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AIRPORT MASTER PLAN <br />imaginary surfacesrelated to airports. To ensure the continued safe and efficient <br />use of the airspace surrounding an airport, it is important that the five civil airport <br />imaginary surfaces remain clear of any obstructions that could pose a hazard to air <br />navigation. It should be noted that some objects may be located within an airports <br />imaginary surfaces as long as they has been properly marked/lighted and an <br />airspace review has been completed and determined that the object will not <br />adversely affect the safe and efficient use of the local airspace. <br />The five civil airport imaginary surfaces described in 14 CFR Part 77.19 are defined <br />below: <br /> Primary Surface A surface longitudinally centered on a runway. When the <br />runway has a specially prepared hard surface, the primary surface extends <br />200 feet beyond each end of that runway; but when the runway has no <br />specially prepared hard surface, the primary surface ends at each end of that <br />runway. The elevation of any point on the primary surface is the same as the <br />elevation of the nearest point on the runway centerline. <br /> Approach Surface A surface longitudinally centered on the extended <br />runway centerline and extending outward and upward from each end of the <br />primary surface. An approach surface is applied to each end of each runway <br />based upon the type of approach available or planned for that runway end. <br /> Horizontal Surface A horizontal plane 150 feet above the established airport <br />elevation, the perimeter of which is constructed by swinging arcs of a <br />specified radii from the center of each end of the primary surface of each <br />runway of the airport and connecting the adjacent arcs by lines tangent to <br />those arcs. <br /> Conical Surface A surface extending outward and upward from the <br />periphery of the horizontal surface at a slope of 20 to 1 for a horizontal <br />distance of 4,000 feet. <br /> Transitional Surface These surfaces extend outward and upward at right <br />angles to the runway centerline and the runway centerline extended at a <br />slope of 7 to 1 from the sides of the primary surface and approach surfaces. <br />Transitional surfaces for those portions of the precision approach surface <br />which project through and beyond the limits of the conical surface, extend a <br />Facility Requirements Chapter Page 54 of 70 <br />October 2020 <br /> <br />