240 Estimating the Impact of Reduced Thrust Takeoff on NOx Emissions

Inventories of NOx emissions at airports are becoming increasingly important with many airports forecasting significant growth in the near future. Today's models rely on engine certification data that typically contains emission factors at 4 distinct power levels: 100% (takeoff), 85% (climb out), 30% (approach), and 7% (idle). An engine typically produces greatest NOx at its highest power setting, takeoff, when the fuel flow and combustion temperatures are greatest. However, many aircraft operators do not takeoff at 100% power for a variety of reasons including operating costs and noise abatement considerations. This leads to a potential overestimation of the total NOx at airports. This paper proposes a model for use in estimating the emission factors for aircraft engines operating at a reduced thrust setting during takeoffs. The model employs the widely accepted Boeing fuel flow method 2and illustrates the effect that accounting for reduced power takeoff at an airport has on annual NOx emissions.