Evaluating Airfield Capacity (2012) / Chapter Skim
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A-1 A-1 Appendix A Prototype Airfield Capacity Spreadsheet Model User's Guide
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A-2 Evaluating Airfield Capacity A-2 INTRODUCTION The Prototype Airfield Capacity Spreadsheet Model (Airfield Capacity Spreadsheet Model) was developed for ACRP Project 03-17, "Evaluating Airfield Capacity," and is intended to serve as a prototype modeling tool to help airport planners understand and determine airfield capacity.
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Appendix A A-3 A-3 The Airfield Capacity Spreadsheet Model calculates average hourly capacity levels for the following general airfield configurations: Single runway Dual parallel runways Dual intersecting runways Each general configuration can be uniquely adjusted to closely fit the conditions of the user's specific airfield through selected input parameters. The flowchart in Exhibit 1 provides a process overview of the steps involved in using the spreadsheet model with the necessary inputs to estimate airfield capacity.
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A-4 Evaluating Airfield Capacity A-4 Determination of airfield capacity is essentially based on the average time of separation between arriving aircraft and/or departing aircraft, which allows for a certain number of arrivals or departures to occur in an hour. The Airfield Capacity Spreadsheet Model attempts to model the interactions of different aircraft classes in a given fleet mix that follow all of the inputs regarding minimum spacing and air traffic rules.
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Appendix A A-5 A-5 OVERVIEW The Airfield Capacity Spreadsheet Model consists of a macro-enabled Excel file (workbook) with several user tabs (spreadsheet tabs)
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A-6 Evaluating Airfield Capacity A-6 To protect the integrity o f the Airfield Capacity Spreadsheet Model's information and formulas, all of the worksheets have been protected ; however, the user can unprotect them as needed. There is no set password for the ancillary tabs, and for the model tabs the password is set as " pass ".
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Appendix A A-7 A-7 Spreadsheet Model, including details of the inputs that the user may enter or adjust to arrive at the hourly capacity output. It is assumed that the user will have limited knowledge of air traffic control rationale or FAA rules and guidelines on air traffic and pilot procedures regarding approach and departure routines.
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A-8 Evaluating Airfield Capacity A-8 SINGLE RUNWAY MODEL The Single Runway Model (Single Model) is the simplest base configuration and will have the smallest number of variables, conditions and potential airfield conflicts.
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Appendix A A-9 A-9 G eneral Inputs , Section 1 In the first section of general inputs the user makes selections regarding the specific operating conditions and air traffic control ( ATC ) practices for the airfield under consideration (Exhibit 9)
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A-10 Evaluating Airfield Capacity A-10 surrounding conditions . Even though the default values have both been set at 2.0 nm in this model, the values for VMC and IMC are not always the same.
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Appendix A A-11 A-11 Exhibit 11 illustrates the second section of general inputs as organized for the Single Runway Model. At a minimum in Section 2, the user must enter share allocations for the O perating Fleet Mix and make selections pertaining to the Runway, Taxiway and A irport Traffic Control Tower availability.
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A-12 Evaluating Airfield Capacity A-12 For example: if a fleet mix has 50% Small-S aircraft operations and 50% Large-Jet aircraft operations, the probabilities for aircraft pairing would be as follows: • 25% S mall-S leading a Small-S • 25% S mall-S leading a Large-Jet • 25% Large-Jet leading a Small-S • 25% Large-Jet leading a Large-Jet A sample set of aircraft for each aircraft class is provided in Exhibit 13. Aircraft weights are based on manufacturers' suggested Maximum Take Off Weight (MTOW)
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Appendix A A-13 A-13 Source: Landrum & Brown . Exhibit 13.
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A-14 Evaluating Airfield Capacity A-14 The model makes some generalized assumptions as to the impact of not having enough properly spaced exits or not having a full parallel taxiway . The user is asked to make selections in only one of the two input cells for Runway Exit Availability OR Full Parallel Taxiway .
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Appendix A A-15 A-15 Advanced Inputs, Section 1 The first section of Advanced Inputs allows the user to introduce a buffer to the average arrival to arrival separation and the average departure to departure separation (Exhibit 15)
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A-16 Evaluating Airfield Capacity A-16 Note: These are minimum separation distances and the resulting capacity outputs represent an optimistic outcome. If observed average arrival runway occupancy times are less than 50 seconds, 2.5 nautical miles can be used as the alternate mi nimum separation gap.
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Appendix A A-17 A-17 Exhibit 17. Single Model Advanced Inputs S ection 3, showing Departure-Departure Separation Requirements.
