Optimizing the Use of Electric Preconditioned Air (PCA) and Ground Power Systems for Airports (2019)

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25 The objective of this report is to identify and document factors that affect the use or non- use of gate electrification systems and to subsequently present potential solutions to optimize utilization. During the report development, a number of airport stakeholders, airlines, pilots, service providers, and equipment manufacturers provided information to the research team concerning the most commonly observed barriers—or challenges—to electric PCA and ground power utilization. This chapter provides information about the challenges reported and expe- rienced by airports and airlines most frequently, some combination of which are likely to occur at most airports. This report intends to provide information that is general enough to be applicable to a broad range of types and sizes of airports located in varied climates, although individual airports may face additional challenges specific to their unique site, location, or operations—among other factors—that may not be captured in this document. The research team identified a list of 19 challenges, organized into six high-level categories that are listed in Sections 3.1 through 3.6. The six high-level categories include: 1. Training and Communications, 2. Operation of Equipment, 3. Maintenance of Equipment, 4. Resource Constraints, 5. Climatic Factors, and 6. Policy and Regulatory Factors. Many of the challenges are interrelated, and several of them could be considered as differ- ent facets of the same challenge. For example, damaged power cables and kinked hoses are listed as separate challenges, but they are also both symptoms of insufficient training of ground crew. Those two items are listed separately, however, due to the frequency with which they were raised as individual issues by industry stakeholders during the report development. In addition, depending on the airport and underlying causes of each challenge, there may be more than one appropriate solution. This project included development of the Self-Assessment Checklist (an Excel-based tool), designed to be used with guidance from the report. The checklist is intended as a high-level screening tool that serves as a resource for stakeholders to identify their challenges and assess how impactful they are to utilization at a particular location. The 19 challenges are listed in the Self- Assessment Checklist by presumed relative impact on utilization and by relative ease of imple- menting solutions (assigned a number 1 through 19). The specific impact of each challenge on utilization rates will vary at individual airports. The lack of data on historic utilization rates makes specific impacts of each challenge impossible to determine for the purposes of this report. Table 1 depicts the challenges by high-level category and their corresponding number on the Self-Assessment Checklist. The checklist organization and further detailed instructions for its use are described in Section 3.7. Potential solutions to the 19 challenges included in this chapter are described in Chapter 4. The solutions are organized according to high-level category and identified as either short-term or long- term solutions (depending on the relative level of effort and resources required to implement). C H A P T E R 3 Challenges Affecting Gate Electrification System Utilization

26 Optimizing the Use of Electric Preconditioned Air (PCA) and Ground Power Systems at Airports 3.1 Training and Communications Challenges A number of problems identified during the focus groups, case studies, and surveys were attributed to either insufficient training or a lack of communication between affected stake- holders. Related challenges are described in this chapter. 3.1.1 Ground Crew Noncompliance with Airline Standard Operating Procedures Most airlines have established maximum allowable times for ground crews to connect both ground power and PCA systems to aircraft upon arrival at the gate (e.g., within 5 or 10 minutes of aircraft arrival at gate). If ground crew do not connect aircraft in a timely manner, pilots are likely to start and use the APU for the duration of time they are parked at the gate. A quick Challenge Category Challenge Corresponding Solutions (Chapter 4) Challenge Number on Self-Assessment Checklist Training and Communications Compliance with airline standard operating procedures 1, 3–6, 8, 12 1 Insufficient number or training of ground crew 1, 5, 6, 9, 11– 13, 26 5 Lack of communication on equipment availability status and equipment use 1–3, 7, 9, 17, 20, 23, 25 10 Operation of Equipment Kinked or improperly positioned PCA hoses 4–9, 11–13 2 Damaged power cables or PCA hoses 4–13 3 Preset PCA temperatures not aligned with ambient temperatures 23, 32 13 Maintenance of Equipment Inoperable equipment (reasons other than those listed above) 4–7, 9, 10, 13, 15–19, 21, 25 4 Lack of on-site spare parts inventory 15–18, 22 7 Damaged aircraft ground power receptacle 17, 21 8 Clogged aircraft air intake duct 15, 17 17 Resource Constraints Insufficient availability of maintenance personnel 19, 22 6 Insufficient maintenance budget for systems 16, 17, 22, 24, 26, 27, 33 9 Insufficient budget for renewing and/or “right- sizing”a systems 26, 27, 33 11 Lack of electric PCA or ground power at hardstands 1, 3, 27 16 Equipment not individually metered; lack of utilization tracking capabilities 2, 3, 27, 33, 34 18 Climatic Factors Ambient temperatures exceed design standards of PCA system 27, 28, 30–33 12 Weather conditions unsafe for ground crew to connect aircraft 29 15 Policy and Regulatory Factors Short aircraft turn timesb precluding use of PCA and ground power 4, 5, 9, 13, 30 14 Lack of regulatory driver 1–3 19 aRight-sizing is having sufficient capacity to condition the aircraft size presently operating at the terminal gate. bTurn time is the time from when an aircraft arrives at a gate to when it departs. Utilization Challenges Table 1. Challenges affecting PCA and ground power utilization.

