Demand. Typical Building Area Functions and Facilities Commonly Found at General Aviation Airports:

OVERVIEW The building area of an airport encompasses all of the airport property not devoted to runways, major taxiways, required clear areas, and other airfieldrelated functions. Typical facilities found at a general aviation airport area shown in the list to the right. This chapter examines the factors that affect the siting of future building area facilities at Mariposa- Yosemite Airport and alternative ways of accommodating projected demand. The focus is on providing direction for the appropriate expansion and use of the core building areas of the airport. The various design issues associated with Mariposa-Yosemite Airport are discussed in the sections that follow. The two most critical concerns are defining the most cost-effective location for additional aircraft storage hangars and a site for a large helicopter parking position. The Building Area Plan enclosed with the Master Plan report presents the recommended layout of facilities for these areas. (FBO) that provides aircraft maintenance, and a general aviation terminal. The County of Mariposa operates and maintains the fuel facility as well as the general aviation terminal. DESIGN FACTORS Many factors influence the planning and future development decisions associated with Mariposa- Yosemite s building area. Most of these factors can be grouped under the five headings that follow. Airport Property The current airport property consists of approximately 150 acres. The runway and taxiway system occupies about 8 acres of this total, while some 9 acres consists of aviation-related buildings (i.e., FBO, aircraft storage hangars). Although it is possible to expand an airport s property (and will be recommended at this airport), the existing property boundary shapes the path of future development. It should be recognized that there are two distinct building areas on the airport. Currently most development is located on the south side of the airport. However, there are some building area facilities located on the north side. The choice of which side of the airport to place facilities will be a reoccurring theme in this chapter. The existing building area contains most of the uses expected at a general aviation airport: aircraft storage hangars, aircraft tiedowns, a fueling facility, fixed base operator Demand Typical Building Area Functions and Facilities Commonly Found at General Aviation Airports: Based aircraft tie downs and storage hangars Transient aircraft parking Administration building/office Pilots lounge/flight preparation area Public restrooms and telephone Fixed Base Operator (FBO) facilities Fuel storage and dispensing equipment Aircraft washing area Perimeter fencing and access control Access roads and automobile parking The demand for additional building area facilities at Mariposa -Yosemite Airport is forecast to increase over the 20-year planning period. As documented in Chapter 2, the number of based aircraft is forecast to increase from the current 32 aircraft to 62 aircraft. The additional based aircraft at Mariposa- Yosemite Airport translate directly to building to building area facilities needed there. Mariposa-Yosemite Airport Master Plan (April 2008) 4-1

All but 1 of the aircraft currently based at Mariposa-Yosemite Airport are single-engine, piston-powered aircraft; there is 1 piston twin. It is anticipated that most of the aircraft based at the airport will continue to be single-engine piston aircraft. Partially this is due to demand, but the runway s length is a limiting factor for larger aircraft. Because Mariposa-Yosemite Airport is used as a means of accessing Yosemite National Park, other local tourist sites (e.g., historic towns), and second homes, transient parking is an important component of this plan. The forecasts presented in Chapter 2 anticipate that peak transient parking demand will increase from 5 to 10 aircraft. Demand for new fixed base operator (FBO) leaseholds is expected to be limited. The most likely source of demand is from the existing maintenance FBO. There is the potential that this operator may wish to expand into a larger hangar or otherwise expand his business. There is also the potential that a specialized FBO may be developed during the life of this plan. However, given the number of based aircraft and relatively remote location of the airport, demand for additional FBO site is uncertain. Setback Distances The interior boundary of the airport building areas is determined in large part by the necessary setback distances from the nearest runway and taxiways. Based upon FAA design standards discussed in the preceding chapter, the following design criteria are applied where appropriate: A minimum of 245 feet from the centerline of Runway 8-26 to any future buildings. A minimum of 125 feet from the centerline of Runway 8-26 to any future aircraft parking positions. A minimum of 45 feet from center of a taxilane to fixed