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7 C H A P T E R 2 This chapter describes the types and functions of commonly used airport GSE and their emis- sions characteristics. Most airport GSE operated on the airside of the airport are typically associated with the servicing of aircraft during the ground-based, airport turnaround process. During this period, there are a number of tasks that are performed using GSE including, but not necessarily limited to, the following (listed in alphabetical order): â¢ Aircraft maintenance and cleaningâincluding engine and fuselage repairs, waste-water and garbage removal; â¢ Aircraft maneuveringâincluding moving aircraft out of a gate, to/from maintenance areas, etc.; â¢ Aircraft refuelingâincluding fuel transfer from fuel trucks or fuel hydrant systems; â¢ Airfield maintenanceâincluding grass mowers, pesticide applicators, and paint stripers; â¢ Deicing and snow removalâincluding aircraft deicing vehicles, snow scoops and plows, etc.; â¢ Emergency responseâincluding aircraft rescue and firefighting (ARFF) vehicles, ambulances and police cars; â¢ Moving payloadsâincluding loading, unloading, and transporting of passengers, baggage and/or cargo; and â¢ Restocking of provisionsâincluding food, beverages, potable water, and lavatory chemicals. Notably, airport GSE typically do not comprise the following: construction vehicles and equipment (i.e., dozers, scrapers, haul trucks, etc.); airport staff fleet vehicles; and airport patron, employee, and cargo GAV that travel to, from, and move about the landside of the airport (i.e., private motor vehicles, hotel vans, public buses, etc.). Representative illustrations and summary descriptions of airport GSE types and functions are provided in alphabetical order. Notably, these types of GSE are limited to powered GSE and do not include non-motorized equipment such as baggage carts, fuel carts, storage tanks, etc., which are typically towed by motorized GSE. For ease of understanding, airport GSE are listed in Table 1. 2.1 GSE Emissions Characteristics This section provides an overview of the types of emissions generated by conventionally fueled airport GSE, pertinent governmental regulations and programs governing their control, and the utility of alternatively fueled vehicles and equipment. 2.1.1 Types of Emissions In general terms, the types of emissions generated by conventionally-fueled airport GSE are comparable to those of other types of motorized vehicles and equipment that burn gasoline and GSE Types, Functions, and Emissions ReferenceâACRP Report 78 contains useful information and data that are translatable to this initiative.
8 Improving Ground Support Equipment Operational Data for Airport Emissions Modeling Aircraft Tractor Aircraft tractors (i.e., pushback and/or tow tugs) as- sist with aircraft movements when an aircraft cannot operate its engines, or does not have sufficient ma- neuverability to move and turn under its own engine power. Most frequently used to push an aircraft back from the gate and onto the aircraft movement area (e.g., taxiway). May also be used to move an aircraft to other locations on an airport (e.g., maintenance hangars). There are two types of pushback tugs/tractors: (1) conventional tugs use tow-bars that are connected to an aircraftâs noise wheel, and (2) towbarless tractors scoop up the aircraft noise wheel and lift it off the ground before moving. Air Conditioner Also referred to as air carts, these units provide condi- tioned (i.e., cooled and heated) air to parked aircraft when their main engines and auxiliary power units (APUs) are off. They are commonly utilized at non- contact gates, or when fixed-gate or centralized pre- conditioned air (PCA) units are not present. Air Start An air start unit delivers compressed air to an aircraft to help start the engines during instances when the on-board APU is not operational or there are no other means for starting the engines. Baggage Tractor Baggage tractors are among the most common and recognizable type of GSE at an airport. Baggage trac- tors are typically used to move carts containing pas- senger baggage and/or cargo between aircraft gated on the apron and terminal baggage processing facili- ties. (See also cargo tractor.) Belt Loader Belt loaders serve to facilitate the loading and unload- ing of baggage and other payloads between an air- craftâs baggage/cargo compartments and the bag- gage/cargo carts. Boarding Stairs Whether towed, pushed, or driven into position, boarding stairs provide a means of loading and un- loading passengers at hardstands (i.e., remote parking positions) and in the absence of jet bridges at the air- port terminal gate. Table 1. Airport GSE.
