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## APPENDIX A1 - Aircraft Emissions Inventory for Criteria Pollutants 

## A1.1 Overview 

This appendix discusses the recommended emissions inventory methodologies, models, and data sources for computing criteria pollutant emissions from aircraft engines. Section 3 ( Sources and Types of Air Emissions ) of the Handbook provides a description of the types of criteria pollutants most commonly associated with aircraft engines and Section 6.1 ( Preparing an Emissions Inventory – Criteria Pollutants ) provides a discussion of the available guidance for preparing and reporting a criteria pollutant emissions inventory for Federal Aviation Administration (FAA) projects/actions. 

For this discussion, three overall approaches, or methods, are addressed and are referred to as the (i) Environmental Protection Agency ( EPA), (ii) Emissions and Dispersion Modeling System (EDMS), and (iii) Aviation Environmental Design Tool (AEDT) methods. First, some common terms and concepts are discussed that apply to all three methods. 

As summarized in Table A1-1 ( Aircraft Uses Categorization ), for emission inventory applications, aircraft are typically categorized by their general use as commercial (including air carrier and cargo), air taxi, general aviation (GA), or military. 

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Source EPA, Procedures for Emission Inventory Preparation, Volume IV: Mobile Sources , December 1992, [EPA-420-R-92- 009]. 

Aircraft engines produce emissions from the combustion of fuel and these emissions depending on aircraft engine type, fuel type, number of engines, power settings, and amount of fuel burned. The criteria pollutants (and their precursors) of primary significance include volatile organic compounds (VOCs), carbon monoxide (CO), oxides of nitrogen (NO $_{x}$), sulfur dioxide (SO$_{2}$), and particulates (PM). 

When computing aircraft engine emissions, it is customary to simulate aircraft activity patterns within the traditional landing and takeoff (LTO) cycle. An LTO cycle consists of the following operational modes: 

• Taxi/idle includes the time an aircraft taxis between the runway and a terminal, and all ground-based delay incurred through the aircraft taxi route. The taxi/idle-delay mode 