or movable object. Existing Facilities Generally, the facilities at Mariposa-Yosemite Airport are expected to remain viable throughout the 20-year planning period. The exception is the aircraft storage hangars on the north side of the airfield. These hangars are in poor condition and will need to be replaced somewhere on the airport. As expected, periodic maintenance will be required to preserve the functionality of airfield pavement, structures, and associated drainage and utilities. Accessibility An important design consideration is the ease of access to individual portions of the building areas from both the taxiway system and public roads. At Mariposa-Yosemite Airport, Taxiway A (the parallel taxiway) provides adequate access to the southern building area. The building area is relatively shallow; most facilities are directly accessible from Taxiway A. There is not sufficient space for an apron edge taxiway. There are two components to vehicular accessibility: access to the airport; and access to the airfield (e.g., hangars). The south side of the airport enjoys very convenient access from California State Highway 49. This highway passes immediately south of the airport. The north side of the airfield is accessed from the Cya Road. The airfield is accessible to the public from three points. On the south side, there is both a vehicle gate and a pedestrian gate that provide access to the airfield from the public parking lot adjacent to the General Aviation Terminal. A third gate provides access to the north side from a road that intersects Highway 49 immediately east of the airport. All are controlled access points, as will be described in more detail later in this chapter. Mariposa-Yosemite Airport Master Plan (April 2008) 4-2

At a general aviation airport, the system of fencing and gates is intended to provide three functions: Exclude stray domestic and wild animals (e.g., cows and deer) Prevent inadvertent entry of people and vehicles onto the airfield operations area Increase the difficulty of determined entry by those with malicious intent (i.e., thieves). There are general Federal Aviation Administration guidelines for fencing and gates. BUILDING RESTRICTION LINE The building restriction line (BRL) establishes the closest location that buildings can be placed relative to a nearby runway or, in some cases, a primary taxiway. The FAA no longer defines a specific BRL setback distance standard, but rather provides guidance on factors to be considered in determining the BRL location. The purpose of a BRL is to ensure safe use of the airport by providing: Clearances necessary for visual and instrument flight operations Clear visibility from the air traffic control tower, when one exists Clear visibility between runways, when multiple runways exist At Mariposa-Yosemite Airport, the BRL for Runway 8-26 is set at 245 feet on each side of the runway centerline. Effectively, the BRL is established to create a visually uniform flight line facing the runway. At the established distance, a 17-foot tall building situated at the same elevation as the runway would not penetrate the 7:1 transitional surface of FAR Part 77. The 17-foot standard is appropriate because this airport is designed to accommodate small aircraft (i.e., those under 12,500 pound gross weight). Typical storage hangars for small aircraft are less than 17 feet in height. BASED AIRCRAFT STORAGE AND PARKING The forecasts prepared as part of this master plan update indicate that demand will exist for storage facilities for up to 32 additional based aircraft by the year 2026. Sites for at least 5 box hangars currently exist, so 27 additional sites are needed. Meeting this forecast demand is contingent upon hangar availability. A need for additional tiedowns to accommodate based aircraft is not anticipated. Hangars Background The demand for specific sizes of hangars cannot be anticipated. The size of new hangars will be determined by market forces (e.g., price), the types of aircraft owned by prospective tenants, and the personal preference of prospective tenants. The best design will be one that permits construction of a variety of hangar sizes. An optimum design would accommodate box hangars from 42 x 36 to 60 x 50 and standard T-hangars. The FAA standards specify that the maximum gradient for taxiways is 2%. Areas in front of hangars and on aprons have a practical limit of 1%. With side slopes greater than 1 % fuel will drain from wing vents while parked. With longitudinal slopes aircraft will be very hard to push in and out of hangars, and will roll if brakes are not set. These shallow gradient limitations narrows the range of possible sites and necessitates filling or cutting into slopes. T-hangars (definition): T-hangars are groups of hangars built in one unit. The placement of interior partitians gives each unit a T shape. Mariposa-Yosemite Airport Master Plan (April 2008) 4-3