GSE Types, Functions, and Emissions 9 Cabin Service Truck Cabin service trucks are designed to provide services and supplies to the aircraft main cabin while parked at the gate. Typically used to deliver beverage and food carts but also used to remove trash and other used materials. They are equipped with a hydraulic lifting system to move the storage compartment to the desired height of the aircraft access door. Most cabin service trucks are equipped and registered to operate both on the airport site and on public roadways (see also catering truck). Cargo Tractor Similar in design and utility to baggage tractors, cargo tractors GSE are used primarily to tow cargo carts from one aircraft or airport location to another. Catering Truck Similar in design and utility to cabin service trucks, catering trucks provide services and supplies to the aircraft main cabin while parked at the gate. Typical- ly used to deliver beverage and food carts but also used to remove trash and other used materials, most catering trucks are equipped and registered to operate both on the airport site and on public roadways. Container Loader Container loaders are highly specialized equipment designed to load and unload cargo containers, pallets, and other vessels from the aircraft cargo hold to a cargo cart or dolly and vice versa. Equipped with pneumatics and rollers to aid in moving the payloads both horizontally and vertically onto and off from the carts, they sometimes also are used to move the cargo containers from one location to another. Container Transporter Similar in design and utility to a container loader, container transporters are used primarily to transport cargo containers, pallets, and other vessels between aircraft or between aircraft and other areas of the air- port. Deicer Deicers are specially designed vehicles equipped with booms or cherry pickers that are used to store, transport, heat, and spray deicing fluid on an aircraft exterior to reduce and/or eliminate ice and snow pri- or to departure. Typically, these GSE contain two en- gines: one to power the vehicle and one to heat the deicing fluids. (continued on next page)
10 Improving Ground Support Equipment Operational Data for Airport Emissions Modeling Table 1. (Continued). Emergency Vehicles Vehicles and equipment designed to respond to and address medical, fire, or other emergencies, including fire trucks, ambulances, and police cars. Fork Lift Commonly used in industrial, manufacturing, and warehousing settings, fork lifts also are used at air- ports to move and transfer cargo form aircraft cargo compartments to other aircraft and locations at the airport (and vice versa). Fuel Truck Self-contained tanker trucks with pumps, filters, hos- es, and valves designed to transport fuel from the air- port fuel storage facility to the aircraft and dispense fuel into the aircraft fuel tanks. Also known as refuel- ers. Glycol Recovery Vehicle Specially designed trucks equipped with a vacuum system and storage tank for the recovery of excess air- craft deicing fluids that collect on the airport aprons, taxiways, and/or designated deicing pads. Ground Power Unit A ground power unit (GPU) is a fuel-powered genera- tor designed to provide electricity to an aircraft when it is parked on the ground and its main engines and on-board APU are off. Heater Specially designed heaters used to heat aircraft en- gines in cold climates to help prevent the freezing of lubricants and other fluids. Also used to heat aircraft cabins and cockpits when the main engines and APU are not operating. A cart equipped with a motor, vacuum device, and storage tank for the recovery of fuel that collects in the hydrant system underground vaults. Hydrant Pit Cleaner
GSE Types, Functions, and Emissions 11 Table 1. (Continued). Hydrant Truck A specially designed truck equipped with pipes, valves, and filters to transfer fuel from the fuel hydrant sys- tem into the aircraft fuel tanks. Lavatory Service A vehicle designed for, and equipped with, a collection system and storage tank for the recovery and transport of aircraft lavatory wastes. Also used to re- plenish the disinfecting chemicals into the aircraft lavatory system. A vehicle designed for, and equipped with, a transfer system (i.e., pipes/hoses, filters, pumps) and storage tank for the provision of water to an aircraft. Maintenance Vehicle A utility truck designed to transport personnel, tools, and equipment to the aircraft for maintenance and repairs. Passenger Bus Buses and other similar vehicles are sometimes used to transport passengers and employees between air- craft and terminals on the airside. Also referred to as people movers and mobile passenger lounges. Snow Removal Equipment Various forms of vehicles and equipment used to re- move snow and ice from runways, taxiways, and ramp areas. Can include loaders, plows, sweepers, and blowers. Used for the collection and removal of dirt, debris, and other objects from runways, taxiways, and aprons that could damage aircraft engines. May include sweepers, vacuum systems, and air blowers. Water Service Source: ACRP Report 78: Airport Ground Support Equipment (GSE): Emission Reduction Strategies, Inventory, and Tutorial. 2013. Sweepers