Challenges Affecting Gate Electrification System Utilization 27 connection is imperative, particularly for aircraft with short turn times (i.e., the time an aircraft arrives at a gate to when it departs). However, in some cases, if the turn time is extremely short, the pilots may leave the APUs running regardless of how quickly gate electrification equipment is connected. This issue was identified by a majority of the pilot survey respondents (greater than 70 percent) as an issue they have experienced that causes them to use the APU instead of PCA or ground power. This challenge could result from ground crew lacking awareness of the airline’s standard operating procedure for connecting aircraft to gate electrification equipment within a specified time, insufficient numbers of ground crew required for proper connection of the aircraft within a specified time frame, or lack of a mechanism for holding crew accountable for following the standard operating procedures. 3.1.2 Insufficient Availability or Training Of Ground Crew Given the need for rapid connection of ground power and PCA systems to an aircraft, a suf- ficient number of properly trained ground crew must be staffed to service aircraft. Ground crew must be properly trained to operate gate electrification systems in accordance with the manu- facturers’ operating instructions, as failure to do so can lead to premature deterioration of the system components. In cases where ground crew members assigned to connecting systems to the aircraft are not immediately available, pilots will likely start and/or leave the APU running. Airport and airline stakeholders reported that high turnover of ground crew employees is a common occurrence. This results in staff with less overall experience and lack of familiarity with proper operation of the equipment. Inexperienced ground crew operating PCA and ground power equipment result in higher incidences of equipment damage from mishandling. Ensuring proper training can be a challenge when organizations experience high turnover. Ground crew employees also may not be aware of the importance of the use of electric PCA and ground power as an economically and environmentally beneficial alternative to the APU. Lack of awareness of the importance of this strategic objective affects the motivation to ensure proper handling of equipment. In addition, ensuring that ground crew are properly trained can be challenging at airports that have multiple types or models of PCA or ground power equipment, each with differing system configurations and operating procedures. The stakeholders responsible for providing ground crew training on the operation of PCA and ground power and for determining the frequency and content of the training may differ from airport to airport. Airlines develop training programs for their own employees and also utilize third-party service providers. Ground service providers also develop their own training programs, and those companies that service multiple airlines at a single airport report that their staff members are required to satisfy the individual training standards set forth by each airline. Although each group has its own training programs in place, inconsistencies between these pro- grams may lead to confusion and errors. Airports may provide training to airline staff or third-party service providers on the proper operation of airport-owned gate electrification equipment. Some airports reported that they provided training to operators through the equipment manufacturers (on site at the airport and at the manufacturers’ facilities). Some airports reported that even though they own the gate electrification equipment, they do not provide training to airline staff or contractors due to liability concerns (e.g., if such staff subsequently cause damage to airline-owned equipment while operating gate electrification equipment). Instead, airports depend on airlines and contractors to train their ground crews according to equipment manufacturers’ specifications.

