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A Guidebook for Airport Winter Operations (2015)

Chapter: Chapter 13 - Investment to Reduce SRE Runway Occupancy Time

« Previous: Chapter 12 - Winter Operations Performance Evaluation
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Suggested Citation:"Chapter 13 - Investment to Reduce SRE Runway Occupancy Time." National Academies of Sciences, Engineering, and Medicine. 2015. A Guidebook for Airport Winter Operations. Washington, DC: The National Academies Press. doi: 10.17226/22221.
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Suggested Citation:"Chapter 13 - Investment to Reduce SRE Runway Occupancy Time." National Academies of Sciences, Engineering, and Medicine. 2015. A Guidebook for Airport Winter Operations. Washington, DC: The National Academies Press. doi: 10.17226/22221.
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Suggested Citation:"Chapter 13 - Investment to Reduce SRE Runway Occupancy Time." National Academies of Sciences, Engineering, and Medicine. 2015. A Guidebook for Airport Winter Operations. Washington, DC: The National Academies Press. doi: 10.17226/22221.
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Suggested Citation:"Chapter 13 - Investment to Reduce SRE Runway Occupancy Time." National Academies of Sciences, Engineering, and Medicine. 2015. A Guidebook for Airport Winter Operations. Washington, DC: The National Academies Press. doi: 10.17226/22221.
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Suggested Citation:"Chapter 13 - Investment to Reduce SRE Runway Occupancy Time." National Academies of Sciences, Engineering, and Medicine. 2015. A Guidebook for Airport Winter Operations. Washington, DC: The National Academies Press. doi: 10.17226/22221.
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Suggested Citation:"Chapter 13 - Investment to Reduce SRE Runway Occupancy Time." National Academies of Sciences, Engineering, and Medicine. 2015. A Guidebook for Airport Winter Operations. Washington, DC: The National Academies Press. doi: 10.17226/22221.
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Suggested Citation:"Chapter 13 - Investment to Reduce SRE Runway Occupancy Time." National Academies of Sciences, Engineering, and Medicine. 2015. A Guidebook for Airport Winter Operations. Washington, DC: The National Academies Press. doi: 10.17226/22221.
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107 The results of performance evaluations described in Chapter 12 may indicate a need to invest in new or additional equipment to reduce SRE runway occupancy time. SRE runway occupancy time, or the time a runway is closed for snow and ice removal operations and subsequent pavement friction testing, is a commonly used measure of SRE performance. Runway occupancy time as an API can be associated with SRE operational effectiveness, operational efficiency, and aircraft flight delay. SRE clearance times for other pavement surfaces may contribute to delays, but the delays are more difficult to measure and attribute to SRE performance. Unless air carriers proactively reduce flight operations in anticipation of severe winter storm conditions, delays are likely to occur regard- less of SRE efficiency and effectiveness, winter operations tactics employed, or resultant runway occupancy times. However, reducing runway occupancy times should result in a reduction in flight delays, particularly at medium- and large-hub airports with more frequent arrivals and departures. SRE investment options should be thoroughly evaluated to justify the resources and capital investment to the decision makers and stakeholders involved in winter operations. This supporting information may be critically important to acquiring funding, particularly if it is to come directly or indirectly from the stakeholders (e.g., through rates and charges). This situation may occur if FAA and state agencies will not authorize equipment purchases through Airport Improvement Program grants, passenger facility charges, or state grants. The challenge for most airports needing to invest in SRE is the lack of industry guidance on how to determine an optimal level of investment. C H A P T E R 1 3 Investment to Reduce SRE Runway Occupancy Time BEST PRACTICE—Coordination with Stakeholders on Equipment Purchases Some airports have reached out to ATC and key stakeholders in advance of a major equipment purchase to determine expectations for performance and capacity dur- ing snow and ice events. Airport operators can then better determine the appro- priate number and type of vehicles needed to perform to customer expectations. Collaboration with air carriers regarding financing options has led to positive out- comes at several airports. Lease terms often obligate air carriers to finance airport vehicle purchases through rates and charges, so air carriers become interested in a proper return on their investment. An effort by airport operators to educate air carrier personnel on equipment options and performance factors will enhance air carrier support of needed equipment. For instance, when considering the cost of high-speed, multi-function SRE, cost savings associated with one operator doing the work of two operators can be factored into life-cycle costs. The speed of the vehicles will result in less runway occupancy time and increased airport capacity. Reduced delays and fewer cancellations are obvious cost savings for air carriers.

