Obstacle-free airspace ensures smooth and safe air traffic
The safety of air traffic as well as the smooth and regular flow of flights are always the main objective of Finavia Corporation's operations. The safety and smooth flow of air traffic are protected by several computational surfaces based on international regulations. These surfaces are in airspace which means that the possible impact of the obstacle on air traffic depends on the joint effect of the height of the structure and the elevation of ground surface.
The safety and smooth flow of air traffic can be compromised by so-called aeronautical obstacles. Almost any object may constitute an aeronautical obstacle: masts, wind power stations, chimneys, cranes, power lines, buildings, trees, and more.
The Aviation Act prescribes that a permit is required for setting up an aeronautical obstacle. Finavia's statement regarding the matter must first be obtained for the flight obstacle permit. This statement is appended to the flight obstacle permit application addressed to Trafi, the Finnish Transport Safety Agency. The actual aeronautical obstacle permit is issued by Trafi.
The aeronautical obstacle must not cause any danger to air traffic, disturb other equipment serving aviation or air traffic, nor may it be placed in such a manner that it could be mistaken for equipment or signs serving air traffic.
Protecting air traffic from aeronautical obstacles
Proximity of aerodromes
The obstacle limitation surfaces surrounding an aerodrome are defined in aviation regulation AGA M3-6. These surfaces extend to 15 kilometres in the direction of runways and to 6 kilometres sideways from them. The purpose of these surfaces is to ensure the safety of air traffic, and they cannot be penetrated.
More extensive areas surrounding an aerodrome
In more extensive areas around aerodromes, the smooth flow and regularity of air traffic is ensured so that aeroplanes can safely take off and land in any weather. The purpose of these zones is to prepare for any exceptional situations an aeroplane may encounter due to weather conditions or technical malfunctions.
The height restriction in these zones does not specify the maximum permissible height of the structure; instead, it specifies the maximum permissible altitude above sea level that the object to be constructed underneath may reach. The permissible height of the structure can be determined by comparing the altitude restriction with the elevation of ground level. If, for example, the altitude restriction is 300 m and the elevation of ground level on that spot is 150 m, enough room is left for constructing an object 150 m high. When the ground level elevation is 50 m, 250 m is available for the structure.
In other words, the maximum permissible height of the structure always depends on the elevation of ground at the site and on any altitude restrictions due to an height restriction zone in the area.
The specified height restriction zones include the buffer zones, i.e., the vertical and horizontal safety margin distances from obstacles that are required for air traffic. This means that the airplanes do not fly at the altitude restriction level but above it, at least by the height of the buffer zone. Typically, the height of the buffer zone is 300 metres, and its width may be as much as 10 km on both sides. The required buffer zones are based on international regulations, and Finavia cannot alter them.
Information on the height restrictions due to air traffic
Finavia has produced a geographic dataset in ESRI shapefile format. It can be utilised for the planning phase of projects. The material can be downloaded from the link at the bottom of the page.
The material describes several areas that have as an attribute value the maximum altitude above sea level the obstacle may reach. In case of overlapping areas, the lowest altitude value takes preference. This material must be further supplemented with ground elevation data in order to determine the maximum permissible height of structures in any given location.
The material is intended for use in an as early planning phase as possible so that locations where high obstacles will not be permitted can be eliminated. It cannot, however, be used for concluding that a certain obstacle will be permitted with certainty. In addition to the zones discussed above, there are several surfaces sloping in various directions that will be taken into account when producing the statement required for applying the flight obstacle permit referred to in section 165 of the Aviation Act. The approximate extent of the obstacle limitation surfaces in the vicinity of aerodromes (aviation regulation AGA M3-6) is marked with a circle in this documentation material.
The material is produced in the EUREF-FIN coordinate system. The elevation system is N60. Attribute field MAX_MSL_M indicates the maximum altitude above sea level (ATC SMAC, FIZ, MSA, TMA) in metres.
> The material is available in finnish
Flight obstacles in brief / What is this all about?
- Any object (mast, building, crane...) can constitute a flight obstacle
- Air traffic is protected from flight obstacles in compliance with international regulations
- Section 165 of the Aviation Act specifies the situations where a permit is required for setting up a flight obstacle
- The geographic dataset produced by Finavia can be used during the planning phase
- The Flight Obstacle Permit is required at the construction phase
About the permit process
- Section 165 of the Aviation Act specifies the situations where a Flight Obstacle Permit is required
- Applications for the permits are submitted to Trafi, the Transport Safety Agency
- The permit application must be accompanied by a statement issued by Finavia
- The statement request and permit application must include detailed information of the location of the site as well as the height of the structure and elevation of the ground level