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HomeMy WebLinkAboutChapter 4 -Demand Capacity Analysis I I I I I I I I I I I I I I I I I I I DEMAND/CAPACITY ANALYSIS OJ'IOI 5!1~1S~IJp~i'~ C~.)~ ~'"\~ HOME 01 PWCAN ,""'.AND I I I I I I I I I I I I I I I I I I I SEBASTIAN MUNICIPAL AIRPORT Mater Plan Update (Irrer SlBAST!AN ~~ HOME Of PU.ICAN ISlAND Chapter 4 - Demand/Capacity Analysis INTRODUCTION The purpose of this Demand/Capacity Analysis is to examine the capability of Sebastian Municipal Airport to meet the needs of its users. In doing so, this task provides an analysis of the ability for the existing airfield to satisfy the forecasted operational demands. This assessment will be expressed in terms of the hourly capacity and annual service volume of the airfield, along with the total estimated annual delay. Also, an analysis of the airspace surrounding Sebastian Municipal is included to determine its capacity. The following chapter, "Facility Requirements," provides specific recommendations intended to address any deficiencies identified in the Airport facilities. AIRFIELD CHARACTERISTIC Methods for determining airport capacity can be found in Advisory Circular (Ae) 150/5060-5 Change 2, entitled "Airport Capacity and Delay" published by the Federal Aviation Administration (FAA). For this Master Plan, airfield capacity was calculated in terms of the hourly capacity of the runways, annual service volume, and annual aircraft delay using the FAA's methodology. The elements that affect airfield capacity are listed below. + Runway Configuration + Aircraft Mix Index + Taxiway Configuration + Airfield Operational Characteristics + Meteorological Conditions When analyzed collectively, the above elements provide the basis for establishing the operational capacity of an airport. The following sections will evaluate each of these capacity related characteristics with respect to Sebastian Municipal. Runway Configuration The airfield configuration for Sebastian Municipal Airport includes two paved runways. The primary runway, Runway 4-22, has a northeast to southwest orientation. Runway 13-31, the crosswind runway, has a northwest to southeast alignment. The two runways at Sebastian are laid out in an X configuration. All active runways have a standard left hand traffic pattern. Even though only one traffic pattern can be used at a time, both runways are still required at Sebastian Municipal. This is due to the characteristics of the area's prevailing winds. Since aircraft takeoff and land into the wind, the FAA recommends that sufficient runways be provided to achieve 95 percent wind coverage. This is calculated by using a 10.5-knot crosswind component for the smaller and lighter aircraft, while a 13-knot crosswind component is utilized for the larger, heavier, aircraft. FAA AC 150/5300-13, Change 6, "Airport Design" suggests that weather for a period of at least ten years be used to determine the wind coverage of an airport. The inventory chapter of this study evaluated the wind coverage for the Airport based data collected in the 1993 Airport Master Plan. This analysis showed that neither Runway 4-22 nor Runway 13-31 could provide 95 percent wind coverage in the 10.5-knot category. Therefore, both runways are required to provide the appropriate wind coverage for the smaller and lighter aircraft that predominately use the airfield. 2002 4-1 I I I I I I I I I I I I I I I I I I I SEBASTIAN MUNICIPAL AIRPORT Mater Plan Update (Irrer SEBAST~ ~' ..-_ ._,.,..," u. - .--" .- HOME Of PWCAN ISlAND Aircraft Mix Index Knowing the operational fleet mix, it is possible to establish the mix index required to compute the airfield's capacity. The aircraft mix index is calculated based on the type or class of aircraft expected to serve an airfield. Exhibit 4-1 provides examples of typical aircraft for each of the FAA's four capacity classifications. The formula for finding the mix index is %(C + 3D) where C is the percentage of aircraft over 12,500 pounds, but less than 300,000 pounds, and D is the percentage of aircraft over 300,000 pounds. At Sebastian Municipal Airport, the current aircraft mix includes only Class A and B aircraft. While some Class C aircraft may operate at the Airport during the planning period, no Class D aircraft are expected to operate at Sebastian Municipal. The Class C aircraft expected to operate at the Airport will only consist of the smaller business and corporate jet aircraft within this classification. Currently, not enough Class C aircraft operate at the Airport to be considered significant; however, for planning purposes, it is assumed that all of the future jet aircraft in the operational fleet mix will be conducted by Class C aircraft. Using the FAA formula, the aircraft mix index will simply increase to five percent by the year 2022 from the Airport's current index of zero. As the mix index rises, the overall airfield capacity is diminished. However, due to the low level of Class C aircraft, the decrease in the overall capacity at Sebastian Municipal will be insignificant. Taxiway Configuration As mentioned in the