Constraints on Possible Hangar Sites Both the south and north sides of the airport were evaluated for possible hangar sites. The generally steep terrain significantly constrained the location of potentially viable hangar sites. It was assumed that sites requiring retaining walls would not be economically viable. The north side of the airport currently has several hangars that directly access the runway via a short taxiway. Due to safety concerns, it would be highly desirable for any new hangars on the north side to be served by a parallel taxiway. At a minimum, a partial parallel taxiway that connects to one of the runway ends would be needed. A direct taxiway connection forces aircraft increases the potential for a runway incursion. A midfield connection forces the pilot to cross the runway to reach the runway end. Pilots who are landing or taking off are also less likely to notice an aircraft entering the runway midfield than at a runway end. It would be physically possible to create a fulllength parallel taxiway on the north side. However, the earthwork volumes required to build this taxiway would make it very expensive. Constructing a full-length parallel taxiway would only be justified if significant development were possible on the north side. Unfortunately, the only location with significant development potential is the site with the existing hangars. Elsewhere along the north side no potential building sites could be created without large retaining walls. Therefore, the only north-side hangar alternative that will be evaluated will consist of redevelopment of the existing hangar site. The south side of the airport property also has variations in slope, but there are less design restrictions. New hangar development on the south west side could capitalize on the existing taxiways and taxilanes. Three general areas could accommodate hangar sites: West of the existing hangar area East of the helicopter parking pads On the western tiedown apron. Within these three areas, a total of six alternative layouts were evaluated. The six alternatives are: 1. North Side Site: The sole alternative located on the north side of the airport. It is centered near the existing hangars. 2. Southeastern Site: The only alternative in the southeastern corner of the airport (east of the helicopter parking pads). 3. Southwestern Site Box Hangars with northsouth orientation: one of three alternatives that would extend the existing hangar area further west. 4. Southwestern Site T-hangars with northsouth orientation: similar to the previous alternative by includes two-sided T-hangars rather than single-sided box hangars. 5. Southwestern Site Box Hangars with eastwest orientation would extend two rows of small, box hangars along an extension of an existing taxilane. 6. West Tiedown Apron Would convert two rows on the existing tiedown apron to T- hangars. The six alternatives are shown in Figures 4A through 4F at the end of this chapter. Table 4A describes each alternative s key features and summarizes its strengths and weaknesses. Mariposa-Yosemite Airport Master Plan (April 2008) 4-4

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Analysis of Alternatives None of the six alternatives are capable of satisfying the forecast demand for hangars alone. Therefore, we are seeking the most efficient combination of alternatives to meet the forecast hangar demand. Evaluation criteria include safety, cost and complexity. The North Side Site (Alternative 1, Figure 4A) would provide space for about 18 small box hangars. A partial parallel taxiway would be created to connect this group of hangars to the western runway end. This alternative raises the most significant safety concerns of any alternative. Aircraft based in these hangars would have to cross the runway to depart to the west the most common direction. This significantly increases the likelihood of an accident with another aircraft that is landing or taking off. A full-length parallel taxiway would reduce this problem. However, these aircraft can be expected to cross the runway because fuel is only available on the south side. This would mean a runway crossing before or after every flight. Additionally, this alternative is already the most expensive (on a per hangar basis) because of the partial-parallel taxiway. The combination of safety concerns and high price make this alternative unacceptable. The Southeastern Site, Alternative 2 (Figure 4B), could accommodate 11 small box hangars. Safety concerns, albeit less significant ones, also exist with Alternative 2. This alternative would connect the hangar taxilanes to the area used for run-ups. The connection is unusual, and as such raises concerns over taxiing accidents. Providing adequate security for the Southeastern Site will be difficult because it is not readily visible from the general aviation terminal. This site s isolation from where most other aircraft are stored reduces the informal security value provided by the presence of other based aircraft owners. The need for the vehicle access to connect the Southeastern