108 A Guidebook for Airport Winter Operations 13.1 FAA Guidance on SRE Procurement Advisory Circular 150/5220-20, Airport Snow and Ice Control Equipment, represents FAA’s current guidance for procuring the minimum SRE for commercial service and non-commercial service airports, as well as for procuring snow and ice removal equipment to meet the snow clear- ance time requirements of AC 150/5200-30, Airport Winter Safety and Operations, presented in Table 13-1. Spreadsheet tools based on both ACs are available from FAA regional offices and state agencies, and are accessible through the Internet. These tools facilitate estimating the number and size of displacement plows, rotary plows (i.e., snow blowers), and brooms to clear designated priority pavement surfaces within applicable clearance times and under the conditions noted in Table 13-1. However, the utility of AC 150/5200-30, AC 150/5220-20, and the related spreadsheet tools is limited for an airport operator attempting to estimate the amount of additional equip- ment required to reduce a runway occupancy time performance target shortfall. 13.2 Variables Affecting SRE Runway Occupancy Time Reducing SRE runway occupancy time by investing in new or additional equipment requires an assessment of the variables that affect this performance measure. Figure 13-1 depicts the key variables. Viewing Figure 13-1 as a mathematical equation, accumulated snowfall depth and den- sity would be in the numerator and represent the primary environmental variables that can increase runway occupancy time as they increase. There are other environmental variables that can increase this time, such as visibility and wind (e.g., drifting), but they cannot be mitigated by adding equip- ment as described below, and thus were not included. To decrease runway occupancy time, the denominator in the equation, shown as snow removal capacity in tons per hour, must increase. Increasing snow removal capacity can be accomplished by adding additional similar equip- ment to the runway clearing operation, or replacing the slowest equipment with versions having a faster operating speed. Additional equipment can reduce runway occupancy time by reducing the total travel distance of the runway team. For example, if a team of two displacement plows travels the length of a runway four times to clear it from edge to edge, then adding a third plow may enable the team to complete the clearing process in three or fewer trips down the runway. Annual Airplane Operations (including cargo operations) Clearance Times for Commercial Service Airports* (hours) Clearance Times for Non-commercial Service Airports* (hours) 40,000 or more 0.5 2 10,000 but less than 40,000 1 3 6,000 but less than 10,000 1.5 4 Less than 6,000 2 6 * These airports should have sufficient equipment to clear 1 inch of falling snow weighing up to 25 lbs/ft3 from priority 1 areas within the recommended clearance times. Source: FAA (2) Table 13-1. FAA AC 150/5200-30 recommended clearance times. Figure 13-1. SRE runway occupancy time as determined by snow clearing capacity.

Investment to Reduce SRE Runway Occupancy Time 109 Faster equipment can reduce runway occupancy time by increasing the operating speed of the slowest piece(s) of equipment in the runway team. This is commonly the rotary plow (i.e., snow blower), when one or more are included on the team. Faster speed typically requires a greater snow removal capacity. These concepts are illustrated in Figure 13-2, which shows that increasing the denominator, decreasing the numerator, or doing both can reduce runway occupancy time. 13.3 Identify Runway Snow Removal Capacity Shortfall To begin the process for determining the SRE needed to achieve a runway occupancy time performance target, first estimate the equipment snow removal capacity shortfall based on the current actual performance and the desired performance target. Advisory Circular 150/5220-20 presents graphical and mathematical methods that can be used to accomplish this task. The AC also addresses specific considerations for snow blowers, displacement plows, snowsweepers (i.e., brooms), and material spreaders. Figure 13-3 identifies a process for estimating equip- ment snow removal capacity shortfall. An identified shortfall is unique to the composition of the deployed snow team fleet and the operating procedures in use at the time the shortfall occurred. Figure 13-2. SRE runway occupancy time determined by maximum operating speed. Figure 13-3. Example process for estimating snow removal capacity shortfall by comparing current and target runway occupancy times under defined winter event conditions.

110 A Guidebook for Airport Winter Operations 13.4 Estimate SRE Needs to Reduce Snow Removal Capacity Shortfall Once the runway snow clearing capacity shortfall is identified, AC 150/5220-20 can be used to assist with estimating additional equipment required to provide increased snow clearing capacity. It should be noted that the equations presented in the AC discount the capacities of SRE through the inclusion of an efficiency factor. The term “efficiency” is not defined in the AC. It appears to account for differences between equipment “design capacity” established through controlled per- formance testing and operations during winter operations events. These differences, or “inefficien- cies,” are associated with overlapping travel paths, equipment turnaround, spillage, and residual snow. While no specific direction is given in the AC as to what efficiency factor is appropriate to use in the calculations, the following values are included as stated assumptions in equipment selection charts and tables in AC 150/5220-20: • Rotary plow efficiency: 70%, • Displacement plow efficiency: 70%, and • Snowsweeper: 80%. Additional noteworthy assumptions included in the AC 150/5220-20 graphs and equations address snow depth, snow density, plow cutting angle, and broom angle. The guidance assumes a consistent 1-inch snow depth (presented in feet) and snow density of 25 lbs/ft3. As described for Figures 13-1 and 13-2, increasing snow depths and densities may increase runway occupancy time, and an airport may set performance targets for conditions exceeding this depth and density. It is also important to consider plow blade and broom angles because the effective blade and broom width at an angle (e.g., 30 degrees) is shorter than the nominal width and, therefore, moves less snow. Figure 13-4 continues the scenario presented in Figure 13-3 and presents a process for estimat- ing additional equipment to eliminate a shortfall in snow removal capacity. The equations in AC 150/5220-20 can assist with translating snow removal capacity shortfall into equipment capacity. This process assumes that the same composition of equipment within a deployed snow team fleet will be maintained (e.g., plows and blowers), but with more equipment of similar capacity added to address the shortfall. However, estimating equipment needs in this manner is not a precise Figure 13-4. Example process for estimating additional blower capacity and plow blade length to address snow removal capacity shortfall for defined winter event conditions.