28 Optimizing the Use of Electric Preconditioned Air (PCA) and Ground Power Systems at Airports 3.1.3 Lack of Communication Between Parties Concerning Equipment Availability Status and Use of Equipment Consistent and trackable communication with regard to gate electrification system status between ground crew and the maintenance provider is essential for ensuring awareness of system availability, and, therefore, utilization. A lack of effective communication from the ground crew to maintenance personnel with regard to an out-of-service system (or consumable part) can lead to delays in repair. Likewise, a lack of prompt communication from maintenance personnel to the ground crew— either directly or through airport operations or airlines—that the equipment has been restored to service may result in the incorrect assumption by ground crew that it is still out of order. In addition, communication between the ground crew and the airline pilots with regard to system availability status is essential for ensuring system utilization. A lack of effective com- munication from the ground crew to the pilot with regard to system availability and connection status may result in the pilot choosing to start and/or leave the APU running, even when gate electrification equipment is operable. 3.2 Operation of Equipment One of the most frequently cited challenges to optimal system utilization is the misuse of and subsequent damage to the equipment by users. This challenge was identified by all stakeholders as a common problem. Misused or mishandled components become damaged, do not func- tion properly, and require repair and replacement more frequently. Many of these problems are symptoms of another challenge; specifically, ensuring sufficient training for ground crew (system operators). However, because these items were identified repeatedly by stakeholders as separate issues, they are listed in this section. Operator errors can be identified by system owners, through a review of maintenance logs and work orders. Comparison of the frequency of repairs and replacement parts needed with the expected useful life of the equipment is another way for system owners to identify reoccurring errors. Simple observation of ramp operations by the system owners, maintainers, and users also yields insights into this challenge (e.g., PCA hoses or power cables run over by ramp equipment, dragged on the ground, or turned off improperly with the emergency stop button). 3.2.1 Improperly Positioned (“Kinked”) PCA Hose A fold, or kink, in a PCA hose can impede air flow to the aircraft (Figure 12), resulting in insufficient heating or cooling of the aircraft cabin. Pilots reported that they will turn on the APU if the PCA cannot keep aircraft cabin temperatures comfortable for passengers. Hose kinks result from ground crew failure to deploy the proper length of hose (e.g., if too much hose is deployed, kinking is more likely), or ground crew do not ensure that hoses are laid flat when deployed. Hoses can also become kinked when they are not stored properly. Over time, frequent kinking of the hose may result in permanent damage to the component, requiring replacement. 3.2.2 Damaged Ground Power Cable or PCA Hose Ground power cables and PCA hoses can become damaged through normal wear and tear but also as a result of improper use. These consumable items is essential to providing power and conditioned air to the aircraft. If either of these items is not in good operating order, pilots are likely to start and/or leave the APU running. For example, if power cable heads are dropped repeatedly or dragged across the ramp area, the cable heads and connecting pins may become bent or broken and render the cable inoperable. PCA hoses can tear or rip if repeatedly dragged

Challenges Affecting Gate Electrification System Utilization 29 across pavement. In addition, if the items are not retracted and stored properly, they may be subject to damage as a result of being run over by jet bridges or other ground support equipment vehicles on the ramp. 3.2.3 Preset PCA Temperature Settings Not Aligned with Ambient Temperatures Centralized PCA systems provide either chilled water or hot water to cool or heat the air, which is then supplied to the aircraft, ensuring passenger comfort and safety. These systems can be programmed to automatically switch from heating to cooling mode and vice versa. Change- over dates are normally selected based on typical seasonal temperature patterns, although daily temperature may fluctuate in many climate zones, particularly in shoulder seasons. Ambient air temperatures may fluctuate from historical patterns at any time of year, as well, resulting in unseasonably warm or cool days. If centralized PCA system settings are not adjusted to account for these temperature fluctua- tions (either day to day or within a 24-hour consecutive period), the system may be unable to effectively cool or heat the aircraft. In this case, pilots may be required to start and/or leave the APU running to control cabin temperatures better. The level of effort to adjust temperatures in real time may depend on the flexibility of the system controls and programming and presents a greater challenge in locations with highly variable weather. 3.3 Maintenance of Equipment Regularly scheduled preventative maintenance of equipment, as well as rapid return-to- service maintenance when equipment requires repair, is essential to maintaining system operability and ensuring high utilization. The following challenges are related to maintenance topics. 3.3.1 Inoperable Ground Power and/or PCA System Airports, airlines, and pilots all reported that inoperable gate electrification equipment is a persistent challenge affecting utilization. Figure 12. Kinked PCA hose (Source: Seattle–Tacoma International Airport).