Site directly to State Highway 49 is also undesirable. It creates another direct access to a highway with its associated turning movements. It is expected that California s Department of Transportation (Caltrans) would not favor this new access, but unknown whether the additional encroachment permit would be granted. Additionally, this access road would need to include provision for a cattle crossing. A cattlecrossing easement currently exists around the east end of the runway. The cow path is fenced to exclude cows from the airfield. It connects grazing land that lies north and south of the airport. The Southeastern Site has several minor safety concerns, and more substantial security problems. It has a degree of complexity and uncertainty not found in any other alternative. While none of these problems makes this alternative infeasible, it certainly makes its less desirable. The next three alternatives considered are all located in the southwestern corner of the airport. They would connect to the taxilanes already serving the hangars in this corner of the airport. All three would require significant fill to provide a relatively level area for the hangars and associated pavement. Alternative 3 (Figure 4C) would create space for 13 small box hangars in a north-south orientation (i.e., the doors would face east and west). The use of box hangars requires access to only one side of each group of hangars unlike T-hangars which require access to both sides. The fill slope for this alternative would extend off of airport property to the south. Therefore, either additional land would need to be acquired or some form of agreement with the landowner created to allow the fill. The north-south orientation of the hangars extends the fill platform further from the native slope than an east-west orientation. This means What is a run-up? Immediately prior to takeoff, piston aircraft perform various engine checks. This requires that the engine be run at a specified RPM while oil pressure and other systems are checked. Aircraft with variable-pitch propellers exercise the propeller to verify that the variable pitch system is operational. These system checks are normally conducted at an apron adjacent to the runway end. Mariposa-Yosemite Airport Master Plan (April 2008) 4-6

that the fill platform is more extensive that it would be for an alternative with an east-west orientation. This increases the cost per hangar. Alternative 3 does not have any significant operational deficiencies. Its only complication is the need for permission from the adjacent land owner to extend the fill slope into grazing land. However, being more expensive per hangar than the east-west alternative makes this alternative less attractive. Alternative 4 (Figure 4D) is very similar to Alternative 3 except that T-hangars are substituted for small box hangars. This configuration results in more hangars: 24 versus 13. Alternative 5 would have lower costs per hangar than Alternative 3. However, its per hangar cost would be higher than alternative 5. It has a functional design with no significant operational deficiencies. Its only complication is the need for permission from the adjacent land owner to extend the fill slope into grazing land. It, too, is an acceptable alternative that is less desirable than a lower cost alternative in this general area. The third, and final, alternative in the southwest corner of the airport (Alternative 5, Figure 4E) would develop two rows of box hangars with an east-west alignment. The two rows of hangars would face each other across an extension of the existing taxilane. This alternative would produce about the same number of hangars as Alternative 4 (25 versus 24), but its east-west orientation would require significantly smaller amounts of fill. This gives it a lower cost per hangar. Of the viable alternatives examined so far, this has the lowest per hangar cost. The only weakness of Alternative 5 is that it places about 35 hangars on one taxilane. An aircraft parked in front of a hangar while being readied for departure would temporarily block the taxilane. This minor complication could be overcome with courtesy and coordination among tenants in this row. The final alternative (Alternative 6, Figure 4F), would utilize two rows on the West Tiedown Apron. It would replace 20 tiedowns with 14 units in two T- hangars. Site preparation would be minimized because the site already has the very shallow slope require for a parking apron. The existing pavement would need to be removed and redesigned to provide proper drainage away from the hangars. Because this tiedown apron was constructed with FAA grant funds, the FAA would have to approve of the conversion to hangars. Clear documentation that the loss of tiedown spaces would not constrain either based or transient demand would be needed. Alternative 6 would fit two rows of hangars on the apron without requiring any reconfiguration of the balance of the apron. This will work only if the