Investment to Reduce SRE Runway Occupancy Time 111 process and may not account for other factors that can affect runway occupancy time (e.g., pave- ment geometry and equipment turning radii). The estimated values for additional blower capacity and plow length may need to be attained through the acquisition of multiple pieces of equipment. Addressing the option of changing SRE runway team composition by replacing existing SRE with new equipment having faster operating speeds and higher snow removal capacities requires airport-specific data on the current runway team and data on the individual SRE snow removal capacities. For example, an airport operator currently using three plows and three brooms to clear its runway may be interested in replacing the six vehicles with three high-speed multi-function vehicles, such as plow-broom-blower combination units. If a target runway clearing rate is estimated to be 6,680 tons per hour to achieve a runway occupancy time per- formance target of 20 minutes, as illustrated in Figure 13-3, the snow removal capacity of the three multi-function vehicles would need to also equal 6,680 tons per hour. Equipment vendors are the best source for product-specific information on capacities and operating speeds to confirm that a performance target can be met. However, evaluate equipment based on the midpoint of its design capacity rather than on the maximum design capacity. Maximum design capacities are measured under controlled, ideal conditions that may not be representative of actual storm event conditions. 13.5 Estimate Benefits of New or Additional SRE Chapter 7 identified that the primary impacts of a longer runway occupancy time are increased aircraft flight delays and associated delay costs to air carriers and passengers. It logically follows that the primary benefits of adding SRE to an existing fleet in order to shorten runway occu- pancy time are reduced aircraft delays and the associated savings. The approach to estimating these potential benefits is best suited for hub airports and airports with substantial cargo traffic that may experience the benefits of aircraft arrival and departure delay savings for passenger and cargo air carriers. The approach is less applicable to small-hub and non-hub airports with fewer flight operations. Similarly, airports without scheduled com- mercial service and general aviation airports may find the approach of limited value because of the limited opportu- nity for delay cost savings. This does not suggest that smaller facilities or their tenants will receive no benefit from reduced runway occupancy times, but rather that these benefits (e.g., safety, customer service, etc.) are less predictable, more indi- vidualized, and difficult to quantify monetarily. Compare delay and cost baseline data described in Chap- ter 7 to projected delay and delay cost data after the addi- tional SRE are in operation to estimate the benefits of adding SRE to reduce runway occupancy time. If an aircraft delay simulation model was used to generate the delay baseline data, then the same model can be used to simulate delays with a new, shorter runway occupancy time performance target. However, if another method was used to generate delay data (e.g., airport operations log or RITA TranStats data), then use the delay data and a set of operational assumptions to project Source: Oshkosh Corporation BEST PRACTICE—Coordination with Air Carriers to Determine Staffing Needs Airports reported success in coordinating with air carriers on financial assumptions and financial modeling in determining appropriate staffing levels for snow and ice control operations. The identification of airline expectations for capacity and operations during winter events is a key factor in determining airport crew complements. A sub- sequent cost-benefit analysis comparing airport staffing costs against airline delay and/or cancel- lation costs will lead to better decision making regarding the optimum crew size necessary to meet customer expectations.

