The reduction in fuel burn and related CO2 emissions continues to be the overriding factor in engine technology developments. However, the higher temperatures and pressures needed for improved fuel efficiency often have a trade-off in the form of increased emissions of nitrogen oxides (NOX) unless mitigated through the design of the engine and control of the combustion process. The engine NOX and nvPM standards26, and the aircraft noise and CO2 standards, define the design space for products to simultaneously address noise, air quality and climate change issues.
26ICAO Annex 16 Volume II contains international aircraft engine emissions standards.