T- hangars are configured in the stacked configuration; a nested configuration would be too wide (see adjacent illustration). This alternative would require relocating the portable hangars already located on these rows. As can be seen in Figure 4F, there is space in the adjacent rows to accommodate these portable hangars. While this would be the least cost alternative, it has one limitation and a one timing complication. Alternative 6 s limitation is that it would restrict visibility of the runway and parallel taxiway from within the general aviation terminal. Currently all of the runway and most of the parallel taxiway can be seen from within the terminal. This allows airport staff to monitor the airfield when they are in the terminal. These hangars would block the view of the western third of the runway and parallel taxiway. While visibility of the airfield is not essential (many general aviation airports do not have it), it is desirable. A clear view of the entire airfield makes it easier for airport staff to identify potential problems (e.g., deer on the runway) or respond to an emergency (e.g., a gear-up landing). Mariposa-Yosemite Airport Master Plan (April 2008) 4-7

The timing complication for Alternative 6 is linked to resolution with the large helicopter parking issue. Currently, a large helicopter is often based at the airport for several weeks each summer as part of wildland fire fighting operations. Typically the helicopter is either a Sikorsky S-64 Aircrane or Boeing CH-47 Chinook. Due to the constrained airfield and steep terrain there are few choices of where to park this helicopter. The optimum site has proven to be the southern tiedown apron. However, these large helicopters utilize the entire southern apron while they are stationed at the airport. This leaves only the western apron available for based and transient aircraft. Under most circumstances, there would be sufficient tiedown spaces for based and transient aircraft even if Alternative 6 was implemented and a large helicopter was occupying the southern apron. However, special events (e.g., organized fly-ins) or unusual occurrences (e.g., several aircraft with large wingspans) could result in a shortage of tiedown spaces. Therefore, if this alternative is used, it is recommended that only the westernmost bank of T-hangars is constructed prior to a large helicopter parking pad being constructed. Selection of Hangar Sites For the reasons presented above, Alternatives 1 and 2 have been eliminated from further consideration. The remaining four alternatives were determined to be viable alternatives, although none are without at lease minor deficiencies. As noted earlier in this chapter, no one alternative can satisfy the forecast 20-year demand for hangars. The best combination is judged to be Alternatives 5 (Southwestern Site box hangar with an east-west orientation) and 6 (West Tiedown Apron). Alternative 5 would be implemented first. Once this area is built out, Alternative 6 would be implemented (assuming FAA concurrence could be obtained). This combination would provide the most cost-effective, least complicated means of providing additional hangars. The Airport Layout Plan incorporates this selection. Based Tiedowns Currently there are two based aircraft that utilize tiedowns. It is anticipated that with new hangar development there will be no additional demand for based tiedowns. If demand for based tiedowns is higher than anticipated, there are sufficient existing tiedowns to accommodate a large number of based aircraft. TRANSIENT AIRCRAFT PARKING Fixed Wing Aircraft Parking As noted in Chapter 2, peak transient fixed-wing aircraft parking demand is forecast to increase from 5 aircraft to 10 aircraft over the next 20 years. During this period, the share of large aircraft (mostly piston twins and turboprops) is expected to continue to increase. The main apron is large enough to accommodate this demand. However, specific parking areas for larger aircraft have not been designated. To better serve Mariposa- Yosemite airport, and the occasional large aircraft, it is recommended that two large aircraft parking positions be defined. This could be accomplished by converting five tiedowns on the northern end of a row on the west apron. A painted rectangle would define the parking area. Helicopter Parking During the summer, the Mariposa-Yosemite Airport serves as a base for helicopters involved in wildland fire fighting operations. The airport also sees use by helicopters on other missions, including: Flight training Utility patrol Law enforcement Military proficiency flights Mariposa-Yosemite Airport Master Plan (April 2008) 4-8

