Aviation background

The aviation sector is a fast growing sector of Europe’s economy and is associated with a wide range of economics and social benefits. However one of the most important drawbacks of the anticipated rate of growth of air transport, despite new deployed technologies, is the environmental impacts.

European demand for air transport is anticipated to grow continuously until 2050 and beyond. Sustainable mobility is required to satisfy this growth and it is essential that travel remains safe, secure, fast, affordable and environmentally friendly.

Industrial competition is fierce, not only from established world regions but also from new, strong challengers. In this context, there is more to be done in the regulatory field within and outside Europe to ensure a global level playing field in the sector.

ACARE and Flightpath 2050 are part of a comprehensive family of initiatives in aeronautics and air transport including the EC’s Framework Programme research FP6, FP7 and Horizon 2020, as well as the SESAR Joint Undertaking. Clean Sky is the vital part of that wide-ranging set of Eurocentric initiatives with a focus on fostering new technologies that will make tomorrow's aircraft greener and more efficient. Clean Sky 2 is setting its sights for the even more stringent environmental challenges of commercial flight in the 2025 to 2050 timeframe

Why PM is important?

Emissions from aircraft have adverse effects on the air quality in and around airports, contributing to public health concerns within neighbouring communities. Therefore, the evaluation of aircraft emissions and dispersion is an important part towards ensuring that local air quality standards in and around airports are not exceeded. Many large airports across Europe are subject to regular assessment of their emissions impact on air quality as a statutory requirement to:

  • meet EU ambient air quality directives;
  • review the impact of planned infrastructural developments;  
  • act as part of a good neighbour-programme.

Particulate Matter (PM) emissions from aircraft engines adversely affect air quality in and around airports, contributing to public health concerns for airport workers and within neighbouring communities.

Scientists and regulators have an increasingly profound understanding of the complex nature of Particulate Matter (PM) in ambient air. PM can be attributed with different properties, dependent of their size and chemical composition from different sources, both natural and anthropogenic. What is less certain, is how PM species and precursors evolve and interact within the atmosphere, and which characteristics of the PM are most harmful to public health. For instance, some particles can form complicated reactions in the atmosphere of chemicals such as sulfur dioxides and nitrogen oxides that are emitted from exhaust engines. Those secondary particles make up the most of fine particles. It is considered that Ultra Fine Particles (UFP), defined as particles of aerodynamic diameter less than 100 nm, may have greater toxicity on an equal mass basis than currently regulated larger particles (PM2.5/PM10 ambient standards) because their vast numbers and small diameters provide a high surface area which is a potentially important toxicological interface. These UFP’s are relevant to civil aviation, and recent studies have shown that aircraft engines emit primary aerosol as non-volatile Particulate Matter (nvPM) as well as secondary aerosol precursor gases such as organic gases, nitrates and sulphates that nucleate within the exhaust plume within this size range. The contribution of UFP from aircraft operations to the ambient concentration in and around airports is therefore largely unknown, and could be significant.

Aircraft particulate emissions, as with emissions of nvPM from other sources, are subject to regulation. Within the current ICAO-CAEP cycle, CAEP/11, a new standard for LTO nvPM mass and number for engine with thrust >26.7kN is being developed, the first standard of its kind. In-production regulatory limit values for nvPM mass and number will be set at a level to allow in production engines to pass and will act as an anti-backsliding standard. However, there remains uncertainty in the methodology surrounding the effects of ambient conditions, fuel composition and sampling system calibration and loss corrections. Furthermore, the regulation does not address the effects on the global atmosphere by excluding cruise conditions and the contribution of nvPM by smaller engines and engines rated on shaft speed. These factors, along with the potential impact of emerging technologies, need to be considered for a future European roadmap for improving current nvPM methodologies and future nvPM measurement technologies and regulation beyond CAEP/11.