inventory, neither runway at Sebastian Municipal has a parallel taxiway running the entire length of the runway. Not counting the runway intersection, there are three exits off of both Runway 4-22 and Runway 13-31 onto the limited taxiway system. Based on the FAA's criteria, the exit factor is maximized when a runway has four exit taxiways within a range determined by the operations using that runway. At Sebastian Municipal, this range is 2,000 feet to 4,000 feet from the landing threshold and each exit must be separated by at least 750 feet. Using these criteria, both runways are considered to have two exits each for airfield capacity calculations. However, because both of these runways are just over 4,000 feet in length, the taxiways are considered to be maximized with respect to their ability to facilitate aircraft exiting. Operational Characteristics Significant operational characteristics that can affect an airfield's overall capacity include the percentage of aircraft arrivals, the sequencing of aircraft departures, and the percentage of "touch and go" operations. Percentage of Aircraft Arrivals The percentage of aircraft arrivals is the ratio of landing operations to the total operations of the airport. This percentage is considered due to the fact that aircraft approaching an airport for landing require more runway occupancy time than an aircraft departing the airfield. The FAA methodology used herein provides for computing airfield capacity with a 40, 50, or 60 percent of arrivals figure. The 40 and 60 percent figures result in an average ASV variance of :l:: 11 percent when compared to the 50 percent level, with the lower percentage (40) having the highest capacity. For general planning purposes, the 50 percent of arrivals value was utilized as an average or neutral effect to determine the overall capacity at Sebastian Municipal. 2002 4-2 I I I I I I I I I I I I I I I I I I I Class A Small single-engine, gl"Q$ MOONEY OVATION Class B Small twin-engine,gr KNi AR 380 Class C Large aircraft, grQs$ OOLFSTREAM IV Class D Large aircraft, gross IlO9IQ 747 CESSNA 152/172 BEECHCRAFT BONANZA CESSNA 182/210 MOONEY 201 PIPER CHEROKEE BEECHCRAFT BARON MITSUBISHI MU-2 CESSNA CITATION I CESSNA 310/402 PIPER NAVAJO BEECH KING AIR 90/100/200/350 GULFSTREAM III/IV FALCON 20/50/90 CESSNA CITATION II BOEING 727/737/767 DOUGLAS DC-9/MD-80 SWEARINGER METRO LEAR 35/55 SAAB 340 DORNIER 228/328 AIRBUS A300/310 BOEING 747 AIRBUS A-340 DOUGLAS DC-8 LOCKHEED L -1011 DOUGLAS MD-11 TYPICAL AIRCRAFT BY CAPACITY CLASSIFICATION ~ Sebastian Municipal Airport City of Sebastian BlJIm a.1'IIUCAN IL\ND I~~ L.. GROUP ~ ~ AIRCRAFT CLASSIFICATIONS EXHIBIT 4-1 I I I I I I I I I I I I I I I I I I I SEBASTIAN MUNICIPAL AIRPORT Mater Plan Update (Irrer SEBASTIAN ~.;:C~.d' ~~~ HOME: OF PnICAN ISLAND Sequencing of Aircraft Departures All four runway ends at Sebastian have only end connector taxiways. This configuration does not allow aircraft to pass if there is a delay for the lead aircraft. Unfortunately, this constraint cannot be modeled using the FAA's methodology for airfield capacity. Therefore, the airfield is considered to have no constraints with respect to aircraft departures. Percentage of Touch and Go Operations The percentage of "touch and go" operations plays a critical role in the determination of airport capacity. "Touch and go" operations are counted as one landing and one takeoff (i.e., two operations) and are normally associated with flight-training activities. Based on interviews with airport management and airport tenants, in the past, the level of "touch and go" operations at Sebastian varied. Currently no "touch and go" operations are allowed, therefore, the Airport falls in the lowest "touch and go" index under the FAA's methodology. Meteorological Conditions Meteorological conditions can adversely affect the decision as to which runway end is used by a pilot. Thus, these conditions have an affect on the overall capacity for the airfield. Runway utilization is normally determined by wind conditions while the cloud ceiling and visibility dictates spacing requirements. Using the breakdown of the area's wind characteristics from the inventory chapter, the percent of use for each runway end was calculated. Based on these wind observations, Runway 4-22 is favored 46.8 percent of the time while Runway 13-31 is favored 53.2 percent of the time. Table 4-1 provides the breakdown for each runway end. [, .../......... .... ..........i. ....//..TABLF:. 4..1..)........ .................. .......... ........ .. . RUNWAY END UTILIZATION ,. Runway Runway End Use Utilization 46.8 % 26.2 % oftotal of total 20.6 % of total 53.2% 33.8 % oftotal of total 19.4 % oftotal Runway End 4 22 13 31 Source: 1993 Master Plan Wind Observations There are three measures of cloud ceiling and visibility conditions recognized by the FAA in calculating the capacity of an airport. These include: + Visual Flight Rules (VFR) - Cloud ceiling is greater than 1,000 feet above ground level (AGL) and the visibility is at least three statute miles. + Instrument Flight Rules (IFR) - Cloud ceiling is at least 500 feet AGL but less than 1,000 feet AGL and/or the visibility is at least one statute mile but less than three statute miles. + Poor Visibility and Ceiling (PVC) - Cloud ceiling is less than 500 feet AGL and/or the visibility is less than one statute mile. 2002 4-4 I I I I I I I I I I I I I I I I I I I SEBASTIAN MUNICIPAL AIRPORT Mater Plan Update (Irrer SlBAST~ ~'~ , 'n ..r'.......... ,._. . - ~...... --~ HOME Of PU.JCAN rsl.AND Sebastian Municipal experiences VFR conditions 97 percent of the time, IFR conditions 2.5 percent of the time, and poor visibility and ceiling conditions 0.5 percent of the time. These percentages are based on data collected by the National Climatic Data Center from the Vero Beach Municipal Airport weather station. AIRFIELD CAPACITY ANALYSIS The preceding characteristics of the airfield's capacity were used in conjunction with the methodology developed by the FAA to determine airfield capacity. As mentioned previously, this FAA methodology generates three different values for measuring airfield capacity. These include the hourly capacity of runways, annual service volume, and annual aircraft delay. Hourly Capacity of Runways Hourly capacity of the runways measures the maximum number of aircraft operations that can be accommodated by the airport's runway configuration in one hour. Based on the FAA methodology, hourly capacity for runways is calculated by analyzing the appropriate VFR and IFR figures for the airport's runway configuration. From these figures, the aircraft mix index and percent of aircraft arrivals are utilized to calculate the hourly capacity base. A "touch and go" factor is also determined based on the percentage of "touch and go" operations combined with the aircraft mix index. These figures also consider a taxiway exit factor, which is determined by the aircraft mix index, percent of aircraft arrivals, and number of exit taxiways within the specified exit range. For both VFR and IFR conditions, the hourly capacity for runways is calculated by multiplying the hourly capacity base, "touch and go" factor, and exit factor. This equation is: Hourly Capacity C* x T x E where: C* = hourly capacity base T = "touch and go" factor E = exit factor An airport's mix index can substantially change the value of the hourly capacity base in the FAA capacity tables. However, since all of the planning years fall into the mix index range of 0 to 20 percent, there will be no change in the hourly capacities for the Airport. A weighted hourly capacity for the Airport is calculated by taking the VFR and IFR calculations and prorating them based on the percent these conditions have been observed at the airport. These following hourly capacity values were calculated for Sebastian Municipal. + VFR Conditions = 102 Operations/Hour + IFR Conditions = 62 Operations/Hour + Weighted Hourly Capacity = 100 Operations/Hour Annual Service Volume The most important value that must be computed in order to understand the capacity at an airport is the annual service volume (ASV). ASV represents a measure of the approximate number of total operations that the airport can support annually. In other words, the ASV represents the theoretical limit of operations that the airport can safely accommodate. Using the FAA's methodology to estimate ASV, first the ratio of annual demand to average daily demand, during the peak month, is calculated along with the ratio of average daily demand to average peak hour demand, during the peak month. These values are then multiplied together and the resulting product is multiplied by the weighted hourly capacity. This equation is: 2002 4-5 I I I I I I I I I I I I I I I I I I I SEBASTIAN MUNICIPAL AIRPORT Mater Plan Update (Irrer Sf.JAST~ ~~ .. ,,- ...,,--," --, _ '.... .""-'. u HOMt Of PWCAN tSLAND Annual Service Volume = Cw x D x H where: Cw D = weighted hourly capacity = ratio of annual demand to average daily demand during the peak month = ratio of daily demand to average peak hour demand during the peak month H The calculated ASV accounts for differences in forecasted activity levels, runway use, aircraft mix, weather conditions, and other factors that occur over a single year. For Sebastian Municipal, the current and projected ASV will remain relatively the same. This is due to the fact that all three elements in the equation are similar. It was stated that the weighted hourly capacity remains the same for each forecast year due to the mix index. In addition, the two other factors (ratios D and H) are also very much alike since the same methodology for calculating the percent of average day peak month and peak hour operations was used for each year in the forecast chapter. Therefore, the anticipated ASV of the Airport for the entire planning period was based on the most conservative calculation, which is 200,313 annual operations. ASV is the approximate measure of an airport's capability in terms of annual throughput capacity. A demand that exceeds the ASV will typically result in significant delays on the airfield. However, no matter how substantial an airport's capacity may appear, it should