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A-18 Evaluating Airfield Capacity A-18 TNG operations are calculated by the spreadsheet and added equally to both the Arrivals Capacity (including TNGs) output and the Mixed Ops-Departure Capacity (including TNGs)
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Appendix A A-19 A-19 Single Runway Model: Quick Reference Guide Step 1 : Cl ick the RESET INPUTS button to restore all default inputs to base conditions. Step 2 : Determine and Input the %VMC if available.
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A-20 Evaluating Airfield Capacity A-20 Step 7: Make a selection as to the existence of runway crossing requirements. Input assumptions as to the number of crossings that oc cur in an hour and how long the average delay is in seconds.
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Appendix A A-21 A-21 The first method is identified as the Gap Spacing or gap stretching method, and it increases the average separation gap between each arrival pair to allow for more departures between arrivals. Gap spacing allows the user to achieve a more balanced operational mix, essentially creating a "one in, one out" condition for 50% arrivals and 50% departures (Exhibit 22)
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A-22 Evaluating Airfield Capacity A-22 DUAL PARALLEL RUNWAYS MODEL The dual parallel runways model (Dual Model) i s developed in the s ame manner as the Single Model and therefore estimates hourly capacity using the same assumptions and methodology.
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Appendix A A-23 A-23 Under IMC, the same situation results when the distance is between 2 , 500 and 3,399 feet . The determinations for dependency in the model follow the criteria in this table.
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A-24 Evaluating Airfield Capacity A-24 The spreadsheet model for dual parallel runways requires additional inputs (beyond those in the Single Model) to account for the spacing requirements between aircraft as n ew conditions exist due to the potential simultaneous operations of two runways.
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Appendix A A-25 A-25 Depending on the distance between the runways, the guidelines on the diagonal distance suggest increasing diagonal separation as centerline distance increases . The diagonal distances associated with the model options range from 1.5 n m to 3.0 n m .
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A-26 Evaluating Airfield Capacity A-26 DUAL INTERSECTING OR CONVERGING RUNWAYS M ODEL The Dual Intersecting Runway s M odel (Intersecting Model) is developed in the same manner as the Single Model and the Dual Model and will therefore estimate hourly capacity using the same assumptions and methodology .
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Appendix A A-27 A-27 Source: Landrum & Brown . Exhibit 31.
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A-28 Evaluating Airfield Capacity A-28 Next the user select s whether or not departure runway thresholds infringe on the Runway Safety Area (RSA) or Runway Protection Zone (RPZ)
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Appendix A A-29 A-29 The Outputs Section in the Intersecting Model is set up similarly to the Outputs Section in the Single Model, but has additional rows within the table to provide capacity estimates for both Runway 1 and Runway 2. Interpretation and sensitivity analysis using either adjustment method should be conducted in the same manner as in the Single Model.
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A-30 Evaluating Airfield Capacity A-30 ANNUAL SERVICE VOLUM E (ASV) DETERMINATIO N DATA NEEDED : - Hourly c apacity levels ( from spreadsheet model )
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Appendix A A-31 A-31 Annual data are readily available through the FAA Terminal Area Forecast database online ( http://aspm.faa.gov/main/taf.asp ) ; and daily traffic data are also available online in the form of operational counts from the FAA ASPM database ( http://aspm.faa.gov/ )
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A-32 Evaluating Airfield Capacity A-32 GLOSSARY Airfield Capacity Terms Used in the Prototype Airfield Capacity Spreadsheet Model Aircraft Class -- A category assignment to all aircraft models that places aircraft in a group with other aircraft of the same weight class. The aircraft classifications used in this capacity model are based on MTOW.
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Appendix A A-33 A-33 Departure Priority -- A mode of airfield operations where departures are given priority and allows for arrivals to occur, but priority is given to departing aircraft unless a safety situation requires an arrival be permitted to land. Departure Runway Occupancy Time (DROT)
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A-34 Evaluating Airfield Capacity A-34 Runway Crossing Demand -- A measurable requirement for crossing the runway to other runways, taxiways, or terminals. Assumes that no other route avoiding runway occupancy is available.
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Appendix A A-35 A-35 CONCLUSION Model Limitations While the model provides for significant input capabilities for a variety of items noted previously, if the airfield configuration is not in the model and/or the airfield is operated in many different configurations, the Airfield Capacity Spreadsheet Model would not reflect a total combined hourly capacity. The model's results present the following information for visual meteorological conditions, instrument meteorological conditions, and an average condition: • Arrivals only capacity (with and without touch-and-go activity)
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