Three helicopter parking positions were constructed east of the fixed-wing tiedowns. The helicopter parking pads connect directly to the parallel taxiway. Each parking position features a 50 x 50 Portland cement concrete pad surrounded by an area stabilized with asphaltic concrete. The design aircraft for these pads is the Bell 212. This helicopter has a rotor diameter of 50 feet and a gross weight of 11,200 pounds. These three helicopter parking positions are adequate to meet typical demand by small helicopters. It is important to understand that these are helicopter parking positions, not helipads. A helipad is a landing facility equivalent to a runway. The three pads are parking positions. Helicopters must make approaches to landings to the runway or other location before parking on these pads. As a part of summer firefighting operations, the airport is also regularly used by larger helicopters such as the Sikorsky S-64 Aircrane or Boeing CH- 47 Chinook. The Aircrane has a rotor diameter of 72 feet and a gross weight of 42,000 to 47,000 pounds (depending upon model). The Chinook s twin rotors each have a diameter of 60 feet; it has a gross weight of 54,000 pounds. Currently there are no facilities designed for parking this class of helicopter. Due to the constrained airfield and steep terrain, the eastern tiedown apron is used for parking this class of helicopter. One helicopter of this type utilizes the entire eastern apron. During the weeks when a large helicopter is based at Mariposa-Yosemite Airport, 18 fixed-wing tiedowns are rendered unusable. Rotor wash from these large helicopters also produces operational problems for those using the general aviation terminal and fuel island. An alternative to using the eastern apron is needed to reduce the operational conflicts. This need could be satisfied by either a helicopter parking position or a helipad designed to accommodate these large helicopters. A helipad would need to be sited at least 700 feet laterally from the runway for its operations to be independent of the runway. It is technically possible to site a helipad within 700 feet of a runway. However, this would mean that the operations on the runway and helipad were dependent; that is, the runway could not be used while a helicopter was landing or taking off from the helipad. As there is no way to ensure that this coordination will occur at a nontowered airport, locating a helipad within 700 feet of a runway is undesirable from a safety perspective. Therefore, only helicopter parking positions will be considered for sites within 700 feet of the runway. Whether designed as a helipad or helicopter parking position, the pad would be 60 feet by 60 feet and constructed of Portland cement concrete. If served by a taxiway, the taxiway would be 35 feet in width. Surrounding the taxiway and pad would be an area stabilized to prevent blowing of dust and debris. Stabilization could be accomplished with pavement or turf. The stabilized area would have a width of 132 feet. Most of the large helicopters using this pad are expected to be associated with wildland fire suppression. Therefore, space needs to be allocated for the supporting facilities that accompany this type of operation. A level site for the portable slurry mixing tank needs to be within about 75 feet of the pad. A level area nearby also need to be provided for a modular office and Mariposa-Yosemite Airport Master Plan (April 2008) 4-9

parking area for support vehicles. The support vehicles will include a fuel truck and service truck. The range of possible sites for a large helicopter parking position or helipad is limited by several constraints: Steep terrain Existing development on the airport Nearby roads Required setbacks from the runway and taxiways. Only two areas on or adjacent to the airport could meet the physical requirements for this parking pad or helipad: south of the existing building area and north of the runway. Each alternative area is examined in the paragraphs that follow. With some additional property acquisition, a large helicopter parking position or helipad could be constructed in the area south of the existing building area. The area is generally open, so a parking position or helipad could be developed almost anywhere along the south side. The only physical constraints are State Highway 49 and the airport entrance road. Three sites were selected to represent the range of possible sites south of the airport building area (see Figure 4G). Site 1 (Southwest) is on the western end, Site 2 is in the center (South-center), and Site 3 (Southeast) is located east of the airport entrance road. Three additional sites have been evaluated in the area north of the runway. Site 4 (Northwest) includes the area currently occupied by four hangars and the airport manager s residence. Site 5 (Northeast) is located further east, near midfield. Site 6 (Far North) is located uphill from Site 4. Table 4B summarizes the strengths and weaknesses of each of the 6 alternative sites. In the paragraphs that follow, the relative importance of the strengths and weaknesses are considered. Sites 1 and 2 have two major problems in common. First, neither would be readily visible to aircraft ready to depart from either end of the runway. This is a significant safety liability. Additionally, these