30 Optimizing the Use of Electric Preconditioned Air (PCA) and Ground Power Systems at Airports In addition to the specific issues identified in Section 3.2 (kinked hoses and damaged power cables), component failures can occur for a variety of reasons. For example, airports and equip- ment manufacturers reported a reoccurring issue in which ground crew use the emergency shutoff button on equipment instead of shutting the equipment down properly. Over time, this action causes equipment to malfunction or wear out more quickly. Airports also reported additional examples of issues leading to inoperable systems, such as water damage to equip- ment installed on the top of jet bridges, equipment short circuits, and unreliable equipment that malfunctions without obvious causes. In addition, as systems reach the end of their useful operating life, component failure rates rise. When system components wear out on older equipment, replacement parts may be difficult or impossible to source, leading to additional costs and time out of service. 3.3.2 Lack of On-Site Spare Parts Inventory As stated in Section 3.3.1, spare parts or replacement units are not always immediately available from manufacturers. Long delays in obtaining spare parts, either due to low stock or component production discontinuation, contributes to system unavailability and affects utilization. This is an especially apparent problem at airports with aging PCA and/or ground power equipment. Some airports keep a spare parts inventory on site for components that fail more frequently or are difficult to obtain. However, a spare parts inventory is not always possible due to insufficient maintenance budgets, or the original equipment supplier no longer supports the product. Even when the airport or provider of maintenance services has a spare parts inventory, other components may need replacing that are not included in the inventory. Keeping a sufficient inventory of spare parts can also be challenging at airports that have multiple types, models, and ages of PCA or ground power equipment. 3.3.3 Damage to Aircraft Power Receptacle Aircraft with damaged power receptacles are often unable to accept ground power, even if the ground power cables are physically able to connect. If the receptacles are unable to accept electric ground power, the pilots often have to start and leave the APU running. Problems with the aircraft receptacle may not be visible or obvious to ground crew. As a result the ground crew may assume that the ground power equipment is damaged or malfunctioning and report to it to the airport for creation of a maintenance work order. 3.3.4 Clogged Aircraft Air Intake It is possible for debris from insulated PCA hoses or other matter to be ingested into the air- craft air-conditioning duct. As such, a pilot may perceive that the PCA is either not turned on or not performing properly due to insufficient air flow within the cabin of the aircraft, which may lead to APU use. This condition is usually discovered when an aircraft is taken out of service for comprehensive maintenance checks, referred to as a “C check.” 3.4 Resource Constraints Various types of resource constraints—such as insufficient numbers of staff or lack of funding for system acquisition, operation, and maintenance—can impact system utilization. These chal- lenges may be the root cause of other issues, such as time needed to repair systems, malfunctioning or out-of-service equipment, and insufficient training.

Challenges Affecting Gate Electrification System Utilization 31 3.4.1 Insufficient Availability of Maintenance Personnel Gate electrification system utilization depends, in large part, on its reliability. In turn, system reliability is affected by maintenance practices. Maintenance personnel must be available and trained to carry out routine or preventative maintenance on system components and to quickly restore systems when problems occur. If an airport, airline, or contractor—whoever is responsible for system maintenance—does not have a sufficient number of maintenance staff on hand with the necessary skill level, system restoration will be delayed. This may be due to system or component failures during off-peak hours, such as evenings or weekends when personnel are on call rather than on location. Some maintenance providers may be located away from the airport and require an extended response window to address each work order as it is received. While systems are down, pilots will have to start and/or leave the APU running. Pilots also reported that they will leave the APU running by default—without even trying the PCA or ground power—when serving airports where they have experienced persistent problems with system reliability. Ensuring adequate numbers of maintenance staff with the necessary skills to repair equipment in a timely manner is both a resource constraint and a training challenge. 3.4.2 Insufficient Maintenance Budget Maintenance budgets may be strained due to labor needs and stock requirements. Budgets must be sufficient to allow for an adequate number of trained staff, a sufficient inventory of spare parts and components to keep systems up and running, preventative or routine main- tenance, and unplanned maintenance. Routine maintenance includes tune-ups, tracking unit warranties, ensuring cables and hoses are in a good state of repair, and periodic component replacements. 3.4.3 Lack of Funding for Renewal or Replacement of Systems Due to age, capacity, or design incompatibility, older ground power and PCA systems and their related components may no longer satisfy the needs of aircraft that they are intended to support. Also, due to market demand changes, airlines are more often using larger aircraft that require higher capacity systems or smaller regional jets that require 28-volt connections instead of 400 Hz systems. To encourage utilization, systems must be sized appropriately to accom- modate the varying needs of airlines. The needs of airlines often change over time based on consumer demand and fleet renewal. Budget constraints, planning processes, uncertainty about future fleet mix, or other reasons may prohibit airports—or other system owners—from replacing or upgrading equipment, as needed. 3.4.4 Lack of Electric Ground Power or PCA at Remote Aircraft Parking Positions Aircraft use hardstands for loading and unloading passengers or for remain-overnight park- ing positions at various airports. Often, these remote parking positions are not equipped with electric ground power or PCA due to their distance from the terminal or their incompatible location of existing electrical infrastructure and the costs associated with running electric cable to these locations. Therefore, aircraft at hardstands or remain-overnight positions use mobile, fossil fuel–powered PCA and GPUs, if available; or they use APUs. Depending on how often hardstands or remain-overnight positions are used, the emissions associated with the use of aircraft APUs or mobile units could be significant.