112 A Guidebook for Airport Winter Operations new delay data and delay cost savings. This approach offers potentially less accurate estimations than modeling, but the rough analysis may be sufficient to support an investment decision. This rough approach uses the spreadsheet summary of past winter season runway closures, esti- mated aircraft delays per runway closure, and associated aircraft delay costs shown in Table 13-2 (originally presented as Table 7-7 in Chapter 7). By replacing the estimated average event ATC run- way closure duration values in the second column of the table with an ATC runway closure duration performance target (assuming the runway closure duration does not include significant additional time for ATC runway reopening) and maintaining all other data, new delay costs can be calculated, as seen in Table 13-3. This table shows that consistent, shorter ATC runway closure durations can result in significant delay cost savings. The estimated delay costs savings, as summarized in Table 13-4, can be compared to the antici- pated cost of the additional or faster SRE needed to achieve the runway occupancy time performance target. This comparison will assist in the alternatives selection process described in Chapter 14. The delay cost savings should also be evaluated against the meteorological data recurrence intervals. This evaluation will further the understanding among the airport operator and its stakeholders of the percent chance that the event conditions will occur and subsequent delay cost savings realized. 13.5.1 Additional Benefits of Multi-Function Equipment High-speed, multi-function equipment offers benefits in addition to reducing runway occu- pancy time. As aging SRE reaches the end of its useful life, multi-function equipment provides Winter Event Date Average Event ATC Runway Closure Duration (min) Number of Event ATC Runway Closures Estimated Aircraft Delayed / ATC Runway Closure Weighted Average Aircraft Block Time Cost / Minute Total Delay Cost / Aircraft Total Event Delay Cost / ATC Runway Closure Total Event Delay Cost 3/3/2011 71 17 12 $74.39 $5,282 $62,500 $1,062,500 1/23/2011 44 16 7 $74.39 $3,273 $24,003 $384,051 1/17/2011 34 12 6 $74.39 $2,529 $14,332 $171,990 12/11/2010 28 6 5 $74.39 $2,083 $9,720 $58,322 2/14/2011 23 3 4 $74.39 $1,711 $6,559 $19,676 12/22/2011 24 2 4 $74.39 $1,785 $7,141 $14,283 Table 13-2. Example summary of ATC runway closure duration, estimated aircraft delay per runway closure, and associated aircraft delay cost data. Winter Event Date Average Event ATC Runway Closure Duration (min) Number of Event ATC Runway Closures Estimated Aircraft Delayed / ATC Runway Closure Weighted Average Aircraft Block Time Cost / Minute Total Delay Cost / Aircraft Total Event Delay Cost / ATC Runway Closure Total Event Delay Cost 3/3/2011 20 17 3 $74.39 $1,488 $4,959 $84,309 1/23/2011 20 16 3 $74.39 $1,488 $4,959 $79,349 1/17/2011 20 12 3 $74.39 $1,488 $4,959 $59,512 12/11/2010 20 6 3 $74.39 $1,488 $4,959 $29,756 2/14/2011 20 3 3 $74.39 $1,488 $4,959 $14,878 12/22/2011 20 2 3 $74.39 $1,488 $4,959 $9,919 Table 13-3. Example summary of runway closures, estimated aircraft delays, and associated aircraft delay costs based on an assumed 20-minute ATC runway closure duration with increased SRE capacity.

Investment to Reduce SRE Runway Occupancy Time 113 an opportunity to switch out two pieces of equipment for one (e.g., one plow and one broom for one combination plow-broom-blower). It also offers potential savings on operator labor, as only one operator is required. If the acquisition of each piece of multi-function equipment results in needing one fewer full-time operator, the savings in salary and benefits can be compared to the annualized capital cost of each piece of equipment. An example of this comparison is provided in Figure 13-5. Winter Event Date Total Event Delay Cost Delay Cost Savings with Increased SRE Capacity Event Duration Total Event Snowfall Average Event Intensity C ur re nt S R E C ap ac ity In cr ea se d SR E C ap ac ity H ou rs R ec ur re nc e In te rv al Sn ow T yp e D ep th (i n) R ec ur re nc e In te rv al In ch es / H ou r R ec ur re nc e In te rv al 3/3/2011 $1,062,500 $84,309 $978,191 14 4.0 Wet 9.9 10 0.71 7.0 1/23/2011 $384,051 $79,349 $304,701 13 1.3 Dry 5.1 3.4 0.39 1.0 1/17/2011 $171,990 $59,512 $112,478 11 1.1 Dry 4.2 2.7 0.38 0.9 12/11/2010 $58,322 $29,756 $28,566 4 0.8 Wet 1.3 1.1 0.33 0.7 2/14/2011 $19,676 $14,878 $4,798 2 0.6 Dry 0.9 0.8 0.45 1.3 12/22/2011 $14,283 $9,919 $4,364 3 0.7 Dry 0.7 0.7 0.23 0.6 Total $1,710,821 $277,723 $1,433,099 Table 13-4. Example summary of aircraft delay costs, delay cost savings, and meteorological data for multiple winter storm events sorted by total event snowfall recurrence interval. Figure 13-5. Example comparison of the annualized cost of a multi-function vehicle purchased to replace an aging plow and broom, and the resulting employee cost savings.

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TRB’s Airport Cooperative Research Program (ACRP) Report 123: A Guidebook for Airport Winter Operations provides direction to airport facilities as they prepare for, operate during, and recover from disruptive winter events. The report also provides tips for managing the overall passenger experience and provides guidance on the levels of investment needed to implement an effective winter operations program.

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