintained by our Innovation Hub in Brétigny, that estimates aircraft engine emissions and fuel burn. In addition to this, AEM analyses flight trajectory data on a flight by flight basis, for air traffic scenarios of almost any scope, from local studies around airports to global aircraft emissions, from gate-to-gate.

AEM can estimate:

• the mass of fuel burned by the main engines of a specified type of aircraft with a specified type of engine flying a specified 4D trajectory;
• the corresponding masses of certain gaseous and particulate emissions which are produced by the burning of that fuel.

It estimates a set of 23 pollutants, including carbon dioxide (CO₂), water vapour (H₂O), the oxides of nitrogen (NOx) and sulphur (SOx), unburnt hydrocarbons (HC), carbon monoxide (CO), volatile organic compounds (VOCs), particulate matters (PMs) and other organic gases (OGs), using the up-to-date methods (BFFM2, MEEM).

AEM is a C++ software suite available for Windows and Linux Red Hat operating systems. It includes a multi-processing calculation tool, available through the command line or a GUI, a geo-filtering preparation tool, and a C++ dynamic library through a DLL API. This enables embedded calculations in other systems, either directly or through a dedicated AEM Python wrapper. The AEM software suite processes text or Parquet files. The AEM python wrapper includes pandas, PyArrow and Dask libraries.

Below 3,000 feet, the fuel burn calculation is based on the landing and take off (LTO) cycle defined by the ICAO Engine Certification specifications. The ICAO LTO cycle covers four modes of engine operation. They are used in AEM to model the following six phases of operation: taxi-out, taxi-in (idle), take-off, climb-out, approach and landing (approach).

The ICAO aircraft engine emissions databank (AEED) for turbofan and turbojet engines, combined with the FOCA databank for pistons (and potentially FOI for turboprops), provides emission indices and fuel flow for a very large number of aircraft engines. The AEM links each aircraft appearing in the input traffic sample to one of the engines in the AEED.

Above 3,000 feet, during the climb, cruise, descent (CCD) phases of flight, the fuel burn calculation is based on EUROCONTROL’s Aircraft Database (BADA). Emission calculations are based on the AEED, but emission factors and fuel flow are adapted to the atmospheric conditions at altitude by using a method initially developed by Boeing (The Boeing Fuel Flow Method 2 – BFFM2). BFFM2 makes it possible to estimate emissions for the NOX, HC, and CO pollutants.

The emissions for the H₂O and CO₂ pollutants are a direct result of the oxidation process of the carbon and hydrogen contained in the fuel with the oxygen contained in the atmosphere. The SOX emissions depend directly on the sulphur content of the fuel used. All three are directly proportional to the amount of fuel burnt. The mass of volatile organic compounds (VOCs) and other organic gases (OGs) are proportional to the mass of unburnt hydrocarbons (HC) produced. Particulate matter (PM) emissions result from the incomplete combustion of fuel.

Since 2000, EUROCONTROL has developed a series of models to support its Member States and, by extension, the entire aviation community, in estimating the magnitude of the environmental impacts that current or future air traffic movements might have. These models have already been significantly improved upon, given that knowledge on aviation and environment modelling has grown and computing technologies evolved.

The current environmental tool suite of EUROCONTROL is composed of three main models: Advanced emission model (AEM), Open-ALAQS, and Impact.

All three of these models successfully passed ICAO’s stress tests in 2008-2009 and have since become part of the approved suite of assessment models used by ICAO’s Committee on Aviation Environmental Protection). These models are designed to assess future regulatory policy options such as introducing tighter aircraft noise and emissions standards and future trends.

AEM, Open-ALAQS and IMPACT are also the recommended models for conducting environmental impact assessments in SESAR.