Obstacle Limitation Surfaces OLS

OLS definition

Defines airspace around aerodrome that must remain free of obstacles to protect aircraft during approach, take-off, and circling.

OLS marking rule

Marking and lighting of an obstacle does NOT remove the operating limitation it imposes.

Inner Horizontal Surface IHS

FLAT at 45 metres above aerodrome elevation. Oval shape. Radius 4,000 metres for precision approach runways.

Conical Surface

5 percent slope rising from outer edge of Inner Horizontal Surface. Extends 100 metres above Inner Horizontal Surface to 145 metres total.

Approach Surface Precision Category I

2 percent slope. Inner edge width 300 metres at threshold elevation. Diverges 15 percent each side. First section 3,000 metres. Horizontal section 3,600 metres.

Transitional Surface

14.3 percent slope which is 1 in 7 gradient. Connects runway strip and approach surface to Inner Horizontal Surface.

Take-Off Climb Surface

2 percent slope. Inner edge width 60 metres OR runway width plus 2 times strip width whichever is greater. Final width 1,200 metres. Length 15,000 metres.

Inner Approach Surface

FLAT at threshold elevation. Precision approach only. Length 300 metres. Width 60 to 120 metres.

OLS slopes to memorize

Approach equals 2 percent. Conical equals 5 percent. Transitional equals 14.3 percent which is 1 in 7. Take-off climb equals 2 percent. Inner Horizontal Surface is flat at 45 metres.

Inner Transition Plane

From cleared runway strip edge extends outward 3,000 metres. Rises from 0 to 45 metres.

Outer Transition Plane

Beyond 3,000 metres extends to 15 kilometres from Aerodrome Reference Point. Rises from 45 metres to 150 metres.

OIS extent

Full Obstacle Identification Surface extent is 15 kilometres radius from Aerodrome Reference Point. Upper limit is 150 metres.

Obstacle marking colour

ORANGE or RED where they do not merge with background.

Mobile objects emergency vehicles

RED or YELLOWISH GREEN as single conspicuous colour.

Mobile objects service vehicles

YELLOW.

Objects with limited mobility air bridges

Low intensity STEADY RED lights at highest point.

Trailers and towed equipment

Low intensity STEADY RED lights at highest point.

Closed runway marking

Large X in WHITE on runway. At each end plus at maximum 300 metre intervals along closed portion.

Closed taxiway marking

Large X in YELLOW on taxiway. At least at each end of closed portion.

Pre-threshold chevron

Paved area more than 60 metres before threshold that is not suitable for normal aircraft use. Chevrons point TOWARD threshold.

Responsibility for obstacle marking

Aerodrome licensee responsible for marking and lighting ALL obstacles on movement area regardless of ownership.

Intermediate obstacle lights

Required at maximum 45 metre intervals between top and ground on tall structures.

OIS purpose

Identifies obstacles that must be considered for aircraft operations and instrument flight procedures.

Approach surface Category II and III

Same as Category I but with additional inner approach surface for closer obstacle clearance.

Approach surface non-precision

2 percent slope. Inner width 150 metres. Different dimensions than precision approach.