be realized that delays can occur even before an airport reaches its stated capacity. In fact, a number of projects that would increase the capacity at an airport are eligible for funding from the FAA. According to FAA Order 5090.3B, "Field Formulation of the National Plan of Integrated Airport Systems (NPIAS)," this eligibility is achieved once the airfield has reached 60 percent of its current capacity. This allows improvements to be made before demand levels exceed the capacity of the facility in order to avoid lengthy delays. Future capacity levels for the airport have been calculated based on the forecasted annual operations and the ASV for the Airport. These levels are depicted in Table 4-2 and are shown graphically in Exhibit 4-2. TABLE 4-2 AIRFIELD CAPACITY LEVELS Year Annual Annual Capacity Operations Service Volume Level Base Year 2000 26,237 200,313 13% Forecast 2007 32,050 200,313 16% 2012 36,974 200,313 18% 2022 49,210 200,313 25% Source: THE LPA GROUP INCORPORATED, 2000. Table 4-2 and Exhibit 4-2 both show that even if no improvements are made to the airfield, Sebastian Municipal should not experience any capacity related problems during the planning period. Overall, the current airfield capacity is considered to be sufficient to accommodate the aircraft operations forecasted. However, as conditions change over the years, the capacity of the airfield may decrease enough to reach the 60 percent threshold. If this occurs, then improvement projects will need to be planned to enhance the overall capacity of the airfield. 2002 4-6 I I I I I I I I I I I I I I I I I I I 200,000 150,000 z 0 - E-o ~ 100,000 ~ 60% ASV ~ 0 120,188 ..:l < ~ 32,050 Z 36.974 Z 50,000 < 2007 2012 2022 YEARS ~ Sebastian Municipal Airport ~ CilyofSebaslian BOIIII. OPnuc.\N1lIIAND I~~ L.... GROUP ==:s. DEMAND VS. CAPACITY EXHIBIT 4-2 I I I I I I I I I I I II I I I I I I I SEBASTIAN MUNICIPAL AIRPORT Mater Plan Update (Irrer SlBAST~ ~-' . . ~_...r- ". ._ _ . _ F.......,......~>_"'i -- HOME Of PWC.Ml ISlAND Annual Aircraft Delay As an airport's level of annual operations increase, so do the times when the airfield experiences periods of delay. Annual aircraft delay allows a total to be estimated for all of the delay incurred by aircraft on the airfield in one year's time. The estimate of annual delay includes arriving and departing aircraft operations under both VFR and IFR conditions. FAA AC 5060-5 Change 2, provides a method by which the annual delay can be quantified. Essentially the ratio of annual demand to ASV is utilized in FAA charts to determine the average delay per aircraft. This value is then applied back to the annual demand to estimate the total amount of annual aircraft delay. The results of these calculations are included in Table 4-3. I TABLE 4-3 I ANNUAL AIRCRAFT DELAY Year Average Delay per Aircraft Total Annual Delay (minutes) (hours) Low High Low High Base Year 2000 0.0 0.1 0 3 Forecast 2007 0.0 0.1 0 3 2012 0.0 0.1 0 3 2022 0.0 0.1 0 3 Source: THE LPA GROUP INCORPORATED, 2000. Based on these values, there is no real delay associated with the aircraft operations conducted at Sebastian. However, the FAA methodology does not allow the calculations to consider skydiving activities at Sebastian. It is assumed that there are times when pilots face some sort of delay, either arrival or departure, when skydivers are descending upon the airfield. Unfortunately, there is no way to measure this type of delay nor is there any way to mitigate it. AIRSPACE CAPACITY Airspace capacity is an essential element of any airport, especially with respect to maintaining the existing and proposed operational characteristics. The airspace above Sebastian is designated as Class E. The only reason the Airport has this controlled airspace, which begins at 700 feet above ground level (AGL) and extends upward to 17,999 feet, is to facilitate the transition of aircraft to/from the Vero Beach Municipal Airport terminal environment. In addition, there are several Victor airways that pass just to the west of the airfield as they approach to or extend from the Vero Beach Very High Frequency Omni directional Range (VOR). Since the last master plan, the capacity of the airspace around Sebastian Municipal has neither increased nor decreased significantly. Overall, the airspace for the Airport is not currently impacted or constrained by any of the other airports in the region. This does not remove the airspace from the potential of some occasional conflicts with other airports or obstructions in the region. While none of these facilities have a direct airspace conflict, the future application of additional instrument approaches, precision or non-precision, will require careful planning to avoid conflicts. For example, if an instrument approach procedure was desired for Runway 4, aircraft on instrument approaches to either Runway 11R or Runway IlL at Vero Beach Municipal might create a conflict. Nonetheless, it is felt that while there are some facilities in close proximity to Sebastian Municipal, they do not present a hazard to the capacity of the Airport's airspace. 2002 4-8