12 Improving Ground Support Equipment Operational Data for Airport Emissions Modeling Figure 1. GSE emission types. 8 The U.S. EPA âcriteriaâ pollutants are pollutants for which there are National Ambient Air Quality Standards (NAAQS) such as carbon monoxide (CO), lead (Pb), ozone (O3), etc. In the case of O3, precursor pollutants include volatile organic compounds (VOCs) and nitrogen oxides (NOx). 9 HAPs are pollutants for which there are no NAAQS, but are regulated and of concern in connection with their potential effects on human health; HAPs comprise air pollutants such as benzene, naphthalene, toluene, etc. 10 GHGs are pollutants that are of concern because of their role in climate change and include carbon dioxide, methane, etc. diesel as an energy source. For computing airport emission inventories, these types of emissions most often associated with GSE comprise the U.S. EPA âcriteriaâ pollutants8 (and their precur- sors), but can also include hazardous air pollutants9 (HAPs) and/or greenhouse gases10 (GHGs). Figure 1 provides a summary listing of these types of emissions as they pertain to airport GSE. As discussed in Chapter 3, the amounts of emissions are typically expressed as the mass (i.e., weight) of pollutants generated over a specified timeframe (i.e., day or year) or activity level (i.e., number of aircraft operations, passengers, etc.). 2.1.2 Emissions Standards The U.S. EPA, under the federal CAA, is provided the underlying authority for the regulation of air emissions from the vast majority of man-made emission sources, including those clas- sifiable as airport GSE. Commonly, airport GSE are also further classifiable under two sub-categories of mobile sources: â¢ On-road vehiclesâVehicles that are licensed to travel on public roadways including automobiles, vans, trucks, buses, etc. For airport GSE, these are mostly limited to catering and cabin service trucks. â¢ Nonroad vehiclesâVehicles and equipment that are not intended to be registered or operated on public roadways. This category broadly includes aircraft, watercraft, locomotives, recreational vehicles, construction vehi- cles, farm equipment, etc. For airport GSE, this represents the vast majority of vehicles and equipment and comprises baggage tugs, belt loaders, push- back tractors, etc. The emissions standards for on-road vehicles are typically much more stringent (i.e., having much lower allowable emission rates) when compared to nonroad vehicles and equipment. NoteâThe vast majority of airport GSE are classified as nonroad equipment and vehicles. This dis- tinction applies to their intended range as well as their emissions characteristics, both of which differ significantly from on-road vehicles.
GSE Types, Functions, and Emissions 13 Importantly, the CAA preempts individual states from adopting or enforcing their own on-road and nonroad emission standards, with California being the only exception. Table 2 lists and summarizes the primary federal statutes and programs relevant to the control of emissions from airport GSE. 2.1.3 Emissions Standards for Nonroad Vehicles and Equipment For the purposes of regulating exhaust emissions from nonroad vehicles and equipment, the U.S. EPA has also subdivided these engines into two broad classes. â¢ Compression ignition (CI) enginesâAlso known as diesel engines and typically fueled with diesel fuel, power is derived from the compression and instantaneous combustion of the Citation Title Airport GSE Relevance CAA Title II: Part A: Motor Vehicle Emission and Fuel Standards 202 â Emission Standards for New Motor Vehicles or New Motor Vehicle Engines 211 â Regulation of Fuels 213 â Nonroad Engines and Vehicles - Sets engine exhaust emission standards for on-road vehicles (cars, vans, catering vehicles, etc.) - Sets limitations on the use of additives, and the levels of certain compounds, including sulfur, in motor vehicle fuels - Sets engine exhaust standards for nonroad vehicles (e.g., belt loaders, tow tugs, forklifts, etc.) Energy Policy Act of 2005 National Clean Diesel Emissions Re- duction Program, also called the Die- sel Emission Reduction Act (DERA), and the SmartWay Program Provides funding assistance to support the deployment of EPA-verified and certified technologies to reduce diesel-related emis- sions Vision 100 Cen- tury of Aviation Reauthorization Act: FAA VALE Program 121 â Low-Emission Airport Vehicles and GSE 158 â Emission Credits for Air Quali- ty Projects 159 â Low-Emission Airport Vehicles and Infrastructure Provides funding for alternative-fueled GSE vehicles as well as low-emission equipment and infrastructure 40 CFR 85 Control of Air Pollution from Mobile Sources Contains emission performance warranty and other information for engines used in on-road vehicles, including airport GSE 40 CFR 86 Control of Emissions from New and In-Use Highway Vehicles and En- gines Contains exhaust emission standards for en- gines used in on-road vehicles, including air- port GSE 40 CFR 88 Clean Fuel Vehicles Contains exhaust emission standards for cen- trally fueled fleets such as on-road airport GSE in certain nonattainment areas 40 CFR 89 Control of Emissions from New and In-Use Nonroad Compression Igni- tion Engines Contains exhaust emission standards (Tiers 1, 2, and 3) for compression ignition (e.g., diesel) engines used in some nonroad vehicles, includ- ing airport GSE 40 CFR 1039 Control of Emissions from New and In-Use Nonroad Compression Igni- tion Engines Contains exhaust emission standards (Tier 4) for compression ignition (e.g., diesel) engines used in some nonroad vehicles, including air- port GSE 40 CFR 1048 Control of Emissions from New, Large Nonroad Spark Ignition En- gines Contains exhaust emission standards for large spark ignition (e.g., gasoline) engines used in some nonroad vehicles, including airport GSE 40 CFR 1060 Control of Evaporative Emissions from New and In-Use Nonroad and Stationary Equipment Contains evaporative emission standards for nonroad engines, including those used in air- port GSE 40 CFR 1068 General Compliance Provisions for Engine Programs Contains basic compliance requirements for engines, including those used in airport GSE CAA â Clean Air Act CFR â Code of Federal Regulations GSE â ground support equipment Table 2. Federal regulations applicable to airport GSE emissions.
