Obstacle Surfaces
MSA – Minimum Sector Altitude (applies to instrument airports)The first part of an approach flight to an instrument airport is called Initial Approach, and here the lowest flying altitude is determined by the MSA surface. This surface is based on the locator for the respective runway and is a circle with a radius of 55 km. This is divided into four quadrants; northwest, northeast, southwest and southeast. Each quadrant is given 300 meters margin to the highest obstacle. Example: The northeast quadrant has a highest obstacle of 155 meters above sea level. The lowest flying altitude in this quadrant towards to the locator will then be 155m + 300m = 455 meters. LFV has MSA maps for all instrument airports. Map: The circle shows the MSA surface for approach path 27, |
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Holding, Racetrack, Intermediate, Final, Missed Approach (applies to instrument airports)Once the approach has begun, air traffic control may place aircraft in a waiting position, i.e. “holding”, due to the traffic situation. This is set in the vicinity of the airport, usually by a radio beacon. When the aircraft is ready for landing it flies out from the beacon and turns back toward the field — racetrack. With the landing field straight ahead the aircraft enters intermediate approach, and then in the final stage is in final approach. If the runway cannot be seen at the lowest altitude (minimum), approach must be interrupted, making a so-called missed approach. A special approach is made so that approach is made to a runway, to then go around the airfield with ground visibility and land on a different runway, which is called “circling”. Common to all surfaces is that the closer the plane gets to the runway’s imagined extension line, the worse the chances are for erecting tall obstacles. Other ways to make approaches are radar guidance and STAR (Standard Arrival Route) approach. In both of these cases a shorter route toward the field is flown. See map on SID/STAR below. In all these occurrences a required obstacle margin must be maintained; LFV has all the data for all of these obstacle surfaces. Map: Obstacle surfaces for racetrack, approach and missed approach for path 27, Norrköping Airport (click on the image for a larger map) |
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ICAO Annex 14 surfaces(applies to everything from instrument airports to small grass field) Map: ICAO Annex 14 surfaces where the arrow-shaped surfaces are climb/approach surfaces and the oval surfaces are horizontal/conic surfaces (click on the image for a larger map). |
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