(1) Definitions. The following definitions apply in this section:

(a) Airport Hazard. Any structure, tree or use of land which obstructs the airspace required for the flight of aircraft in landing or taking off at an airport, or is otherwise hazardous to such landing or taking off of aircraft.

(b) Approach Surface Base Line. A horizontal straight line at runway and elevation 200 feet outward from the end of each runway measured along the extended runway center line, said approach surface base line being in a horizontal plane and being perpendicular to such extended center line and extending 500 feet therefrom in each direction in the case of Runway 6-24 and 250 feet in the case of Runway 15-33.

(c) Lateral Edge. The two edges of any approach surface extending outward from the approach surface base line.

(d) Lateral Surface Base Line. A line on each side of a runway parallel with the center line of the runway connecting the end of one approach surface base line with the end of the approach surface base line at the other end of the runway.

(e) Mean Sea Level. United States Coast and Geodetic Survey zero datum plane.

(f) City Datum. A datum plane 5.62 feet above mean sea level.
(g) Outer Edge. The edge of any approach surface farthest from the end of any runway.

(h) Runway Center Line. The long axis of the runway surface.

(i) Runway End Elevation. Elevation at the intersection of the runway center line and the end of the runway.

(j) Slope. The ratio of horizontal to vertical distance.

(k) Structure. Any object constructed or installed, including without limitation, buildings, towers, smokestacks, poles and overhead wires.

(l) Trees. Any object of natural growth.

(m) Zoning Reference Point. The point of intersection of the center line of Runway 6-24 with the center line of Runway 15-33.

(n) All runways referred to in this section are references to runways and their dimensions and locations shown on Zoning Plan A for North Philadelphia Airport dated August 14, 1957. Whenever the term "runway" or "runways" is used without identification, the reference is to Runways 6-24 and 15-33, as shown on the aforesaid Zoning Plan.

(2) No part of any structure or tree shall be at an elevation greater than any of the following assumed surfaces:

(a) Horizontal Surfaces: A horizontal circular plane 215 feet above mean sea level and having a radius of 5,000 feet measured from the intersection of said plane with a vertical line extending through the zoning reference point.

(b) Approach Surfaces: Sloping trapezoidal planes beginning at each approach surface base line beyond the end of each runway and extending upward and outward for a horizontal distance measured along the extended runway center line of 50,000 feet in the case of Runway 6-24, and 40,000 feet in the case of Runway 15-33, such approach surfaces having a slope measured in a vertical plane passing through the extended runway center line of 50:1 in the case of Runway 6-24 and 40:1 in the case of Runway 15-33. Each approach surface widens uniformly to a width of 16,000 feet at its outer edge in the case of Runway 6-24, and 8,500 feet in the case of Runway 15-33.

(c) Transitional Surfaces: Sloping parallelogrammatic planes beginning at the lateral edges of each approach surface and extending upward and outward at a slope of 7:1 measured in a vertical plane perpendicular to the extended runway center line and extending for a horizontal distance of 5,000 feet measured perpendicular to the extended runway center line.

(d) Lateral Surfaces: Sloping planes symmetrically located on each side of each runway, beginning at each lateral surface base line and extending upward and outward for a horizontal distance of 1,200 feet measured perpendicular to the runway center line and having a slope of 7:1 measured in a vertical plane perpendicular to the runway center line.

(3) No part of any structure or tree shall be at an elevation greater than 300 feet above mean sea level within 10,000 feet of the zoning reference point, this maximum height sloping upward and outward radially beyond the said 10,000 feet for an additional four and one-third statute miles in the ratio of 100 feet for each additional statute mile of distance, except that any structure or tree may be at greater elevation up to but not in excess of 100 feet above the ground level existing at the effective date of this ordinance.

(4) The Zoning Board of Adjustment is authorized to grant special exceptions to the terms of this section whenever it determines, after public hearing, that the proposed structure, tree or use of land will not constitute an airport hazard and the special exception will not be contrary to the general purpose and intent of this section.

(5) Any provision in this section to the contrary notwithstanding, applications for zoning permits for the erection or alteration relating to the height of any structure within the area designated by the zoning regulations adopted by the Joint Airport Zoning Board pursuant to the Act of April 17, 1945, P.L. 237, shall be referred to the Zoning Board of Adjustment, whenever a structure in excess of the maximum allowed by such regulations is sought to be erected.