14 Improving Ground Support Equipment Operational Data for Airport Emissions Modeling fuel/air mixture. GSE with CI engines are usually used for moving large payloads and include aircraft tractors and cargo loaders. Emission standards for nonroad CI engines have been established for car- bon monoxide (CO), non-methane hydrocarbons (NMHC), oxides of nitro- gen (NOx), particulate matter (PM), and smoke output. EPA has organized these emissions standards into classes (or tiers) based on the date of manufac- ture and rated engine output (e.g., horsepower), with greater stringency (i.e., lower emissions) associated with increasing emission control levels (i.e., tier 0 < 1 < 2 < 3 < 4) over time. These emission standards and associated require- ments are directed primarily at engine manufacturers, but the owners/operators also bear some responsibilities. For example, manufacturers of nonroad CI engines must produce and offer for sale engines that meet the appropriate tier levels of emission standards and provide the necessary maintenance instruc- tions and servicing procedures for the engine owner or operator to follow. Similarly, it is the responsibility of the owner/operator to follow the manufacturerâs main- tenance instructions, thus enabling the engine to perform as designed and meet the appli- cable emission standards. These regulations also prohibit the disabling of emission controls on an engine or equipping an engine with an emissions defeat device. Since 2010, nonmilitary owners and operators of CI nonroad engines and equipment must also use ultra-low sulfur diesel fuel. â¢ Spark ignition (SI) enginesâAlso known as gas engines and typically fueled with a more volatile fuel, such as gasoline. Power is derived from the ignition of the fuel/air mixture with a spark plug. GSE with SI engines are usually used for moving lighter payloads and include baggage tugs, service trucks, etc. The federal emission standards for SI nonroad engines have been promulgated for equip- ment produced after 2004. They are also tiered to reflect increasing emissions controls over time based on the date of manufacture and horsepower, but include both exhaust emissions standards and evaporative emissions standards. As with CI engines, the emissions standards and associated requirements are directed primarily at engine manufacturers, but the ultimate owner or opera- tor does have some responsibilities related to emissions. Again, manufac- turers of SI nonroad engines must produce and offer for sale engines that meet the appropriate level of emissions standards and provide the necessary maintenance and servicing procedures. Similarly, it is the responsibility of the owner/operator to follow the maintenance and service instructions. Fuel regulations require that in those parts of the United States with the worst air quality, SI engines must use reformulated or oxygenated gasoline to help reduce the formation of air pollutants. With the emergence of alternative fuels and technologies, other fuels now are becoming more commonly used with airport nonroad GSE as discussed in Section 2.1.7. 2.1.4 Emissions Standards for On-Road Vehicles Emissions standards for on-road vehicles apply primarily to exhaust (i.e., tailpipe) emissions as well as evaporative emissions and are largely a function of the vehicleâs age (i.e., date of manu- facture), class of vehicle, type of fuel, and capacity and type of engine. As with nonroad engines, engines used in on-road vehicles may be either CI or SI. As with nonroad vehicles, the newer on-road vehicles have more restrictive emissions standards than the older, preceding models. In air quality nonattainment areas, owners or operators of centrally fueled fleets may be required to participate in the U.S. EPAâs clean fuel fleet program requiring the use of low-emission NoteâThe most commonly used and recognizable GSE at most airports are baggage tugs, which are largely powered by CI engines burning gasoline. ReminderâAccording to ACRP Report 78, nearly 40% of the nationwide GSE fleet have SI engines (i.e., are gas-powered) and about 35% have CI engines (i.e., are diesel-powered).