two alternatives would be the least compatible with adjacent land uses. The pad location would force the large helicopters to overfly the community of Mount Bullion at low altitudes during arrivals and departures. These two sites have, therefore, been eliminated from further consideration. Site 3 has similar safety problems. A helicopter on the pad would be visible from the end of Runway 26, but not the end of Runway 8. More significantly, large helicopters arriving or departing to the east would have to pass very low over Highway 49. This would be a very significant safety hazard. Therefore, Site 3 has been rejected. The three remaining sites are all located north of the runway. Sites 4 and 5 are similar in that they could be connected to the runway with a loop taxiway. This is the source of important strengths and weaknesses of these two sites. Unlike most smaller helicopters, the large helicopters that will use this pad have wheels. A landing helicopter would make its approach down the runway, land on the runway and then taxi to the parking pad. This proximity to the runway makes Sites 4 and 5 readily visible to fixed-wing aircraft, both from the ground and air. It also raises the potential that the rotor wash from these helicopters could interfere with landing or departing aircraft. The FAA minimum separation between the parking pad and runway centerline is 165 feet. In order to reduce the potential for rotor wash to affect operations on the runway, increasing the pad setback to 300 feet is proposed. Site 4 is superior to site 5 in that the parking pad can be shifted further from the runway without the need for retaining walls or property acquisition. Mariposa-Yosemite Airport Master Plan (April 2008) 4-10

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However, Site 4 has the disadvantage of requiring removal of four hangars and the airport manager s residence. This negative factor is somewhat reduced by the fact that three of the hangars lie within the building restriction line and two of these hangars are at the end of their useful life. Of these two alternatives, Site 4 is judged to be superior because of the relative ease of placing the pad further from the runway; this is judged to be a key safety criteria. Therefore, Site 5 will be removed from further consideration. The final site, Site 6, is located uphill from site 4. Operationally, it differs from the other alternatives north of the runway in two ways. First, the terrain makes it impractical to connect this site to the runway with a taxiway. Second, this distance enables the pad to be designed as a helipad. That is, helicopters can fly directly to this pad. Their arrival-departure pattern would remain north of the pattern used by fixed-wing aircraft. This makes these helicopter operations independent of those on the runway. It also keeps these helicopter operations further from residential uses than the other sites. Two physical features complicate approaches from or departures to the east. First, the north side s access road runs immediately east of the pad. Although most vehicles would pass below the eastern approach surface for the helipad, it would not be safe for the road to be in use during arrivals from or departures to the east. This road is accessible only through an automatic gate equipped with a card-reader. The volume of traffic is also very low; it is limited to three aircraft owners and the airport manager. These two factors mean that the potential for conflict between a helicopter and vehicle is low. A reasonable means of reducing the potential for conflict below a level of significance is to place informational and stop signs on the access road. The signs would direct those driving on the road to stop and check for helicopter operations. Annual reminders could also be given prior to fire season (when the pad is most likely to be active) to the owners of aircraft based on the north side. This approach is similar ones routinely used at commercial service airports. The second physical feature is less easily to work around: terrain closely underlies the approach surface. The helipad would only be used during daylight and under VFR conditions. So this terrain would be clearly visible to helicopter pilots. However, the close proximity of terrain to the approach path is undesirable. It would be especially problematic during gusty wind conditions. However, the helipad would meet all FAA helipad design standards, and must be considered a viable alternative. Based upon the preceding analysis, all but Site 4 (Northwest) and Site 6 (Far North) have been eliminated. Neither site is ideal, but both can meet or exceed all FAA design standards. The independence of Site 6 from other airfield operations is an important asset. However, Site 6 s proximity to terrain and interaction with the onairport access road, and Cya Road make it less operationally acceptable than Site 4. Therefore, a helicopter parking position at Site 4 has been incorporated