32 Optimizing the Use of Electric Preconditioned Air (PCA) and Ground Power Systems at Airports 3.4.5 Gate Electrification Equipment Not Individually Metered or No Ability to Track Utilization at Individual Gates The lack of monitoring and tracking capabilities can inhibit utilization as it prevents the airport and airline from gaining an understanding of historic and real-time utilization rates. Without individual electrical or hour meters and/or sensors on equipment, airports and airlines cannot accurately track equipment use to ascertain the utilization (i.e., the amount of time the equip- ment is available for use to an aircraft parked at the gate versus the amount of time the equipment is actually in use with APUs off). Without accurate data, stakeholders may experience difficulty identifying patterns and determining possible causes of suboptimal utilization. 3.5 Climatic Factors Staff from airports in a range of climate zones were interviewed and surveyed for this project. Regardless of their geographic location, they all reported that climate and weather factors impact utilization of gate electrification equipment. 3.5.1 Ambient Temperatures Exceed the Design Limits of PCA System One of the most frequently cited challenges (from all stakeholders) that prevents utilization of electric PCA systems is when ambient temperatures are too hot for the PCA to effectively cool the aircraft. The same holds true for airports located in colder climates, where ambient tempera- tures may get too cold for PCA to effectively heat the aircraft (although this problem is not as frequently reported by stakeholders as temperatures that are too hot for PCA to be effective). PCA systems are designed to condition air to a temperature, humidity level, and air flow rate suitable for passenger comfort and safety within the aircraft cabin. In cases of extreme hot or cold ambient outdoor conditions, the intake air may exceed the design limits of the PCA system, meaning that the system cannot overcome the differential between the intake air temperature and the specified delivery air temperature and volume (rate) into the aircraft. For example, ambient ramp air temperature of 110°F is beyond the capabilities of some PCA systems to cool to a temperature (e.g., 68°F) that will satisfy existing airline customer service standards for cabin air temperature. Since pilots are responsible for maintaining passenger comfort and safety, they often choose to augment PCA in these circumstances with onboard aircraft air-conditioning systems, which are powered by the APU. Interviews with airline and airport staff revealed that APU utilization is virtually continuous during periods of the year in which the ambient ramp air temperature exceeds the design limits of PCA systems, which may reflect conditions spanning upwards of 3 months or more. All airlines use a variety of ways to maintain adequate aircraft cabin temperatures while minimizing APU use. However, these methods are not effective for prolonged periods of either high-temperature days or low-temperature days. While system owners and maintenance providers cannot control the climate, systems should be designed, sized, and maintained to accommodate typical climatic conditions. 3.5.2 Unsafe Weather Conditions Preventing Ground Crew Working on Ramp Thunderstorms (i.e., lightning) or other unsafe weather conditions may prevent ground crew from connecting ground power and PCA systems to the aircraft, resulting in the necessity for pilots to start and/or leave the APU running. This challenge affects airports throughout the U.S., although it is of greater significance at airports that experience frequent summer thunderstorms, such as those in the Southeast and Great Plains.

