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operational models (i.e. SIMMOD) and the databases shown in Table A1-5 ( Taxi Time Input Data Sources ). 

<img src='content_image/520059.jpg'>

Source: FAA; and BTS, 2013. 

## A1.3.4 Emission Factors 

EDMS/AEDT contains a database of aircraft engine emission factors for CO, NO$_{x}$, PM, SO$_{2}$, and VOCs based on engine make and model for each of the four engine operating modes ( i.e., taxi/idle, takeoff, climb out, approach). These emission factors are based on the ICAO Engine Exhaust Emissions Databank 10 , manufacturer data, and for older aircraft, data contained in EPA’s AP-42, Volume II, Section 1. 11 

Notably, EDMS/AEDT estimates aircraft main engine PM emissions only for aircraft with ICAO certified engines using the First Order Approximation FOA3/FOA3a methodology (see Section A1.2 , EPA Methodology ). 

EDMS/AEDT does not report Pb emissions directly, but many users calculate Pb emissions as a post-processing step to running EDMS /AEDT. Thus, one should use EDMS’s/AEDT’s fuel consumption information (only for GA aircraft piston engines that use Avgas) coupled assumptions of how much Pb is in the fuel and how much Pb remains in the engine Equation A1-4 , Lead Emission Calculation ). 

Generally, aircraft engine emission factors are expressed as grams of pollutant emitted kilogram of fuel burned or pounds of pollutant per 1000 pounds of fuel consumed. When these are multiplied by the fuel flow rates in kilograms per second or pounds per second, emission rates in grams-per-second or pounds-per-second, respectively, are produced. 

