OBSTACLE LIMITATION SURFACES SURVEY

 

These Obstacle Limitation Surfaces (OLS) “define the airspace around aerodromes to be maintained free from obstacles so as to permit the intended aeroplane operations at the aerodromes to be conducted safely and to prevent the aerodromes from becoming unusable by the growth of obstacles around the aerodromes.”

Obstacle Limitation Surfaces 

 Assumes that the aircraft is operating normally 

 Provides volumes of airspace around and above an airport for an aircraft in normal flight

Obstacle: All fixed (temporary or permanent) and mobile objects or parts thereof that are located on an area intended for the surface movement of aircraft or that extend above a defined surface intended to protect aircraft in fight

Obstacle Limitation Surfaces Eight Obstacle Limitation Surfaces: 

• Conical Surface 

• Inner Horizontal Surface 

• Approach Surface 

• Inner Approach Surface 

• Transitional Surface 

• Inner Transitional Surface 

• Balked Landing Surface 

• Take-off Climb

IMAGINARY SURFACES FOR OBSTRUCTION EVALUATION

Primary Surface: A surface longitudinally centered on a runway. When the runway has a specially prepared hard surface, the primary surface extends 200 feet beyond either end of the that runway; but when the runway has no specially prepared surface, or planned hard surface, the primary surface ends at the physical ends of the runway. The elevation of any point on the Primary Surface is the same as the elevation of the nearest point on the runway centerline. Primary surface widths vary with the classification of the runway; however, the width is uniform throughout and is based on the most precise approach existing or planned for either end of that runway.

APPROACH SURFACE 

Definition 

The approach surface is defined such as an inclined plane or combination of planes preceding the threshold. The inner edge is located at a distance before the Threshold of 60 meters, with a width of 300 meters both side of the centerline. This inner edge is horizontal and perpendicular to the extended centre line of the runway. The two sides originating at the inner edge diverge uniformly at a rate of 15% from the extended centerline of the runway. 

The surface comprises three sections: 

First section: 

With a slope of 1.8% and a length of 2500 m, the final edge reaches a height of 45 m above the level of the middle point of the Threshold. 

Second Section: Consist in a horizontal plane extending 1500 m beyond the previous section, with a constant height of 45 m over the threshold. 

Third Section: With a slope of 2.5% and a length of 4000 m, the final edge reaches a height of 145 m above the level of the middle point of the Threshold. 

Fourth Section: The final section is a horizontal plane with a height of 145 m above the level of the middle point of the Threshold and a length of 7000m. 

Transitional Surface:

A surface extending outward and upward, at right angles to the runway centerline and runway centerline extended, from the sides of the Primary Surface and the Approach Surfaces.

1. The slope is 7-1 (14.3 percent) and the surface extends until it intersects the Horizontal or Conical Surface.
2. A Precision Instrument Runway Approach Surface that project beyond the limits of the Conical Surface extends a distance of 5,000 feet measured horizontally from the edge of the Approach Surface. The slope is 7-1 (14.3 percent).

Horizontal Surface:

A horizontal plane 150 feet above the established Airport Elevation, the perimeter of which is constructed by swinging arcs of specified radii from the center of each end of the Primary Surface of each runway. Tangents then connect the adjacent arcs. Size of arcs as follows:

1. For all runways designed visual or utility, the radius of each arc is 5,000 feet.
2. For PIR and Non-Precision Instrument Runways, the radius of each arc is 10,000 feet.

The radius of the arcs specified for each end of a runway will have the same numerical value, that value being the highest determined for either end of the runway. When a 5,000 foot arc is encompassing by tangents connecting two adjacent 10,000 foot arcs, it shall be disregarded.

Conical Surface:

A surface, which extends upward and outward from the outer limits of the Horizontal Surface for a horizontal distance of 4,000 feet. The slope of the conical surface is 20-1 (5 percent) measured in a vertical plane.