Challenges Affecting Gate Electrification System Utilization 33 3.6 Policy and Regulatory Factors This category of challenges refers to policy decisions or regulatory constraints that may affect gate electrification system use at airports. 3.6.1 Short Aircraft Turn Times Precluding Use of Gate Electrification Systems Airlines often direct pilots to use APUs while at an aircraft parking position if the time spent servicing an aircraft between flights (i.e., turn time) is shorter than a specified time (e.g., 30 to 45 minutes), as determined by an individual airline’s state of repair. Since airlines must ensure that flight schedules remain on a precise timetable, short turnaround times may not warrant sufficient time to connect and disconnect the aircraft to gate electrification systems. If the PCA and ground power equipment are not designed in a way that facilitates a quick deployment and storing, then misuse or accidental damage (e.g., hoses or power cables that are heavy and cumbersome to move and position properly) may be more likely. 3.6.2 Lack of a Regulatory Driver or Policy Requirement None of the U.S. airport staff interviewed or surveyed for this project mandate that airlines use PCA and ground power when such equipment is available, although a few airports have policies encouraging the use of these systems. Zurich International Airport in Switzerland was the only airport interviewed for this project with a requirement that airlines use PCA and ground power (when available) in lieu of APUs. There may be a greater incentive for airports to implement policies that encourage or require—when feasible—the use of gate electrification systems (and for airlines to consis- tently use these systems) if the airport is located in NAAQS nonattainment or maintenance zones, is subject to state air quality regulation, or if the airport has ambitious air quality and greenhouse gas emissions reduction goals. Conversely, there may be less of an emphasis on the strict use of gate electrification systems for airports located in regions that have not had problems with poor air quality or have not faced political or community pressure to address air quality. Growing awareness of the environmental benefits of these systems—in addition to the eco- nomic benefits associated with reduced fuel use and less APU maintenance—strengthens the airline argument that use of these systems should be encouraged or required. 3.7 Identification of Challenges at Individual Airports A self-assessment checklist was developed by the research team to assist airports and airlines in identifying the specific challenges to gate electrification system use at their sites. The checklist is intended to serve as a high-level screening tool for users to assess the challenges that have the greatest relative impact on use and to assist users in determining the relative level of effort (i.e., time and resources) required to address each challenge. The tool is contained in an accompany- ing Excel spreadsheet available for download. Detailed instructions for its use are included on the first tab. 3.7.1 Self-Assessment Checklist The Self-Assessment Checklist is not intended to identify every possible barrier or challenge to utilization, given the wide range of variables across airports in the U.S. However, it does

34 Optimizing the Use of Electric Preconditioned Air (PCA) and Ground Power Systems at Airports provide a starting point for assessing the 19 most commonly identified challenges, described in previous sections. The checklist includes default ratings for both the relative significance of each challenge (i.e., how much of an impact it may have on system utilization) and the relative ease of addressing each challenge. The default settings were selected based on feedback obtained from airports, airlines, pilots, and equipment manufacturers during the research. These ratings are relative, as there are not enough data available on actual utilization rates to determine specific impacts that individual challenges have on overall system use. In addition, the actual resources required to address each challenge will vary by airport. Users of the tool may change these settings for each challenge (by clicking on the drop-down list in each cell) to better reflect the situation at their airport. Column E of the spreadsheet contains the default rating for how impactful the challenge is to gate electrification system utilization (in relation to the other challenges). This rating can be changed based on the unique situation at the airport in question. Users can select ratings from the drop-down menu in each cell. Column F of the spreadsheet contains the default rating for how resource-intensive each challenge is to address in relation to other challenges. This rating can be changed based on the unique situation at the airport in question. Users can select ratings from the drop-down menu in each cell. Challenges that are both highly impactful and least resource-intensive to address are listed at the top of the checklist and are color-coded accordingly. Challenges that have the greatest rela- tive potential to impact the use of gate electrification systems are colored green. Those challenges with potential to have a moderate impact are colored yellow. And those with the least potential impact on use are colored red. Likewise, challenges that are least resource-intensive to address are color-coded green. Moderately resource-intensive challenges are yellow. And those that are likely to require the greatest resources to address are colored red. Challenges get simultaneously less impactful to utilization and more difficult to address the further down the checklist. Again, these ratings will vary from airport to airport. Column G of the spreadsheet allows users also select the relative significance of each challenge—very significant, moderately significant, least significant, or not a challenge—to the individual gate, terminal, or entire airport from the drop-down menu. These ratings are also color-coded as green, yellow, red, and gray, respectively. Items rated as “not a challenge” and colored gray can be removed from consideration. Once the checklist is complete, the user will be able to easily identify those challenges that have the greatest potential impact on gate electrification system use and are least resource-intensive to address (i.e., items that are colored green in Columns E, F, and G). The items that are highly impactful and require the least amount of resources should be addressed before challenges that are less impactful and more difficult to address (yellow or red). The first tab of the checklist document, labeled “Read Me First—Instructions,” provides more detailed instructions for use, as well as an explanation of the type of information contained in each column and the color-coding system. The information in the checklist can be used to guide conversations with other stakeholders— airports, airlines, maintenance providers, equipment manufacturers, and ground crews—about gate electrification equipment utilization. Figure 13 depicts a screenshot of the first three chal- lenges listed in the checklist.

Figure 13. Example Self-Assessment Checklist.