into the Airport Layout Plan. FIXED BASE OPERATIONS As was noted in Chapter 1, Mariposa-Yosemite Airport currently has one fixed base operation (FBO). This FBO provides aircraft maintenance services. The FBO is located in one bay at the west end of the box hangars. The County provides several products, services, and facilities that are often provided by FBOs. This include fuel from a fuel island, pilot supplies, a computer and telephone for pre-flight planning, as well as other pilot support facilities in the general aviation terminal. What is VFR? VFR stands for visual flight rules. Federal Aviation Administration has established regulations that apply to both visual and instrument flight conditions. In the airspace surrounding Mariposa-Yosemite Airport, the visual flight rules require that during daylight hours pilots have 1 mile of forward visibility and remain clear of clouds. Mariposa-Yosemite Airport Master Plan (April 2008) 4-12

There may be demand for leaseholds for FBOs during the 20-year life of this plan. The most likely source of demand is for the existing FBO to expand its facility. There is also potential demand for leaseholds for specialty FBOs (e.g., those offering only a limited number of services). It is not anticipated that there would be sufficient activity to support a full-service FBO by the end of the planning period. Given the small based aircraft population and relative remoteness of the airport, the demand for FBO leaseholds is uncertain. Chapter 5 contains a discussion of factors affecting FBO development and optimum means of attracting additional FBOs. Should demand occur, it is expected to be for one or two hangars and limited area for aircraft parking. Because the demand is expected to be limited, and the airport has limited available space, a separate area for FBO leaseholds has not been shown. An FBO could be established in the area designated for larger box hangars. It is not expected that the volume of turbinepowered aircraft will support introduction of Jet A fuel service. Should the volume of turbine use be greater than anticipated, Jet A fuel service could be established either of two ways: fueling from a truck or from a fuel island. Turbine users prefer fueling from trucks because it avoids the necessity of an additional engine start. Turbine users count engine starts because they affect the longevity of the engine. If a truck were used, a fuel storage tank would need to be established. Given the limited available space, placing the Jet A tank next to the 100 low-lead tank is a possible choice. This location would also make it possible to fuel a turbine aircraft after hours using a credit card selffueling system. SECURITY Fencing and Gates The events of 9/11 dramatically increased public and agency concerns over aviation security. Although most attention is focused on airports with scheduled passenger service, all airports have seen security concerns increased. At general aviation airports such as Mariposa-Yosemite Airport, the physical requirements for increased security focus on controlling entry to the airfield. Macready Way is the only access point on the south side. There are vehicle and pedestrian gates located at the main parking area adjacent to AIRCRAFT FUEL STORAGE AND DISPENSING Mariposa Airport provides 100 low-lead fuel. Dispensing is from self-serve pumps located north of the general aviation terminal. The location is expected to continue to be adequate throughout the 20-year planning period. Mariposa-Yosemite Airport Master Plan (April 2008) 4-13

the general aviation terminal. The vehicle access point is secured with a card reader and the pedestrian gate with a key pad. The only vehicle access to airport property on the north side is via a gated access road off of Cya Road. This gate is secured with a card reader access system. The north access road provides entry to the Airport Manager s house, hangars and future helicopter parking. The perimeter of the airport property is surrounded by cattle fencing which includes cattle gates at various locations. Chain link fencing is used in the terminal area. Currently, the existing airport fencing is adequate. The terrain surrounding the airport makes inadvertent entry unlikely. Unless mandated by the FAA, this master plan does not recommend fencing changes throughout the 20 year planning period. Vehicle Access and Parking Vehicle access to the general aviation terminal is obtained from Macready Way. Macready Way connects Mariposa-Yosemite Airport with State Highway 49. Public parking is available in front of the terminal. With the exception of special meetings or large events the parking facilities has sufficient capacity for current operations and longterm growth. Additional parking could be created by relocating the vehicle access gate farther west and utilizing the space between Macready Way and the hangar area. Mariposa-Yosemite Airport Master Plan (April 2008) 4-14

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