APPENDIX A3$_{ }$ APPENDIX A3 - Ground Support Equipment Emissions  Inventory for Criteria Pollutants A3.1  Overview  This appendix discusses the methodologies for computing emissions from ground support  equipment (GSE). GSE is a term used to describe the vehicles that service aircraft after arrival  and before departure (i.e., while aircraft are unloading and loading passenger s and/or freight).  Emissions from these sources are based on the number and type of equipment used to service  each aircraft along with the amount of time the equipment is in use per aircraft landing -takeoff  (LTO) cycle and the equipment fuel type.  There are a wide variety of GSE that service  aircraft; a list of the most common GSE types,  along with a brief description, follows:  • Air Start Units  — Provide large volumes of compressed air to an aircraft’s main  engines for starting. Air start units are also called air compressors.  • Air Conditioning Units  — Provide conditioned air to ventilate and cool parked  aircraft.  • Aircraft Tugs/Tractors  — Tow aircraft in the terminal gate area or on the tarmac.  They also tow aircraft to and from hangers for maintenance. These are broken into  two categories: tugs/tractors for narrow body aircraft and tugs/tractors for wide body  aircraft.  • Baggage Tugs/Tractors  — Equipment used at airports to haul baggage between the  aircraft and the terminal.  • Belt Loaders  — Mobile conveyor belts used at airports to move baggage between the  ground and the aircraft hold.  • Buses  — Shuttle personnel between facility locations.  • Cargo Moving Equipment  — Variety of types of equipment employed to move  baggage and other cargo around  the facility and to and from aircraft. This category  includes forklifts, lifts, and cargo loaders.  • Deicers  — Vehicles used to transport, heat, and spray deicing fluid.  • Ground Heaters  — Mobile units that provide heated air to heat the parked aircraft.  • Ground Power Unit (GPU)  — Mobile ground-based generator units that supply  aircraft with electricity while they are parked at the facility. GPUs also are called  generators.  • Light Carts  — Mobile carts that provide light.  • Other  — Small miscellaneous types of equipment commonly found at facilities such  as compressors, scrubbers, sweepers, and specialized units.  • Pickups  — Move personnel and equipment around the facility.  13$_{ }$