“Fuel Flow Method2” for Estimating Aircraft Emissions

In recent years there has been increasing interest in quantifying the emissions from aircraft in order to generate inventories of emissions for climate models, technology and scenario studies, and inventories of emissions for airline fleets typically presented in environmental reports. The preferred method for calculating aircraft engine emissions of NOx, HC, and CO is the proprietary “P3T3” method. This method relies on proprietary airplane and engine performance models along with proprietary engine emissions characterizations. In response and in order to provide a transparent method for calculating aircraft engine emissions non proprietary fuel flow based methods ^1,2,3 have been developed. This paper presents derivation, updates, and clarifications of the fuel flow method methodology known as “Fuel Flow Method 2”. While not as rigorous as the P3T3 method used for emissions certification, fuel flow methods can give reasonable approximations of emissions on the order of ± 10 to 15% for NOx as compared to the P3T3 method. In depth studies of variation for HC and CO have not been undertaken, though a limited examination of the data indicates a much broader spread, with a range on the low end similar to NOx, while up to almost a factor of two on the high end, depending on engine and thrust rating.