GSE Types, Functions, and Emissions 15 vehicles (40 CFR 88). Additional standards apply to fuels, fuel additives, and fueling, particularly limitations on volatile components, sulfur, and certain toxic compounds such as benzene (40 CFR 80). In those nonattainment areas having a motor vehicle inspection/maintenance (I/M) program to reduce emissions, the vehicle owner/operator is responsible for meeting the stateâs requirements for periodic inspection and maintenance. These types of vehicles may be fueled by a variety of types of fuels, including conventional petroleum-based fossil fuels such as gasoline and diesel, and cleaner-burning fuels such as natu- ral gas, propane, ethanol, methanol, biodiesel, hydrogen, electricity, and other fuels. 2.1.5 Emissions Standards in the State of California As noted, California presents an exception to the federal preemption of state emission standards for on-road and nonroad mobile sources. For example, Section 209(e) of the CAA allows Califor- nia to adopt and enforce standards and other requirements relating to the control of emissions from nonroad engines or vehicles (other than construction or agricultural engines or vehicles smaller than 175 horsepower and locomotive engines), the only stipulation being that the Cali- fornia standards are at least as protective of public health and welfare as the applicable federal standards. In addition, other states may choose to adopt the California standards. Consequently, the California Air Resources Board (CARB) has adopted emissions standards that apply to both CI and SI nonroad engines and vehi- cles. Of particular importance to owners/operators of GSE in California is the In-Use Offroad Diesel Vehicle Regulation (13 CCR Article 4.8 Sections 2449, 2449.1, 2449.2, and 2449.3) originally adopted in July 2007. In December 2010, CARB amended the regulation so that owners/operators of nonroad CI vehicles greater than 25 horsepower (including GSE) are required to reduce emissions of diesel PM and NOx. Importantly, these vehicles are subject to âfleet averagingâ to meet the emissions standards that can be accomplished, if necessary, by engine retro- fits or fleet turnover. The standard also requires enforcement of a 5-minute idling restriction as well as other requirements. The initial compliance date for the largest fleets was 2014, and smaller fleets have later compliance dates. 2.1.6 FAAâs Voluntary Airport Low Emission (VALE) Program Because of its relevance to airport GSE emissions, the FAA VALE program is further discussed here. Under the Vision 100 Century of Aviation Reauthorization Act, the FAA VALE program is intended to offer financial and regulatory incentives to airports to reduce emissions of air emis- sions voluntarily in geographical locations of the United States that are classified by the U.S. EPA as being nonattainment (or maintenance) with respect to the National Ambient Air Quality Standards (NAAQS). While numerous types of airport projects are eligible for grants under the VALE program, generally it focuses on alternative-fueled GSE vehicles and low-emission technology infrastruc- ture. GSE acquired through the VALE program can be owned by the airport and made available for use (e.g., leased) by another operator, such as an airline or fixed-base operator (FBO) that is a tenant at the airport. The VALE program also permits an entity other than the airport, such as a tenant airline or FBO, to acquire and use alternatively fueled GSE, but that entity must commit to certain restrictions with regard to the use and disposition of the equipment. NoteâCalifornia-based emissions standards for mobile sources such as airport GSE are a special case that is unique across the United States. Guidebook users are advised to refer to CARB for information and data on airport GSE emissions characteristics in that state.
16 Improving Ground Support Equipment Operational Data for Airport Emissions Modeling 2.1.7 Alternatively Fueled GSE The use of alternatively fueled and electric-powered GSE is swiftly emerging as an option to conventionally fueled (i.e., gasoline and diesel) GSE at many airports. Presently, the primary alternative fuels known to be used in GSE include compressed natural gas (CNG), liquefied petroleum gas (LPG, also known as propane), ethanol, and biodiesel. These alternative fuels typically generate lower air emissions than the conventional fuels, particularly with respect to CO and PM. Electric-powered GSE generate almost no emissions on-site but have some air qual- ity impacts when accounting for off-airport electric power generation impacts. A more detailed discussion of benefits and challenges of alternatively fueled GSE is presented in ACRP Report 78.